Characterisation of rendering mortars by squeeze-flow and rotational rheometry

F.A. Cardoso a, V.M. John a, R.G. Pileggi a , P.F.G. Banfill b

a Department of Construction Engineering, Escola Politécnica, University of São Paulo 05508 900, São Paulo, Brazil

b School of the Built Environment, Heriot-Watt University Edinburgh, EH14 4AS, United Kingdom

This paper reports the first experimental comparison between squeeze-flow at controlled

displacement rate and rotational shear at controlled speed for evaluating the rheological

behaviour of mortars. Several Brazilian and European rendering products showed a wide

range of workability behaviour in both testing modes. The flow curves and hysteresis effects

during the shear cycle varied significantly, since the mortar’s composition affects

structural breakdown, interfacial slip and phase segregation. The latter plays a critical role

during squeeze-flow and is the main reason for the higher loads required to deform the

samples at lower rates. A gravimetric-based methodology was developed to assess phase

segregation induced by rotational tests. Encouraging agreement between the methods was

observed, with yield stress in the structured (unsheared) state showing a good linear

correlation. For some mortars showing low segregation it was possible to compare shear

viscosity and extensional viscosity and Trouton ratios between 20 and 40 were obtained.

Keywords: Rheology (A), Mortar (E), Squeeze flow.

1. INTRODUCTION

Corresponding author

e-mail address: rafael.pileggi@poli.usp.br (Rafael G. Pileggi)

phone number: +55 1130915442

Inorganic mortars, besides being a fundamental portion of concretes, are also widely used

for bonding ceramic tiles, masonry and many rendering functions. Nowadays, rendering

products vary according to their use and/or placement method, with speciality mortars often

designed to meet more specific demands. The rheological requirements associated with the

various uses and processing combinations are, therefore, expected to be diverse as well.

Therefore proper rheological evaluation is crucial to providing useful information for the

optimisation of fresh mortar performance.

Rotational rheometry is capable of overcoming the limitations of the traditional single-point

methods, by evaluating concretes and mortars under a considerable range of shear rates

generated through the varying the rotation speed of the impeller or sample container [1-7].

The rheometer Viskomat (and its predecessor ViscoCorder), based on the latter setup with a

concentric stationary impeller on which torque is measured [1,2,7], has been extensively

applied to evaluate the flow behaviour of mortars and to determine the influence of mix

proportions [1,2,8-10], binder type [11], mineral and slag additions [2,10,12], sand

characteristics [13,14], admixtures [1,8,9,12,14-17] and fibres [18] on the Bingham

rheological parameters g and h (equation 1). In equation 1 T is torque, N is speed of

rotation and g and h are respectively proportional to yield stress and plastic viscosity [1-3].

T = g + hN Equation 1

However, problems were reported regarding wall slip during evaluation of low workability

(stiff) mortars in the equipment [1,8] and, moreover, phase segregation can be an issue

when testing highly fluid mortars such as self-compacting compositions, which has led to 2

the use of a basket probe to avoid both slippage and segregation [7,14]. The development /

evolution of methods for concretes and mortars generally seeks more adequate

experimental conditions through the use of specific devices / geometries and testing

routines [3-6,19] aiming to fulfil the basic physical requirements of no slip or segregation

for the proper application of rheological models and/or to simulate flow situations of

scientific or technological interest.

In this sense, squeeze-flow testing – i.e. compression of a cylindrical sample between

parallel plates – which is widely used in food, pharmaceuticals and suspensions [20-23],

has been applied as an alternative / complementary technique to assess the flow behaviour

of building materials such as cement paste [24-27], lime paste [28], gypsum plaster [29],

and mortars for adhesives [30-32], rendering [33-36], masonry [37], extrusion [38] and

fibre-reinforcement [39,40]. Its geometry change during gap reduction makes the method

particularly interesting, as it creates flow conditions similar to those involved in processing

and application of pastes and mortars (for example, flow through a narrow nozzle during

pumping or spraying; spread over a surface and then finishing; squeezing between bricks;

extrusion of cement-based materials). Furthermore, properties of the plate(s) such as

roughness [24,36,37] and absorption [27,37], can be altered in order to better simulate

application of the material to different substrates. The method may also be considered for

the mortar fraction of concretes, which is squeezed locally between coarse aggregates

during fresh concrete flow.

3

The radial flow caused by a squeezing force or displacement occurs by shear and/or biaxial

extension (or elongation) of the material, depending on the geometric setup (the likelihood

of shear increases with the sample’s diameter / height ratio) and on the boundary conditions

at the material-plate interfaces: for a no-slip condition, pure shear occurs but, conversely,

for perfect slip (no friction), only the extensional flow occurs [20,22,36]. In practice, both

types generally happen, but depending on the experimental setup (d/h and plate roughness)

and on the lubrication characteristics of the material, one or the other can be predominant

[20-22,36].

For building materials, previous publications [24,26] have employed both squeeze-flow and

rotation to investigate pure and modified cement pastes, and the comparison of methods

indicated significant differences between the behaviours measured. However, no systematic

comparison between the methods on the mortar scale has been reported. Therefore, the

main goal of this work is to compare the rheological behaviour of rendering mortars

evaluated by squeeze-flow and rotational rheometry.

2. EXPERIMENTAL

2.1 Materials

Fourteen proprietary factory-produced mortars (Table 1) were investigated, including

Brazilian (G, H, K, P, S, Z and Alfa) and European products from Scandinavia, Portugal

and UK (Eur1, Eur3, Eur4, Eur5, Eur6, Eur7 and Eur16) [36] designed for different

rendering purposes or application methods such as: (i) general render with multi-coat

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application (some also for masonry), (ii) one-coat render for external and/or internal areas,

(iii) final coat with smooth or scratched finish, (iv) renovation render of brick walls and (v)

final coat to receive dry dashing. Most products have both cement and lime as binders and

are recommended for manual application (manufacturers’ information) with exceptions

noted in Table 1. The products were delivered in bags and kept in airtight containers until

used.

Table 1 also shows aggregate (>75m) and matrix (<75m) contents (determined by

sieving, ASTM #200) and specific gravity (Helium pycnometry, Multi Pycnometer -

Quantachrome Instruments) of the dry mortar mixes, maximum aggregate size D99 (99% of

aggregates below this diameter as determined by laser diffraction using free fall dispersion

method, Malvern MSS Mastersizer) as well as specific surface area (N2 BET,

Micromeritics ASAP 2010) of the fines.

Table 1 - Mortar characteristics: type of rendering use, specific gravity (), aggregate and matrix volumetric contents, matrix specific surface area (SSA), maximum aggregate size (D99), water to solids weight percentage (w/s), fresh density at 15 minutes (Fresh), air content at 15 (Air15) and 55 minutes (Air55) after mixing of the batches used for rotational and squeeze tests.

2.2. Mixing procedure

Two-kilogram batches of the dry mortars were prepared in a five-litre capacity planetary

mixer (Hobart - N50) with the water content specified by the manufacturer’s information

on the bag (Table 1). The mixing procedure used consists of two steps, starting with the dry

mortar in the bowl and mixer at speed I: (1) continuous addition of half of the water content

5

in a constant rate (5g/s, during approximately 40s) followed by mixing until 60s; (2)

repetition of step 1, with the rest of the water. Total mixing time was 120s [36]. Distinct

batches were prepared for squeeze-flow and rotational experiments, and the times discussed

below are reckoned from the start of mixing.

2.3. Fresh density and air content

Apparent density was determined by gravimetric method with a 225ml container (Brazilian

standard ABNT NBR 13278) immediately after and 50min after mixing, respectively

ascribed as 15 and 55min values to facilitate association with the rheological results . In the

meantime the mortars remained at rest in the covered bowl. Air content was calculated

from the apparent density, water content and specific gravity.

2.4. Squeeze-flow

Squeeze-flow tests were conducted on a two-column universal testing machine (JJ Lloyd

Instruments - M5K) with a 6kN load cell. The bottom plate (200x150mm) was mounted

over the fixed compression base of the equipment and the top plate (diameter = 101mm)

fixed to the load cell at the crosshead. Plates were made of steel with smooth surfaces.

Immediately before testing, a cylindrical sample of fresh mortar (diameter = 101mm, height

= 10mm) [36] was cast over the clean and dry bottom plate using a plastic ring mould. The

squeeze-flow tests consisted of compressing the samples, at speeds of 0.1, 1 and 3mm/s, to

a maximum displacement of 9mm or maximum load of 1kN (whichever was reached first).

Squeeze-flow tests at the different speeds were performed consecutively on different

6

samples over a 10min period in the order 3, 1 and 0.1mm/s. The 15min tests were thus

complete by 25min after mixing and the 55min tests by 65min.

2.5. Rotational rheometry

The rheometer for pastes and mortars used (Viskomat NT - Schleibinger Testing Systems)

is a rotating cylindrical sample container plus a measuring head that monitors the torque

generated on the concentrically-fixed impeller due to the shear resistance of the material

flowing around its blades [1,2,7]. The details of the measuring system (Figure 1) are as

follows: sample volume ≈ 400ml; container diameter = 83mm; distance impeller - container

bottom ≈ 2mm; mortar impeller 3 (diameter 60mm) [11], distance blades 3 - container wall

= 13mm; mortar impeller 4 (diameter 49.6mm) [11], distance blades 4 - container wall =

18.2mm; the scraper was not used.

Fig. 1 Viskomat NT testing geometry (schematic).

Mortar impeller 4 (shorter blades) had to be utilized for the evaluation of stiff mortars K

and S due to torque overload with impeller 3, which was employed for all other products .

The correlation procedure is mentioned when appropriate.

The testing routine comprised a shear cycle (from 0 to 200rpm) applied through 15s steps at

50, 100, 150rpm and a 30s step at 200rpm, followed by a decrease to 150, 100, 50, 10, 0

rpm taking 180s in all. Samples were placed in the container up to the marked level a few

7

minutes before the tests, which were started 15, 35 and 55min after mixing started. There

was neither remixing nor reuse of specimens. Additional 35min-samples from the squeeze-

flow batches were also tested for control purposes.

2.6. Phase segregation tests

10 of the 14 products were subjected to the segregation tests based on gravimetric methods.

New batches of the mortars were prepared following the mixing procedure described in 2.2.

Segregation experiments consisted of three steps:

Step 1 – Rotation: Fresh mortar samples (400ml) were subjected to the same rotational

program used on Viskomat tests (2.5). The experiments were performed in the Poli-USP

rheometer [36] using a rotating container with the same dimensions as the Viskomat’s

container, but with no impeller shearing the sample.

Step 2 – Determination of water content: Immediately after the device stopped rotating, the

sample was divided in two parts (Border and Centre) using a metallic tool (internal

diameter = 56mm). Both portions were weighed before and after microwave drying

(Electrolux MEX55 - 1500W) for 20min.

Step 3 – Determination of particle size: Both dried mortar portions, Border and Centre,

were gently crushed by hand in a plastic bag and sieved. The material was sieved /

dispersed using a soft brush to break the agglomerates and to “clean" the aggregates from

the fine particles and then the samples were actually sieved with vibration for 1 hour. The

sieves used were: 2.8mm, 1.7mm, 1.0mm, 0.8mm, 0.6mm and 0.5mm.

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3. RESULTS AND DISCUSSION

3.1. Squeeze-flow

Fig. 2 shows the squeeze-flow results of the mortars tested 15 min after mixing. The load-

displacement curves show two distinct regions of behaviour: (i) viscous flow or plastic

deformation at low loads, with a roughly linear increase in deformation with small

increasing load, which undergoes a transition to (ii) strain hardening with a small increase

in deformation achieved in spite of a large increase in load [24,35,36]. The materials

presented a wide range of behaviour. High workability mortars flowed easily (G, Eur3,

Eur4 and Eur16), with a viscous flow stage at very low loads and extending for most of the

curves. The transition to the strain hardening stage occurred only at large displacements (>

6.5mm). The results obtained at different displacement rates were similar, with the curves

at 0.1mm/s in all cases shifted to higher loads than those at 3mm/s.

Fig. 2 - Squeeze-flow results of the mortars tested at 0.1 and 3mm/s, 15min after mixing.

Low workability or stiff mortars (K, P and S), on the other hand, were very difficult to

deform and the viscous flow stage was absent, with instead an intense strain hardening

stage, even at low strains. Curves at different displacement rates could be easily

9

differentiated. The behaviour of the mortars in the middle range of workability (H, Z, Alfa,

Eur1, Eur5, Eur6 and Eur7) varied in terms of the load level and extent to which the plastic

deformation / viscous flow stage occurred. Additionally, these mortars were influenced

more significantly by the displacement rate, with the loads at 3mm/s considerably lower

than those at 0.1mm/s, which resulted in an extended plastic deformation stage as well as

greater final displacement.

The strain hardening behaviour is associated with the friction between particles due to

geometry restriction or increase of solids concentration in the central region between the

plates [25,35,36,38]. The first occurs when the gap reaches a critical value near the

maximum particle size present in the material being tested, while the latter is related to

liquid-solid segregation. For granular suspensions and especially those like mortars that are

highly concentrated with macroscopic particles [25,35,36,38], radial migration of liquid

plays an important part in the rheological behaviour under squeeze-flow, as it causes an

increase of solids concentration in the central region of the sample and, consequently, of the

required loads. When the sample is squeezed at slow speeds the liquid has a long time to

flow outwards throughout the porous structure of packed particles (fines and aggregates),

and thus the likelihood of phase segregation is high. Conversely, when the sample is tested

at high displacement rates, the liquid may not have enough time to flow separately and the

chance of segregation is lower. The likelihood of segregation also increases as the

displacement increases and is inevitable at some stage if the gap is continuously reduced

[25,35,36,38] .

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For mortars, it has not yet been established experimentally whether the fluid-solid

segregation is due to water bleeding through fine particles or to paste separating from

aggregate, because the experiments reported so far were based on visual observations of

drainage [38] and water content measurements [36]. Nevertheless, phase segregation

depends on mortar characteristics as well [25,35,36,38]. The ease of flow of liquid through

the sample depends on its viscosity and the permeability of the packed particles: low

viscosity and high permeability result in compositions prone to segregation. This was

probably the case of Brazilian products K, P and S, since their results indicated that even at

3mm/s phase segregation was occurring and flow was still difficult. In contrast, the high

workability mortars (G, Eur3, Eur4 and Eur16) showed a lower likelihood of segregation

(probably due to their high air content 20-30%, which enhances the paste’s cohesion)

and could be deformed up to high strains even at 0.1mm/s.

The products with intermediate behaviour (H, Z, Alfa, Eur1, Eur5, Eur6 and Eur7) flowed

much more easily at 3mm/s than at 0.1mm/s and, except for Eur1, exhibited substantially

increased final displacement. The intense dependence of the rheological behaviour of these

mortars on the displacement rate suggests that the critical rate (minimum speed to obtain

homogeneous flow for most of the test [25,38] for each material lay within of near the 0.1-

3mm/s range.

It is also important to point out that, for each mortar, the plastic deformation (or viscous

flow) stage occurred at basically the same load level regardless of the displacement rate

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applied, and the point where the curves started to differ from each other is probably at the

displacement where fluid migration begins to affect the flow at 0.1mm/s more significantly.

Fig. 3 illustrates the relationship between the maximum displacement achieved during

squeeze-flow tests and the maximum particle size of the aggregates. Fig. 3(a) shows a

reasonable correlation at 3mm/s if mortars K, P, S and Eur1 are excluded, suggesting that,

when segregation is absent or minimal the material behaves like a homogeneous fluid, and

the maximum displacement is inversely proportional to D99 (99% by volume of aggregates

smaller than this value) and the minimum gap tends to this value. At 0.1mm/s (Fig. 3(b)),

the only data points that remained in the same region of the linear behaviour at 3mm/s

(dashed line) were those of mortars G, Eur3, Eur4 and Eur16 (which had a low segregation

tendency), while the others were scattered.

Fig. 3 - Maximum displacement under squeeze-flow vs. maximum particle size (D99) of the aggregates portion of the mortars tested 15min after mixing at (a) 3mm/s and (b) 0.1 mm/s. Linear regression of data at 3mm/s excluding K, P, S and Eur1 values is shown in (a) and displayed also in (b) as a dashed line just to guide the eyes.

3.2. Rotational rheometry

Raw rotational rheometry results (torque) for the mortars submitted to the speed profile

shown by the continuous black line at 15 and 55min after mixing are shown in Fig. 4 and

are presented as flow curves (torque vs speed) in Fig. 5. They group themselves into three

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types of behaviour. In the first group, the highly flowable mortars G, Eur4 and Eur16 (air

content 20-30%) the torque remained below 50N.mm and the flow curve showed a

Bingham plastic response (Fig. 5). The behaviour did not change significantly from 15 to

55min, and little or no structural breakdown was observed, as shown by the close

coincidence of the up and down curves and nearly zero hysteresis area (Fig. 5(a)). The

Bingham model was applied to the down curves and the parameters g and h and the

correlation coefficient (R2) are shown in Table 2. h was around 4N.mm.s for G and Eur16

and 2N.mm.s for Eur4, while g remained in the 15-30N.mm range. Table 2 also presents

the torque at 10rpm (T10rpm) during the upcurve, which can be taken as a proxy for the initial

yield stress in an unsheared (fully structured) condition. For these mortars, g and T10rpm

were very similar since there was little or no structural breakdown.

Fig. 4 - Torque vs. time results of the mortars tested in the Viskomat 15 and 55min after mixing.

In the second group, products Eur5, Eur6 and Eur7 were stiffer and displayed higher torque

levels (40-90N.mm). Eur7 showed little structural breakdown even after 55min because it is

a lime-based mortar. Neither did Eur6 at 15min (Fig. 5(a)) but, after 55min, the torque

levels of Eur6 increased significantly, and there was significant structural breakdown. Eur5

had the highest torque values and the greatest hysteresis area of this group. It is also

important to point out that the Eur5 curves (torque vs. time, Fig. 4) were the most scattered

of all results, probably due to its large maximum aggregate size (4mm) interfering with the

flow between the impeller and the container wall. The common feature of all Eur5, Eur6

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and Eur7 curves is an increase of torque at 10rpm at the end of the tests, which can be

observed in both Figures 4 and 5, and seems to be a designed thixotropic behaviour, since

these three mortars are from the same producer. Because of this behaviour, the linear fitting

of the downcurves was difficult (resulting in some negative h values), and, for Eur6 and

Eur7 the linear fitting excluded the torque values at 10rpm (Table 2). Table 2 shows that for

these three mortars T10rpm is much higher than g, confirming the structural breakdown. g

was practically the same ( 40-50N.mm) for these materials (and about double that of G,

Eur4 and Eur16), while h was 4-5N.mm.s for Eur5 and 1-3N.mm.s for Eur6 and Eur7.

Fig. 5 - Flow curves showing torque vs. rotation speed for the mortars tested 15 min after mixing. Torque values taken at the end of each speed step.

In Fig.4b and Fig.5b at 15min mortars Z and Eur3 behaved similarly to G, Eur4 and Eur16

with little structural breakdown and nearly zero hysteresis but at higher torque levels. At

55min Z showed some breakdown during the upcurve, but the down curves practically

coincide and consequently g and h values are very similar at 15 and 55min (Table 2). On

the other hand, at 55min Eur3 showed some signs of structural breakdown and, most

importantly, underwent the highest shift of torque over time. This behaviour can be

ascribed mainly to its substantial loss of entrained air, from 23.5 to 13% (Table 1). At

55min, Eur3 also showed an increase of torque at 10rpm (like Eur5-7) and this value had to

be eliminated from the fitting.

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Mortars H and Eur1 (Fig. 4b) showed the typical breakdown pattern of an increase of

torque with rotation speed followed by its decrease during the dwell time at each speed [1-

3] at both tested times. For Eur1 this pattern was more intense and occurred at higher

torques, especially at 55min. Hysteresis area (even at 15min) was large for both mortars

(Fig. 5b) and, although T10rpm was considerably higher (especially for H) than for the other

mortars, and g of both H and Eur1 was similar (40N.mm, Table 2), h of Eur1 (20N.mm.s)

was twice that of H, and both were considerably higher than h of the other materials (Table

2). Besides lying at the same torque levels of Eur1, the behaviour of mortar Alfa was the

reverse, as it presented only a little structural breakdown at the beginning of the test (small

hysteresis area), the highest g and T10rpm (Table 2) and low h (4N.mm.s at 15min).

Table 2 - Rotational parameters of the mortars tested 15 and 55min after mixing: T10rpm = torque at 10rpm during accelerating curve; g = torque proportional to Bingham yield stress; h = parameter proportional to Bingham plastic viscosity; R2 = coefficient of determination of the linear regression (downcurves).

The final group were the stiff mortars K, P and S and their results are shown in Figures 4c

and 5c. Due to their stiffness, products K and S could not be tested using the mortar

impeller 3 because the torque overloaded the transducer and the instrument cut out. Hence,

these mortars were tested with impeller 4 (with shorter blades) and a calibration curve was

constructed from the ratio of the results of mortar P tested with both impellers at 35min. In

Figure 4c, an intense reduction of torque during the upcurve can be seen for all three

mortars (K, P and S) and, then, the torque remained almost constant for mortar P, while for

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K and S it continued reducing slightly. As a consequence, flow curves (Fig. 5c) show a

significant drop during the upcurves and an almost horizontal line for the downcurves.

Such unusual behaviour may be a result of slippage at the mortar-container interface due to

their very low workability [1] and the smooth container surface. A second possibility is the

loss of contact between the blades and the material during the test. After the first few

revolutions of the container, a hole in the centre of the sample may be created if the

material is insufficiently fluid to flow back after being deformed. In these plastic mortars

with high yield stress the impeller could be underestimating the resistance to flow. Visual

confirmation of this possibility is hindered by the design of the instrument.

Thirdly the behaviour may be due to phase segregation, with the aggregates moving

radially out of the measuring zone. The fact that mortars K, P and S presented very low

displacements during squeeze-flow tests (Fig.2), which were characterized by a strain-

hardening behaviour caused by phase segregation (liquid phase migrates radially and

increases solids concentration in the central region) is consistent with this suggestion.

Furthermore, previous work on fibre cement composites reported that stiff compositions

with strain-hardening behaviour in a cone consistency test resulted in heterogeneous

products when cast by spinning [41].

Further investigation of the segregation in these stiff mortars under rotational testing is

described in the next section but it is clear that the results of K, P and S are compromised.

3.3 Phase segregation

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The occurrence of phase segregation during rotational testing was assessed by simulating

the rotation program by gravimetric methods. Table 3 confirms that all mortars contained

more water in the centre than in the border of the sample, although the relative difference

was small (around 1%) for most of the products. Mortars P and Eur5 presented higher

values of approximately 3%, while mortar S, with almost 10%, showed the most fluid-solid

segregation.

Table 3 – Water content and difference in water content between the Centre and Border of

the samples subjected to rotational segregation tests.

As the container rotates a centripetal acceleration is generated and, for the configuration

with paddle 3, at 200rpm (maximum rotation speed) this acceleration varies from 7m/s2 at

the middle of the blades to 18m/s2 near the container wall. Depending on the viscosity of

the paste and the size of the aggregates, the latter moves radially outwards of the measuring

zone, hence increasing the water content in the centre.

Segregation as a function of particle size was small, but also took place as can be seen in

Table 4. Most of the mortars presented a slightly higher content of bigger particles in the

border (positive values), while the centre had more particles smaller than 0.6mm (negative

values). Mortars Eur5 and Eur6 displayed more significant differences of particles greater

than 1mm.

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Table 4 – Particle content as a function of size and difference in particle content between

the Centre and Border of the samples subjected to rotational segregation tests.

Among the stiff mortars, S showed the most liquid-solid segregation, while P showed a

moderate difference in water content and K’s water content remained practically

homogeneous. The differences in particle size distribution between centre and border were

very low for all three products. Therefore, it seems that phase segregation cannot explain

the unusual rheological results for P, K and S, since a more significant segregation was

measured only for S. While segregation is certainly occurring for these mortars, it is not

clear whether these levels of segregation have any measurable influence on the rheological

behavior.

3.4. Comparison of rheological parameters

In order to compare the results of rotational and squeeze-flow testing it is necessary to use

fundamental units of stress and viscosity.

3.4.1. Yield stress

As already noted, the initial yield stress was taken from the torque at 10 rpm (T10rpm ) in the

upcurve. There are two reasons for this: (1) in the very beginning of the rotational test there

is no influence of phase segregation or slippage and (2) the squeeze-flow tests were

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performed on unsheared specimens. Prior calibration of impeller 3 [11] gives the initial

yield stress 10rpm in Pa as

10rpm = 6.417 x 10rpm Equation 2

The squeeze-flow yield stress assumed for the comparison was the normal stress (load /

area of the top plate) at 0.5mm of displacement 0.5mm) (5% strain) taken from the low

speed (0.1mm/s) tests.

The comparison of yield stress results in Fig. 6 indicates a coherent behaviour between the

values obtained by the different techniques. If the stiff mortars (K, P and S) are excluded

there is a reasonable linear correlation, which is an encouraging result from this, the first

comparative investigation of rotational and squeeze-flow rheometry. Further work to

resolve the approximately five-fold difference in yield stresses is justified. Factors that

could contribute to this difference are (i) the fact that the calibration of the Viskomat is

based on the behaviour of the flowing material, leading to a yield stress obtained by

extrapolation to zero shear rate [1], whereas initial yield stress is a static measurement, and

(ii) the state of the structure existing in the mortar at 10rpm in the Viskomat and at 0.5mm

squeeze-flow displacement may not be identical, particularly since structure is very

sensitive to shear history in the early stages of shearing [3].

Fig. 6 - Shear stress at 10rpm during accelerating curve (10rpmvs. squeeze stress at 0.5mm and 0.1mm/s 0.5mm). Linear regression: K, P and S (green); other mortars tested at 15 (blue), 55 (red) and 15 + 55min (black).

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3.4.2. Viscosity

Comparison of viscosity results is a more complex issue because rotational rheometry

estimates shear viscosity but during squeeze-flow both extensional and shear strains occur

and which is dominant depends on the interfacial slip conditions. In the present work, the

boundary condition was defined as a perfect-slip interface owing to the use of smooth

metallic plates, so a biaxial extensional model was assumed [21,35]. However, as the

rheological models require that the fluid remains homogeneous during the tests, extensional

viscosity curves were calculated as follows, for only those mortars that displayed low

segregation – G, Eur3, Eur4 and Eur16. The biaxial extensional strain rate ( ε̇B ) is equal to

one-half the vertical Hencky strain rate ( ε̇ H ) [21,35]:

ε̇ B=ε̇H

2= v

(2 h ) Equation (3)

where: h is the instantaneous height of the sample, v is the displacement velocity of the

top plate. The extensional viscosity (ηB ) is defined as the ratio between the biaxial

extensional stress (σB ) , which is the squeezing load divided by the top plate area, and the

extensional strain rate:

ηB=σ B

ε̇ B=2 L[ h0−(vt )

vπR2 ] Equation (4)

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where: L is the load, h0 is the initial height and R is the radius of the sample [21,35].

Fig. 7 shows biaxial extensional viscosity curves as a function of the extensional strain rate,

for the mortars tested both at 0.1 and 3mm/s. Viscosity values increased when the strain

rate increased as a result of gap reduction for all the tested samples, however after a

compaction phase that occurs at the beginning of each curve a plateau value is reached after

which the viscosity starts to increase significantly as strain-hardening starts The plateau

value is taken as the biaxial extensional viscosity and varies by almost two orders of

magnitude, indicating that extensional viscosity of mortar is very sensitive to the

displacement rate used in the test.

Fig. 7 - Biaxial extensional viscosity B) vs. biaxial extensional strain rate °B) curves of

mortars G, Eur3, Eur4 and Eur16 tested 15min after mixing. Curves showing the variation of biaxial extensional strain rate °

B) with displacement at each speed are also shown.

Because mortar is non-Newtonian comparisons of viscosity between different techniques

must be done at the same strain rate. From equation 3 and Fig. 7 the extensional strain rate

at 5mm of displacement is 0.01 s-1 at 0.1mm/s and 0.3 s-1 at 3mm/s. The apparent viscosity

app of a Bingham material under rotational shear at a shear rate γ̇ is given by:

ηapp=τγ̇=

τ0+μ γ̇γ̇ Equation 4

21

where τ 0and μ are the yield stress and plastic visosity, respectively. To ensure a similar

degree of structural breakdown in each technique, the torque value at 10rpm during the

upcurve (T10rpm) is used. The corresponding yield stress is given by [1]:

τ 0=K

G×T 10rpm Equation 5

where K

G=6. 42

by calibration of the Viskomat [11]. The plastic viscosity, obtained from

h, the slope of the downcurve, is given by [1]:

μ=1G

×hEquation 6

where 1

G=0 . 709

by calibration [11]. Using equations 4, 5 and 6, the apparent viscosity

under rotational shear can be calculated at the two shear strain rates of 0.01 and 0.3 s -1.

Table 5 summarises the resulting shear and extensional viscosities.

Table 5 – Comparison of viscosities at strain rates of 0.01 and 0.3s-1. Shear: apparent viscosity at 0.066rpm (app0.066) and 1.98 rpm (app1.98). Biaxial extension: viscosity at displacement of 5mm and velocities of 0.1mm/s B0.1) and 3mm/s B3).

The clear points to emerge from Table 5 are that the two measurement techniques place the

viscosity of the four mortars in the same rank order, that viscosity decreases with increasing

shear rate and that extensional viscosity is 20-40 times the shear viscosity. These are further

22

encouraging results from this comparison of rotational and squeeze-flow rheometry. The

ratio between extensional and shear viscosity, the Trouton ratio, for a Newtonian liquid in

biaxial extension is 6 [42], while for non-Newtonian liquids, such as polymer solutions,

which are prone to entanglement of chains and show significant elasticity, values up to

3000 have been reported. The results in Table 5 are consistent with mortar being a granular

but relatively inelastic material.

4. CONCLUSIONS

The first systematic comparison of squeeze-flow and rotational rheometry (Viskomat) for

evaluation of rendering mortars with a wide range of workability levels has been

performed. The products presented three main groups of behaviour when tested by squeeze-

flow. The first group included mortars that could be easily deformed up to large

displacements with low loads both at slow and fast displacement rates, without phase

segregation. On the other hand, a group of stiff mortars were very difficult to squeeze (even

at faster rates) and required high loads to achieve only small deformations, mainly as a

result of phase segregation in the test. The intermediate group was mainly composed of

materials that were sensitive to the rate of squeeze-flow displacement: at higher rates the

loads were lower and consequently larger maximum displacements were achieved, while at

lower rates phase segregation had time to occur and mortar flow was more difficult.

Besides the occurrence of segregation, which also depends on mortar characteristics such as

paste viscosity and aggregate packing permeability, the results showed that the maximum

particle size in the material limits the maximum displacement (or minimum gap) that can be

achieved.

Rotational test results not only confirmed the wide range of torque levels of the materials

tested, but also pointed out differences in measured rheological parameters (plastic

viscosity and yield stress) and structural breakdown. In general, the results agreed between

23

the two test methods, which were able to arrange the materials in the same rank order.

Yield stresses in squeeze-flow were about five times those in rotation, while extensional

viscosities were 20-40 times the shear viscosities.

The stiff mortars were difficult to evaluate properly by rotational rheometry, resulting in

unusual flow curves, due either to wall slippage (on the mortar-container interfaces) or to

loss of contact between mortar and impeller blades. While low to moderate liquid-solid and

particle size segregation took place during rotational testing, this does not seem to be the

main cause of the behaviour of the stiff mortars (K, P and S). Nevertheless, an experimental

methodology for the evaluation (both identification of type and quantification) of the

segregation phenomenon was successfully developed and can be used as complementary

technique to provide a better understanding of the rheological results of concentrated

suspensions containing macroscopic particles.

ACKNOWLEDGEMENTS

The authors would like to thank: the Brazilian agencies FAPESP and CNPq for funding;

Fábio Campora (ABAI – Brazilian Association of Mortar Industries), CONSITRA

(Brazilian Consortium for Innovation of Rendering Mortars Technology), Votomassa and

Cimpor Brasil for support; Dr. Paul Houang and Weber Saint-Gobain (Brazil and Europe)

for major assistance with European products; Andy Cowland (CPI Euromix) for mortar

samples; and at Heriot-Watt University, Dr. Gerry Starrs for rheometer instructions and

James Maguire for laboratory assistance.

REFERENCES

24

[1] P.F.G. Banfill, Use of the ViscoCorder to study the rheology of fresh mortar, Mag. Concr. Res. 42 (153) (1990) 213 – 221.

[2] P.F.G. Banfill, The rheology of fresh mortar, Mag. Concr. Res. 43 (154) (1991) 13 – 21.

[3] P.F.G. Banfill, Rheology of fresh cement and concrete, Rheol. Rev. (2006) 61–130 [British Society of Rheology].

[4] E.P. Koehler, D.W. Fowler, Summary of concrete workability test methods, ICAR Report 105.1, International Center of Aggregates Research, Austin, 2003.

[5] C.F. Ferraris, L.E. Brower (editors), Comparison of concrete rheometers: International tests at LCPC (Nantes, France), NISTIR 6819, National Institute of Standards and Technology, Gaithersburg, 2001.

[6] R.G. Pileggi, V.C. Pandolfelli, A.E. Paiva, J. Gallo, Novel rheometer for refractory castables, Am. Ceram. Soc. Bull. 79 (2000) 54-58.

[7] Schleibinger Testing Systems. http://www.schleibinger.com.

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[9] M.P. Seabra, J.A. Labrincha, V.M. Ferreira, Rheological behaviour of hydraulic lime-based mortars, J. Eur. Ceram. Soc. 27 (2007) 1735–1741.

[10] L. Senff, J.A. Labrincha, V.M. Ferreira, D. Hotza, W.L. Repette, Effect of nano-silica on rheology and fresh properties of cement pastes and mortars, Constr. Build. Mater. 23 (2009) 2487-2491.

[11] A. Montier, Rheology of mortar containing hydraulic lime binders. MSc Dissertation. Heriot-Watt University, Edinburgh, 2007.

[12] M. Palacios, P.F.G. Banfill, F. Puertas, Rheology and Setting of Alkali-Activated Slag Pastes and Mortars: Effect of Organic Admixture, ACI Mater. J. 105 (2008) 140-148.

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[14] U. Stark, K. Ostheeren, Rheology of SCC-Mortars with sands of different shape, in 18 Colloquy and Workshop: Rheological Measurements of Building materials, Regensburg, (2009) electronic.

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[15] J. Golaszewski, J. Szwabowski, Influence of superplasticizers on rheological behaviour of fresh cement mortars, Cem. Concr. Res. 34 (2004) 235-248.

[16] M.P. Seabra, H. Paiva, J.A. Labrincha, V.M. Ferreira, Admixtures effect on fresh state properties of aerial lime based mortars, Constr. Build. Mater. 23 (2009) 1147–1153.

[17] H. Paiva, L.P. Esteves, P.B. Cachim, V.M. Ferreira, Rheology and hardened properties of single-coat render mortars with different types of water retaining agents, Constr. Build. Mater. 23 (2009) 1141–1146.

[18] P.F.G. Banfill, G. Starrs, G. Derruau, W.J. McCarter, T.M. Chrisp. Rheology of low carbon fibre content reinforced cement mortar, Cem. Concr. Comp. 28 (2006) 773–780.

[19] M.R. Geiker, M. Brandl, N. Thrane, D.H. Bager, O. Wallevik, The effect of measuring procedure on the apparent rheological properties of self-compacting concrete, Cem. Concr. Res. 32 (2002) 1791-95.

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[21] J.F. Steffe, Rheological Methods in Food Process Engineering, Freeman Press, USA, 1996.

[22] G.H. Meeten, Constant-force squeeze flow of soft solids, Rheol. Acta 41 (2002) 557–566.

[23] E.C. McIntyre, F.E. Filisko, Squeeze flow rheology of zeolite suspensions, Appl. Rheol. 19 (2009) 44322.

[24] B.H. Min, L. Erwin, H.M. Jennings, Rheological behavior of fresh cement paste as measured by squeeze flow, J. Mater. Sci. 29 (1994) 1374-1381.

[25] P.H. Phan, M. Chaouche, Rheology and stability of self-compacting concrete cement pastes, Appl. Rheol. 15 (2005) 336.

[26] R.G. Pileggi, A.M. Betioli, F.A. Cardoso, V.M. John, Extended rheological characterization of cement pastes: squeeze flow plus rotational rheometry, in Proc.12th Int. Congress on the Chemistry of Cement, Montreal, (2007) electronic.

[27] W.S. Barbosa, V.M. John, R.G. Pileggi, Alteration of rheological behavior of cement pastes due to the presence of porous substrates, in Proc. VII Brazilian Symposium on Mortar Technology, Curitiba, (2009) electronic (in Portuguese).

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[29] F.A. Cardoso, A.K. Agopyan, C. Carbone, V.M. John, R.G. Pileggi, Squeeze flow as a tool for developing optimized gypsum plasters, Constr. Build. Mater. 23 (2009) 1349.

[30] Y.V. Póvoas, Evaluation of film formation on adhesive mortars and its influence on adhesion, Doctoral thesis, Department of Construction Engineering, University of São Paulo, São Paulo, 2005 (in Portuguese).

[31] M.R.M.M. Costa, M.A. Cincotto, R.G. Pileggi, Comparative analysis of adhesive mortars and their rheological behaviour, in Proc. VI Brazilian and I Int. Smposium on Mortar Technology, Florianopolis, (2005) 382-394 (in Portuguese).

[32] E.K. Kudo, F.A. Cardoso, R.G. Pileggi, Squeeze-flow applied to adhesive mortars: influence of experimental parameters: setup and displacement rate, in Proc. IX Brazilian Symposium on Mortar Technology, Belo Horizonte, electronic (2011) (in Portuguese).

[33] F.A. Cardoso, R.G. Pileggi, V.M. John, Rheological characterisation of mortars using a squeeze-flow test, in Proc. VI Brazilian and I Int. Symposium on Mortar Technology, Florianopolis, (2005) 121-143 (in Portuguese).

[34] Antunes, R.P.N. Influence of rheological behaviour and impact energy on the Bond strength of rendering mortars. Doctoral thesis, Department of Construction Engineering, University of São Paulo, São Paulo, 2005 (in Portuguese).

[35] F.A. Cardoso, V.M. John, R.G. Pileggi. Rheological behavior of mortars under different squeezing rates, Cem. Concr. Res., 39, 748-753, 2009.

[36] F.A. Cardoso, Mix design method for rendering mortars based on particle size distribution and rheological behaviour, Doctoral thesis, Department of Construction Engineering, University of São Paulo, São Paulo, 2009 (in Portuguese).

[37] R. Hendrickx. The adequate measurement of the workability of masonry mortar, Doctoral Thesis, Katholieke Universiteit Leuven – Faculty of Engineering, Leuven, 2009.

[38] Z. Toutou, N. Roussel, C. Lanos, The squeezing test: a tool to identify firm cement-based material’s rheological behaviour and evaluate their extrusion ability, Cem. Concr. Res. 35 (2005) 1891-1899.

[39] R.P. Silva, Polypropylene fiber-containing mortars – evaluation of rheological and mechanical behaviours, MSc Dissertation, Department of Construction Engineering, University of São Paulo, São Paulo, 2006 (in Portuguese).

[40] F. Chalencon, L. Orgéas, P.J.J. Dumont, G. Foray, J.Y. Cavaillé, S. Maire, S.R Roscoa, Lubricated compression and X-ray microtomography to analyse the rheology of a fibre-reinforced mortar, Rheol. Acta 49 (2010) 221-235.

27

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[42] C.J.S. Petrie, Extensional viscosity: a critical discussion, J. Non-Newtonian Fluid Mech. 137 (2006) 15-23.

Figures

28

Fig. 1 Viskomat NT testing geometry (schematic)

29

0

200

400

600

800

1000

0 1 2 3 4 5 6 7 8 9

Load

(N)

Displacement (mm)

(a)

G_0.1

G_3

K_0.1mm/s

K_3mm/s

H_0.1 H_3

Z_0.1

Z_3

0

200

400

600

800

1000

0 1 2 3 4 5 6 7 8 9

Load

(N)

Displacement (mm)

(b) Eur1_0.1

Eur1_3P_0.1mm/s P_3mm/s

Eur3_0.1

Eur3_3

Eur16_0.1

Eur16_3

Alfa_0.1

Alfa_3

0

200

400

600

800

1000

0 1 2 3 4 5 6 7 8 9

Load

(N)

Displacement (mm)

(c)

Eur4_0.1

Eur4_3

S_0.1mm/s

S_3mm/s

Eur5_0.1 Eur5_3Eur7_0.1

Eur7_3

Eur6_0.1

Eur6_3

Fig. 2 - Squeeze-flow results of the mortars tested at 0.1 and 3mm/s, 15min after mixing.

30

GH Z

Alfa

Eur3Eur4

Eur5Eur6

Eur7Eur16

KP

S

Eur1y = -0.6802x + 9.7358

R² = 0.605

0

2

4

6

8

10

0 1 2 3 4

Max

imum

disp

lace

men

t (m

m)

D90 (mm)

(a) 3mm/s

G

H

KP

S

Z Alfa

Eur1

Eur3Eur4

Eur5Eur6

Eur7

Eur16

0

2

4

6

8

10

0 1 2 3 4

Max

imum

disp

lace

men

t (m

m)

D99 (mm)

(b) 0.1mm/s

Fig. 3 - Maximum displacement under squeeze-flow vs. maximum particle size (D99) of the

aggregates portion of the mortars tested 15min after mixing at (a) 3mm/s and (b) 0.1 mm/s.

Linear regression of data at 3mm/s excluding K, P, S and Eur1 values is shown in (a) and

displayed also in (b) as a dashed line just to guide the eyes.

31

0

50

100

150

200

10

50

90

0 1 2 3

Spee

d (r

ev/m

in)

Torq

ue (N

.mm

)

Time (min)

(a)G_55min G_15min Eur4_55 Eur4_15Eur16_55 Eur16_15 Eur5_55 Eur5_15Eur6_55 Eur6_15 Eur7_55 Eur7_15

0

50

100

150

200

10

50

90

130

170

0 1 2 3

Spee

d (r

ev/m

in)

Torq

ue (N

.mm

)

Time (min)

(b)H_55min H_15min Z_55 Z_15Alfa_55 Alfa_15 Eur1_55 Eur1_15Eur3_55 Eur3_15

0

50

100

150

200

10

50

90

130

170

210

250

290

0 1 2 3

Spee

d (r

ev/m

in)

Torq

ue (N

.mm

)

Time (min)

(c)K_55min K_15min P_15S_55 S_15 Speed

Fig. 4 - Torque vs. time results of the mortars tested in the Viskomat 15 and 55min after

mixing.

32

10

50

90

0 50 100 150 200

Torq

ue (N

.mm

)

Speed (rev/min)

(a)G Eur4 Eur16Eur5 Eur6 Eur7

10

50

90

130

170

0 50 100 150 200

Torq

ue (N

.mm

)

Speed (rev/min)

(b)H Z Eur1 Eur3 Alfa

10

50

90

130

170

210

250

290

0 50 100 150 200

Torq

ue (N

.mm

)

Speed (rev/min)

(c)K P S

Fig. 5 – Flow curves showing torque vs. rotation speed for the mortars tested 15 min after

mixing. Torque values taken at the end of each speed step.

33

KP

S

K

S

y = 0.12x + 1.19R² = 0.96

y = 0.21xR² = 0.92

y = 0.19xR² = 0.63

y = 0.20xR² = 0.80

0.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

0 2 4 6 8 10 12

10

rpm

(kPa

)

0.5mm (kPa)

K P S

15min

55min

Linear (15+55min)

Fig. 6 - Shear stress at 10rpm during accelerating curve (10rpmvs. slow speed (0.1mm/s)

squeeze stress at 0.5mm 0.5mm). Linear regression: K, P and S at 15 and 55min (green);

other mortars tested at 15 (blue), 55 (red) and 15 + 55min (black).

34

0

1

2

3

4

5

6

7

8

9

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E-03 1.E-02 1.E-01 1.E+00

Disp

lace

men

t (m

m)

B

(Pa.

s)

.B (s-1)

GEur3Eur4Eur16

0.1mm/s3mm/s

Fig. 7 - Biaxial extensional viscosity B) vs. biaxial extensional strain rate °B) curves of

mortars G, Eur3, Eur4 and Eur16 tested 15min after mixing. Curves showing the variation

of biaxial extensional strain rate °B) with displacement at each speed are also shown.

Tables

Table 1 - Mortar characteristics: type of rendering use, specific gravity (), aggregate and

matrix volumetric contents, matrix specific surface area (SSA), maximum aggregate size 35

(D99), water to solids weight percentage (w/s), fresh density at 15 minutes (Fresh), air

content at 15 (Air15) and 55 minutes (Air55) after mixing of the batches used for rotational

and squeeze tests.

AgregMatrix SSA D99 w/s Fresh Air15 Air55 Air15 Air55

(g/cm3) (%v) (%v) (m2/g) (mm) (%wt) (g/cm3) (%) (%) (%) (%)

G generalc 2.68 80.2 19.8 2.5 2.2 15.0 1.68 23.6 21.5 22.8 18.9H one coatd 2.85 60.2 39.8 1.6 1.4 16.5 1.99 12.2 11.6 12.8 -K general 2.47 71.6 28.4 5.1 0.6 18.0 1.99 1.4 0.1 1.4 0.5P generalc 2.69 66.9 33.1 4.1 0.8 16.0 2.00 8.2 - 9.7 9.0S generalc 2.72 83.9 16.1 4.0 2.0 17.0 1.99 8.6 7.5 8.2 -Z one coat 2.79 76.0 24.0 1.1 1.9 17.2 1.71 22.7 20.7 24.4 -

Alfa one coat 2.65 73.3 26.7 1.8 2.7 15.0 1.91 12.5 10.5 - -Eur1 internal 2.67 73.1 26.9 2.0 1.8 16.0 1.91 11.8 8.9 13.6 -Eur3 one coate 2.66 64.2 35.8 1.1 3.0 21.0 1.58 23.5 13.0 19.1 12.7Eur4 generald 2.68 71.1 28.9 1.7 2.7 18.0 1.67 21.6 - 18.1 16.8Eur5 scratched 2.74 76.0 24.0 3.8 4.0 16.0 2.06 6.7 - 5.5 4.3Eur6 renovationf 2.60 78.6 21.4 2.7 2.7 18.0 1.80 14.0 - 11.2 8.9Eur7 smoothg 2.61 68.5 31.5 4.6 1.2 24.0 1.77 11.0 - 7.6 5.3Eur16 dash receiv.e 2.62 85.7 14.3 - 0.6 20.0 1.43 31.6 - 30.9 27.4

Mortar Renderinguse

Rotational rheometry Squeeze-flow Anhydrous characteristics

c also used for masonry; d also for spray application; e for spray application; f hydraulic lime-based mortar; g lime-based mortar.

Table 2 - Rotational parameters of the mortars tested 15 and 55min after mixing: T10rpm =

torque at 10rpm during upcurve; g = torque proportional to Bingham yield stress; h =

parameter proportional to Bingham plastic viscosity; R2 = coefficient of determination of

the linear regression (downcurves). 36

G Eur4 Eur16 Eur5 Eur6 Eur7 H Z Eur1 Eur3 Alfa K P ST10rpm (N.mm) 28 27 17 83 63 67 123 67 85 54 130 271 214 282

g (N.mm) 26 20 16 37 39 43 41 39 42 42 80 31 70 49h (N.mm.s) 5.3 1.8 4.6 4.0 1.8 1.3 10.3 5.9 20.1 8.1 3.4 2.5 2.8 1.3

R2 0.98 0.99 0.98 0.82 0.83 0.97 0.99 0.97 0.99 0.98 0.88 0.45 0.88 0.42T10rpm (N.mm) 33 33 20 109 129 84 137 90 136 124 172 357 - 405

g (N.mm) 29 22 19 49 48 49 48 44 48 94 78 36 - 78h (N.mm.s) 3.8 1.6 4.3 5.0 3.6 1.5 9.4 4.4 23.7 5.7 7.3 2.4 - 0.1

R2 0.99 0.95 0.99 0.70 0.92 0.90 0.95 0.93 0.99 0.86 0.98 0.51 - 0.01Obtained by linear fitting excluding torque at 10rpm

Mortar

15m

in55

min

Parameter

Table 3 – Water content and difference in water content between the Centre and Border of

the samples subjected to rotational segregation tests.

37

G 13.04 12.70 12.85 12.75 0.15 1.17K 15.25 14.86 14.98 14.91 0.12 0.81P 13.79 13.51 13.94 13.71 0.43 3.16S 14.53 13.65 15.06 14.35 1.41 9.83Z 14.68 14.36 14.64 14.50 0.28 1.94

Eur3 17.36 17.01 17.13 17.07 0.11 0.67Eur4 15.25 14.98 15.16 15.06 0.18 1.18Eur5 13.79 13.06 13.42 13.23 0.36 2.72Eur6 15.25 14.89 15.11 15.00 0.22 1.45Eur7 19.35 19.03 19.23 19.12 0.21 1.07

h Centre-Border; i 100*(Centre-Border)/Total

Water content (%wt) Difference (%)

Absoluteh RelativeiMortar

Nominal Border Centre Total

Table 4 – Particle content as a function of size and difference in particle content between

the Centre and Border of the samples subjected to rotational segregation tests.

38

<0.6 0.6-1.0 >1.0 <0.6 0.6-1.0 >1.0G 73.4 22.6 3.9 0.12 -0.14 0.02K 98.5k 1.4l 0.1m -0.045k 0.04l 0.005m

P 97.9 2.1 0.0 0.10 -0.10 0.00S 92.3 4.9 2.8 -0.20 0.07 0.13Z 92.5 6.0 1.5 -0.12 0.14 -0.02

Eur3 78.8 9.1 12.1 -0.58 0.47 0.10Eur4 87.8 8.1 4.1 -0.57 0.13 0.44Eur5 55.5 11.1 33.4 -1.22 0.00 1.22Eur6 69.6 15.1 15.2 -0.93 -0.70 1.63Eur7 93.8 6.0 0.2 -0.30 0.32 -0.02

j Border particle content-Centre particle contentk <0.5mm; l 0.5-0.6mm; m >0.6mm

Mortar Total Absolute difference j

Size (mm)

Particle content (%wt)

Size (mm)

39

Table 5 – Comparison of viscosities at strain rates of 0.01 and 0.3s-1. Shear apparent

viscosity at 0.066rpm (app0.066) and 1.98 rpm (app1.98). Biaxial extension: viscosity at

displacement of 5mm and velocities of 0.1mm/s B0.1) and 3mm/s B3).

0 η app0.066 η app1.98 ηB0.1 ηB3 0.01s-1 0.3s-1

Pa Pa.s kPa.s kPa.s kPa.s kPa.s ηB/η app ηB/η app

G 180 3.8 18 0.6 460 12 25.6 19.9Eur3 347 5.7 35 1.2 1177 30 33.9 25.8Eur4 173 1.3 17 0.6 458 12 26.5 20.8Eur16 109 3.3 11 0.4 430 10 39.4 27.3

Shear Extensional ComparisonMortar