determination of reactions and integrity of cement

1

DETERMINATION OF REACTIONS AND INTEGRITY OF CEMENT-

MUDSTONE INTERFACES

A thesis submitted to The University of Manchester for the degree of Master of Science

in the Faculty of Physical Sciences

2016

JORGE ARTURO MENDOZA ULLOA

SCHOOL OF EARTH, ATMOSPHERIC AND ENVIRONMENTAL SCIENCES.

THE UNIVERSITY OF MANCHESTER

9 September 2016

2

Table of contents

List of tables ........................................................................................................................ 4

List of figures ...................................................................................................................... 4

ABSTRACT ........................................................................................................................ 6

Chapter 1: Introduction ..................................................................................................... 10

1.1 Rationale .................................................................................................................. 11

1.2 Aims......................................................................................................................... 12

1.3 Objectives ................................................................................................................ 12

Chapter 2: State of the art .................................................................................................. 13

Introduction ................................................................................................................... 13

2.1 Experiments on interaction between clays and hyperalkaline solutions ................. 13

2.2 Experiment with low-pH cement ............................................................................. 18

Chapter 3: Materials .......................................................................................................... 21

Introduction ................................................................................................................... 21

3.1 Mudstones ................................................................................................................ 21

3.1.1 The Whitby Mudstone ...................................................................................... 21

3.1.2 Kimmeridge Clay Formation ............................................................................ 24

3.1.3 Holywell shale .................................................................................................. 27

3.1.4 Pyritiferous Shale .............................................................................................. 28

3.2 Cement ..................................................................................................................... 30

3.2.1 Microcement ..................................................................................................... 32

3.2.2 CEM II/A-LL 42,5N ......................................................................................... 33

3.3 Silica fume ............................................................................................................... 33

3.4 Nirex Reference Vault Backfill ............................................................................... 35

3

3.4.1 Limestone flour ................................................................................................. 35

3.4.2 Hydrated lime.................................................................................................... 36

3.5 Sample formulation and nomenclature .................................................................... 37

3.6 Sample preparation .................................................................................................. 39

4 Methodology .................................................................................................................. 43

Introduction ................................................................................................................... 43

4.1 Ligth microscopy ..................................................................................................... 43

4.2 ESEM and analysis .................................................................................................. 44

4.3 EMPA analysis ........................................................................................................ 46

4.4 Cement permeability ................................................................................................ 48

4.4.1 Oscillating Pore Pressure Method ..................................................................... 48

4.4.2 Permeability procedures.................................................................................... 52

4.5 Cement Porosity ...................................................................................................... 56

Chapter 5: Results ............................................................................................................. 57

5.1 Transmitted and reflected light microscopy ............................................................ 57

5.2 ESEM analysis ......................................................................................................... 62

5.4 Permeability ............................................................................................................. 90

5.4 Porosity .................................................................................................................... 99

Chapter 6 Discussion ....................................................................................................... 101

Chapter 7 Conclusions .................................................................................................... 104

REFERENCES ................................................................................................................ 105

19657

4

List of tables

Table 1: Compilation of the state of the art regarding the interaction between Clay-

bearing rocks and cement. Ref. (Dauzeres et al , 2010) ....................................................... 20

Table 2: Summary of clay rocks used in this research. ..................................................... 29

Table 3: Shorthand form of chemical compounds found in Portland cement ................... 31

Table 4: Chemical composition of the most common types of microsilica ...................... 34

Table 5: Composition of Hydrated Lime .......................................................................... 36

Table 6: Composition (wt%) of the 7 mixtures utilized in this research. .......................... 38

Table 7: The cement mixtures and clay-bearing lithologies used in the experiments ...... 38

Table 8: Resume of all samples analysis. .......................................................................... 88

Table 9: Test conditions for every sample ........................................................................ 91

Table 10: Porosity results. Porosities obtained with the Digital Helium Porosimeter .... 100

List of figures

Figure 1 Whitby Mudstone ESEM. ................................................................................... 24

Figure 2: Kimmeridge Clay ESEM. .................................................................................. 27

Figure 3: Special mould specifications and details. .......................................................... 40

Figure 4 Cement mixing procedures.. ............................................................................... 41

Figure 5 Thinsection making. ........................................................................................... 42

Figure 6: Zeiss Axioskop 50 ............................................................................................. 43

Figure 7: ESEM. ................................................................................................................ 44

Figure 8: Thin section detail. ............................................................................................. 46

Figure 9: EPROBE. ........................................................................................................... 47

Figure 10 Oscillating pore pressure readings. ................................................................... 50

Figure 11: Space solution for equation 1. ......................................................................... 52

Figure 12: Permeameter scheme.. ..................................................................................... 53

Figure 13 Cement cores for permeability tests.. ................................................................ 54

5

Figure 14 DHP -100. ......................................................................................................... 56

Figure 15: OPC4 optical analysis. ..................................................................................... 58

Figure 16: PMS4 optical analysis ..................................................................................... 59

Figure 17: OPC2 optical analysis. ..................................................................................... 60

Figure 18: OPC4 SEM analysis. ....................................................................................... 64

Figure 19: OPC4 element mapping.. ................................................................................. 65

Figure 20: OPC4 Si map from SEM ................................................................................. 66

Figure 21: OPC4 SEM analysis.. ...................................................................................... 67

Figure 22: OPC4 element mapping. .................................................................................. 68

Figure 23: OPC4 Si map from SEM. ................................................................................ 69

Figure 24: OPC4 SEM analysis. s. .................................................................................... 70

Figure 25: OPC4 element mapping.). ................................................................................ 71

Figure 26 PMS3 element mapping.. .................................................................................. 73

Figure 27 OPC5 element mapping. ................................................................................... 74

Figure 28: OPC4 EPMA analysis. ..................................................................................... 79

Figure 29: OPC4 EPMA analysis.. .................................................................................... 80



Figure 32 PMS4 Ca map by EPMA analysis. ................................................................... 83

Figure 33: PMS4 Si map by EPMA analysis. ................................................................... 84

Figure 34: PMS4 Al map by EPMA analysis(Left) .......................................................... 85

Figure 35: PMS4 element map detail by EPMA analysis ................................................. 86

Figure 36: NRV5 element maps by EPMA.. ..................................................................... 87

Figure 37: MPC5 permeability results .............................................................................. 92

Figure 38: OPC permeability results ................................................................................. 93

Figure 39: PMS5 permeability results .............................................................................. 94

Figure 40: NRVB permeability results............................................................................. 95

Figure 41: PMS permeability results ................................................................................. 96

Figure 42: MPC3 permeability results .............................................................................. 97

Figure 43: Summarised permeability results. .................................................................... 98

6

ABSTRACT

This research examined the cement-rock/clay interface at an initial setting stage by

undertaking a series of experiments involving setting of cement against clays and mudstone

and examining the boundaries formed in terms of mineralogy, permeability and porosity.

Reactions and integrity will be study within the context of the Deep Geological

Repositories for Nuclear Waste.

The experiments were undertaken in cement cores of around 2.5cm (for porosity and

permeability). Polished thin sections were employed to analyse the interface and look at the

reactions between cement and rock. The preparation of the samples is also described where

some special moulds and methods were developed in order to make cement core samples

that could be subject to permeability test. Environmental Electron Scanning Microscope

and Electron Probe Micro Analysis were employed in the attempt to identify the

interactions that took place in the interface between both materials (cement and rock).

Petrophysical equipment such as permeameters and porosimeters were also employed to

test cement cores and measure their flow properties. These equipment and methods are also

described.

Experiments ‘results indicated a clear Ca depletion zone near to the interface with the

rock. This alteration was found only in common cement mixtures, whereas the specially

designed mixtures did not show any alteration after 28 days of interactions with pore water.

The usage of pore water is a difference with other researches since groundwater is mainly

used. All of the cement samples investigated proved to have a very low permeability

compared with the probable host rock for the repository. A particular result regarding the

porosity of NRVB was found, where this cement shows a porosity of 44% and still keeps a

very low value for permeability meanwhile other cements mixtures shows porosity of 10 to

20%.

Cracking and shrinkage due to water loss was present in samples with high water-cement

ratios. Therefore it was not possible to relate cement alteration with a change in porosity of

permeability due to technical problems in the process of sample making (mostly cracking

and shrinkage of cement samples). This was tried to be overcome by testing partially

saturated samples (with pore water from curing) but results were not satisfactory due to

lack of consistency.

7

DECLARATION

No portion of the work referred to in the thesis has been submitted in support of an

application for another degree or qualification of this or any other university or other

institute of learning.

8

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and in The University’s policy on Presentation of Theses

9

ACKNOWLEDGEMENTS

I would like to thank my supervisors Prof. Richard Pattrick and Dr. Julian Mecklenburgh

of the School of Earth and Environmental Sciences for his expertise, guidance and support

through this research.

I would also like to thank Prof. Ernest Rutter, Dr. Rochelle Taylor and Experimental

officer Stephen May from the Rock Deformation Laboratory in SEES for all their help,

assistance, training and willingness in the use of the facilities for sample preparation and

permeability tests. Thanks as well to Dr. Jonathan Fellowes for his training and assistance

in the operation of the Environmental Scanning Electron Microscope and the Electron

Probe Micro Analyser which was a key aspect in the development of this research.

Very special thanks to Prof. Ernest Rutter and Prof. Kevin Taylor from SEES for the

provision of the rock samples used in this research.

10

Chapter 1: Introduction

Cement is the most common material used in the construction of all kinds of

infrastructure and much of this construction involves the interaction of cement with many

other materials, both natural and manmade

Nowadays there is also a special concern regarding our legacy of radioactive waste and

the challenge to safe dispose of it. Among the proposals to deal with this problem the

accepted final disposal method is the deep Geological Disposal Facility (GDF) also called

Deep Geological Repository (GDR). A Deep Geological Repository is a facility, with more

than 300m depth, that provides isolation for radioactive waste deep inside a suitable rock

volume to ensure that no harmful quantities of radioactivity ever reach the surface

environment. Such isolation is provided by the natural geological barrier and the

Engineered Barrier System (EBS) which may itself comprise a variety of sub-systems or

components, like the waste form which is the nuclear waste itself, canister which might

have different systems like a copper canister or drums in some cases, buffer or backfill

surrounding the canister, seals and plugs (Apted & Ahn, 2010).

Within the many concepts of the GDR, clay-rich geological formations have been

proposed as host rock for different countries like France, Switzerland and Belgium.

Commonly, cement is used in the form of concrete to provide a rigid and strong structure

for a wide variety of purposes. In other cases cement is used in the form of mortar or grout

to work as a binder between two surfaces or to provide isolation and sealing to avoid

leaking of a fluid such as gas or oil, such as in the case of petroleum well-bores.

It is important to note that the use of cement would have to be optimized in order to

minimize the influence of cement - based materials to the surrounding environment. This

has led to the development of new low pH grouts. High pH conditions of grout materials

have been studied and found to limit uranium solubility by forming uranyl–oxides, -

hydroxides and uranate salts (Serne, LeGore, Ames, LindenmeiRr, & Richland, 1993),

however the solubility of uranium in cement waste forms has been investigated generally in

undersaturated conditions. Other studies have shown that solubility of uranium could rise at

11

high pH and high carbonates levels if aerobic conditions happen to develop (Sutton,

Warwick, Hall, & Jones, 1999). Interaction of groundwater with high pH cement

(conventional cement) can lead to carbonation and then to an acceleration of the release of

uranium, increase its mobility and change the solubility of other materials that might be

used as buffer, such as bentonite by reducing swelling capacity and sorptive properties

(Gascoyne, 2002).

1.1 Rationale

Regardless the different geological disposal concepts that are currently being

investigated and developed there is the need to use cement-based materials during the

construction and operation of the repository, mostly for practical reasons, (access tunnel

floors, constraint of water ingress, backfilling and sealing of tunnels, sarcophagus for

intermediate level waste). In Deep Geological Repositories for nuclear waste disposal,

cement – based materials will be exposed to very aggressive environments. For geological

disposal, in particular, the engineered repository is expected to last for up to 100,000 years.

The very long time performance expected for these projects implies the need to deeply

understand the behavior and interactions of cements with the surroundings materials.

No suitable site has been chosen so far in the United Kingdom to function as DGR, but

clay-rich formations are likely to be seriously considered. Clay-rich formations and cement

have very contrasting chemistries. Cements will be altered and release ions (mainly OH-,

K+, Na

+ and Ca

2+), resulting in high-pH porewater ranging between 10 and 13.5 and

generating a phenomenon called hyperalkaline plume which is likely to produce

physicochemical alterations not only in the host rock, but in other repository materials such

as artificial barriers(ECOCLAY II, 2005) (Alonso, Bárcena, Alonso, Pettersson, & Bodén,

2009). Since cementitious materials are likely to be used in GDF as structural elements,

backfill or waste matrix, interaction between cement and the host rock would lead to

mineralogical alterations in both faces which could have an impact in physical and

functional properties such as permeability.

12

Interactions between cement-based materials and rock interfaces take place in many

projects around the world such as tunnels, foundations, wells, etc. This research will only

focus in the interactions between cementitious materials and clay in the context of a GDF

for nuclear waste.

A brief description of the different cement mixtures that were used (such as regular

cement based grout, Nirex Reference Vault Backfill (NRVB) and other mixtures

specifically design to provide low pH that includes the addition of microsilica up to 40%) is

given in the first chapters. Litholigies involved in this research are mudstones and

claystones from England such as the Whitby Mudstone, Kimmeridge Clay, Yorkshire Clay

and Holywell Clay are also described focusing on mineralogy descriptions.

1.2 Aims

The aim of this research is to provide a more detailed and complementary knowledge

regarding to the interactions between cementitious materials and clays that might be in

interactions in the Deep Geological Repositories (DGR) for Nuclear Waste.

1.3 Objectives

The main objective of this thesis it to determine the interactions between different cement

mixes and mudstones in candidate lithologies that might host the UK´s geological facility

and determine the permeability of those different mixes.

To produce a series of samples of cement mixes containing a variety of UK mudstones

that will allow observation of the nature of cement-rock interfaces.

To determine chemical change at the interface by using optical imaging and micro-

elemental mapping.

To determine the effect of addition of microsilica to the cement on the interaction

between cement and mudstones.

13

Chapter 2: State-of-the-art

Introduction

Hyperalkaline solutions are expected to be found in the GDR, mostly from cement-based

materials in contact with the host rock or other components within the repository. The

research seems to have focused first to understand the interactions between clay rocks and

hyperalkaline solutions, by undertaking experiments in batch reactor or analysing natural

analogies, like the Khushaym Matruk and Maqarin sites in Jordan that may give more

detailed information about the interactions that might take place over the years.

Low-pH cements have arisen as an option to be used in the DGR context. Some of those

cements involves the addition of silica fume (Holt, 2008).

Furthermore, there is no much information about the interactions with hyperalkaline

solutions with clay rocks from the UK. Much of the research also has focused to understand

the alteration after months or even years of interaction.

2.1 Experiments on interaction between clays and hyperalkaline solutions

Much research has been undertaken in recent years regarding to the reactions in the

cement-mudstone interface and a compilation is presented in Table 1. Experiments in batch

reactors have been undertaken to investigate the effects of high-pH solutions in clay rocks.

X- ray diffraction and Scanning Electron Microscope techniques have been applied to

analyse the effects .Most of the rock samples are clay-rich rocks such as the Opalinus Clay,

the Tournemire argillite and the Callovo - Oxfordian argillite (Adler, Mader, & Waber,

1999; Chermak, 1992, 1993; Claret, Bauer, Schafer, Griffault, & Lanson, 2002; Devol-

Brown, Tinseau, Bartier, Mifsud, & Stammose, 2007; Elie et al., 2004; Ramirez et al.,

2005).

The evolution of the pore water chemistry during degradation of commercial cement has

been investigated (Berner, 1992; Taylor, 1990) showing that pH plays an important role in

the cement degradation that takes place once the concrete is saturated with ground water.

Initially generating a aqueous solution rich in K, Na, Ca ions of pH > 13, it is followed by a

14

fluid with pH dominated by equilibrium with Ca(OH)2 (pH 12.4) and finally by equilibrium

with the Calcium silicate hydrate minerals, termed hereafter as C-S-H minerals, which is

the main component of the product of the hydration of Portland cement (pH ≥ 10). This

degradation sequence found with commercial cement can be modified by using low pH

cement which would decrease the disturbing effects in clays (Glasser, 1996).

Experiments conducted in the interaction between CEM I –SR cement (Sulphate resisting

Portland Cement class I) and samples of mudstones collected at 490m depth on the

Callovo- Oxfordian Formation in the Meuse and Haute Marne Depart, in France; showed a

low carbonation that does not clog the interface between cement and mudstone. This lack

of clogging allows the diffusion of aqueous species and the consequent degradation of the

cement. The portlandite dissolution and reduction of CaO/SiO2 in the C-S-H resulted in

decalcification of the cement material (Dauzeres et al 2010).

Interactions between bentonite and concrete has also been investigated, given that

Bentonite has been envisaged as an engineered barrier in DGR, due to its extremely low

permeability, high swelling pressure to provide a good contact with host rock, small pore

sizes and reduced water activity to suppress microbial activity; and its ability to limit the

rate of transport of radionuclides (NDA, 2014). The effects of the alkaline plume caused by

concrete on bentonite has been investigated in Phases I and II of the of the project

ECOCLAY between 1997 - 2000 and 2000 – 2003(ECOCLAY II, 2005; Huertas et al.,

2000). This project contained two types of experiment, batch reactions at temperatures

ranging from 24 to 200°C mixing the Spanish reference Bentonite FEBEX and

hyperalkaline solutions (NaOH/KOH/Ca(OH)2) with pH ranging from 10 to 13.5; and

transport cell experiments where compacted FEBEX bentonite (1.5 cm thickness, dry

density of 1.2 g/cm2 ) and Ordinart Portland Cement mortar (1.5cm thickness) were

introduced in order to investigate physico-chemical changes in bentonite after the

interaction with the cement. (Cuevas et al., 2006)(Cuevas & Leguey, 2006). Cuevas found

zeolites, analcime and phillipsite formed at high temperatures at the interface, whereas

Magnesium-clay precipitated and tobermorite-type hydrated calcium silicate was found.

These results are consistent with the dissolution of montmorillonite, (primary compound of

bentonite) which can be identified by the presence of analcime and tobermorite.

15

Montmorillonite dissolution allows the pH to decrease by equilibrium with C-S-H minerals

(Savage, Arthur, Watson, & Wilson, 2010).

In situ studies have been also carried out in the Boom Clay/Portland Cement interactions

at different temperatures (Read et al, 2001). Boom clay is a marine clay deposit in Belgium

consisting of clay minerals (30-60 %, mainly illite and kaolinite), quartz (15-60%), calcite

(1-5%), K-feldspar and albite (both 1-10%), pyrite (1-5%) and ≈5% organic carbon (De

Craen, Wang, Geet, & Moors, 2004) The depth of the degradation zone in the cement paste

was found to be about 100 - 150 µm after 18 months where a portlandite dissolution was

observed as well as a porosity increase. The phases precipitated included magnesium -

aluminate hydroxide, Mg3Si4O10(OH)2 (magnesium - silicate hydroxide) and a low

crystallinity gel. In the Tournemire site in France a second in situ experiment was

conducted on Tournemire argillite/concrete interactions. 4 major phases are the components

of Tournemire argillite: silicate phase (clays, quartz, feldspars, micas) (≈86%), sulphide

phase (pyrite) (≈3%), carbonated phase (calcite, dolomite) (≈10%) and organic kerogen

form (≈1%). Within the clay minerals SEM observations indicated the presence of chlorite,

kaolinite, and a mixed layer of illite/smectite. Mineralogical characterization obtained by

X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed on the

clay/concrete interface after interaction of 7, 15 and 125 years in samples taken from an

ancient tunnel railway which is now part of the Tournemire experimental station. Analysis

showed recrystallization of the mixed layer illite/smectite and gypsum precipitation within

the saturated zone of the clay. Chlorite and kaolinite were dissolved near the interface and

important dolomite dissolution was identified (Tinseau, Bartier, Hassouta, Devol-Brown, &

Stammose, 2006).

Experiments in batch reactors were performed in the Tournemire clay rock where clay

was used in powder or fragments with a hyperalkaline solution (NaOH and KOH solutions

with pH≈13). Aqueous chemistry and solid analysis showed dissolution of pyrite, dolomite

and organic carbon, with the precipitation of calcite. SEM analysis revealed localized

zeolites and K-feldspars precipitations but only observable by SEM analysis. . (Devol-

Brown et al., 2007).

16

The impact of the porewater of cements materials on clay materials is the main

interaction investigated. In experiments often an alkaline fluid (pH=13.2) is used as an

analogy to the cement porewater (Claret et al., 2002). Samples from the Callovo-Oxfordian

formation were studied in batch reactor experiments conducted at 60 °C with alkaline

solutions in order to investigate the chemical degradation of the clay rock. Smectite

degradation and precipitation of a tobermorite - like phase were found in the clay.

Several studies have been performed also in the Opalinus Clay from Mont Terri,

Switzerland. Experiments with different types of alkaline fluids at different temperatures

were conducted: pH 13.2 (with the addition of potassium, sodium, and calcium hydroxides)

at 30 °C (Adler et al., 1999), pH 13 and 12 (sodium hydroxide NaOH and potassium

hydroxide KOH) at 150 to 200 °C (Chermak, 1992, 1993). During the high temperature

experiments zeolite - type analcime, phillipsite, (Na , K) rectorite were observed.

A series of experiment conducted at 70 °C in order to investigate the rate and reaction

mechanism of cement - pore fluids (sodium, potassium, and calcium-bearing) with silicate

minerals (quartz, feldspars, micas and clays). Results showed a C-S-H precipitation. The

rate of growth of C-S-H was limited by the rate of supply of silicon by the dissolution of

primary silicates (quartz, feldspars, micas and clays) (Savage et al 1992). Different

experiments (bulk dissolution in batch reactor and in situ atomic force microscopy)

conducted on the dissolution of montmorillonite under alkaline conditions (pH=13.3) at 30,

50 and 70 °C found that dissolution rates of individual particles is independent on the

particle size, morphology and stacking (3.39-12

, 1.75-11

and 5.81-11

mol/m2 s, respectively).

Initial concentrations of SiO2 produced by montomorillonite dissolution were high in early

stages in bulk experiments and reached a steady state after 136 hours. (Yokoyama et al

2005). Other experiments were carried out in sandstones (Braney et al 1993), where the

analysis of the evolution of minerology of alkaline fluids showed quartz and feldspar

dissolutions and phase precipitation of C-S-H and hydrated calcium alumino-silicate.

Experiments in batch reactors with smectite and kaolinite dissolutions at 35 °C and 80 °C

in potassium hydroxide solutions, with different solid-mass/solution-volume ratios, indicate

difference dissolution rates between the minerals (smectite and kaolinite), explained by

structural differences (Bauer et al 1998). Interactions between alkaline fluid and minerals

17

were also investigated after a review of the experimental and modelling studies regarding to

the expected interaction between alkaline fluids and potential host rocks in a radioactive

waste repository environment. Such interactions were investigated by experiments with

Ca(OH)2 solution containing muscovite and chlorite at 85 °C. Solids were analysed by

analytical transmission electron microscopy (ATEM) showing the formation of C-S-H

phases and precipitation of local zeolites (Hodgkinson et al 1999). Another series of

experiments studied the impact of circulation of portlandite - saturated water on MX-80

bentonite or a mixture of compacted mudstone (Manois argillite) and calcareous sand for

periods of 3, 6 and 12 months at 20 and 60 °C. Results indicate low degradation of the sand

mixture that could be related to the high proportion of calcite (about 60% of the mixture)

and therefore the limit quantity of minerals susceptible to dissolution when exposed to high

pH environments. In contrast, a high degradation in the bentonite mixture was found given

by dissolution of clay particles, which increases porosity of the sample. (Cuisinier et al

2008). The effects of diffusion properties and the diffusion of alkaline cations (K+, Ca

2+,

Na+, Cs

+ and Cl

-) in presence of alkaline solution through clay materials (mudrock from

Callovo-Oxfordian layer and compacted MX-80 bentonite) was also studied. Results

showed Cl- diffusion coefficient to be one to two orders of magnitude lower than the rest of

the cations which leads to the conclusion that assigning single diffusion coefficient to all

the dissolved species for a given material is yet a debate. (Melkior et al 2004, 2007). The

effects of different pH solutions ranging from 10 to 12 on (Na, Ca) smectite were

examined. Results showed that the use of KOH solution causes a partial substitution of

calcium by potassium and a significant replacement of sodium by potassium. (Na, Ca)

smectites were partially replaces by zeolites (merlinoite), feldspars and a C-S-H type

tobermorite-like phase in the presence of potassium carbonates (K2CO3). At higher

temperatures the precipitation of quartz was observed (Mosser et al 2004). The effect of

montmorillonite dissolution in compacted bentonite exposed to an alkaline solution was

also investigated, resulting in an increase in porosity caused by the dissolution of

montmorillonite. (Nakayama et al 2004).

Alteration of cement materials by clay solutions like groundwaters has been less studied.

Experiments with CEM I paste and a clay solution representing the Callovo-Oxfordian

Formation showed the degradation processes associated with an exogenous calcite crust

18

formed in the initial surface of the cement paste were inhibited by this precipitation

(Dauzeres et al 2009). Other experiments were undertaken with different aqueous fluids

and different cement materials (Albert et al, 2002; Kamatil et al, 2008; Planel et al, 2006;

Badouix et al, 2000; Kurashige 2007). The evolution of calcium leaching compared with

the precipitation of calcium carbonate was observed by (Kurashige, Hironaga, & Niwase,

2007), when working with hydrogenocarbonates and chloride - charged water.

Clay/concrete interactions have been simulated using chemistry-transportation coupled

models in several studies. Simulation of the short term interactions (15 years) at the

mudstone and concrete interface were undertaken (Windt et al 2008). Long term interaction

(100,000 years) simulation using HYTEC (Windt et al 2004) or ALLIANCES was also

undertaken (Montarnal et al 2007). Simulation of the effects of an alkaline plume in a clay

barrier was also modelled using PHREEQC (Gaucher et al 2004), PRECIP (Savage et al

2002) or KINDIS (Vieillard et al 2004). Modelling on the interactions between a fractured

marl and a high-pH plume (Soler et al 2003) and between cement - pore solutions and a

crystalline rock were also studied (Savage et al 1993).

2.2 Experiment with low-pH cement

The impact of low-pH cement on Friedland Ton (70% montmorillonite and 30%

muscovite) was conducted with very interesting results. Compared with solutions generated

by commercial and common cement (high-pH), the low-pH cement generated a very small

content in potassium and therefore a negligible illitisation of Friedland Ton (Push et al

2003). Analysis using XRD and a cationic-exchange-capacity (CEC) were performed in

order to study the chemical behaviour between the Callovo-Oxfordian clay from the

Meuse/Haute Marne area and an alkaline solution. A closed-system experiment with a

representative solution of CEM I containing NaOH, KOH and Ca(OH)2 was performed at

different temperatures (from 60 to 120 °C) and different timescales (from 6 to 168 h).

Results show precipitation of zeolite, tobermorite and katoite while mica and chlorite

showed no change contrasting with smectite and illite - smectite interstratifications which

were strongly reactive. This study allowed the authors to suggest three different alterations

in phyllosilicate in relation to pH and chemical composition of the solution: (1) pH of 10 or

12, precipitation of solution components; (2) pH of 14 for NaOH and KOH, precipitation of

19

amorphous phases + alkali silicates, and (3) pH 14 for a solution in equilibrium with

portlandite, precipitation of amorphous phases + silicates (Ramirez et al 2005).

20

Table 1: Compilation of the state of the art regarding the interaction between Clay-bearing rocks and cement. Ref. (Dauzeres et al ,

2010)

Materials Solutions T (°C) Times Results Reference

Opalinus Clay NaOH150–175–

20050 days Analcime, vermiculite, Na-rectorite Chermak, 1992

Opalinus Clay KOH150–175–

20050 days Philipsite, K-feldspar, K-rectorite Chermak, 1993

Opalinus ClaypH 13.2 with NaOH, KOH,

Ca(OH)230 540 days

Zeolites formation, C–A–S–H, dolomite

dissolution, calcite, Fe-hydroxydes,

syngenite

Adler et al , 1999

Clashach Sandstone Ca(OH)2 equilibrium 25 280 daysQuartz and feldspar dissolution,

C–S–H precipitationBraney et al , 1993

Friedland ClaypH 9.4 and 8.1 (equilibrium

with a low-pH cement)5 months No evolution. Low Illitization Push et al , 2003

Tournemire Argillite pH 13 25–70 1 to 3 monthsDolomite and pyrite dissolution.

Calcite precipitationDevol - Brown et al , 2007

Sandstone+Clays+

FeldsparsCa(OH)2 solution 20–40 250 to 730 days

C–S–H and alkaline silica gels

precipitationVan Aardt et al , 1977

Maqarin Biomicritic ClaysNatural water hyperalkaline

Ca–OH–SO4 (pHN12.5)100000 to 1 million years

C–S–H gels, ettringite and thaumasite

precipitationMilodowski et al , 2001

Searles Lake Clayey RockNatural waters-low

alcalinity (9bpHb10)3 millions years

Smectite replacement (70%) by Fe-illite,

analcime and K-feldspar precipitationSavage et al , 2010

Callovian–Oxfordian

Argillite

pH 13.2 (NaOH, KOH,

Ca(OH)2)60 1 year

Smectite partial dissolution and illite.

Microcrystalline quartz dissolution.

Solubilization of organic matter.

Tobermorite type C–S–H formation.

Claret et al , 2002


ClaysNaOH, KOH, Ca(OH)2 60–90–120 6, 24, 168 h

Analcime, chabazite, phillipsite, katoite

and tobermorite formation. Smectite

dissolution in illite/smectite mixed layer.

Ramirez et al , 2005


Argillite

pH 12.7; Portland

cement type solution20 4 days

Alkaline solution impact on the organic

matter compounds.Elie et al , 2004

Clayey rocks

21

Chapter 3: Materials

Introduction

The origin, composition and description of the clay rocks used in this research are presented

in this chapter. A summary of the four clay rock samples is presented in Table 2. The

composition of different types of cement used in the preparation of grouts is also explained, as

well of additives such as silica fume. For the Nirex Reference Vault Backfill (NRVB), the

description of the components of this designed grout based in Ordinary Portland Cement is

also provided (limestone flour and lime). Finally, the elaboration of the samples examined is

described, as well as the nomenclature used.

3.1 Mudstones

3.1.1 The Whitby Mudstone

The Whitby Mudstone Formation consists in a 70 – 90 m of exposed black and grey

mudstones and shales exposed at the coast of northeast England. Its mineralogy is well

described in a previous research (Pye, 1985). Three facies were identified by Morris (1979) in

the Whitby Mudstone: bituminous shale, weakly laminated restricted facies shales and normal

facies shales and the Whitby Mudstone Formation was divided into five sub-units by Powell,

(1984). Those units were denominated the Grey Shale Member, Jet Rock Member, Alum

Shale Member, Peak Mudstone Member and Fox Cliff Siltstone Member. Compared to many

mudstones (Clarke, 1924), the Whitby Mudstones contain less Si, Mg, Ca and Na but more Al,

Ti, Fe and K.

Regarding to the formation conditions of each of the sub-units, The Grey Shale Member, Jet

Rock Member and much of the Alum Shale Member were deposited during a period of marine

transgression. Sediments become thinner up from the base of the sequence, having the finest

sediments in the middle of the Alum Shale Member and having a rapid increase in quartz silt

content above this level. The Peak Mudstone Member and the Fox Cliff Siltstone Member are

mostly silty.

Four type of shale facies were also recognized in Morris, 1979:

22

a) Normal shale facies.

Consisting of grey silty mudstones with dispersed siderite concretions, trace fossils and

diverse fauna are abundant in these facies. These facies have a large content of quartz, micas,

chlorite and kaolinite. Less than a 10% of siderite and calcite are found and there are also

traces of plagioclase, K- feldspar and carbonate-apatite. Calcite and dolomite are almost

absent. Normal facies have a grey and weakly laminated appearance. Images from BSEM

show little preserved grain–size lamination. Compared with the bituminous facies shales,

normal facies show high degree of isotropy however micas show a preferred orientation. The

sizes of quartz grain are around 60 µm with an angular or sub–angular shape. Biotite and

muscovite micas with dimensions up to 100 µm can be found. The majority of quartz, chlorite

and mica are detrital but some mica have suffered post–depositional alteration. Some of those

micas have split parallel to the cleavage plane in such a way that allows crystals like

authigenic pyrite, kaolinite, carbonate and anatase to grow between the parted sheets. Stacks

composed completely of authigenic kaolinite can also be found in the normal shale facies.

Authigenic pyrite can occur in both as framboids and larger euhedral crystals. Carbonate is

also present in the form of randomly dispersed rhombs, patches of intergranular cement in the

more silty sediments and irregularly shaped grains. Pyrite is usually found enclosed by siderite.

b) Restricted shale facies.

This consists of poorly laminated dark grey shales with dispersed calcareous concretions.

These facies differ little from the normal facies in mineralogy. On average the siderite content

is lower. Pyrite is abundant but carbonate is rare. Restricted shale facies from the lower Alum

Shale Member contain more kaolinite but less detrital particles and chlorite than the ones in

the Grey Shales. Bioturbation has not completely destroyed the grain size lamination of the

restricted facies shales of the upper Grey Shale Member and a preferred orientation is by the

micas in the burrowed areas. Grain size was found to have a maximum of 60 µm but the

majority of grains are finer than 15 µm. Kaolinite appears to be partly diagenetic in origin, it is

present in the form of packets between the quartz and micas grains. Pyrite framboids and

rhombs are present but less than in the bituminous facies shales. In the lower Alum Shale the

restricted shale facies are poorly laminated. The absence of micro grain–size laminations is

confirmed by the BSEM examination which also reveals a moderate degree of bedding–

23

parallelism of the micas. Sediments contain quartz and silt grains that consist mostly of fine–

grained biotite and muscovite micas, chlorite, illite and kaolinite. The size of those grains is

normally larger than 10 µm.

c) Bituminous shale facies.

This consists of finely laminated black shales with numerous large calcite concretions with

some pyrite skins. The main minerals contained within the bituminous shale facies are quartz,

kaolinite, fine-grained micas, illite – smectite, chlorite, pyrite and calcite. Feldspar, carbonate

– apatite and subsidiary dolomite are also present. Figure 1 provides details of bituminous

facies in the Whitby Mudstone. Siderite is not present in these facies. Dolomite is the most

abundant mineral in bituminous shale facies in the Whitby formation (Clarke, 1924). There is

a higher content of Ca, Fe and P than the restricted shale facies and also a higher content of S

and organic C according to Gad et al (1968). Bituminous facies are thinly laminated.

Regarding to the size of the grains, most of them are smaller than 15 µm and the maximum

size is 50 µm. Quartz grains are angular shaped. The size of micas is up to 80 µm in the coarse

laminae and in the fine laminae just a few exceed 15 µm. Quartz grains and micas are partially

supported by a matrix of kaolinite and illite–smectite. Much of the clay is detrital but some

kaolinite appears to be authigenic. Pyrite and carbonate minerals are a major constituent of the

rock. Pyrite is about 5 – 10 µm with a framboid shape. Carbonates appear as imperfectly

formed rhombic crystals of calcite and dolomite. The large size of those rhombs is up to 25

µm together with the relation with surrounding clay-rich sediments is a clear evidence of the

authigenic origin. The surrounding clay matrix has been deformed in many cases around the

rhombs which indicates an early pre-compactional origin. Bituminous shales are not notably

fissile despite the high degree of parallelism and their well-developed lamination found in

micas and clay minerals.

24

The sample analysed in this research comes from the bituminous shale facies of the Whitby

formation. ESEM analysis was undertaken to determine the characteristics of this sample (see

Figure 1).

3.1.2 Kimmeridge Clay Formation

According with Morgans-Bell et al. (2001), the Kimmeridge Clay Formation consists

essentially of mudrocks that are usually characterized as medium–dark – grey, dark–grey–

black laminated, greyish–brownish–black. Other mudstones are inserted in between layers

with the above characteristics and are characterized from medium–grey to creamy–white

coccolith limestone, and minor grey and pale–yellow limestones and dolostones. The top of

the formation comprises siltstones and silty mudstones. Other variations of these mudrocks

occur within the formation on a small and large scale (0.5 to 1.5m and tens of meters).

According with (MacQuaker & Gawthorpe, 1993), five lithofacies have been identified in the

formation: clay rich mudstones, silt–rich mudstones, nanoplankton–rich mudstones, laminated

mudstones, and concretionary carbonates. Components of these facies are allochthonously

derived from the surrounding landmasses consisting of silt–grade quartz of biogenic carbonate,

Pyrite

Quartz

Organic matter

Mica Clay matrix

Figure 1: Whitby Mudstone ESEM. ESEM detail of a bituminous shale facies

from the Whitby Mudstone Formation

25

phosphate, as well as organic matter and diagenetic sources consisting of pyrite, ferroan and

nonferroan concretionary carbonates, authigenic clay minerals and organic matter.

a) Clay–Rich Mudstones: Hand specimens look grey and tend to break up into small lath –

shaped fragments <5mm. They don’t usually show sedimentary structures but shell

pavements and bioturbation can be observed. Clay–rich mudstones are composed mostly

of detrital clay comprising predominantly muscovite, illite/smectite, and kaolinite. They

also contain some disseminated organic matter, silt–grade quartz and crushed molluscan

shell debris. Pyrite is present in the form of framboids and shell fragments. Calcareous

nanoplankton is only a minor component.

b) Silt-Rich Mudstones. Hand specimens appear typically pale grey and can contain an

abundant shelly fauna in the presumed source area. In regions away from the possible

source area they are typically dark brown to black and are commonly very light weight

with low fauna diversity. Silt–rich mudstones contain abundant silt–grade quartz in a

clay and amorphous organic matter matrix. They are more organic–rich than clay–rich

mudstones and typically contain just a minor nanoplankton component. Significant

quantities of macro–shell debris are sometimes present. Most of these mudstones are

non-laminated but some show residual lamination.

c) Nannoplankton–Rich Mudstones. These mudstones have a range of compositions.

Coccoliths form thin, well–cemented ledges that are easily differentiated from the

surrounding mudstones and are usually referred to as “coccolith limestones”. When they

are relatively carbonate-poor they appear pale–grey and covered with small white

“blebs”. They usually show only bioturbation and shell pavements but no other

sedimentary structures. Nanoplankton–rich mudstones contain a low diversity of benthic

fauna. In thin sections samples show little evidence of microlamination, however the

weathered unit may present some fissility due to flattened organic matter. Pristine

coccolliths and other calcareous nannoplankton compose a significant proportion of the

carbonate material. Fine–grained clays (such as muscovite, illite/smectite, and minor

kaolinite), amorphous organic matter, and framboidal pyrite compose the rest of the

matrix. Compared with the silt–rich mudstones, detrital quartz silt is relatively

26

uncommon. Early carbonate and diagenetic kaolinite can be found within microfossil

tests. In thin section samples show little evidence of microlamination, however the

weathered unit may present some fissility due to flattened organic matter. Pristine

coccolliths and other calcareous nanoplankton compose a significant proportion of the

carbonate material. Fine–grained clays (such as muscovite, illite/smectite, and minor

kaolinite), amorphous organic matter, and framboidal pyrite comprise the rest of the

matrix. Compared with the silt –rich mudstones, detrital quartz silt is relatively

uncommon. Early carbonate and diagenetic kaolinite can be found within microfossil

tests.

d) Laminated Mudstones. In hand specimen they are commonly brown and usually

extremely ‘lightweight’ and they look laminated in cut surfaces. Mineralogical

variations make the laminae visible, like pyrite/carbonate layers within organic matter or

the presence of flattened organic matter. Pyrite concretions and intraformational, angular

rip–up clast can also be present. In thin section laminated mudstones can be identified as

either composed of flattened organic matter or can intercalate layers of carbonate and

organic matter. Organic carbon concentrations in the laminated mudstones may be as

high as 42.4% and is dominated by organic matter of algal origin. Organic-rich samples

(>30%) also contain some silt–sized quartz and clay. Laminated mudstones with less

than 30% of TOC also contain some carbonate in the form of scarce coccoliths and an

authigenic assemblage consisting of ankerite and ferroan and nonferroan dolomite. In

carbonate – rich samples calcareous macrofossil debris can be common.

e) Concretionary Carbonates. Concretionary carbonates form major erosion – resistant

ledges. Carbonates show a poorly laminated structure and contain diverse trace – fossils

assemblage. In thin section can be observed than concretionary carbonates are composed

of equigranular, inclusion–rich authigenic iron–rich carbonates (90%), ferroan dolomite,

ferroan calcite, and ankerine. Total organic carbon concentration is up to 12%. Other

minor components of the concretionary carbonates are dispersed coccolith plates, pyrite,

clay minerals and amorphous organic matter.

27

The sample used in this research correspond to a laminated mudstone based on the images

obtained by ESEM, see Figure 2, Pyrite, organic matter and quartz silt are easy to identify.

Laminae are clearly observed in the images obtained from this sample.

3.1.3 Holywell shale

The Holywell Shale formed in an early Carboniferous organic – rich basin. This formation

has received many different names (e.g. Holywell Shales, Hodder Mudstone, Worston Shales,

Sabden Shale, Caton Shale, etc.) (Andrews, 2013) and Waters et al. (2009) confirm that the

Holywell Shale Formation is the former name for what is now called collectively called the

Bowland Shale Formation. The shale consists of dark marine mudstones with intercalated

feldspathic sandstone and impure limestone and the Holywell Shale Formation formally

referred to the dark grey euxinic shales in North Wales.

Fewtrell and Smith (1980) explain that the Bowland Shale Formation comprises sandstones,

shales, and disturbed thin limestones. Shales from this formation are thinly bedded, black and

pyritiferous and are quite different from shales of lower Carboniferous formations.

Figure 2: Kimmeridge Clay ESEM. ESEM detail of a laminated mudstone from

the Kimmeridge Formation

Pyrite

Clay

Quartz silts

28

Sandstones are laterally impersistent and interbedded with shales. There are only a few thin

limestones which are coarse and turbiditic.

3.1.4 Pyritiferous Shale

Pyritiferous shale is a member of the Redcar Mudstone Formation which constitutes the

“Lower Lias” in the Cleveland Basin. The greater part of the formation is exposed at Robin

Hood’s Bay. This formation is about 225 to 250 m thick at the coast and up to 280 m or more

inland. It thins to the west to only 194 m near Thirsk and to the south in the margin of the

Cleveland Basin with only 30 or 40 m thick.

The Redcar Mudstone Formation has been divided into four parts. The lower part is called

the Calcareous Shale Member which comprises numerous thin beds of medium shelly

argillaceous limestone; this member tends to become sandier upwards. XRD analysis indicates

47% content quartz, 37% mica, 17% kaolinite, 3% dolomite, 2% illite/smectite, 1% calcite, 1%

pyrite and 1% albite. Above the Calcareous Shale Member appears the Siliceous Shale

Member which is about 30 m thick and comprises silty mudstones with calcareous siltstone

and sandstone intercalated. XRD analysis shows 38% quartz, 32% mica, 15% kaolinite, 4%

illite/smectite, 1% dolomite and 1% albite. The top of the Redcar Formation is divided into the

Pyritiferous Shale and the Ironstone shale. The Pyritiferous Shale comprises siltstones and

grey fissile mudstones with thin beds of shelly limestones occurring in the middle of the

formation. Pyritiferous shales are usually grey to dark grey shales, clearly micaceous, soft and

a with large replacement of fossils by pyrite and also small nodules of pyrite. XRD analysis

shows a 37% content of mica, 29% of quartz, 21% of kaolinite, 8% calcite, 3% pyrite and 2%

illite/smectite. Ironstone shale comprises mudstones with sideritic ironstone nodules. XRD

analysis show a 42% content of mica, 24% quartz, 21% kaolinite, 6% calcite, 3%

illite/smectite, 2% pyrite, 1% chlorite and 1% gypsum.

29

Table 2: Summary of clay rocks used in this research.

Clay rock Description

Whitby

Mudstone

This consists of finely laminated black shales with numerous

large calcite concretions with some pyrite skins. The main

minerals contained within the bituminous shale facies are

quartz, kaolinite, fine-grained micas, illite – smectite,

chlorite, pyrite and calcite. Feldspar, carbonate – apatite and

subsidiary dolomite are also present

Kimmeridge

Clay

Consists essentially of mudrocks that are usually

characterized as medium – dark – grey, dark – grey – black

laminated, greyish – brownish – black. Organic-rich samples

(>30%) also contain some silt – sized quartz and clay.

Holywell Shale The shale consists of dark marine mudstones with

intercalated feldspathic sandstone and impure limestone

Pyritiferous

Shale

Comprises siltstones and grey fissile mudstones with thin

beds of shelly limestones occurring in the middle of the

formation. Pyritiferous shales are usually grey to dark grey

shales, clearly micaceous, soft and a with large replacement

of fossils by pyrite and also small nodules of pyrite

30

3.2 Cement

Hewlett & Massazza, 2003 and Blezard, 2003 defined cement as adhesive substance with

the property of uniting fragments of solid matter to a compact whole. According to CEMEX,

cement is the adhesive that binds particles of fine aggregate together. The mixture of cement

with water to form a paste is called the fine matrix. Cements depend upon a reaction with

water rather than air for strength development, hence are called hydraulic materials. The

chemical reaction that takes place when water is added to cement is called hydration. It begins

immediately and continues while water is still present.

There are two mains types of cementitious commercial materials, lime mortars and Portland

cements.

Lime mortars generally harden and gain strength by the evaporation of the water and by

absorbing carbon dioxide from the atmosphere. This transforms, gradually, lime into calcium

carbonate.

Lime mortar: It is made by burning chalk or limestone (CaCO3) to produce quicklime (CaO)

which is later mixed with water to form hydrated lime. This mixture hardens and reacts with

carbon dioxide (CO2) from the air to form again chalk (CaCO3)

Chalk/limestone is burn to produce quicklime

CaCO3 + HEAT = CaO + CO2

Hydration of quicklime to produce hydrated lime

CaO + H2O = Ca(OH)2

Reaction of hydrated lime to produce chalk

Ca(OH)2 + CO2 = CaCO3

31

Portland cement: It is made by burning limestone or clay (at very high temperatures (1400

to 1600 °C).

In manufacturing process of Portland cement, calcium carbonate (CaCO3) is decomposed

into Calcium oxide (CaO) and Carbon dioxide (CO2) at around 900 °C. With an increase of

temperature above 900 °C CaO starts reacting with silica to form dicalcium silicate (Ca2SiO5)

which is one of the main compounds in Portland cement. Alite (Tricalcium silicate) is formed

by 1300 – 1550°C. Other phases melted such as Calcium aluminate and calcium ferrite react to

form Tricalcium aluminate and Tetracalcium aluminoferrate.

There are four main compounds in the Portland cement. Given the complexity of its

chemical composition, a shorthand notation of the chemical compounds is found in literature

as shown in Table 3. Gypsum is added to the cement clinker to retard the reaction with

Tricalcium aluminate and provide resistance to sulphates.

Table 3: Shorthand form of chemical compounds found in Portland cement

Compound Formula Shorthand form

Calcium oxide CaO C

Silicon dioxide SiO2 S

Aluminium oxide Al2O3 A

Iron oxide Fe2O3 F

Water H2O H

Sulphate SO3 S

Tricalcium silicate Ca3SiO4 (C3S) – Large amounts of heat are produced from the reaction

between tricalcium silicate and water, and calcium silicate hydrate is formed. It is the main

contributor to the early strength of cement hydrate.

Tricalcium silicate + water calcium silicate hydrate + lime + heat

2C3S + 6H C3S2H3 + 3CH, H = 120 cal/g

Dicalcium silicate Ca2SiO5 (C2S) – It reacts slowly with water and forms calcium silicate

hydrate, as well as C3S. The heat generated by this reaction is dissipated because of the slow

32

reaction and significant temperature rises do not occur. It contributes to strength to at later

ages.

Dicalcium silicates + water → calcium silicate hydrate + lime

C2S + 4H C3S2H3 + CH, H = 62 cal/g

Tricalcium aluminate Ca3Al2O6 (C3A) – It releases a relatively large amount of heat since it

reacts very rapidly with water. The addition of gypsum can retard this reaction if it is added

during the grinding stage.

Tricalcium aluminate + gypsum + water → ettringite + heat

C3A + 3CSH2 + 26H C6AS3H32, H = 207 cal/g

Ettringite then reacts with the remaining tricalcium aluminate to form monosulfate aluminate

hydrate crystals.

Tricalcium aluminate + ettringite + water → monosulfate aluminate hydrate

2C3A + 3 C6AS3H32 + 22H → 3C4ASH18

Tetracalcium aluminoferrite Ca4Al2Fe2O10 (C4AF) – reacts rapidly with water but does not

produce much heat or strength. It reacts in two progressive steps, first by reacting with water

and gypsum to form ettringite and then reacting with the formed ettringite to produce garnets.

Ferrite + gypsum + water → ettringite + ferric aluminium hydroxide + lime

C4AF + 3CSH2 + 3H → C6(A,F)S3H32 + (A,F)H3 + CH

3.2.1 Microcement

MICROCEM 650 is a controlled fine cement produced by the company TARMAC. It is made

by finely grinding Portland cement clinker with small quantities of additives. Microcements

are usually used as injection grouts since they have an excellent performance in tight fissures

33

and low - porosity soils. MICROCEM 650 is particularly suitable for injection into cracks,

joints to produce a water - tight mass of grouted rock (Lafarge Tarmac, 2014).

3.2.2 CEM II/A-LL 42,5N

This is a cement denominated as Portland-limestone cement (PLC) produced by the

company TARMAC that contains between 80 to 94% of Portland cement clinker, 6 to 20%

limestone and 0 – 5% of minor additional constituents. It is very similar to the conventional

Portland cement (CEM I) and in most cases can be interchangeable however some differences

can be recognised:

Concrete containing PLC will demand slightly less water than conventional Portland cement

and once hardened it will be lighter in colour and will have a smoother surface than CEM I

concrete.

3.3 Silica fume

Microsilica or silica fume is a by–product of the production of alloys containing silicon or

elemental silicon. High–purity quartz is heated usually to 2000 °C in an electric arc furnace

producing very fine non–crystalline silica. More than 95% of the particles are less than 1 µm

and most of the particles are in spherical shape. The specific surface area of microsilica varies

from 15000 and 30000 m2/kg. The specific gravity of silica fume (2.2) is lower than Portland

cement, then the addition of silica fume does not increase the concrete density. Typical

chemical composition of microsilica is shown in Table 4. Content of silica fume is usually

higher than 80wt% Si. Microsilica can also contains small amounts of CaO, Al2O3, Fe2O3 and

other alkali contents. Carbon content is usually less than 2%. Mineralogical composition of

silica fume consists mainly of an amorphous silica structure with little crystalline particles.

34

Table 4: Chemical composition of the most common types of microsilica

Content of fume (wt%)

Si FeSi

75%

FeSi 75%

(heat

recovery)

FeSi

50%

FeCrSi CaSi SiMn

SiO2 94 89 90 83 83 53.7 25

Fe2O3 0.03 0.6 2.9 2.5 1.0 0.7 1.8

Al2O3 0.06 0.4 1.0 2.5 2.5 0.9 2.5

CaO 0.5 0.2 0.1 0.8 0.8 23.2 4.0

MgO 1.1 1.7 0.2 3.0 7.0 3.3 2.7

Na2O 0.04 0.2 0.9 0.3 1.0 0.6 2.0

K2O 0.05 1.2 1.3 2.0 1.8 2.4 8.5

C 1.0 1.4 0.6 1.8 1.6 3.4 2.5

S 0.02 0.1 2.5

MnO 0.06 0.2 0.2 36.0

LOI 2.5 2.7 3.6 2.2 7.9 10.0

Silica fume was first tested in Norway in the early 1950s proving to increase the strength of

concrete and to provide a better performance in sulphate environments. The cohesiveness of

concrete mixture increases when very fine particles of microsilica are added. The

incorporation of silica fume to concrete affects its microstructure. Microsilica has the effect of

reducing the large pores of cement paste into smaller pores consequently changing the

structure of the cement paste (Yogendran and Langan, 1987). Permeability is also affected by

the addition of microsilica. Water penetration showed to be up to 6 times lower than for a

normal concrete mixture (Fidjester and Frearson, 1994).

Silica fume has also proved to enhance concrete durability and improve the physical and

chemical properties of concrete. Microsilica can have a paradoxical effect regarding to

carbonation of mortars and concretes. In one side, microsilica consumes calcium hydroxide of

the cement paste which can increase the risk of carbonation; however microsilica reduces the

permeability of concrete which may result in lower carbonation (Vennesland and Gjorv, 1983).

35

Incorporation of silica fume has showed to provide a better resistance to mortars and concretes

against sulphate solutions. A replacement of at least 15% of silica fume for normal Portland

cement proved to give a satisfactory resistant even after 4 years of immersion in sulphate

solution. (Fiskaa & Betong, 1983)

3.4 Nirex Reference Vault Backfill

The Nirex Reference Vault Backfill (NRVB) is a high-pH backfill developed by former UK

body (NIREX) to analyse safety and environmental matters regarding deep geological disposal

of nuclear waste. NRVB is composed of Portland cement, hydrated lime and limestone flour.

It was designed to provide a reduction in radionuclide migration from the near field to a

Geological Disposal Facility. NRVB was designed to have a relatively low strength, to be

highly porous in order to promote homogeneous chemical conditions within the GDF,

allowing waste retrievability and to allow gas migration.

The composition of NRVB is shown in Francis et al., 1997:

Portland Cement (‘Ordinary Portland cement’) = 450 kg/m3

Limestone flour = 495 kg/m3

Lime (‘Limbux hydrated lime’, from Tarmac) 170 kg/m3

Water (mains tap water) = 615 kg/m3

The same proportions were used in order to create a homogenous paste to make the samples.

3.4.1 Limestone flour

Calcium carbonate or limestone is a hard, compact, considerably impervious, fine to very

fine grained calcareous sedimentary rock. Calcareous rocks have a high compressive strength

(60 – 170 MPa) and very low porosity. Limestone powder can be produced by grinding of

high purity limestone. The addition of large amounts limestone to concrete reduces the

strength; however the addition of up to 10% of limestone does not reduce it significantly.

Limestone slightly increases the shrinkage of cement mixture, according with a study of

Adams & Race, 1990 where they investigated the effects of limestone addition to Portland

cement types I and II, however Alunno-Rosetti & Curcio, 1997 concluded that limestone had

36

no effect of shrinkage of cements from two different plants comparing samples with no

limestone addition against a 20% limestone addition.

Permeability of concrete is decreased with the new refined pore structure caused by the

nucleation effect of the fine particles of calcium carbonate which causes a reduction in the

pore connectivity. Other studies have confirmed that limestone addition to Portland cement

decreases its permeability regardless of the amount of limestone added.

3.4.2 Hydrated lime

Hydrates lime is made by crushing, grinding, washing and screening typically hard - rock

Carboniferous limestone and then burning it at approximately 950 °C. The resulting product is

called quicklime (CaO) which is then mixed with water to obtain hydrated lime (Ca(OH)2).

The requirements for construction hydrated lime are contained in the British Standard BS EN

459-1 . The composition of Hydrated Lime used to form NRVB cement in this research is

shown in Table 5.

Table 5: Composition of Hydrated Lime

Calcium Hydroxide - Ca(OH)2 97.0% (min 95.0)

Magnesium Hydroxide - Mg(OH)2 0.50% (max. 1.4)

Carbon Dioxide - CO2 0.70% (max. 1.00)

Silica - SiO2 0.70% (max. 1.00)

Alumina - Al2O3 0.10% (max. 0.20)

Iron Oxide - Fe2O3 0.06% (max. 0.10)

Sulphur - S 0.01% (max. 0.025

Moisture - H2O 0.25% (max. 0.75)

Arsenic - As 0.3 ppm (max. 1.0)

Fluorine - F 65 ppm (max. 110)

Lead - Pb 1.3 ppm (max. 5.0)

Manganese - Mn 175 ppm (max. 250)

Loss on ignition 24.80%

37

3.5 Sample formulation and nomenclature

A total of 7 cement mixes, usually referred as mortars, were used in this research. Two

different types of Portland Cement were used (MICROCEM 650 and CEM II/A-LL 42,5N).

Formulation of the 7 cement mortars and nomenclatures is described in Table 6. OPC and

PMS mortars are the only two mixes containing aggregates such as sand, since they are regular

constructions grouts. MPC3 is a standard high-pH grout with a high water-to-binder-ratio (w/b)

and addition of superplasticizer described in Table 6, MPC5 is also a standard high-pH grout

with no addition of superplasticiser. PMS3 is a low-pH grout mixture which has been

proposed by POSIVA Oy, which is a research company for nuclear waste disposal, (Holt,

2008), with an addition of silica fume ≈40%. PMS5 has the same composition of PMS3 but

with no addition of superplasticiser. The aim of testing different mortars is to provide a wide

range of cement - based mixtures that might be likely to be used as a backfill or sealing in the

GDF context and can be found in the literature (Kim et al., 2011,Kronlöf, 2005; Swift et al.,

2010). All mixtures were elaborated according with the British Standard BS EN 998-2:2010.

NRVB and mortars MPC5, PMS5, MPC3, MPS3 were elaborated according with the literature

procedures since they are neither standard nor commercial grouts/mortar and their elaboration

methods have not been yet established. The interaction in the cement/clay interface was

undertaken by combining these grouts with pieces of clay rocks described in Table 2. Table 7

shows the combinations of cement mixture/lithology interfaces examined. Further details in

the elaboration of specimens are provided in Chapter 4.

38

Table 6: Composition (wt%) of the 7 mixtures utilized in this research.

CODE OPC MPC Sand MS Ca(OH)2 CaCO3 SP W w/b w/c

OPC 28.58 57.14 14.28 0.50 0.50

PMS 27.7 55.41 2.77 0.27 13.85 0.45 0.50

MPC5 55.19 44.81 0.81 0.81

PMS5 24.42 16.8 58.75 1.42 2.41

MPC3 54.95 0.44 44.61 0.81 0.81

MPS3 24.27 16.7 0.67 58.36 1.42 2.41

NRVB 26.01 9.83 28.61 35.55 1.37 1.37

OPC= Ordinary Portland Cement, MPC= Micro Portland Cement, Sand= Regular

construction sand, MS= Microsilica, Ca(OH)2= Hydrated lime, CaCO3= Limestone flour,

SP= Superplasticiser, W= Water, w/b= water-binder ratio, w/c= water-cement ratio.

Table 7: The cement mixtures and clay-bearing lithologies used in the experiments

SAMPLE

NUMBER

MIXTURE LITHOLOGY

OPC1 Mortar of Ordinary Portland cement (OPC mixture) Kimmeridge clay

OPC2 Mortar of Ordinary Portland cement (OPC mixture) Holywell clay

OPC3 Mortar of Ordinary Portland cement (OPC mixture) Yorkshire clay

OPC4 Mortar of Ordinary Portland cement (OPC mixture) Whitby Mudstone

PMS1 Mortar of Ordinary Portland cement with 10% silica

fume (PMS mixture)

Kimmeridge clay


fume (PMS mixture)

Holywell clay


fume (PMS mixture)

Yorkshire clay


fume (PMS mixture)

Whitby Mudstone

NRV5 Nirex Reference Vault Backfill ( NRVB mixture) Whitby Mudstone

NRV6 Nirex Reference Vault Backfill ( NRVB mixture) Holywell clay

39

3.6 Sample preparation

All samples were cured for 28 days under saturated conditions before any testing. Curing is

the required process of concrete and other cement-mixtures where strength is gained.

In order to perform permeability tests, it was necessary to manufacture small moulds with

cylindrical shape of 2.5 cm diameter and 10 cm length. Once the samples were ready they

were unmould and then cut into smaller plugs to perform permeability test described in

Chapter 4.

With samples MPS3 and MPC5 described in Table 6, it was not possible to elaborate

cylinders due to shrinkage so it was necessary to elaborate small grout blocks that were then

drilled after curing in order to obtain the 2.5cm plugs needed to perform porosity and

permeability tests. The samples for the analysis of the permeability at the cement/mudstone

interface were elaborated by placing a 1.5cm diameter mudstone core at the centre of a

cylindrical mould of 2.5cm diameter and 10 cm height where cement mixture was poured

when fresh. This was done with a small holding ring as shown in Figure 3, designed to keep

NRV7 Nirex Reference Vault Backfill (NRVB mixture) Yorkshire clay

NRV8 Nirex Reference Vault Backfill (NRVB mixture) Kimmeridge clay

OPC5 Ordinary Portland Cement grout w/c 1.4 (OPC mixture

with water-cement ratio of 1.4)

Whitby Mudstone



Holywell clay

OPC7 Ordinary Portland Cement grout w/c 1.4(OPC mixture


Yorkshire clay



Kimmeridge clay

PMS5 Ordinary Portland Cement grout with 40% silica fume Whitby Mudstone

PMS6 Ordinary Portland Cement grout with 40% silica fume Holywell clay

PMS7 Ordinary Portland Cement grout with 40% silica fume Yorkshire clay

PMS8 Ordinary Portland Cement grout with 40% silica fume Kimmeridge clay

40

the mudstone core from moving during the curing and which was easily removed by cutting

the outer extreme where the holding ring was placed. All samples were cured for 28 days

under saturated conditions before any test.

A standard food mixer was utilized for cement mixing in a stainless bowl. Dry components

were mixed first and then water was added. If superplasticiser was needed, it was added at last.

All components of mixtures were weighted in a laboratory scale according to the required

1.5cm

2.8cm

2.5cm

10

cm

1.5 cm

2

.5

cm

1.5 cm

2

.5

cm

Figure 3: Special mould specifications and details. (Top left) Photograph of the

acrylic glass pipe used as mould. (Left below) Schematic of the rings used to keep

mudstone cores in place. The ring on the left is placed on the top of the mould to

prevent the mudstone core from moving and at the same time allowing cement

paste to flow through the spaces at the sides. The right one is placed at the bottom

of the mould. It is not totally pierced so mudstone cores can be fixed by the space

in the middle and at the same time it functions as a cap preventing cement paste

from escaping the mould. (Right) Diagram of the acrylic mould specially

fabricated. The thickness of the wall is 3mm with 25mm internal diameter. When

15mm mudstone core is used it is placed in the middle by the cap in the bottom and

the ring on the top.

.

41

formulation. Once the mixture was ready it was poured into the acrylic moulds as shown in

Figure 4.

For mineralogical and element mapping in the cement-mudstone interface, small quantities

of mixtures were poured into small containers with around 2 - 3cm diameter and then

fragments of mudstones were immediately added to the mixture (see Figure 5). The resultant

disks were then removed from the moulds and cured. Samples were then sliced in order to

identify the areas where the cement was making contact with the mudstone. Once identified,

polished sections of these areas were made for ESEM and electron probe microanalysis

Figure 4: Cement mixing procedures. (Above left) Food mixer with stainless

bow utilized for cement mixing in the laboratory. (Below left). Portland cement

being weighted. (Above right) Cement paste ready after mixing. (Below centre)

Cement paste being poured into acrylic mould with mudstone core being held by

cap and ring. (Below right) Cement sample after 24 hours.

42

(EPMA). Five out of seven mixtures were used to perform element mapping using the ESEM

and EPMA.

.

Figure 5: Thinsection making. (Above left) Cement paste being poured into

moulds (2.5cm diameter 2cm height). Small pieces of mudstone were placed

inside. (Up right) Disk of cement paste with a visible mudstone piece within it

ready to be sent to the sectioning laboratory to obtain polished thin sections.

(Down left) Polished thin sections ready.

43

4 Methodology

Introduction

Thinsections of the samples were subject to a series of analysis using Optical Microscope,

Electron microscope and Electron microprobe. Cement plugs were subject to permeability and

porosity measurements. Descriptions of methods and equipment are presented in this chapter.

4.1 Light microscopy

All of the thinsections were examined with transmitted light microscope in order to identify

optical changes in the interface of cement/clay rocks. The equipment was a Zeiss Axioskop 50

as shown in Figure 6. Images were acquired with an AxioCam MRc5 installed in the

microscope.

Figure 6: Zeiss Axioskop 50

44

4.2 ESEM and analysis

The ESEM equipment utilized in this research was a Philips FEI XL30 shown in Figure 7.

The ESEM is a non-destructive electron optical technique capable of producing images from

hydrated samples in their near natural state (Donald et al., 2000). It can operate from high

vacuum to a pressure level such that wet specimens can be analysed (Danilatos, 1994).

Therefore an ESEM has all the advantages of a conventional SEM but removes the high

vacuum restrictions given the characteristic of analysing wet, oil, dirty or non – conductive

samples in their natural state without preparation or modification.

Figure 7: ESEM. FEI XL30 Environmental Scanning Electron Microscope-Field Emission

Gun in the Williamson Research Centre

A scanning electron microscope consists of an electron column, a sample chamber, detectors

and a viewing system. In the top of the column an electron gun generates the electron beam.

This electron beam is accelerated down the column to the sample. The electron beam can be

generated with different electron guns (tungsten, lanthanum hexaboride and field emission),

all of them sharing the same purpose of generating a directed electron beam with sufficient

current and with the smallest possible size. The electron beam is then re-converged and

focused into a de-magnified image with a series of magnetic lenses and apertures in the

column. The final lenses focus the beam in to the smallest spot possible on the surface. The

beam then exits the column into the sample chamber. The sample chamber contains a stage

45

where the sample can be manipulated and an airlock to insert and remove the sample and to

access detectors and other accessories.

Images obtained by the SEM are generated by constructing a virtual image from the signals

emitted by the sample. It is achieved by scanning its electron beam line by line. The beam

illuminates only a single point at a time to create the overall image in the pattern, the signals it

generates vary in strength, reflecting differences in the sample. Other modern instruments can

convert the analogue output signal into a series of numeric values than can be then

manipulated as desired.

There are two main signal types produced by the electron beam: secondary electrons (SE)

and backscattered electrons (BSE). Secondary electrons are atoms with very low energy that

have been ejected by the interactions with the primary electrons of the beam. They can escape

only regions near the sample surface which means that they represent the topography of the

sample. Backscattered electrons are high energy electrons that have been scattered by elastic

collisions with the nuclei of sample atoms, and their intensity is controlled by atomic number.

Backscattered images therefore provide important information about the sample composition

(Johnson, 1996).

Thin sections analysed in the ESEM were carbon-coated before placed in the sample holder. A

conductive tap was also put from top of the thin section to the holder as shown in Figure 8.

The test was conducted with a pressure of 1.24 x 10-4

mBar with beam energy of 15 Kv.

46

Figure 8: Thin section detail. Polished thin section placed in the sample holder of the ESEM

4.3 EMPA analysis

The Electron Microprobe Cameca SX-100, shown in Figure 9, is the equipment used to

analyse samples in this research. Electron probe - microanalysis is a qualitative and

quantitative elemental microanalysis that involves bombardment of a solid with a focused

electron beam of electrons, focussed down to 1 micron (Macphee & Lachowski,

2003)(“EPMA: Electron Probe Micro-Analysis,” n.d.). X-ray photons emitted by the various

elemental species have characteristic energies and wavelengths and their intensity is collected

by wavelength sensitive spectrometers (Wavelength Dispersive Spectroscopy (WDS)). The

identification of elements by WDS is based in Bragg's law which states the angles for coherent

and incoherent scattering from a crystal lattice (Bragg, 1913) and EMPA uses various

moveable, shaped monocrystals as monochromators.

47

Figure 9: EPROBE. Cameca SX-100 Electron Microprobe in the Williamson Research

Centre

EMPA allows a non-destructive elemental analysis of up to micron - sized volumes, with

sensitivity at the level of 100sppm. EMPA is equipped with a built - in microscope tools that

allow SEM, BSE imaging, simultaneous X-ray and sophisticated visible light optics with

magnification ranging from 40 to 400 000x.

The high resolution and wavelength spectrometry produces higher resolution chemical

mapping and quantitative analyses to complement the qualitative spectra of SEM/EDS. EMPA

is the primary solid phase analyser for microscale compositions mostly used in geochemistry,

mineralogy, geochronology, physical metallurgy, nuclear metallurgy, material science,

48

cements, etc. The elements analysed were Ca, Al, Si, Fe, K, Na and Mn. It was done by setting

the spectrometers at the wavelength of the highest counts of an element as defined by the

standards CaSiO3, Al2O3, SiO2, FeO, KAlSi3O8, NaAlSi3O8, MnO2.

4.4 Cement permeability

Besides strength, permeability is one of the parameters that directly affect the durability of

cement based mixtures (Abbas & Carcasses andJ-P Ollivier, 1999). Permeability is a very

important property, especially in applications such as the isolation of waste materials. Within

the Nuclear Waste management context, cement based mixtures are likely to be used as

backfill material or immobilisation material for the matrix of waste where radionuclide

containment is the main function of those mixtures. Many disposal concepts include the use of

cement in different phases of the project. Those mixtures should meet low voidage, adequate

strength and low permeability requirements(Ian G Crossland & Vines, 2001).

Permeability plays an important role in producing an effective seal to a depository to avoid

water or gas borne radionuclides escaping (I G Crossland & Vines, 2001) and also in the

containment of radionuclides inside the wasteform matrix (waste immobilisation). The latter is

achieved by controlling pH and therefore chemical conditions are expected inside the waste

matrix. In contrast to forming an impermeable seal it is sometimes advantageous to have large

porosities and relatively high permeability conditions to encourage reactions and homogeneity

within the matrix.

Most of the repository concepts consider one material for immobilisation of the waste

matrices and another for backfilling the repository. Potential mixtures to be used in the

wasteform matrix are usually Ordinary Portland Cement based mixtures with some additives

such as fly ash, blast-furnace slag, or polymers.

4.4.1 Oscillating Pore Pressure Method

Given the low permeability value for cement mixtures found in the literature, with values

ranging from 𝑘 =10-15

to 𝑘 =10-19

m2 (Atkinson, 1985)

for regular concrete, an Oscillating

Pore Pressure Method was chosen to determine the permeability of the samples used in this

research. Argon gas was used as pore fluid.

49

Methods with oscillating boundary conditions have been used to measure thermal diffusivity

(Cerceo & Childers, 1963). The method developed by Kranz 1990 and is well explained in

Bernabé, 2006. The method consists in a way to use pore pressure oscillation to determine k.

A jacketed sample is placed within a vessel where a confining pressure is applied; the sample

is then loaded with the desired pore pressure by an upstream and downstream reservoir.

Through a computer-controlled pump, an oscillation of the upstream fluid 𝑃𝑈 = 𝐴𝑈𝑒𝑖(𝜔𝑡+𝜃𝑈)

is applied to the sample and the resulting downstream variations in the reservoir, 𝑃𝐷 , are

logged. The terms in the equations are as follows:

PU = Upstream pressure

PD = Downstream pressure

AU = Upstream amplitude

AD = Downstream amplitude

θU = Upstream phase

θD = Downstream phase

ω = angular velocity

PTr = Transient pressure

The response in the downstream reservoir, 𝑃𝐷, generally consists of three terms, a transient

term 𝑃𝑇𝑟 which approach to zero over a long-time limit, a noise term with a small amplitude

and a broad spectrum, and finally the major response, 𝐴𝐷𝑒𝑖(𝜔𝑡+𝜃𝐷).

Several tens of cycles are run in order to have enough data to overcome the short-time

transient term. A series of cycles at the beginning may be simple discarded because of this

effect. An example of upstream and downstream signals from one of the samples tested in the

experiments is shown in Figure 10. Transient phase is found in 3 cycles before it reaches the

steady – state oscillation.

50

Figure 10 Oscillating pore pressure readings.

Fourier analysis is then applied to the remaining cycles and 𝐴𝐷𝑒𝑖(𝜔𝑡+𝜃𝐷) is obtained

corresponding to a sharp peak.

The downstream to upstream amplitude ratio is denoted as 𝐴 = 𝐴𝐷 𝐴𝑈 < 1⁄ , and the phase-

shift as 𝜃 = 𝜃𝐷 − 𝜃𝑈 > 0.

The square-root of the 𝜔 components of the downstream and upstream power spectra give

the amplitude ratio 𝐴. 𝜃 is the phase of the 𝜔 components of the cross-spectrum. By plotting

𝐴 and 𝜃 against time 𝑡 it is possible to verify that early time transient effect has vanished away.

For homogeneous materials, 𝐴 and 𝜃 can be written in the long-time limit as

𝐴𝑒−𝑖𝜃 = (1 + 𝑖

√𝜉𝜂sinh [(1 + 𝑖)√

𝜉

𝜂] + cosh [(1 + 𝑖)√

𝜉

𝜂])

−1

Where ξ and η are dimensionless parameter defined by

𝜉 =𝑆𝐿𝛽

𝛽𝐷, 𝜂 =

𝑆𝑇𝑘

𝜋𝐿𝜇𝛽𝐷

Where

S= sample cross-section area

L= sample length

9.4

9.6

9.8

10

10.2

10.4

10.6

200 400 600 800 1000 1200 1400 1600 1800 2000

Pu

/Au

an

d P

d/A

d

Time

Downstream pressure Upstream pressure

Transient behaviour

51

β= sample storativity

𝛽𝐷= downstream reservoir storage

k= sample permeability

µ= fluid viscosity

The relationship between 𝜉, 𝜂, 𝐴 and 𝜃 can be represented in a nomogram, like shown in

Figure 11, where the limits for physical meaning of 𝜉 and 𝜂 can be clearly identified.

The nomogram shows lines of constant 𝜂 and 𝜉 plotted in a log10(𝐴, 𝜃) space. The values of

log10( 𝜂) are indicated by horizontal numbers and the values of ξ by vertical numbers. The

space enclosed between 𝜉 = 0 and 𝜉 = ∞ lines contain the physically meaningful region.

Points in the left of 𝜉 = 0 and to the right of 𝜉 = ∞ are in principle not possible. A negative

value in 𝜉 would indicate a negative storativity.

52

Eq. (1) is no linear and it must be solved numerically for 𝜉 and 𝜂. 𝑘 and 𝛽 can be obtained

once 𝜉 and 𝜂 are calculated using Eq. (2). An iterative method is common to solve those

equations. First a starting point is chosen (𝜉0, 𝜂0) and then (𝐴0, 𝜃0) is calculated and compared

with the logged data (𝐴, 𝜃)

4.4.2 Permeability procedures

Once the 2.5cm cylinders of cement mixture were cured they were cut into smaller plugs of

up to 5 cm length based on the equipment capabilities and the permeability expected for each

of the different mixtures. Permeability was measured as a function of effective pressure.

Figure 11: Space solution for equation 1. Nomogram where 𝐥𝐨𝐠𝟏𝟎(𝑨,𝜽) are plotted

and 𝜼 and 𝝃 can be obtained. Ref. (Bernabé et al., 2006)

Log10( )

53

Figure 12: Permeameter scheme. Diagram of the sample placed inside the pressure vessel.

The computer displays the downstream signal and controls the upstream pore pressure

oscillation by moving a piston that uses a servo – controlled motor on the volumometer.

In some cases it was necessary to adjust the downstream reservoir volume since the

permeability was relatively high to be measured with the pore pressure method and too low to

be measured with the constant flow permeameter and it was not convenient to make the plug

any shorter.

All samples were dried in the oven at 50 °C and once they were dried they were kept in it if

they were not being tested. Samples with high water-cement ratio and high calcium carbonate

content showed fractures when they were being drying even after a few minutes of water loss.

Those fractures made it worthless to measure the permeability in that condition since the gas

would pass through the fractures and would in no way represent the permeability of the

cement structure. Thus it was not possible to test those samples in a dry condition. In order to

overcome this issue and to obtain meaningful measurements, mixtures were made again and

poured into sealed bags where they were left to cure with pore water for 28 days and then

plugs were drilled from them. Those samples were labelled and kept in sealed bags in order to

avoid any additional water loss and the subsequent cracking. Those plugs were later trimmed

to the desire length for testing.

54

Once the plugs were trimmed they were jacked in order to be tested at different effective

pressures by varying the confining pressure and keeping constant the pore pressure (See

Figure 13). Samples were tested with effective pressures ranging from 5 to 30 MPa while

maintaining a constant pore pressure of 10 MPa in order to analyse the effects of effective

pressure in permeability.

Besides the delay caused by the cracking of some of the samples, for some samples, it was

necessary to adjust the period of the wave in order to get a response in the downstream

pressure. Most of the samples were tested with periods ranged between 100 and 200 seconds,

Figure 13 Cement cores for permeability tests. (Above left) Cement sample OPC after

being unmoulded. (Above right) Cement sample after being unmoulded. In the left part the

cap used is visible the cap to prevent cement escaping from the mould. Lower left) Cement

mixture (water – cement ratio = 1.4) after being cut and ready to be tested.

55

whereas some other samples, like MPC3, were tested with 10000 seconds periods in order to

obtain a response in the downstream pressure. This caused a more serious delay in the

progress of the experiments, since for every effective pressure it was necessary to get at least

10 cycles in order to overcome the transient effect, sometimes more. It was achieved only after

27 hours test for one sample for one effective pressure. All this impeded to repeat the test

several times like it was done with other samples.

MPS3 sample did not even produce a response in the downstream pressure with a 10000

seconds period, so it was just considered as impermeable since it was being tested partially

saturated due to cracking presented when sample was subject to water loss. With such a long

period other problems raised with the equipment such as leakage in the pipes inside the

permeameter which leaded to a revision of the equipment and more delay in the progress of

the research. The equipment was left overnight with a known pressure and the pressure was

logged every second to find out if pressure was decaying. The effect of leaking was not a

problem for periods under 12 hours, but for longer tests it was a problem that caused resulting

data not to be as precise as desired.

56

4.5 Cement Porosity

5 samples were tested in the Digital Helium Porosimeter DHP -100, shown in Figure 14,

which relays in Boyle’s law method to determine porosity based in gas volume difference and

pressure (Draper, 1861). The determination of effective porosity is achieved by placing the

sample into a core holder with a known volume. Then helium is allowed to expand at a

constant temperature inside the holder until the pressure reaches equilibrium. Grain volume is

calculated by the new gas pressure measurement. Bulk volume is calculated by determining

the volume of the sample. Effective porosity is then calculated by the difference between grain

volume and bulk volume (Aplin, 1999). The same samples tested in the permeameter were

tested in the porosimeter.

∅ℎ𝑐 =(𝑉𝑏 − 𝑉𝑔)

𝑉𝑏

Where:

∅ℎ𝑐= Effective porosity

𝑉𝑏=Bulk volume

𝑉𝑔=Grain volume

Figure 14: DHP -100. Digital Helium Porosimeter from ResLab manufacturer.

57

Chapter 5: Results

5.1 Transmitted and reflected light microscopy

Prior to ESEM analysis, the polished thinsections sample were examined using transmitted

and reflected light microscopy in order to identify areas where possible chemical alteration

may have occurred. All samples were analysed but it was only possible to identify 2 samples

where a very clear optical alteration was present. Samples PMS4 and OPC4 (mortar of

Ordinary Portland Cement and mortar of Ordinary Portland Cement with 10% of microsilica,

both with Whitby Mudstone) both showed a visible alteration all around the interface between

the cement matrix and the mudstone. The cement matrix in PMS4 and OPC4 seemed to be

altered in such a way that it had the appearance to be slightly more transparent near the

interface, however no visible change was observed in the adjacent mudstone (see Figure 15

and Figure 16). All other samples didn´t show any clear visible alteration under the optical

microscope as shown in Figure 17 and Figure 18 (samples OPC2 and PMS3 respectively), but

analysis under ESEM was, nonetheless, performed in attempt to identify minor changes.

58

Cement matrix

Whitby Mudstone

Figure 15: OPC4 optical analysis. (Left) OPC4 polished thin section under transmitted cross polarized light. The darker

area at the top corresponds to the Whitby Mudstone meanwhile the bottom area with some white sand grains corresponds to

the cement paste. It is possible to identify the lighter colour of the cement paste near the interface. (Red dotted line). The

fracturing of the quartz will have happened during cement formation. (Right) Same sample under plane transmitted light.

The interface line between the cement paste and the Whitby Mudstone is clearer. An intermittent gap along the interface and

also identify the change in colour within the cement paste. There is no observable evidence of alteration within the

mudstone.

Cement matrix

Whitby Mudstone

59

Figure 16: PMS4 optical analysis. (Left) PMS4 polished thin section under transmitted cross polarized light. The

darker area at the right corresponds to the Whitby Mudstone meanwhile the area to the left shows fractured sand grains

correspond to the cement paste. It is possible to identify the lighter colour of the cement paste near the interface, as in

the OPC4 sample. (Right) Same sample under the transmitted plane polarised light. The interface line between the

cement paste and the Whitby Mudstone is clear. It is also possible to appreciate some sort of gap along the interface and

also identify the change in colour within the cement paste. There is no observable evidence of alteration within the

mudstone.

Whitby Mudstone

Cement matrix

Whitby Mudstone

Cement matrix

60

Figure 17: OPC2 optical analysis. (Left) OPC2 in transmitted cross polarised light. The interface line is barely

distinguishable since cement paste and claystone show the same interference colours, however claystone (Holywell clay)

is slightly darker. (Right) Same sample under the transmitted plane polarised light. Colour in cement paste appears to be

uniform in the entire matrix as well as the claystone where there is no optical evidence of any disturbance or alteration.

Interface line was drawn in red.

Holywell shale

Cement matrix

Holywell shale

Cement matrix

61

Figure 17: PMS3 optical analysis. (Left) PMS3 sample in transmitted crossed polarised light. Cement paste and mudstone

show different colours. Cement paste matrix does not show any optical variation. It is possible to observe a fracture that

passes through the mudstone in the left of the image and through the interface line to the right. Sand grains are easily

identifiable as well as a small bubble trapped by the resin during the manufacturing of the section. (Right) Same sample

under the transmitted plane polarised light. Two different facies (cement paste and mudstone) are easily distinguishable. The

fracture is clearly seen. There is no optical evidence of disturbance or alteration in the cement paste or the mudstone.

Cement matrix

Yorkshire shale Yorkshire shale

Cement matrix

62

5.2 ESEM analysis

Once the possible zones were identified, the same thin section samples were analysed under

the ESEM. BSE light images were obtained and element mapping was performed. Element

mapping for Al, C, Ca, K, Mg, Mn, S and Si was undertaken for all the samples (Figure 19,

Figure 20, Figure 22, Figure 25, Figure 26 and Figure 27). Even with the elements maps from

ESEM it was still unclear what interactions were taking place in the zones with lighter colour

found in samples OPC4 and PMS4 since there was no evidence of change in the elements like

an exchange of Ca or Al

Element mapping did reveal the different facies/minerals within the mudstones and

claystones and also identified the formation of calcite crystals within the cement paste, and the

binding with grains of sand in the case of OPC4 and PMS4. From the element mapping it was

also clear that in the interface different facies were exposed to the cement paste (micas,

organic matter, pyrite concentration), but this did not correspond to colour changes.

OPC4 BSE image is shown in Figure 18 and Ca, Al and Si maps are shown in Figure 19 and

Figure 20. Ca appears abundant in the cement matrix while is almost absent in the mudstone

matrix. Al is present in both cement and mudstone matrix, abundant in the mudstone and

concentrated in some facies within the cement. The interface line is very clear from the BSE

image and from the Al maps. There is no evidence to support the idea that the Ca migration is

linked to any particular facies/mineralogy within the Whitby Mudstone Si map shows the

presence of this element in both matrixes. Bright Si concentration within the cement matrix

corresponds to sand grains used in OPC mortar. Despite the alteration zone spotted with

optical microscopy in OPC4 sample, it was not possible to spot a particular change in this area

with element maps from ESEM.

A BSE detail of OPC4 with higher magnification is given in Figure 21. Al map of OPC4

(Figure 22) with higher magnification showed a small exchange of Al from the mudstone into

the cement matrix and Ca from the cement paste to the mudstone. Si map did not reveal any

interaction in the interface (Figure 23). Another more detailed of OPC4 is showed in Figure 24.

Again Ca and Al maps suggest a migration of Al from the mudstone into the cement matrix,

and a migration of Ca from the cement matrix into the mudstone (Figure 25), however the

63

images are not clear enough to prove it. This was also present in PMS3 Al, and Ca maps

(Figure 26). Both Al and Ca appear to cross the interface, however it was not yet very clear if

the exchange was taking place and since ESEM element mapping does not provide

concentration element mapping, it was not possible to determine the cause of the clearer

colour along the interface in OPC4.

BSE image of OPC5 is shown in Figure 27. The interface is well defined and there are no

signs of alteration of migration of Ca or Al.

64

Figure 18: OPC4 SEM analysis. Cement-mudstone interface of the OPC4 sample

(Portland cement and Whitby Mudstone) taken with the ESEM using BSE. A small gap

between the cement and the mudstone matrix is clearly seen. In the mudstone is also

possible to identify some micaceous and organic facies. Big grains on the left of the

image correspond to sand grains (very high Si content) as part of the cement paste.

Cement matrix

Whitby Mudstone

65

Figure 19: OPC4 element mapping. (Top) Calcium map from OPC4 taken with the ESEM.

Blue colour shows areas where there is a Ca concentration. It is clear that cement paste (left of

the image) is Ca rich meanwhile Whitby Mudstone has little or none calcium. The interface line

is very clear and does not show an exchange of calcium from the cement paste to the mudstone.

Black spots in the cement paste indicate the presence of sand grains. Brighter areas of Ca in the

cement paste show indicate the presence of calcite crystals. (Down) Aluminium map of the

same sample taken with the ESEM. Higher Al concentrations are mostly in the right side of the

image which corresponds to the Whitby Mudstone. Small Al spots can be identified in the

cement paste which is common for Ordinary Portland Cement. Interface line is also very easy to

identify. From Al map is possible to see the small gap formed in between the cement paste and

the mudstone. Black spots in the Whitby Mudstone correspond mainly to S concentration

(pyrite).

66

.

Figure 20: OPC4 Si map from SEM Silica map from OPC4 taken with the ESEM. Si is

found mainly in the irregularly shaped sand grains within the cement matrix. It is also

present in the cement phases and in the mudstone.

67

Figure 21: OPC4 SEM analysis. OPC4 cement (left) - mudstone (right) interface. Interface

line is marked in red. The larger clastic grains in the mudstone are fine grained clay-matrix

(right) and the different components of the mudstone are adjacent to the cement.

68

Figure 22: OPC4 element mapping. (Top) Al concentration is highest in the Whitby

Mudstone (right). The interface line is clear and it does not show a real Al migration

from the mudstone into the cement paste. The Al concentrations found within the cement

paste represent the Ca-Al phases. Maps appear to be a little blurry and it could be caused

by the magnification of the image. (Below) Ca map of OPC4 ESEM map. It shows

abundant Ca concentration in the cement paste (left) and little Ca concentration in the

mudstone (right). At the interface higher Ca is seen the mudstone areas (indicated by the

two arrows)

69

Figure 23: OPC4 Si map from SEM Silica is found in the Whitby Mudstone as

well as in the cement matrix. Two different tones of colour can be identified

from Si map. One corresponds to the right of interface (red line) which is a

brighter colour than the one in the left of the interface. Si in the cement paste

indicates the presence of Ca - Si phases.

70

Figure 24: OPC4 SEM analysis. Cement (left) -mudstone (right) interface of

OPC4. The interface is shown by the red line. The bright aggregate of grains in the

top right are pyrite and the elongate grains (centre) are micaceous/clay phases.

71

Figure 25: OPC4 element mapping. (Top) Calcium map of area displayed in Figure 24.

Cement paste area is well defined by the Ca concentration and does not seem to pass over

the interface line which indicates that Ca is not migrating into the mudstone. (Down) Al

map obtained with the ESEM with a magnification of 6400x. Meanwhile Ca

concentrations is well defined, Al concentration is not at all clear and appears blurry near

the interface line and does not really seem to pass over the interface. Black spots within

the Al concentrations refer to pyrite concentrations (S rich).

72

Element mapping was also performed in samples PMS3 (Figure 26), OPC2, OPC5 (Figure 27)

that did not show any alteration under the optical microscope. Those samples did not show any

alteration or element migration under the analysis with the ESEM; however Ca, Al and Si

maps were useful to identify facies within the mudstone. Analysis with EMPA focused on

OPC4, PMS4 and NRV5. OPC4 and PMS4 were the only two samples that showed a visible

alteration found by optical and element mapping form ESEM. NRV5 sample did not show any

alteration at the interface but it was chosen to be studied with EMPA element maps in order to

analyse the facies within the cement paste.

73

Figure 26 PMS3 element mapping. (Top left) BSE ESEM image of cement -

mudstone interface of PMS3 sample (Ordinary Portland Cement with microsilica

addition with Yorkshire Clay). The bright (charging) grains are quartz. (Top right) Al

map obtained with the ESEM. The clay matrix of the Yorkshire Clay. From Al maps

there is no evidence of Al migration to the cement paste. (Down left) Ca map obtained

with the ESEM. Cement matrix is clear and coincides with the interface line which

indicates lack of Ca migrating into the mudstone. (Down right) Si map obtained with

the. Quartz grain is visible within the clay matrix of the Yorkshire clay. The presence of

high Si content in the cement matrix corresponds to microsilica used in the mixture.

74

Figure 27 OPC5 element mapping.

(Top left) ESEM BSE image of the OPC5 sample. The interface is shown by the red

line. Acicular salt crystals, likely to be from pore fluids in the cement, can be seen in

the centre. (Top right) Ca map obtained with the ESEM. Cement matrix is well defined

and matches with the interface line. There is no evidence that suggest any Ca

migration from the cement paste into the Yorkshire Clay. (Bottom left) Al map

obtained with the ESEM. Clay matrix is well defined and the borders match with the

interface line. (Bottom right) Si map obtained with the ESEM. Irregularly shaped

grains appear with a bright colour within the Yorkshire Clay. It is worth noting that

there is no Si grains in the cement paste since sand was not used in the formulation of

this mixture.

75

5.3 EMPA analysis

Samples OPC4, PMS4 and NRV5 were analysed under the EPMA in order to identify and

quantify alterations in the cement matrix. With the EPMA it was possible to map element

concentration. From Ca maps in samples OPC4 and PMS4 it was clear that Ca was being

depleted from the interface towards the cement matrix. This area was up to 250 µm across the

surface into the cement matrix. At the beginning it was supposed that Ca was being swapping

but it was not possible to identify any other element that changed either in the cement matrix

or the mudstone.

Al maps did not show any particular alteration close to the interface. Fe, K, Mg, Mn, Si and

S maps did not show either alterations or interactions with the cement paste.

From ESEM images there was an indication that some Ca migrated into the mudstone

matrix, however EPMA images revealed that what appeared to be Ca migrating into the clay

matrix was in fact a portion of the cement matrix that remained attached to the mudstone core

before the interface cracked.

Ca depletion was not present in other samples and other element maps did not show either

any alteration. It is still not clear the process that causes Ca to deplete near the interface but it

is clear that it was present in only one mudstone (Whitby Mudstone) and it was also only

present with the commercial mixtures and not with the specially designed low pH mixtures.

Because of the lack of alteration in the mudstone and claystones it was attempted to analyse

Ca absorption by placing small pieces of mudstone (around 1mm diameter) into a 0.5 M

solution of Calcium Chloride CaCl2 for 72 hours and then polished blocks were made where

the pieces of mudstones was held by resin and then cut in order to be able to analyse the edge

under the EPMA, however again there was no evidence of alteration or Ca absorption in any

of the samples.

It was possible to identify the most common mineralogical phases within the cement matrix

(Oss, 2005). Tricalcium silicate, Dicalcium silicate and Tricalcium aluminate were spotted by

comparing Ca, Al and Si element maps (see Figure 31 and Figure 35). Maps were analysed at

different concentration index in order to identify minor changes but besides Ca depletion,

76

there is no evidence that suggest Ca migration from the cement matrix into the mudstone or Al

migration from the mudstone into the cement or any other alteration. Maps from other samples

different than OPC5 and PMS5 do not show evidence of alteration; however mineralogical

facies were also identified from Al, Ca and Si. Some high content Ca zones were identified as

unhydrated cement particles.

Special attention is given to the NRVB sample since it was not found element mapping

images in the literature. In the NRVB cement, there was no evidence of alteration in the

cement or claystone. Element maps from EPMA was useful to identify some Calcium

Hydroxide facies were high Ca content was found but Si and Al were low within the cement

matrix.

Figure 28 shows a BSE image of OPC4 sample on the right and Ca map on the left, both

obtained with EPMA. Ca map showed that Ca concentration is decreasing towards the

interface, however there no indications that Ca is migrating into the mudstone. Fractures

within the cement paste appeared to have created 3 different Ca concentration zones. The first

zone, Zone 1, goes from the interface with the mudstone up to 250 μm towards the cement

matrix. Zone 2 goes up to 200 μm from limit with Zone 1 towards the cement matrix. Zone 3

coincides with other fractures and sand grains edges and it shows a more homogeneous Ca

concentration. Fractures in this zone do not appear to create new Ca concentration zones.

By comparison with Al and Si maps, also from EMPA, some mineral were identified within

the cement paste. Unhydrated cement particles appear as red spots in Ca map. This high Ca

concentration spots do not match with Si or Al concentration. They are indicated with a white

arrow.

Al map of OPC4 is shown in Figure 29, as well as BSE image. Aluminium appears

abundant in the mudstone matrix. It is also present in the cement matrix but only a few spots

with high Al concentration can be identified.

Si appears also abundant in the mudstone matrix as shown in Figure 30. High Si

concentrations is also found in sand grains form the cement matrix. However there are a few

other high-Si spots within the cement matrix. A particular zone from the OPC4 EMPA

77

element mapping was chosen to compare Ca, Al, and Si concentration. This are is contained

within the black square in top left corner in Figure 30 and it is presented in Figure 31.

Figure 31 shows Ca, Al and Si maps from the same zone contained in the black square in

Figure 30. Left image shows Ca concentration, Central image shows Al concentration and

right image shows Si. White arrows in Ca and Si element maps indicate zones matching high

Ca and Si concentration, which presumably indicates the presence of alite. Black arrows show

matching high Ca and Al concentration. This presumably indicates the presence of Tricalcium

aluminate.

Point analysis was attempted to undertake in EMPA, however thin sections appeared to be

not enough uniform to properly perform a point analysis.

PMS4 is shown in Figure 32. On the right a BSE image is presented. On the left a Ca map is

presented. In this sample it was possible to identify 2 different zones based on Ca

concentration. Zone 1 goes from the interface up to 200 – 250 µm towards the cement matrix.

The limit is defined mostly by the edges of sand grains. A crack seems to divide cement

matrix from the mudstone. Some Ca concentration is spotted within the mudstone, which

might suggest the migration of this element into the rock. However from optical analysis

showed in Figure 16 the presence of that particular Ca concentration in the edge of the

mudstone correspond actually to cement matrix, since the fracture occurred within the cement

matrix and not between the contact surfaces. Si map from Figure 33 shows abundance of this

element in the mudstone matrix. It is also present in sand grains in the cement matrix. Other

spots with high Si are indicated with arrows, this does not correspond to sand grains. Al map

from Figure 34 shows abundance of Al in the mudstone. From this element map it can be also

observed that part of the cement matrix is attached to the mudstone and a crack was formed

within the cement paste as observed in Figure 16. Some high-Al spots are marked with arrows.

The black square in Al map contains a zone that is analysed in Figure 35. In this last figure, Si

map is shown in left, Al map at centre and Ca map on the right. Black arrow in Si map (left)

shows a high-Si spot that also contains high-Ca concentration. This presumably indicated the

presence of alite. In Al map (centre), white arrow indicates a high-Al concentration that has

also high-Ca concentration, which can presumably be linked to Tricalcium aluminate.

78

NRV5 is shown in Figure 36 containing BSE, Ca, Al, and Si maps. Ca appears to be

abundant in the NRVB matrix. Al is abundant in the Yorkshire rock. Very high Ca

concentration spots in NRVB are indicated with black arrows. These spots does not match

with high Al or Si content, actually Al and Si appear to be particularly low where these high-

Ca concentration spots are presented. This is presumably related to unhydrated phases within

the NRVB matrix.

79

Figure 28: OPC4 EPMA analysis. (Left) Ca map of sample OPC4 polished thin section using EPMA. The Ca

concentration decreases away from the interface. Red spots within the cement matrix correspond to calcite crystals. Black

spots correspond to irregularly shaped sand grains. The fractures within the cement matrix coincide with the 2 different limits

between Zone 1 and Zone 2 and between Zone 2 and Zone 3. Zone 1 goes up to 250 µm from the interface towards the

cement matrix and the limit coincides with the fractures and the sand grains edges. Zone 2 goes up to 200 µm from limit with

Zone 1, the limit with Zone 3 coincides with other fractures and sand grains edges. Zone 3 has a more homogeneous Ca

concentration and fractures within Zone 3 do not appear to create new sections where Ca concentration decreases. There is

no evidence for Ca migration into the mudstone. High Ca spots correspond to unhydrated cement particles. (Right) BSE

image of sample OPC4 from a polished thin section. Three optically distinct zones (1, 2 and 3) in the cementitious materials.

Z

one

1

Unhydrated

cement particles Zone 1

Zone 2

Zone 3

Zone 1

Zone 2

Zone 3

Unhydrated

cement particles

80

Figure 29: OPC4 EPMA analysis. (Left) Al map of sample OPC4 polished thin section using EPMA. There is high Al

concentration in the clay matrix within the Whitby Mudstone. There is also Al concentration within the cement matrix which

forms Tricalcium aluminates facies. Black spots correspond to sand grains in the cement matrix. There is no indication of Al

variation in the 3 different zones where Ca appears to change. (Right) BSE image of sample OPC4 from a polished thin

section.

Zone 1

Zone 2

Zone 3

Zone 1

Zone 2

Zone 3

81

Figure 30: OPC4 EPMA analysis. (Left) Si map of sample OPC4 polished thin section using EPMA. There is high Si

concentration in the sand grains within the cement matrix. Si is also found in the mudstone with high concentrations spots

appearing in yellow and orange. Within the cement paste, some high Si concentrations appear in clear blue but there is no

evidence to suggest Si variation within the cement matrix or the mudstone. Places where Si is high within the cement paste

indicate the presence of Tricalcium silicate. The square in the top left of the image is the detailed area described in Figure 31.

(Right) BSE image of sample OPC4 from a polished thin section.

Zone 1

Zone 2

Zone 3

Zone 1

Zone 2

Zone 3

82

Figure 31: OPC4 EPMA analysis. (Left) Detailed Ca map of sample OPC4 polished thin section using EPMA. White

arrow indicate high-Ca zones matching high-Si zones in cement matrix which may indicate which indicates the presence of

Tricalcium silicate (Alite (CaO)3SiO2). (Centre) Detailed Al map where high-Al spot within the cement matrix is indicated

with black arrow. The same spot presents high-Ca concentrations which may indicate the presence of Tricalcium aluminate

((CaO)3Al2O). (Left) Detailed Si map .White arrow indicates high-Si content within cement matrix matching high-Ca

content.

83

Zone 1

Zone 2

Zone 1

Zone 2

Figure 32 PMS4 Ca map by EPMA analysis (Left) Ca map obtained with the EPMA of a polished thin section of PMS4.

There are two well delimited areas named Zone 1 and Zone 2. Ca has a lower concentration near the interface (Zone 1); this

zone goes towards the cement matrix for up to 200 µm. There are no visible fractures within the cement matrix. Black spots

correspond to irregularly shaped sand grains. Red spots correspond to calcite crystals. The limit between Zone 1 and Zone 2

mostly matches the edges of the sand grains. In the mudstone (lower part of the image) it is possible to find Ca

concentration, however from other optical analysis it was found that the fracture between cement matrix and mudstone

actually occurred within the cement matrix so a thin layer of cement remained attached to the mudstone. Ca depletion is also

present in this thin layer of cement. Even one calcite crystal appears to be fractured and a small portion of it remained

attached to the mudstone (left of the image). (Right) BSE image of the same area obtained with the EPROBE. There two

well differentiated areas within the cement matrix.

84

Zone 1

Zone 2

Zone 1

Zone 2

Figure 33: PMS4 Si map by EPMA analysis (Left) Red spots in the top of the image are mostly irregularly shaped sand

grains. Whitby Mudstone shows to have a high Si content within its clay matrix. Some of the red spots in the cement

matrix do not correspond to sand grains since they present a high Al content (See Figure 34). High Si spots that do not

correspond to sand grains are indicated with arrows. (Right) BSE image of the same area obtained with the EPROBE.

High Si spots are indicated wit arrows.

85

Zone 1

Zone 2

Zone 1

Zone 2

Figure 34: PMS4 Al map by EPMA analysis. (Left) Most of the high Al content is found in the clay matrix of the

Whitby Mudstone; however some high Al spots are easily identified within the cement matrix. Black frame in the

centre of the image correspond to the detailed area described in Figure 35 (Right) BSE image of the same area

obtained with the EPROBE. High Al spots are indicated with arrows.

86

Figure 35: PMS4 element map detail by EPMA analysis (Left) Detail of Si map from PMS4. Si facies are spotted in

green while sand grains appear red. Si matrix matches with Ca matrix from the image in the right which indicates the

presence of Tricalcium silicate (Alite (CaO)3SiO2). Special spot where high Si concentration and high Ca

concentration match is indicated with a black arrow. (Centre) Detail of Al map from PMS4. Al facies are spotted

green and red within the cement matrix. Black spots correspond to sand grains. A particular spot where Tricalcium

aluminate ((CaO)3Al2O) can be appreciated is indicated with a white arrow. (Right) Detail of Ca map from PMS4. Ca

facies appear green, yellow and red. Black spot correspond to sand grains. Black arrow indicated Tricalcium silicate

since it matches with Si concentrations found from Si maps. White arrow indicates Tricalcium aluminate.

87

Figure 36: NRV5 element maps by EPMA. (Top left) BSE image obtained by EPMA of

NRVB cement with Yorkshire clay. The cement matrix correspond to the top left of the

image. There is no evidence of alteration either in the NRVB or the claystone. (Top right)

Ca map from NRV5. Calcium facies are clearly present in the cement matrix with high Ca

concentration spots. Some high Ca spots are indicated with arrows. (Bottom left) Si map

from NRV5. High Si content is found in the claystone but also in some areas in the cement

matrix. There is no evidence of alteration in Si distribution however a few darker areas can

be observed where Ca content is high (marked with arrows). (Bottom right) Al map from

NRV5. Clay matrix from Yorkshire Claystone shows high Al content. Some Al content is

also found in the cement matrix. Al content is found to be low where cement matrix has a

high Ca content (marked with arrows).

88

Table 8: Resume of all samples analysis.

SAMPLE

NUMBER

Cement mixture – lithology Results after 28 days

interaction with pore water

OPC1 Mortar of Ordinary Portland cement -

Kimmeridge clay

None


Holywell clay

None


Yorkshire clay

None

OPC4 Mortar of Ordinary Portland cement – Whitby

Mudstone

Ca depletion in the interface up

to 250µm

PMS1 Mortar of Ordinary Portland cement with 10%

silica fume - Kimmeridge clay

None


silica fume - Holywell clay

None


silica fume - Yorkshire clay

None


silica fume - Whitby Mudstone

Ca depletion in the cement

matrix near the interface up to

250µm

NRV5 Nirex Reference Vault Backfill - Whitby

Mudstone

None

NRV6 Nirex Reference Vault Backfill - Holywell

clay

None

NRV7 Nirex Reference Vault Backfill - Yorkshire

clay

None

NRV8 Nirex Reference Vault Backfill - Kimmeridge

clay

None

OPC5 Ordinary Portland Cement grout w/c 1.4 - None

89

Whitby Mudstone

OPC6 Ordinary Portland Cement grout w/c 1.4 -

Holywell clay

None


Yorkshire clay

None


Kimmeridge clay

None

PMS5 Ordinary Portland Cement grout with 40%

silica fume - Whitby Mudstone

None


silica fume - Holywell clay

None


silica fume - Yorkshire clay

None


silica fume - Kimmeridge clay

None

90

5.4 Permeability

The original objective of manufacturing cylindrical cement samples with a rock core was to

measure permeability in the altered interface; however these samples were not appropriate to

perform the test since they cracked when water loss was present (i.e. drying to allow gas from

permeameter to flow). This cracking was not present when the cement samples did not contain

a rock core; therefore the measurement of six unweathered cement samples was undertaken

with the oscillating pore pressure test in order to measure the permeability of cement mixes.

Samples tested are described in Table 9. NRVB sample was tested using a constant flow

method. The only sample that was not tested was the result of cracking due to water loss.

Despite of trying to test the sample partially saturated with pore water from curing, it was not

possible to obtain any measurement of permeability neither with the oscillating pore pressure

method or constant flow method.

In most of the samples the test was repeated in order to study the effect of effective pressure

in the cement permeability, however most of the samples showed not to be affected by

changes in effective pressure since the results show negligible variation in permeability.

MPS3 sample was very difficult to measure due to shrinkage and cracking. It was necessary

to test the sample with partially saturated cores (form pore water) but results were inconsistent

and it was necessary to use very long periods in order to obtain a downstream pore pressure

signature which made very difficult test repletion. One test was 27 hours long.

All results are summarised in Figure 43.

91

Table 9: Test conditions for every sample

CODE Period

(seconds)

Amplitude

(MPa)

Pore

pressure

(MPa)

Number of test

performed

Test

OPC 100 0.5 10 3 Oscillating pore pressure

PMS 200 0.5 10 3 Oscillating pore pressure

MPC5 100 0.5 10 2 Oscillating pore pressure

PMS5 50 0.5 10 3 Oscillating pore pressure

MPC3 10000 0.5 10 1 Oscillating pore pressure

MPS3 10000 0.5 10 1 Oscillating pore pressure

NRVB 2 Constant flow method

MPC5 sample was tested twice and did not show to be affected significantly by effective

pressure. Values range from 5 x 10-17

m2

for 5MPa effective pressure in the first cycle to 4.43

x 10-17

m2 for 30 MPa effective pressure in the second cycle, which is practically negligible

compared with the variation of permeability of other materials like mudstone which variates in

orders of magnitude with effective pressure (McKernan, Rutter, Mecklenburgh, Taylor, &

Covey-Crump, 2014). Results are shown in Figure 37.

92

Figure 37: MPC5 permeability results

OPC was tested twice and did not show to be affected by effective pressure since the values

of permeability were almost the same in both tests. Results are presented in Figure 38.

Permeability values range from 2.69 x 10-17

for 10 MPa effective pressure in the first cycle to

2.49 x 10-17

m2

for 30 MPa effective pressure in the second cycle, which is a small change.

This value is within the same order of magnitude than MPC5. Results are shown in Figure 38.

93

Figure 38: OPC permeability results

PMS5 was tested 3 times. This sample showed to be slightly affected by effective pressure

since it decayed with every test. For the same effective pressure (5 MPa) permeability changed

from 2.73 x10-17

m2 for the first test to 1.59 x10

-17 m

2 for the third test. All test matched at 30

MPa effective pressure with a value of 1.39 x10-17

m2 . The second point (10 MPa) in the first

test does not match with the trend line from all the other points. It is still unclear why this

happened since the sample was not moved during the test and all the parameters, except for

effective pressure were kept constant. A leakage can be discarded since the rest of the points

show more consistency one to another.

94

Figure 39: PMS5 permeability results

NRV sample was tested with constant flow method in the same equipment that the

oscillating pore pressure method by making the rotor in the upstream to move until a constant

differential pressure was obtained between upstream pore pressure and downstream pore

pressure. It was done manually by turning on and off the rotor every test since the equipment

is designed to operate automatically only the oscillating pore pressure test. Results are

presented in Figure 40. It appears like effective pressure has a slight effect in permeability

since it decreases in the second cycle of test. NRVB was tested 4 times with constant flow

method. The first test shows a decrease in permeability as effective pressure was increased,

permeability decreased from 1.84 x 10-17

m2 to 9.29 x 10

-17 m

2. The second, third and fourth

test resulted in the same values for every effective pressure and it only decreases from 1.06 x

10-17

m2 to 9.29 x 10

-18 m

2. It makes clear that effective pressure did not affected significantly

permeability after the first test, however the decrease in permeability in the first test is

negligible compared with other materials within the repository such as mudstones and shales.

95

Figure 40: NRVB permeability results

PMS was tested three times at only two effective pressures (10 and 30 MPa) and 3 effective

pressures in last cycle (10, 20 and 30 MPa). This was due a time limitations since it was the

last sample to be tested. Permeability values range from 1.88 x 10-18

m2 to 3.78 x 10

-19 m

2 for

10 MPa effective pressure and it decreased up to 4.95 x 10-19

m2 for 30 MPa effective pressure.

Results are shown in Figure 41.

96

Figure 41: PMS permeability results

MPC3 was tested only once due to the very long period needed to obtain a downstream pore

pressure signature. Data was processed several times since the permeability somehow changed

from one processing to another. Data was processed with the same MATLAB process than all

the other samples and yet permeability values for 30 MPa effective pressure was scattered.

This sample was tested partially saturated with pore water which could be the reason for the

very low permeability found (10-21

m2). MPC5 appear to be more affected by effective

pressure than all the other samples tested since permeability decreases a whole order of

magnitude from 5 MPa effective pressure to 30 MPa effective pressure. Results are shown in

Figure 42.

97

Figure 42: MPC3 permeability results

98

When compared k results all together, the effect of Effective pressure in permeability does

not seem to be significant. Results show k values ranging from 10-21

to 10-16

m2. Effective

pressure ranged from 5 to 30 MPa. Almost all the samples showed to have a constant k value

regardless of the Effective pressure. Only MPC3 showed to be affected more by effective

pressure

Figure 43: Summarised permeability results.

Typically a downstream to upstream amplitude ratio 𝐴𝐷 𝐴𝑈 ≈ 0.5⁄ is enough to reach a

reliable data processing. To achieve this it was necessary to adjust parameters such as T and

sometimes the downstream volume. The NRVB sample has the higher permeability (k=10-16

)

and it was not possible to obtain k with the oscillating pore pressure test since all the solutions

were out of the solution space in the nomogram. To overcome this issue a constant flow test

99

was performed with the same equipment. In the constant flow test gas was made to pass

through the sample at a constant flow rate and then the pressure differential was recorded in

order to obtain the permeability. From literature the common permeability values for gas in

concrete or grout range from 10-18

to 10-16

m2 (Abbas, Carcasses, & Ollivier, 1999).

The lower permeability value of 10-21

corresponds to the sample MPC3 which was measured

partially saturated with pore water. It was not possible to measure this sample in a dry state

since it started to crack with water loss.

5.4 Porosity

4 samples were tested in the Digital Helium Porosimeter. The addition of Microsilica and

the usage of Microcement seemed to reduce the porosity in the samples. The regular cement

mixture (OPC) which contains sand and Ordinary Portland Cement has a porosity of 19.25%

and the addition of 10% Microsilica (PMS) reduces its porosity to 13.95%. The usage of

microcement instead of ordinary Portland cement reduces porosity in the same order than

microsilica.

One interesting result is that the special cement NRVB has a very large porosity found by

testing two samples of NRVB where porosities of 42.68 and 44.99% were obtained. This

mixture loses almost half of its weight when drying but at the same time keeps permeability

with in an average range.

MPC5 resulted with a porosity of 13.39 %. Results are summarised in Table 10. 3 samples

were attempted to measure porosity while partially saturated (PMS5, MPC3 and MPS3), but

cracking and shrinkage and were present during the test due to water loss, so it was not

possible to make any porosity measurement.

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Table 10: Porosity results. Porosities obtained with the Digital Helium Porosimeter

The porosity values obtained are porosity of undisturbed samples. The change in porosity in

cement matrix was not able to measure with helium porosimeter due to lack of reaction

between the cement matrix and the mudstone and to the cracks that appeared in the samples

with mudstone core embedded. Therefore the porosity of unaltered cement plugs was

measured in samples that were not affected by shrinkage due to water loss.

Sample P1 P2 Weight 1.0" disc in Disc volume GV GD BD porosity

(ID) (Bar) (Bar) (Grams) matrix cup (ml) (ml) g/cm3

g/cm3

%

NRV 7.606 4.184 15.997 532100 39.75 7.2012 2.2214 1.27 42.68

NRV 7.604 4.059 18.003 532000 37.93 8.0960 2.2237 1.22 44.99

OPC 7.598 4.295 57.006 432000 24.63 23.1414 2.4634 1.99 19.25

OPC 7.587 4.478 32.318 531000 35.80 13.2227 2.4441 1.99 18.63

PMS 7.595 4.597 32.687 531000 35.80 13.9282 2.3468 2.02 13.95

MPC5 6.851 4.413 20.823 540000 39.82 11.5762 1.7988 1.56 13.19

101

Chapter 6 Discussion

The Ca depletion alteration in the cement matrix was already found in other research with

regular concrete mixture and Opalinus Clay (Jenni, Mäder, Lerouge, Gaboreau, & Schwyn,

2014). Decrease in Ca concentrations has been related to dissolution of Ca phases such as

portlandite. However, this alteration was found to take place after a considerable amount of

time (2.2 years) and interaction with groundwater. It also showed Mg enrichment in the

cement paste near interface which was not found in this research.

Temperature used in this research was room temperature (20-25 °C). Literature has covered

a wide range of temperatures in the cement-clay interaction, from 25 °C (Dauzeres et al., 2010)

up to 150 °C (Mohammed, Pusch, Warr, Kasbohm, & Knutsson, 2015). Alterations in the

cement matrix and clay minerals within the rock occur at faster rates and are more extensive

when temperature is enhanced. Cement is found to be degraded by decalcification, sulphate-

attack and carbonation. When carbonation occurs, a high-Ca zone is found in the surface

expose to CO2 or H2O leading to a calcite precipitation which competes with portlandite

dissolution (caused by low-Ph due to carbonation) generating a decalcification in the cement

matrix.

Sulphur migration from clay rocks into cement matrix are generated by the low-pH in the

cement matrix caused by carbonation. The dissolution of portlandite creates an increase in

cavities where ettringite is able to precipitate. This precipitation does not occur near the

carbonated zone (low-pH) but when S reaches a pH high enough for precipitation.

Carbonation is plausible to be the cause of the decalcification found in samples OPC4 and

PMS4. These could be caused by the exposure to water from curing process and CO2/HCO3

migrating from the clay into cement. Literature also shows that the addition microsilica

decreases portlandite content which lead to low carbonation (Taylor, 1990). This would

explain why samples with up to 40% of microsilica addition showed no alteration under

ESEM and EMPA.

In the other hand, the results of the special cements such as the NRVB indicates that

alterations between the cement matrix and the surrounding host rock might not be an issue in

102

an early stage of interaction. Silica fume appears to play an important role in decreasing

porosity and avoiding the alteration of the cement matrix by reducing the voids as found by

Blandine et al., 2008.

The mechanism of alteration of cement matrix might be dissolution of calcium hydroxide

phases by carbonic acid create by the dissolution of carbon dioxide into the aqueous phase.

CO2 + H2O → H2CO3 (aq)

And then

Ca(OH)2(s) → Ca2+(aq) + 2OH−

(aq)

When carbonation occurs, Portlandite dissolution leads to an increase in porosity in the

weathered zone. These cavities created by Portlandite dissolution are commonly zones where

calcite and ettringite precipitate, thus refilling voids within the cement matrix. When cement

reacts with a clay rock, porosity conditions changes over time leading finally to a clogging

where porosity in the interface is strongly reduced. This clogging leads to a reduction of fluids

across the interface, which basically would stop geochemical alteration process and slow

down mass transport across the interface (Kosakowski & Berner, 2013). However, the

precipitation of crystal minerals such as calcite leads to a significant increase in cracks within

the cement matrix, which increase permeability, allowing fluids to reach the unweathered

cement matrix (Ruiz-Agudo, Kudłacz, Putnis, Putnis, & Rodriguez-Navarro, 2013).

Permeability and porosity of cement mixtures are found consisting with literature. Despite

the failure to obtain samples to analyse the permeability of cement-clay interface, the

permeability of cement matrix was measured and compared with the permeability of the

Whitby Mudstone (one of the potential host rocks) which ranges from 10-21

to 10-18

m2

(McKernan et al., 2014) when measured with oscillating pore fluid pressure. The lowest value

corresponds to permeability measured perpendicular to layering. MPC5 sample showed a

particular low permeability value. This can be caused by having measured the sample when

partially saturated since it would crack when exposed to drying. For the rest of the samples,

103

permeability ranges between 10-18

to 1016

m2. PMS sample show the lowest permeability from

the samples measured in dry condition. This is not surprising since the addition of microsilica

reduces the porosity and permeability of cement. Cements samples show little or none

pressure sensitivity. This is due to fluid flowing through equant pores rather than crack-like

pores like the case of the Whitby Mudstone, for instance.

Cracking of cement samples due to water loss is a major concern. Besides not allowing to

manufacture samples to measure permeability in dry conditions, cracks are likely to appear in

GDF since saturated conditions are not necessarily predominant at all times. Groundwater is

expected to eventually saturate the GDF, but during the operation and filling of the repository,

cement is likely to be exposed to air, which would lead to a temporary water loss. Further

investigation is needed in order to assess the performance of cement mortars during water loss

conditions.

Further investigation is recommended regarding the chemical interaction of cement-clay

interfaces with possible UK host rocks (Whitby Mudstone, Yorkshire Clay, Kimmeridge, Clay,

and Holywell Shale). It would be recommended to undertake experiments in a longer period of

time and with different temperatures (suggested 70 °C) and hyperalkaline fluids. This would

allow investigating the interaction in the long term rather than the short term where clearly

there is not much of interaction taking place. Regarding permeability measurements, a

different arrange of the cement-clay interface is needed since the proposed arrange of rock

core in cylindrical cement samples is strongly affect by cracks appearance. Porosity of

potential altered cement can be measured with Mercury intrusion rather than helium

porosimeter.

Further analysis with small cuts of the interface zone are recommended to be undertaken

since equipment such as ESEM does not require samples to be in the form of a thin section for

SEM analysis.

In the special case of NRVB, permeability found with the constant flow method was slightly

lower by one order of magnitude than the one reported in the literature (Ian G Crossland,

2007). Values in this research found permeability to be 10e-17 whereas literature report 10e-

16 m2. It is worth nothing the difficulties found in measuring permeability in NRVB since it

104

was not achieved with the oscillating pore pressure and the test had to be adapted to perform

the constant flow method; however it was possible to replicate the results by repeating the test.

Porosity in NRVB appears to be the characteristic that makes the difference with the other

cement mixtures proposed. NRVB shows a porosity of 44 %, more than double that other

cement mixtures, which create voids where CaOH2 can be dissolved and buffer the

groundwater pH to limit migration of radionuclides.

The usage of conventional mortars such as OPC4 and PMS4 might be not advised as a

buffer or backfill in the repository. Ca depletion showed in an initial stage of reaction indicates

that these two samples can be strongly degraded with time and conditions within the

repository. NRVB does not show these problems.

Chapter 7 Conclusions

Little reactivity between proposed cement mixtures and possible host rocks for GDF in the

UK has been found in an initial setting stage of 28 days. SEM and EMPA analysis do not

show any evidence to suggest that the cement or the clay matrix within the rock is being

subject to alterations. Only two samples (OPC4 and PMS4) showed a clear decalcification

zone near the interface with the Whitby Mudstone. The addition of high quantities of

microsilica to cement mortars appears to decrease the reactivity of cement by decreasing the

content of soluble Ca-phases like Portlandite. This Ca-depletion zone is likely to be originated

by carbonation however further investigation is advised to undertake to corroborate this

observation.

Permeability of the cement-clay composite was not possible to measure due to cracking of

the cement hence permeability and porosity was measure in unweathered cement samples

when cracks did not appear due to water loss. They show low permeability as expected from

the literature and when compared with permeability of one of the possible host rocks in the

UK (Whitby Mudstone) cements are not likely to be more permeable than permeability

parallel to layering, however cracking due to water loss is an issue that need to be addressed

and further research in this matter is encouraged.

105

REFERENCES

Abbas, A., Carcasses, M., & Ollivier, J.-P. (1999). Gas permeability of concrete in relation to

its degree of saturation. Materials and Structures, 32(1), 3–8.

http://doi.org/10.1007/BF02480405

Abbas, A., & Carcasses andJ-P Ollivier, M. (1999). Gas permeability of concrete in relation to

its degree of saturation. Materials and Structures/Matdriaux et Constructions, 32, 3–8.

Adams, L. D., & Race, R. M. (1990). Effect of limestone additions upon drying shrinkage of

Portland cement mortar. Carbonate Additions to Cement, 41. JOUR.

Adler, M., Mader, U. K., & Waber, H. N. (1999). High-pH alteration of argillaceous rocks: an

experimental study. Schweizerische Mineralogische Und Petrographische Mitteilungen,

79(3), 445–454. Journal Article.

Alonso, J., Bárcena, I., Alonso, M. C., Pettersson, S., & Bodén, A. (2009). ( Contract Number :

FI6W-CT-2004-508851 ) Module 4 ( Temporary Sealing Technology ) Final report,

4(January).

Alunno-Rosetti, V., & Curcio, F. (1997). A Contribution to the Knowledge of the Properties of

Portland-Limestone Cement Concretes, with Respect to the Requirements of European

and Italian Design Code. In Proceedings of the 10th International Congress on the

Chemistry of Cement (pp. 2–6). CONF, H. Justnes.

Andrews, I. (2013). The Carboniferous Bowland Shale gas study: geology and resource

estimation. Retrieved from http://nora.nerc.ac.uk/id/eprint/503839

Aplin, A. C. (1999). Muds and Mudstones: Physical and Fluid-flow Properties. Geological

Society of London. Retrieved from

https://books.google.com/books?id=mstp2mwx1jYC&pgis=1

Apted, M., & Ahn, J. (2010). Multiple-barrier geological repository design and operation

strategies for safe disposal of radioactive materials. Geological Repository Systems for

Safe Disposal of Spent Nuclear Fuels and Radioactive Waste, 3–28.

http://doi.org/10.1533/9781845699789.1.3

Atkinson, A. (1985). the Influence of Wasteform Permeability on the Release of

Radionuclides From a Repository, 5, 2–3.

Bernabé, Y., Mok, U., & Evans, B. (2006). A note on the oscillating flow method for

measuring rock permeability. International Journal of Rock Mechanics and Mining

Sciences, 43(2), 311–316. http://doi.org/10.1016/j.ijrmms.2005.04.013

Berner, U. R. (1992). Evolution of pore water chemistry during degradation of cement in a

radioactive waste repository environment. Waste Management, 12(2–3), 201–219.

http://doi.org/10.1016/0956-053X(92)90049-O

Blandine, A., Essaïd, B., & Bernard, G. (2008). Comparison of the weathering behavior of a

very high strength concrete with that of a standard concrete. Cerâmica, 54(332), 388–394.

http://doi.org/10.1590/S0366-69132008000400002

Blezard, R. G. (2003). The History of Calcareous Cements. Lea’s Chemistry of Cement and

Concrete, 1–23. http://doi.org/10.1016/B978-075066256-7/50013-8

106

Bragg, W. H., & Bragg, W. L. (1913). The Reflection of X-rays by Crystals. Proceedings of

the Royal Society of London A: Mathematical, Physical and Engineering Sciences,

88(605), 428–438. JOUR. Retrieved from

http://rspa.royalsocietypublishing.org/content/88/605/428.abstract

Cerceo, M., & Childers, H. M. (1963). Thermal Diffusivity by Electron Bombardment Heating.

Journal of Applied Physics, 34(5), 1445. http://doi.org/10.1063/1.1729598

Chermak, J. a. (1992). Low-temperature experimental investigation of the effect of high pH

NaOH solutions on the Opalinus Shale, Switzerland. Clays and Clay Minerals, 40(6),

650–658. Journal Article. http://doi.org/10.1346/CCMN.1992.0400604

Chermak, J. a. (1993). Low-temperature experimental investigation of the effect of high pH

NaOH solutions on the Opalinus Shale, Switzerland. Clays and Clay Minerals, 41(3),

365–372. Journal Article. http://doi.org/10.1346/CCMN.1993.0410313

Claret, F., Bauer, A., Schafer, T., Griffault, L., & Lanson, B. (2002). Experimental

investigation of the interaction of clays with high-pH solutions: A case study from the

Callovo-Oxfordian formation, Meuse-Haute Marne underground laboratory (France).

Clays and Clay Minerals, 50(5), 633–646. Journal Article.

http://doi.org/10.1346/000986002320679369

Clarke, F. W. (1924). The data of geochemistry (RPRT, 5th ed.). Bulletin. Retrieved from

http://pubs.er.usgs.gov/publication/b770

Crossland, I. G. (2007). Cracking of the Nirex Reference Vault Backfill: A Review of its

Likely Occurrence and Significance.

Crossland, I. G., & Vines, S. P. (2001). Nirex Report Why a cementitious repository ? Nirex

Report N/034.

Crossland, I. G., & Vines, S. P. (2001). Why a cementitious repository. Nirex Report N/034,

(June).

Cuevas, J., & Leguey, S. (2006). The alkaline reaction of FEBEX bentonite : a contribution to

the study of the performance of bentonite / concrete engineered barrier systems. Journal

of Iberian Geology 32 (2) 2006: 151-174, 32(2), 151–174. Retrieved from www.ucm.es

/info/estratig/journal.htm

Cuevas, J., Sánchez, L., Vigil de la Villa, R., Ramírez, S., Fernández, R., & Leguey, S. (2006).

The alkaline reaction of FEBEX bentonite: a contribution to the study of the performance

of bentonite/concrete engineered barrier system. Journal of Iberian Geology; Vol 32, No

2 (2006): Research and Development for the Deep Geological Disposal of Radioactive

Wastes (II). JOUR. Retrieved from

http://revistas.ucm.es/index.php/JIGE/article/view/JIGE0606220151A/32785

Danilatos, G. D. (1994). Environmental scanning electron microscopy and microanalysis.

Mikrochimica Acta, 114–115(1), 143–155. http://doi.org/10.1007/BF01244538

Dauzeres, A., Le Bescop, P., Sardini, P., Cau, C., & Coumes, D. (2010). Physico-chemical

investigation of clayey/cement-based materials interaction in the context of geological

waste disposal: Experimental approach and results. Cement and Concrete Research, 40,

1327–1340.

De Craen, M., Wang, L., Geet, M. Van, & Moors, H. (2004). Geochemistry of Boom Clay

107

pore water at the Mol site.

Devol-Brown, I., Tinseau, E., Bartier, D., Mifsud, A., & Stammose, D. (2007). Interaction of

Tournemire argillite (Aveyron, France) with hyperalkaline fluids: Batch experiments

performed with powdered and/or compact materials. Physics and Chemistry of the Earth,

32(1–7), 320–333. Journal Article. http://doi.org/10.1016/j.pce.2006.02.046

Donald, A. M., He, C., Royall, C. P., Sferrazza, M., Stelmashenko, N. A., & Thiel, B. L.

(2000). Applications of environmental scanning electron microscopy to colloidal

aggregation and film formation. Colloids and Surfaces A: Physicochemical and

Engineering Aspects, 174(1), 37–53. JOUR.

Draper, J. W. (1861). A Textbook on chemistry. Harper & Bros. Retrieved from

https://books.google.com/books?id=HKwS7QDh5eMC&pgis=1

ECOCLAY II. (2005). Effects of Cement on Clay Barrier Performance – Phase II. Rapport

Européen EUR21921.

Elie, M., Faure, P., Michels, R., Landais, P., Griffault, L., Mansuy, L., & Martinez, L. (2004).

Effects of water-cement solutions on the composition of organic compounds leached

from oxidized Callovo-Oxfordian argillaceous sediment. Applied Clay Science, 26(1–4),

309–323. Journal Article. http://doi.org/10.1016/j.clay.2003.12.016

EPMA: Electron Probe Micro-Analysis. (n.d.). Retrieved January 11, 2016, from

http://www.cameca.fr/instruments-for-research/epma.aspx

Fewtrell, M., & Smith, D. (1980). Revision of the Dinantian stratigraphy of the Craven Basin,

N England. Geological Magazine. Retrieved from

http://journals.cambridge.org/abstract_S0016756800033082

Fidjester, P. Frearson, J. (1994). High-Performance Concrete Using Blended and Triple

Blended Binders. Proceedings of the ACI International Conference on High Performance

Concrete. article.

Fiskaa, O. ., & Betong, I. (1983). “Alunskifer (in Norwegian).” Norges Festekniske Inst, 101.

article.

Gad, M. a., Catt, J. a., & Le Riche, H. H. (1969). Geochemistry of the Whitbian upper Lias

sediments of the Yorkshire coast. Proceedings of the Yorkshire Geological Society, 37(1),

105–139. http://doi.org/10.1144/pygs.37.1.105

Gascoyne, M. (2002). Influence of grout and cement on groundwater composition. POSIVA

Working Report, 7. JOUR.

Holt, E. (2008). Durability of Low-pH Injection Grout.

Huertas, F., Farias, J., Griffault, L., Leguey, S., Cuevas, C., Ram�rez, S., … Vieillard, P.

(2000). Effects of cement on clay barrier performance - Ecoclay project.

Jenni, a., Mäder, U., Lerouge, C., Gaboreau, S., & Schwyn, B. (2014). In situ interaction

between different concretes and Opalinus Clay. Physics and Chemistry of the Earth, 70–

71, 71–83. http://doi.org/10.1016/j.pce.2013.11.004

Johnson, R. (1996). Environmental scanning electron microscopy. An Introduction to ESEM.

Philips, Eindhoven: Robert Johnson Associates. JOUR.

Kim, J. S., Kwon, S., Choi, J. W., & Cho, G. C. (2011). Properties of low-pH cement grout as

108

a sealing material for the geological disposal of radioactive waste. Nuclear Engineering

and Technology, 43(5), 459–468.

http://doi.org/http://dx.doi.org/10.5516/NET.2011.43.5.459

Kosakowski, G., & Berner, U. (2013). The evolution of clay rock/cement interfaces in a

cementitious repository for low- and intermediate level radioactive waste. Physics and

Chemistry of the Earth, 64, 65–86. http://doi.org/10.1016/j.pce.2013.01.003

Kranz ’, R. L., Saltzman, J. S., & Blacic~, J. D. (1990). Hydraulic Diffusivity Measurements

on Laboratory Rock Samples Using an Oscillating Pore Pressure Method. Int. J. Rock

Mech. Min. Sci. & Geomech. Abstr, 27(5), 345–352.

Kronlöf, A. (2005). Injection Grout for Deep Repositories – Low pH Cementitious Injection

Grout for Larger Fractures : Testing Effect of Superplasticizer on Technical Performance

Injection Grout for Deep Repositories – Low pH Cementitious Injection Grout for Larger

Fractures.

Kurashige, I., Hironaga, M., & Niwase, K. (2007). Effects of hydrogen carbonate and chloride

in groundwater on leaching of cementitious materials.

Lafarge Tarmac. (2014). MICROCEM TECHNICAL INFORMATION. Retrieved December

16, 2015, from http://www.tarmac.com/media/756316/microcem-product-data-sheet.pdf

Macphee, D. E., & Lachowski, E. E. (2003). Cement Components and Their Phase Relations.

Lea’s Chemistry of Cement and Concrete, 95–129. http://doi.org/10.1016/B978-

075066256-7/50015-1

MacQuaker, J. H. S., & Gawthorpe, R. L. (1993). Mudstone lithofacies in the Kimmeridge

Clay Formation, Wessex Basin, southern England; implications for the origin and

controls of the distribution of mudstones. Journal of Sedimentary Research.

http://doi.org/10.1306/D4267CC1-2B26-11D7-8648000102C1865D

Massazza, F. (2003). Pozzolana and Pozzolanic Cements. Lea’s Chemistry of Cement and

Concrete, 15(1993), 471–635. http://doi.org/10.1016/B978-075066256-7/50022-9

McKernan, R. E., Rutter, E. H., Mecklenburgh, J., Taylor, K. G., & Covey-Crump, S. J.

(2014). Influence of Effective Pressure on Mudstone Matrix Permeability: Implications

for Shale Gas Production. In SPE/EAGE European Unconventional Resources

Conference and Exhibition. Society of Petroleum Engineers.

http://doi.org/10.2118/167762-MS

Mohammed, M. H., Pusch, R., Warr, L., Kasbohm, J., & Knutsson, S. (2015). Interaction of

clay and concrete relevant to the deep disposal of high-level radioactive waste. Applied

Clay Science, 118, 178–187. http://doi.org/10.1016/j.clay.2015.08.008

Morgans-Bell, H. S., Coe, A. L., Hesselbo, S. P., Jenkyns, H. C., Weedon, G. P., Marshall, J.

E. a, … Williams, C. J. (2001). Integrated stratigraphy of the Kimmeridge Clay

Formation (Upper Jurassic) based on exposures and boreholes in south Dorset, UK.

Geological Magazine, 138(5), 511–539. article.

http://doi.org/10.1017/s0016756801005738

Morris, K. a. (1979). A classification of Jurassic marine shale sequences: an example from the

Toarcian (Lower Jurassic) of Great Britain. Palaeogeography, Palaeoclimatology,

Palaeoecology, 26, 117–126. http://doi.org/10.1017/S0260210500114846

109

NDA. (2014). A Review of the Development of Bentonite Barriers in the KBS 3V Disposal

Concept. NDA Technical Note No. 21665941, March, 1–74. Retrieved from

https://rwm.nda.gov.uk/publication/a-review-of-the-development-of-bentonite-barriers-

in-the-kbs-3v-disposal-concept/

Oss, H. Van. (2005). Background facts and issues concerning cement and cement data.

Retrieved from http://www.starnewsonline.com/assets/pdf/WM11702525.PDF

Powell, J. H. (1984). Lithostratigraphical nomenclature of the Lias Group in the Yorkshire

Basin. In Proceedings of the Yorkshire Geological and Polytechnic Society (Vol. 45, pp.

51–57). Conference Proceedings, Geological Society of London.

Pye, K. (1985). Electron-Microscope Analysis of Zoned Dolomite Rhombs in the Jet Rock

Formation (Lower Toarcian) of the Whitby Area, Uk. Geological Magazine, 122(3),

279–286. Journal Article.

Ramirez, S., Vieillard, P., Bouchet, A., Cassagnabere, A., Meunier, A., & Jacquot, E. (2005).

Alteration of the Callovo-Oxfordian clay from Meuse-Haute Marne underground

laboratory (France) by alkaline solution. I. A XRD and CEC study. Applied

Geochemistry, 20(1), 89–99. Journal Article.

http://doi.org/10.1016/j.apgeochem.2004.03.009

Read, D., Glasser, F. P., Ayora, C., Guardiola, M. T., & Sneyers, A. (2001). Mineralogical and

microstructural changes accompanying the interaction of Boom Clay with ordinary

Portland cement. Advances in Cement Research, 13(4), 175–183. Journal Article.

http://doi.org/10.1680/adcr.13.4.175.39287

Ruiz-Agudo, E., Kudłacz, K., Putnis, C. V, Putnis, A., & Rodriguez-Navarro, C. (2013).

Dissolution and carbonation of Portlandite [Ca(OH)2] single crystals. Environmental

Science & Technology, 47(19), 11342–9. http://doi.org/10.1021/es402061c

Savage, D., Arthur, R., Watson, C., & Wilson, J. (2010). An Evaluation of Models of

Bentonite Pore Water Evolution. Report Number, 12, 2000–456.

Serne, R. J., LeGore, V. L., Ames, L. L., LindenmeiRr, C. W., & Richland, W. (1993). Leach

testing of in situ stabilization grouts containing additives to sequester contaminants.

JOUR.

Sutton, M., Warwick, P., Hall, A., & Jones, C. (1999). Carbonate induced dissolution of

uranium containing precipitates under cement leachate conditions. Journal of

Environmental Monitoring : JEM, 1(2), 177–82. Retrieved from

http://www.ncbi.nlm.nih.gov/pubmed/11529097

Swift, B., Bamforth, P., Hoch, A., Jackson, C., Roberts, D., & Baston, G. (2010). Cracking ,

Flow and Chemistry in NRVB Report to the NDA RWMD, (3), 155.

Taylor, H. F. W. (1990). Cement chemistry. Library (Vol. 20). T. Telford.

http://doi.org/10.1016/S0958-9465(98)00023-7

Tinseau, E., Bartier, D., Hassouta, L., Devol-Brown, I., & Stammose, D. (2006).

Mineralogical characterization of the Tournemire argillite after in situ interaction with

concretes. Waste Management, 26(7), 789–800. Journal Article.

http://doi.org/10.1016/j.wasman.2006.01.024

Vennesland, O., & Gjorv, O. E. (1983). Silica Concrete-Protection Against Corrosion of

110

Embedded Steel, 11, 719–729. article.

Waters, C., Waters, R., Barclay, W., & Davies, J. (2009). A lithostratigraphical framework for

the Carboniferous successions of southern Great Britain (Onshore). Retrieved from

http://nora.nerc.ac.uk/8281/

Yogendran, V, Langan, B. . (1987). Utilization of Silica Fume in High Strength Concrete. In

Proceedings of the Symposium on Utilization of High Strength Concrete. incollection,

Stavanger: Tapir Publishers, Trondheim.

determination of reactions and integrity of cement

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