E07013037

International Journal of Engineering Research and Development
e-ISSN: 2278-067X, p-ISSN: 2278-800X, www.ijerd.com
Volume 7, Issue 1 (May 2013), PP. 30-37
30
Influence of Type of Concrete, of Size of the Body of
Evidence Cylindrical and of Type of Laboratory in
Determining the Compressive Strength of Concrete
Suélio da Silva Araújo1
, Gilson Natal Guimarães2
and André Luiz Bortolacci
Geyer3
1
Masters Degree in Civil Engineering from the Federal University of Goiás, Brazil (2011), School of Civil
Engineering, Research Assistanship from CNPq - National Council of Scientific and Technological
Development. Rua A, Número 141, Bairro Mato Grosso, CEP: 76.200-000, Iporá, GO – Brasil.
2
PhD.,University of Texas at Austin, USA (1988). Full Professor at the Federal University of Goiás, Brazil.
Universidade Federal de Goiás, Escola de Engenharia Civil, Laboratório de Estruturas. Av. Universitária, Pça.
Universitária, s/n, Setor Universitário, CEP 74640-220, Goiânia, GO – Brasil.
3
Doctorate in Civil Engineering from the Federal University of Rio Grande do Sul, Brazil (2001). Associate
Professor II at the Federal University of Goiás. Universidade Federal de Goiás, Escola de Engenharia Civil,
Laboratório de Materiais de Construção. Av. Universitária, Pça. Universitária, s/n, Setor Universitário, CEP
74640-220, Goiânia, GO – Brasil.
Abstract:- This paper presents a comparative analysis of the results obtained for testing the
compressive strength by means of an interlaboratory test program in hardened concrete, developed in
two different laboratories in the Goiânia, GO region, to identify and assess the influence of some
factors affecting the results of compressive strength test. For this, we sought to determine the outcome
of compressive strength, the influence of the concrete (Class C30 and CAR - High Strength Concrete),
the size of the body of proof cylindrical (100 mm x 200 mm and 150 mm x 300 mm) and the type of
laboratory. It was concluded that the type of concrete and type of lab results influenced the
compressive strength. Moreover, it is noteworthy that the bodies of evidence dimension 100 mm x 200
mm of concrete Class C30 and of CAR (Class C60) presented the results with the highest dispersion.
Keyword:- Concrete; Basic Dimension; Compressive Strength; Interlaboratory; Dispersion.
[1]. INTRODUCTION
The resistance of a material is its ability to withstand tension without breaking. Sometimes, the break is
identified by the appearance of cracks. However, the microstructural investigations indicate that in ordinary
concrete, unlike the structural materials, concrete contains fine cracks before being subjected to external
stresses. Given the above, the research aims to study and evaluate the influence of variables influence the type
of concrete (C30 and Class CAR - High Strength Concrete), the size of the cylindrical specimen (100 mm x 200
mm and 150 x 300 mm) and the type of laboratory (Laboratory laboratory a and B) result in the compressive
strength in hardened concrete and to check the variability of the experimental results.
[2]. EXPERIMENTAL PROGRAM
The experimental program was developed from an interlaboratory evaluation of compressive strength
of concrete, developed in two different laboratories concrete located in the region of Goiânia, Goiás.
Considering the characteristics of interlaboratory program, where you can not fix all the independent variables,
so we decided to study the following situation:
 Type of concrete (in two levels: class C30 and CAR);
 Dimensions of the test specimens at two levels: 100 mm x 200 mm and 150 mm x 300 mm;
 Type of Laboratory (in two levels: The lab and lab B).
As limitations of the study have been:
 They kept all specimens in the same moisture condition;
 Testing machine with load control with application rate of 0.6 MPa / s, the phase of the study;
 Materials used in the manufacture of concrete: CP V ARI Portland cement (high early strength),
lithology and size of coarse aggregate (granite maximum dimension of 19 mm) and sand type (artificial sand);

Influence of Type of Concrete, of Size of the Body of Evidence Cylindrical and…
31
 Compressive strength fc (28days) 30 MPa and 60 MPa;
 Finishing the top of the specimens (capping with sulfur).
The evaluation of the independent variable of basic dimension of the specimen is justified because the
resistance specified for concrete are increasingly high and the capacity constraints of the testing machine did not
follow this requirement, forcing laboratories to use the basic dimension (100 x 200) mm in the control tests
technology. Therefore, it is important to assess the impact of this factor on the experimental results of the
compressive strength.
To reduce the influence of the humidity of the specimens, they were demolded 24 hours after mixing,
identified and stored in storage tanks for 28 days, with controlled humidity and temperature as specified by
ABNT NBR 5738:2008. Once this term storage, the specimens were removed from the storage tank and stored
in a dry environment at room temperature.
The levels defined for the concrete sample and concrete class C30 CAR (Class C60)
were obtained by setting the concrete mix resistance (fc) of the order of 30 to 60 MPa.
Through the graphical behavior of concrete traces were obtained for concretes with strength estimated at 28
days at 30 MPa and 60 MPa. These traits are presented in TABLES 2.1 and 2.2.
TABLE 2.1 - Concrete mix for fc = 30 MPa
Material Proportioning by m³ of concrete
Mix design (1 : 3.78 : 4.23 )
W/C ratio = 0.73
Materials
Conventionally Vibrated Concrete
Quantity per m³
Cement CP V ARI 236 kg
Artificial sand 891 kg
Gravel size 1 (19 mm) 999 kg
Water 172 kg
Polyfuncitonal Additive 1.65 kg (0.7% of cement)
Superplasticizer 0.94 kg (0.4% of cement)
Silica Fume 18.9 kg (as replacement for 8% of cement in weight)
Fresh Concrete Properties:
Consistency 130 mm
Air 2 %
TABLE 2.2 - Concrete mix for fc = 60 MPa
Material Proportioning by m³ of concrete
Mix design (1 : 1.928 : 2.58 )
W/C ratio = 0.42
Materials
Conventionally Vibrated Concrete
Quantity per m³
Cement CP V ARI 398 kg
Artificial sand 765 kg
Gravel size 1 (19 mm) 1028 kg
Water 167 kg
Polyfuncitonal Additive 2.79 kg (0.7% of cement)
Superplasticizer 1.59 kg (0.4% of cement)
Silica Fume 31.87 kg (as replacement for 8% of cement in weight)
Fresh Concrete Properties:
Consistency 120 mm
Air 1.5 %
Were cast ten (10) specimens for compressive strength for each type of concrete, for each dimension of
the specimen and for each type of laboratory (Lab A and Lab B), to meet the test methods ABNT NBR
5739:2007.

32
2.1 Technical Evaluation
Was applied to the statistical analysis technique of variance (ANOVA), contained in Statistica Statsoft
Software 7 ® to the results found in individual laboratories for the A and B samples C30 and concrete class
CAR (Class C60) separately and together. The test methodology consists of the application of the Fisher test
(F).
[3]. PRESENTATION AND DISCUSSION OF RESULTS
As for the main analysis of this study, it is noteworthy that the specimens were tested in replicates (with
10 units per study situation) and randomized prior to testing of compressive strength. This randomization
minimizes the effects of variables that were not or could not be considered in the experiment, such as: molding
process of the specimen, the distribution of aggregates in concrete, installation of the measuring instrument,
among others. In addition, if any dependency mechanism between the results of subsequent experiments, the
randomization of the execution of experiments allows this dependency is diluted among all study situations and
thus not favoring either situation.
In Table 3.1 presents the means, standard deviations and coefficients of variation of the results for all
study situations obtained for samples molded concrete C30 and CAR, with a confidence interval of the mean
(for 95% confidence) and a significance level of 5% for property compressive strength.
TABLE 3.1 - Statistical analysis of the results – Compressive Strength
——— ——— CAR 38 65,8 5,5 8,3
——— ——— C30 37 35,9 1,9 5,3
150X300 ——— CAR 19 65,4 4,4 6,7
100X200 ——— CAR 19 66,3 6,4 9,7
150X300 ——— C30 19 36,2 0,76 2,1
100X200 ——— C30 18 35,6 2,6 7,3
——— LABORATORY A CAR 19 69,3 4,03 5,8
——— LABORATORY B CAR 19 62,4 4,4 7,1
——— LABORATORY A C30 19 34,6 1,6 4,6
——— LABORATORY B C30 18 37,2 1,1 2,9
LABORATORY A C30 9 33,2 1,2 3,5
LABORATORY A CAR 9 71,1 2,4 3,4
LABORATORY B C30 9 37,9 0,94 2,5
LABORATORY B CAR 10 61,9 5,8 9,4
LABORATORY A C30 10 35,9 0,54 1,5
LABORATORY A CAR 10 67,7 4,6 6,8
LABORATORY B C30 9 36,6 0,804 2,2
LABORATORY B CAR 9 62,8 2,3 3,6
Coefficient of
Variation (%)
Compressive Strength (MPa)
OBS.: - Type of concrete: concrete Classe C30 for dimensions 100 mm x 200 mm e 150 mm x 300
mm e CAR (High Strength Concrete) for dimensions 100 mm x 200 mm e 150 mm x 300 mm.
- Five of the individual results were considered as spurious values.
150X300
100X200
Situation of Study
N°. of
Specimen
Size (mm)
Type of
Laboratory
Type of
Concrete
Average
(MPa)
Standard
Deviation
(MPa)
In TABLE 3.2, is the analysis of the significance of factors studied for the compression resistance property.

33
TABLE 3.2 - ANOVA - Analysis of the Global Experiment - Compressive Strength
SQ F p
17409,46 273,49 0,000
609,29 ——— ———
18018,75 ——— ———
——— 0,17 0,682
——— 9,57 0,003
——— 1848,56 0,000
——— 0,02 0,893
——— 1,88 0,175
——— 48,47 0,000
——— 8,56 0,005
Factors Studied Result
significant
Coefficient of Determination Model (R²) = 0,96
Model Study
Error (residual)
Total ———
———
Where: SQ = sum of squares; F = parameter of Fischer to the test of significance of the effects; p =
probability of error involved in accepting the observed result as valid, this is, as representative of the
sample; Result = result of the analysis, indicating that the effect is significant or not,
R² = (1 - SQerro/SQtotal).
not significant
significant
significant
not significant
not significant
significant
Dimension Body of Proof
Type of Laboratory
Type of Concrete
Dimension Body of Proof x Type of Laboratory
Dimension Body of Proof x Type of Concrete
Type of Laboratory x Type of Concrete
significantDimension x Type of Laboratory x Type of Concrete
The analysis of variance showed compression strength of the resulting value of the coefficient of
determination adopted (R ²) was 0.96, which means that 96% of the total variance of the data compression
strength can be explained by variable adopted. Therefore, uncontrolled factors accounted for approximately 4%
of the variations observed in the study.
With respect to the influence of intensity, taking as a basis the magnitude of F values, it can be seen the
great influence of the type of the laboratory and the results of concrete compressive strength.
The interaction effects were also statistically significant, that is, for each type of laboratory used depending on
the size of the specimen and the type of concrete, the compression strength of concrete presents difference result
(different behavior).
In column F values of Table 3.2, the interactions involving the effect of the size of the specimen x type
laboratory showed the lowest values, indicating less influence of this variable on the results of compressive
strength. Stands out even the individual effect of variable dimension of the specimen is not significant, ie, the
dimensions of the specimens studied (100 mm x 200 mm and 150 mm x 300 mm), alone and interacted with
type laboratory or type of concrete does not significantly influence the results of compressive strength.
As a result of ANOVA - Compressive Strength (Table 3.2) have revealed the significant effects of the variables
type of laboratory and type of concrete, there was the grouping of homogeneous medium by the method of
Duncan, in order to observe the similarities and differences the obtained results.
In this method, it was shown that laboratories A and B show similar results, as the average overall
compressive strength of the laboratory was 52.0 MPa and average overall compressive strength of laboratory B
was 50.1 MPa, this is the lab a had only 4% higher overall average compressive strength compared to laboratory
B. Therefore, depending on the laboratory used for the test, the values of resistance to compression approach.
After taking the average of the grouping factor type of concrete by the method of Duncan, it was shown, as
expected, that the specific type of influence values of compressive strength as the overall average compressive
strength of the concrete was Class C30 35.9 MPa and average overall resistance to compression (CAR high
strength concrete) was 65.8 MPa, that is, the CAR was more than 83% overall mean compressive strength
compared with concrete class C30 .
FIGURE 3.1 shows the graphical analysis of the study, showing the results for each variable.

34
Figure 3.1 shows the values of compressive strength are shown next to two dimensions of the
specimens. As for specimens with dimensions 100 mm x 200 mm, the results of the compressive strength of the
concrete class C30 and CAR (High Strength Concrete) in the laboratory, shown in Figure 3.1, showed averages
of 33.2 and 71 MPa, 1 MPa, and their coefficients of variation were 3.5% and 3.4%. In contrast, in laboratory B
the results showed average compressive strength of 37.9 MPa and 61.9 MPa, and their coefficients of variation
were 2.5% and 9.4%. As regards the size 100 mm x 200 mm, it was found that the concrete class C30 showed
greater dispersion in the laboratory, ie the concrete class C30, 1% more than the coefficient of variation in the
laboratory with the laboratory B. Already, CAR showed greater dispersion B in the laboratory, or CAR was
more than 6% coefficient of variation B in the laboratory compared with the laboratory A.
As for the test specimens with dimensions 150 mm x 300 mm, the results of the compressive strength
of the concrete class C30 in the laboratory and CAR, shown in Figure 3.1, show averages of 35.9 MPa and 67.7
MPa, and its coefficients of variation were 1.5% and 6.8%. In contrast, in laboratory B the results showed
average compressive strength of 36.6 MPa and 62.8 MPa, and their coefficients of variation were 2.2% and
3.6%. As regards the size 150 mm x 300 mm, it was found that the concrete class C30 in the laboratory showed
greater dispersion B, ie, concrete class C30 had more than 0.7% coefficient of variation in lab lab B in relation
to A. Already, CAR showed greater dispersion in the laboratory, or CAR was more than 3.2% coefficient of
variation in the laboratory compared with the laboratory B.
Because of the samples with dimension 100 mm x 200 mm had the highest dispersion of results, the
variable dimension of the specimen was highlighted in subsequent analyzes presented by FIGURES 3.2 and 3.3.

35
Figure 3.2 shows the effect of the type of concrete, having CAR (high strength concrete) presented the
results of compressive strength higher than average. As for the test specimens with dimensions 100 mm x 200
mm, the results of the compressive strength of the concrete class C30, and CAR, shown in Figure 3.2, show
averages of 35.6 MPa and 66.3 MPa, and the coefficients of variation were 7.3% and 9.7%. Now, as the
specimens with dimensions 150 mm x 300 mm, the results showed average compressive strength of 36.2 MPa
and 65.4 MPa, and the coefficients of variation were 2.1% and 6.7 %.
As for the concrete class C30, it was found that the samples with dimension 100 mm x 200 mm higher
dispersion (coefficient of variation 5.2% higher) compared to specimens with dimensions 150 mm x 300 mm.
As for the CAR, it was found that the samples with dimension 100 mm x 200 mm higher dispersion (coefficient
of variation 3% higher) compared to specimens with dimensions 150 mm x 300 mm.

36
Figure 3.3 shows the effect of the type and size laboratory test body, and the laboratory results
presented compressive strength greater.
As for the test specimens with dimensions 100 mm x 200 mm, the results of compressive strength in
laboratories A and B shown in Figure 3.3, show averages of 52.2 MPa and 50.5 MPa, and their coefficients of
variation were 37.5% and 25.8%. Now, as the specimens with dimensions 150 mm x 300 mm, the results of
compressive strength in laboratories A and B showed averages of 51.8 MPa and 49.7 MPa, and the coefficients
of variation were 32.1 % and 27.3%.
As for the laboratory, it was found that the specimens with dimensions 100 mm x 200 mm higher
dispersion (coefficient of variation 5.4% higher) compared to specimens with dimensions 150 mm x 300 mm.
Regarding lab B, it was found that the specimens with dimensions 150 mm x 300 mm higher dispersion
(coefficient of variation 1.5% higher) compared to specimens with dimensions 100 mm x 200 mm.
[4]. CONCLUSION
The true scope of a search is to provide data capable of supporting answers and solutions for the
unknowns in the different fields of human knowledge. Thus, the final considerations aimed at compiling the
most important information, cast off the results and settle the practical aspects of the study, facilitating access
through technical scientific discoveries.
The final considerations drawn from the presentation and analysis of results presented earlier
considered: the influence of the concrete class, the size of the specimen, the type of laboratory test, and the
comparison between these variables obtained in the study and their applicability in the analysis and inspection
of concrete structures.
The knowledge of the compressive strength of concrete is a matter of fundamental importance, both in
the design and implementation stages as in the case of assessments of the quality of the structures in use. It is
necessary to understand the concepts of the test requirements and the variables that influence, to interpret the
results and to rule out possible discrepancies caused by deficiencies of the test equipment or operator.
1.As for the concrete class C30, it was found that the samples with dimension 100 mm x 200 mm higher
dispersion (coefficient of variation 5.2% higher) compared to specimens with dimensions 150 mm x 300
mm. As for the concrete class C60, it was found that the samples with dimension 100 mm x 200 mm higher
dispersion (coefficient of variation 3% higher) compared to specimens with dimensions 150 mm x 300 mm
(Figure 3.2). Therefore, specimens with dimensions 100 mm x 200 mm higher dispersion. This behavior
was also obtained by the research of Martins (2008).
2.As for the laboratory, it was found that the specimens with dimensions 100 mm x 200 mm higher dispersion
(coefficient of variation 5.4% higher) compared to specimens with dimensions 150 mm x 300 mm.
Regarding lab B, it was found that the specimens with dimensions 150 mm x 300 mm higher dispersion
(coefficient of variation 1.5% higher) compared to specimens with dimensions 100 mm x 200 mm (Figure
3.3).
3.Although the results obtained from specimens 100 mm x 200 mm have a higher dispersion (higher
coefficient of variation), the difference is not significant with respect to these results obtained from
specimens 150 mm x 300 mm (evidenced in table 3.2).
4.The participating laboratories test showed wide divergence of results, although they were following the
standard guidelines. This serves as a warning of the need for further investigations, especially in regard to
the influence of the concrete types, dimensions of test specimens and the different processes used by the
laboratories involved in the study.
5.Although the results obtained from specimens 100 mm x 200 mm have a higher dispersion (higher
coefficient of variation), the difference is not significant with respect to these results obtained from
specimens 150 mm x 300 mm (evidenced in table 3.2).
In general, the steps inspection of concrete structures involve a series of activities ranging from the
collection and analysis of designs and specifications to the planning and development of research methodology.
Furthermore, the effectiveness of the evaluation depends on the knowledge and experience on the part of the
researcher. The successful application of the correlations obtained in this study is deeply associated with the
professional expertise and prior knowledge about the method of determining the compressive strength of
concrete.
It is noted that the results obtained here are valid for materials and test conditions adopted, therefore,
should consider this limit research.

37
Acknowledgements
To all of the Master Course in Civil Engineering, School of Civil Engineering, Federal University of
Goiás To all Company Carlos Campos Consulting and Construction Ltd.., The unconditional support and
assistance in the execution of the experimental program. To all the staff of Furnas, the suggestions, availability,
willingness and readiness to always demonstrated. To all of Realmix and all the Quarry Anhanguera, for
providing access aggregates and cement, that every question or request, were always ready to help.The tutor
Gilson Natal Guimarães and co-supervisor Professor André Luiz Bortolacci Geyer, the teachings transmitted.
And the teachers of the Master Course in Civil Engineering, School of Civil Engineering, Federal University of
Goiás (CMEC - EEC - UFG), the valuable information provided.
This study was conducted with the support of the Federal University of Goiás and the National Council
for Scientific and Technological Development - CNPq - Brazil.
In Brazilian society, which, by the Federal University of Goiás, CNPq and Procad / Capes have
provided my scholarship and funded the materials needed for research.
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