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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 2
R. C. C. Lintz | A. E. P. G. A. Jacintho | L. L. Pimentel | L. A. Gachet-Barbosa
The results of simple compressive strength at 14 days were ana-
lyzed statistically through Analysis of Variance - ANOVA, depend-
ing on the percent replacement factor of natural aggregate by
CDW. At 14 days of age (R14), the percentage factor replace-
ment is statistically significant at 95% significance level (pValue
= 0.0025).
Through the multiple comparison procedure [Table 3] applied de-
pending on the percentage factor replacement, there are three
statistically different groups. These groups are indicated by letters
a, b and c in Figure 11, which shows the average strength of the
blocks at 14 days.
The results of compressive strength at 28 days were analyzed sta-
tistically using analysis of variance – ANOVA, depending on the
percentage factor replacement of natural aggregate by CDW.
At 28 days of age (R28), the percentage factor replacement is sta-
tistically significant at 95% significance level (pValue = 0.0025).
Through the multiple comparisons procedure [Table 4] applied de-
pending on the percentage of substitution, there are three statisti-
cally different groups. These groups are indicated by letters a, b
and c in Figure 12, which shows the average strength of the blocks
at 28 days.
By the statistical analysis with multiple comparison of compressive
strength results of concrete blocks, presented in Tables 3 and 4
and Figures 11 and 12, it is observed that for traits with replace-
ment of 50%, 80% and 100% of natural aggregates by CDW, the
compressive strength values do not differ statistically, among each
other, with less than 5% significance level , at 14 days and also at
28 days of age.
For the cylindrical concrete specimens the compressive strength
limits the incorporation of CDW in 50%.
The substitution of 50% of natural aggregates for recycled construc-
tion waste allowed the production of blocks with compressive strength
which meets the specification of NBR6136:2007[22] for B class.
Concerning water absorption of concrete blocks, according to
NBR6136: 2007 [22], the content accepted for concrete hollow
blocks using regular aggregates must be less than or equal to
10%. Therefore it is noted that for all doses studied on concrete
blocks this question is answered.
Table 3 – Results of Multiple Comparison Test
for compression strength at 14 days of age
Multiple Comparison Test
Mix
Average
Homogeneous
Groups
E 4
4,165
X
E 3
3,4083
X
E 2
4,180
X
E 1
6,07
X
E 0
7,742
X
Figura 11 – Average of compressive
strength at 14 days
Table 4 – Results of Multiple Comparison Test
for compression strength at 28 days of age
Multiple Comparison Test
Mix
Average
Homogeneous
Groups
E 4
X
E 3
X
E 2
X
E 1
X
E 0
X
4,771
4,936
5,244
7,181
8,751
Figure 12 – Average of compressive
strength at 28 days