PSI - Issue 5

Adelaide Cerveira et al. / Procedia Structural Integrity 5 (2017) 1116–1122 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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in the mixture.

The means and the standard deviations for compressive strength, dependent variable, as a function of the two factors, humidity and quantity of ashes in the blinders, are presented in Table 1.

Table 1. Comparative mean bonding of compressive strength for the interaction. Ash / filler ratio 20% 40% 60%

̅ ±

̅ ±

̅ ±

80% ̅ ± 9.04 ± 0.71 j

100% ̅ ± 11.93 ± 1.07 l, m 9.84 ± 1.14 i, j, n

Humidity 3.89 ± 0.50 a, * 4.71 ± 0.30 a, d 6.33 ± 0.52 g 3.07 ± 1.18 a, b 3.61 ± 0.34 a, b, d, e 5.92 ± 0.54 d, g, h 7.17 ± 0.97 g, k 75% 5.70 ± 0.36 c, d, g, h 3.99 ± 0.53 a, b, d, e, f 4.50 ± 0.75 a, c, d, f, h, i 8.02 ± 0.37 i, j, k, l 11.19 ± 1.22 m,o * Different alphabets mean significantly different values at the 0.05 level. 25% 50%

The values presented in the Table 1 shows differences in the mean values within of each factor, as well as in the interaction of them, which is also verified in the graph analysis, figures 1, 2 and 3. A two-way ANOVA test with interaction was conducted two evaluate the effects of the three humidity conditions and five filler/precursor ratio on the compressive strength. The results show statistically significant differences for at least one humidity value (F(2,127) = 31.647; p<0.001) as well as one inert/precursor ratio (F(4,127) = 371.635; p<0.001) and for interaction (F(8,127) = 9.330; p<0.001). Because the overall F Test was significant follow-up tests were performed to evaluate pairwise differences among the means. In table 2 and 3 are presented the results of the Post h oc comparisons from Tuckey’s test, as well as a 95% confidence intervals (CI) for the pairwise differences. Table 2 reveals that the humidity value of 50% presented statistically significant differences regarding the remaining two values, 25% and 75%. In addition, it is observed that this humidity value (50%) leads to lower compressive strength values.

Table 2. Comparative means and CI of compressive strength for humidity factor.

95% Confidence Interval Lower Bound Upper Bound

(I) Humidity (J) Humidity

Mean Difference (I-J) Sig.

25%

50% 75% 75%

1,2931 * .000 .3168 .135 -,9763 * .000

.9100 -.0732 -1.3641

1.6762 .7068 -.5885

50%

* The mean difference is significant at the 0.05 level.

Concerning the inert/precursor ratio, Table 3, the nonsignificant differences only occur between the 20% and 40%, i.e. , between the inert/precursor ratio 80/20 and 60/40. Furthermore the compressive strength values increase, in general, as the ash percentage increases, which can be seen in Fig.2.