analysis of the mechanical characteristics of facade …...analysis of the characteristics of facade...

Analysis of the mechanical characteristics of facade render samples

retrieved in-situ

António Armando Ortiz Soares

Extended abstract

Júri

Presidente: Prof. Augusto Martins Gomes

Orientadora: Profª. Inês dos Santos Flores Barbosa Colen

Orientador: Prof. Jorge Manuel Caliço Lopes de Brito

Vogal: Doutora Maria do Rosário da Silva Veiga

Março de 2011

Analysis of the characteristics of facade samples retrieved in-situ

1

1. Introduction and objectives

Coating mortars (renders) perform the function of protecting the walls from the degradation agents to which

they are subjected. It becomes necessary, then, to evaluate their service performance, so as to understand if

they can carry out the function attributed to them. For this purpose, the chemical, physical and mechanical

properties of the render under analysis must be studied.

In what concerns the mechanical characteristics of the renders, there are still some difficulties in their

assessment, for which reason the present work focuses on this matter, with particular detail on the evaluation

of the compressive strength of samples retrieved in-situ. In this manner, this work allows to deepen the

knowledge on the parameters to be considered in the compressive strength tests of render cores, with the

main objective of relating it with the compressive strength of normalised test specimens

2. Mechanical characteristics of coating renders

Several authors have tried to evaluate the compressive strength of coating mortars from samples retrieved in-

situ. In order to study the compressive strength of irregular samples of historic mortars retrieved in-situ, a

project was developed by LNEC (Magalhães & Veiga, 2006) in order to create a simple adaptation of the

method of determining the compressive strength defined by EN 1015-11 (CEN, 1999), to allow compressive

strength test of irregular samples in old buildings. The adaptation in question consists of producing a

confinement mortar, with a strength superior to that of the sample being tested, applied over the two parallel

faces of the irregular sample (Figure 1).

Figure 1 - Detail of samples prepared with the confinement mortar over the two more parallel faces of the samples

(Magalhães & Veiga, 2006)

As a means to evaluating the method, reference specimens were used, with dimensions 20 x 40 x 80 [mm3],

resulting from the cutting of specimens with 40 x 40 x 160 [mm3], to which the confinement mortar was

applied for the compressive strength test. The values of the compressive strength obtained with these

specimens were compared to those resulting from the testing of normalised specimens, and a high correlation

coefficient (R2 ≈ 0.96) was achieved for a linear relation.

Flores-Colen (2009) also studied the compressive strength of samples of render by comparing the

compressive strength of square cores with 50 mm length and 15 mm height retrieved in-situ, resulting from

the pull-off adhesion test with the compressive strength obtained through the testing of normalised

specimens of the same product, relating the obtained strengths through a power trend line with a correlation

coefficient R2 ≈ 0.78.

However, the results of the compressive strength of cores after the adhesion tests displayed variation

coefficients between 25-51% in some products, which the author attributes to the state of the core after the

process of heating to remove the metallic disk, to the control of the compressive strength testing machine, to

eventual variations of the thickness of the cores or to the sample’s state of degradation.

Extended abstract

2

The same author studied the possibility of directly relating the value of the compressive and tensile strength

with the adhesion strength. This study resulted in the graphic presented in Figure 2, where satisfactory

correlation coefficients are found for the relationship between adhesion strength and strength of normalised

specimens of the same products.

Legend: Rt - flexural tensile strength of normalised specimens; Rc - compressive strength of normalised specimens; Rc

ad -

compressive strength of samples after the adhesion test; fu - adhesion strength

Figure 2 - Relationship between adhesion strength and strength of the products tested (translated from Flores-Colen, 2009)

In the same study, mechanical tests were performed in campaigns conducted in-situ. It was then possible to

compare the results obtained in laboratory with real cases. In the case of the relationship between pull-off

adhesion strength and compressive strength extrapolated from the values of cohesive fracture (related to the

material’s straight tensile strength), a correlation coefficient of R2

= 0.95 was obtained between the

relationships established in laboratory and those verified in-situ.

Thus, the direct relationship between adhesion strength and compressive strength seems to be a good method

to evaluate the mechanical characteristics of the coating mortars. However, since fracture in the pull-off

adhesion test may be adhesive or cohesive on the substrate, part of the information pertaining to the internal

structure of the coating mortar is lost, since only the lower strength limit being known. As such, this method

is only possible when there are straight cohesive ruptures in the mortar, which occur mostly in “weak”

mortars.

Due to the few existing studies on the evaluation of the strength of mortars from samples of render, studies

related to the behaviour of concrete are referred to as a means to understanding some of the parameters

which may affect the value of compressive strength in test cores.

When a cylindrical concrete specimen is subjected to compression, it tends to expand sideways. However,

there is a friction force at the surface of contact between the plates of the testing machine and the specimen,

leading to lateral compression forces, which are responsible for the formation of a confinement area which

originates a cone at the moment of rupture, as can be seen in Figure 3. When that friction force is eliminated,

the lateral compression forces disappear, and a cracking rupture is reached. However, it is difficult to

eliminate the friction force, for which reason it is regarded as viable to consider the lateral restriction along a

certain length and consequent confinement area (Kim & Yi, 2002; Kim et al., 1998).


3

Figure 3 - Cylindrical concrete specimen subjected to a compression load (Kim et al., 1998; Kim & Yi, 2002)

Chung (1979), cited by Mohiuddin (1995), studied the effect of the h/d1 ratio on the compressive strength of

concrete cores and concluded that confinement, exerted by the plates of the compression machine on the

sides of the core, creates a triaxial state of tension in the concrete that originates an increase in the

compressive strength as the core’s h/d ratio decreases.

In the beginning of the 20th century, Connerman (1925) showed that the compressive strength decreases with

the increase of the h/d ratio of the specimen being studied, tending to infinite, for values of h/d lower than

0,5. The same author also defined an interval for the h/d ratio in cylinders, between 1,5 and 2,5, where the

difference in strengths is not significant, having as reference a specimen with h/d ratio = 2.

More recently, other researchers, while studying the effect of the relationship between height and diameter or

lateral dimension, also reached curves with power trend lines, as is the case of Leonhardt & Mönning (1977),

cited by Costa & Appleton (2008), as represented in Figure 4 where the reference specimen is the cube, for

which reason the reference value (of one) occurs for the geometric relation h/d = 1.

Figure 4 - Relation between h/d and the compressive strength of concrete specimens (translated from Leonhardt & Mönning,

1997, cited by Costa & Appleton, 2008)

When references are made between specimens produced with concrete identical to that used on site, their

strength will be different from the one determined in-situ, even if the possibility of achieving perfect cores,

identical in size to the test specimens, is considered, due to divergences in compacting and curing

(Indelicato, 1997).

Therefore, the need to estimate the strength of normalised specimens from cores retrieved in-situ emerged.

Thus, the concept of estimating the actual or in-situ strength referred to cubic specimens was used when

values of strength resulting from cores are used for structural calculations to represent the strength of the

existing structure, and the concept of potential strength estimate is used when there are doubts about the

quality of the concrete used (Concrete Society, 1976).

1 The h/d ratio defines the slenderness of the test specimen through the relation between height (h) and diameter or lateral dimension

(d)

Extended abstract

4

Thus, Equation 1 can be used (Concrete Society, 1976; BSI, 1983) to estimate concrete’s strength from cores

retrieved in-situ.

Eq. 1

Where:

Estimated strength [N/mm2];

Measured strength of the concrete core [N/mm2];

h/d ratio between the height (h) and the lateral dimension or diameter of the concrete core;

Experimental constant which depends on the type of estimate (D = 2.5 for the estimate of the actual

strength of a cubic specimen from a core retrieved horizontally in relation to concreting).

Another way of relating the strength of a normalized concrete specimen with a non normalized one is

through Equation 2, obtained through the theory basis of the non linear mechanical fracture of concrete,

presented by Kim et al. (1998) for cylindrical specimens and not taking into account the concrete’s strength

class, nor any restrictions on the maximum dimension of the aggregate used.

Eq. 2

Where:

Compressive strength of normalised cylinders [N/mm

2];

Compressive strength of a non normalised cylinder [N/mm2];

Cylinder height[mm];

Cylinder diameter [mm];

Ratio between height (h) and lateral dimension or diameter (d).

3. Characterisation of the experimental work

In the experimental phase, the following were applied over bricks: traditional multi-layer renders

(spatterdash, under coat and final coat), traditional control renders (a layer with the composition of the under

coat of a multi-layer render) and industrial renders with the thicknesses presented in Table 1.

Table 1 - Thicknesses of render

Type of

render

Traditional render (mm) Industrial

render

(mm) Spatterdash

Under

coat

Final

coat

Type 1 3 15 6 -

Type 2 3 25 6 -

Type 3 - - - 15

Type 4 - - - 30

Type 5 - 15 - -

Type 6 - 25 - -

For the production of traditional render, river sand was chosen as aggregate, and CEM II/B-L 32.5 N cement

was used as binder, presenting the compositions indicated in Table.


5

Table 2 - Characteristics of each layer of the traditional render used

Layers Ratio (volume) Water/cement ratio

Spatterdash 1:2 0.70

Under coat 1:4 1.00

Final coat 1:4.5 1.06

In the case of industrial render, a mineral regularization render was used, with the characteristics presented in

Table 3, to display a compressive strength value (5.06 N/mm2) close to the average indicated by producers of

general use industrial mortars (Flores-Colen, 2009).

Table 3 - Characteristics of the industrial mortar used, adapted from Flores-Colen (2009)

Components Cement (type I)

[%]

Water repellent

[%]

Water retainer and plasticiser

(cellulose ether) [%] Water/product ratio

Type Binder Admixture Admixture Characteristic

Quantity 15 - 25 0.10 – 0.50 0.05 – 0.10 0.17

Reference specimens (Figures 5 and 6) with the same characteristics of the renders applied (as a way of

simulating cores) and normalised cores, were used.

Figure 5 - Moulds with the under coat in fresh state and

spatterdash in hardened state

Figure 6 - Final aspect of a reference specimen

Upon application of the plaster and production of the specimens, the samples were stored in a curing

chamber of controlled environment up to the test date, with a temperature of 20 ± 2 ºC and relative humidity

of 65 ± 5 %, according to EN 1015 - 11 (CEN, 1999). For the initial curing, polyethylene bags were resorted

to for the durations indicated in Table 4.

Table 4 - Initial curing time in polyethylene bags

Type of

product or

render layer

Types 1 and 2 in brick or

reference specimens Types 3 and 4

in brick or

reference

specimens

Types 5 and 6

in brick or

reference

specimens

Specimens with

normalised size

Spatterdash Under

coat

Final

coat

Traditional

mortar

Industrial

mortar

Initial

curing

(days)

14 11 3 11 11 11 11

Compressive strength tests were performed at 7, 14, 28 and 90 days. The flexural strength test was

performed to obtain 2 half normalised specimens (NS) for compressive strength tests for each NS produced,

and the pull-off adhesion test to obtain cores for the compressive strength test, using a heating process to

Extended abstract

6

remove the pull-off metallic disk. Table 5 presents the general distributions of tests by age, according to the

type of section, specimen and products used.

Table 5 - General distribution of the compressive strength tests by test age

Average number of compressive

strength tests

by test age

CB RS NS

Total Tr

Id

Tr

Id T

r I

d

Section Ml S

l M

l S

l

Round d= 50 mm 12 6 12 8 8 8 - - 54

Square 40 x 40 mm2 8 4 8 8 7 8 6 6 55

Square 50 x 50 mm2 4 2 4 8 8 8 - - 34

Total 24 12 24 24 23 24 6 6 143

Legend: CB - cores; RS - reference specimens; NS - normalised specimens; Tr - traditional render; Id - industrial render; Sl - single-

layer render; Ml - multi-layer render

Some of the tests had to be repeated, and it was not possible to use a few of the cores or comparison

specimens for the compressive strength test, due to their being damaged during the process of removal of the

metallic disk (in the case of the cores) or unmolding (in the case of the reference specimens). Thus, the total

quantity for the 4 testing ages was 678 compressive strength tests, from which 649 were valid, a total of 334

cores having been produces, from which a total of 237 valid adhesion tests were obtained.

4. Analysis of results

Due to the need of using the pull-off adhesion test to extract render cores, the hypothesis of comparing

adhesive strength to compressive strength, and considering the existence of different geometric shapes of

cores (round and square), it was considered important to evaluate the influence of the crosss-section in the

pull-off adhesion test. In this respect, a reference (Figure 7) between the adhesive strength of round cores

with 50 mm of diameter and square ones (with 40 and 50 mm), obtained from the same brick and with the

same type of rupture (cohesive fracture in the substrate), was made, in order to restrict the variables. It is

concluded that the shape of the cross-section does not significantly influence the results as long as the area is

equivalent.

Square section Relationship Correlation coefficient

40 x 40 mm2

50 x 50 mm2

Legend: fuRound - adhesive strength of cores with round section; fu

Square - adhesive strength of cores with square; T17 - designation of

the set of cores from the same brick excluded from the relation

Figure 7 - Relationship between adhesive strength of round and square cores of industrial render with cohesive fracture in

the substrate


7

At 14 days, for the industrial render, it was possible to obtain a linear relation between the adhesive strength

(fu) and the compressive strength of cores (RcCB

) with R2 = 0.86 which is close to that found by Flores-Colen

(2009) for the relationship between adhesive strength (fu) and compressive strength of normalised specimens

(RcNS

), as seen in Figure 8.

Reference Relation Correlation coefficient

Present study, at day 7

Present study, at day 14 0

Flores-Colen (2009) 0

Flores-Colen (2009) 0

Legend: fu - adhesive strength; RcCB - compressive strength of cores; Rc

NS - compressive strength of normalised specimens; RtNS -

flexural strength; T,45,2 e T,45,5 - designation of the cores tested at 14 days excluded from the relationship

Figure 8 - Relationship between adhesive strength and compressive strength of industrial render

In order to analyze the viability of producing reference specimens (RS), with the same product and similar

size to those of cores extracted from render applied on brick (CB) for comparison in the compressive

strength test, the specimens were organised by groups of thickness and lateral size, so as to assess the

relationship between cores (CB) and reference specimens (RS) for each type of product and section (square

or round). Relationships with good correlation coefficients were obtained, which indicates the potential for

using reference specimens (RS) to study of compressive strength, especially for traditional multi-layer

render.

Product Relationship Correlation coefficient

All

Types 1 and 2

Types 5 and 6

Types 3 and 4

Legend: RcCB - compressive strength of cores; Rc

RS - compressive strength of reference specimens; Types 1 and 2 - traditional

multi-layer render with a under coat 15 and 25 mm thick respectively; Types 5 and 6 - traditional single-layer render 15 and 25 mm

thick respectively; Types 3 and 4 - industrial render 15 and 30 mm thick respectively

Figure 9 - Relationship between compressive strength of cores and square reference specimens

0

10

20

30

0 10 20 30 40

RcRS[N/m

m2 ]

RcCB [N/mm2]

Types 1 e 2

Types 5 e 6

Types 3 e 4

Linear (All)

Linear (Types 1 e 2)



Linear (y=x)

Extended abstract

8

To study the possibility of evaluating the compressive strength of traditional multi-layer render through that

obtained for traditional single-layer render (produced with the same mix and size used at the under coat of

the multi-layer render), a comparison between the strength obtained with two products both for cores (CB)

(Figure 10) and reference specimens (RS) was made.

Age Relationship Correlation coefficient

All

7 days

14 days

28 days

0

90 days

All w/o 7 days

0

Legend: RcMl - compressive strength of traditional multi-layer render; Rc

Sl - compressive strength of traditional single-layer render

Figure 10 - Relationship between compressive strength of cores of traditional multi- and single-layer render

Analysing the relationship between the strength obtained with single- and multi-layer render cores, it was

found that the 7-day relationship has a slope of around 0.87 (which is close to y=x), with a correlation

coefficient R2 = 0.76 (Figure 10), while at the remaining ages, with similar correlation coefficients, the slope

is close to 3, except for the results obtained at 28 days which present a slope of 4.2 with R2 ≈ 0.38.

The traditional multi-layer render tested at 7 days was produced without applying of the final coat,

possessing only spatterdash and under coat. This particularity of the cores tested at 7 days, together with the

fact that this age in which the slope closest to y=x was obtained, with a good R2, may indicate that the

spatterdash (the layer with the strongest ratio of cement) does not significantly influence compressive

strength.

Analysing the relation between the strength obtained with reference specimens of traditional single- and

multi-layer renders, it was also found that the trend line with the slope closest to y=x is that determined from

the results obtained at 7 days, for the same reasons referred in this type of relationship in cores.

However, while good correlations were obtained analysing the relationship between single- and multi-layer

renders for cores (CB) and reference specimens (RS) treated separately, low correlation coefficients were

obtained while trying to relate cores of traditional multi-layer render with reference specimens of traditional

single-layer render.

5

10

15

20

25

30

35

40

5 10 15 20 25

RcSl[N/m

m2 ]

RcMl [N/mm2]

7 days

14 days

28 days

90 days

Linear (All)

Linear (7 days)

Linear (14 days)

Linear (28 days)

Linear (90 days)

Linear (y=x)

Linear (All w/o 7 days)


9

In evaluating compressive strength as a function of the h/d ratio, it was chosen, based on studies already

conducted2, to use a strength index (I

S), which translates the increase in strength in each item in relation to

the strength obtained for NS of the same product, indicated in Equation 3.

Eq. 3

Where:

IS Strength index;

RcCBorRS(Measured)

Measured compressive strength of cores or reference specimens [N/mm2];

RcNS(Measured)

Average of the compressive strengths of normalised specimens [N/mm2].

Thus, it is convenient to consider the compressive strength obtained in the normalised specimens (Table 6).

Table 6 - Measured compressive strength of normalised specimens (NS)

Compressive strength of

normalised specimens (NS)

[N/mm2]

Age [days]

7 14 28 90

Traditional render 8.8 10.6 10.8 13.1

Industrial render 4.7 5.2 7.6 9.3

In the present study, as indicated in Figure 11, it was possible to obtain a relation of the same kind of those

observed by Gonnerman (1925) and by ASTM (1992), cited by Tokyay & Özdemir (1997).

Type of plaster Relation Correlation coefficient

All types

Id Industrial

Tr Multi-layer

Single-layer

Legend: IS - strength index; h/d - ratio between height (h) and diameter (d); Id - industrial render; Tr - traditional render

Figure 11 - General relationship between h/d and strength index (IS)

2 Tokyay & Özdemir (1997) and ASTM (1992) cited by the same author; Kim et al. (1998); Kim & Yi (2002); Gonnerman (1925);

Leonhardt & Mönning (1997) cited by Costa & Appleton (2008)

0

2

4

6

8

10

12

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1

IR

h/d

Traditional multi-layer

Traditional single-layer

Industrial

Potencial (All types)

Potencial (Traditional multi-layer)

Potencial (Traditional single-layer)

Potencial (Industrial)

Extended abstract

10

However, bearing in mind the differences between the correction factors obtained in the various studies

(including the present work), it is concluded that in all of them it is possible to describe the relationship

between h/d and IS through a power trendline.

In the analyses made of this parameter, good correlation coefficients were registered, since no significant

differences were found in the trend lines with changes to the geometry of the cross-section (square or round),

the type of specimen (core or comparison specimen), age and type of product.

It was observed in the same analysis that, for values of h/d < 0,4, independently of the type of product or the

type of specimen (core (CB) or comparison specimen (RS)), the value of compressive strength (Rc) increases

significantly, displaying high oscillations in the value of Rc for small variations of h/d. Thus, the use of

specimens with h/d ≥ 0,4 is advised in the study of compressive strength of CB or RS. Thus, if a specimen

with for an example 50 mm of diameter is used, it is suggested that it is at least 20 mm of thick.

Higher values of Rc were observed in normalised specimens with (h/d = 1) than in CB or RS (with h/d < 1),

when Rc tends to decrease with the increase in h/d. This may be related to the different methods of

compacting used according to the type of specimen produced.

Studying the expressions used to estimate the compressive strength (Rc) of concrete, applied in the estimate

of Rc of cores of mortar, it was found that they do not supply reliable results. However, it is considered

necessary to ascertain if this occurred due to their application to the study of mortar or to the fact that the

specimens of mortar used display a ratio of h/d < 1, while the expressions were deducted for specimens with

h/d ratio between 1 and 2.

5. Conclusions

According to the study conducted, it was possible to establish which parameters affect compressive strength

of cores of render retrieved from building façades. These are succinctly presented in Table 7.

Table 7 - Parameters which may or may not affect compressive strength

Parameters Degree of

influence

Ratio between height and lateral dimension (h/d) (strength increases with decrease in h/d) (++)

Number of layers (depends on the constitution of each layer) (+)

Spatterdash (layer in the traditional multi-layer render with the strongest ratio in binder) (--)

Under coat (main layer of the traditional multi-layer render) or type of product in the case of industrial

render (++)

Final coat (layer in the traditional multi-layer renderer with the weakest ratio in binder) (++)

Age (++)

Geometry of the section (--)

Test machine (++)

Heat for removal of the metallic disk (-)

Existence of remains of brick in the surface of the brick (-)(r.d.)

Legend: (++) - clearly affects; (+) - affects; (-) - does not affect; (--) - clearly does not affect; (r.d.) - requires further development

The comparison of the compressive strength of cores or reference specimens with that of normalised

specimens through a strength index indicating relative strength, as occurs in concrete, proved to be a good

way of evaluating strength. Thus, and considering the values of IS close to 1 obtained as a function of the h/d

ratio, shapes and sizes of the cores to use, according to the thickness and type of render to apply, are

suggested in Table 8.


11

Table 8 - Recommended cross-sections of cores

Recommended cross-sections of cores

Render thickness [mm]

Traditional (multi-layer) Industrial

Minimum Maximum Minimum Maximum

Square 40 x 40 mm

2 20 31 19 31

50 x 50 mm2 25 38 24 39

Round D = 50 mm 26 40 26 39

Considering the different methods of evaluating the compressive strength of cores retrieved from rendered

façades, and their potential, Table 9 was prepared, wherein the methods advised for each type of render to

analyse are indicated.

Table 9 - Methods to estimate compressive strength of cores retrieved in-situ

Types of render Methods

RS NS fu MCo CBSl

Render of weak mortars, or of advanced state of degradation - - - ‡

(n.d.) -

Traditional multi-layer independently of the type of fracture in the pull-off test † - - -

Industrial

render

Cohesive fracture in the pull-off test ◘ - -

Adhesive or cohesive fracture in the pull-off test - - -

Legend: RS - comparison with reference specimens with the same number and constitution of layers; NS - comparison with

normalised specimens; fu - relationship with adhesive strength; MCo - use of confinement mortars (Magalhães & Veiga, 2006); CBSl

- comparison with single-layer; - advised method; - method which may be used; † - the finishing layer conditions the

compressive strength; ◘ - only if the h/d ratio is high (greater than 0.4); ‡ - weak mortars can sustain damage upon removal of the

metallic disk of the pull-off test; (n.d.) - not deal with in this study

While reference specimens are the most indicated to evaluate the compressive strength only of traditional

multi-layer render, they may contribute to future studies as a means of defining aspects or parameters which

affect compressive strength without the need of cores.

Thus, the use of reference specimens for the study of compressive strength presents the following

advantages:

Variables introduced by the base (such as water absorption) are eliminated;

A better control of the thickness of layers is achieved (than in the case of render applied on brick,

where the latter’s irregularities may affect the control of the thickness);

Specimens do not need to go through the process of removal of the pull-off adhesive test’s metallic

disk (through exposure to heat);

Specimens do not require correction of the surface of contact with the plates of the compression

machine;

Greater ease of transport and storage in laboratory due to the lower weight, and due to occupying

less space than bricks or others.

Due to the elimination of a number of variables such as contact with the brick’s surface, or because the

process of compacting of coating mortars applied on a surface differs from that used in reference specimens,

these do not rigorously represent the cores retrieved in-situ.

Extended abstract

12

References

ASTM (1992) - “ASTM C42 - Standard method of obtaining and testing drilled cores and sawn beams of

concrete. Philadelphia: American Society for Testing and Materials.

BSI (1983) - “Testing concrete - Part 120. Method for determination of the compressive strength of concrete

cores”. BS 1881. London: British Standards Institution.

CEN (1999) - “Methods of test for mortar for masonry - Part 11: Determination of flexural and compressive

strength of hardened mortar”. EN 1015-11:1999 (Ed.1). Brussels: Comité Européen de Normalisation.

Chung, H. (1979) - “Effect of length/diameter ratio on compressive strength of drilled concrete core - a semi

rational approach”. Cement, Concrete and Aggregates 1 (2), pp. 68-70.

Concrete Society (1976) - “Concrete core testing for strength - technical report. 11”. London: The Concrete

Society.

Costa, A.; Appleton, J. (2008) - “Estruturas de betão I. Parte II - Materiais”: IST, 65 p.

Flores-Colen, I. (2009) - “Metodologia de avaliação do desempenho em serviço de fachadas na óptica da

manutenção predictiva”. PhD Thesis in Civil Engineering: IST, 487 p.

Gonnerman, H. (1925) - “Effect of size and shape of test specimen on compressive strength of concrete”.

ASTM Proc. 25, Part II, pp. 237-250.

Indelicato, F. (1997) - “Estimate of concrete cube strength by means of different diameter cores: A statistical

approach”. Materials and Structures 33 (3), pp. 131-138.

Kim, J.; Yi, S. (2002) - “Application of size effect to compressive strength of concrete members”.

SĀDHANĀ - Academy Proceedings in Engineering Sciences 27 (4), pp. 467-484.

Kim, J.; Yi, S.; Park, C.; Eo, S. (1998) - “Size effect on compressive strength of plain and spirally reinforced

concrete cylinders”. ACI Structural Journal 96 (1), pp. 88-96.

Leonhardt, F.; Mönning, E. (1977) - “Construções de concreto, Vol. 1: Princípios básicos do

dimensionamento de estruturas de concreto armado”. Rio de Janeiro: Interciência, 305 p.

Magalhães, A.; Veiga, M. (2006) - “Avaliação da resistência de amostras de argamassas históricas recolhidas

em obra - Metodologia e correlação de resultados”. Report 259/06 – NRI, Lisbon: National Laboratory of

Civil Engineering (LNEC), 34 p.

Mohiuddin, N. (1995) - “Use of small diameter cores in evaluation of in-situ concrete strength in Eastern

Saudi Arabia”. MSc Dissertation in Science in Civil Engineering. Dharan: King Fahd University of

Petroleum & Minerals, 95 p.

Tokyay, M.; Özdemir, M. (1997) - “Specimen shape and size effect on the compressive strength of higher

strength concrete”. Cement and Concrete Research 27 (8), pp. 1281-1289.

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