Issue 59

T. Djedid et alii, Frattura ed Integrità Strutturale, 59 (2022) 580-591; DOI: 10.3221/IGF-ESIS.59.38

given confirm that fillers first fill the voids around the sand grains to the optimum. On the other hand, with a large amount of fillers, the voids are completely filled with additions and the fillers take the place of the sand grains, resulting in a decrease in the proportion of sand, and consequently in the density of the mixture.

Figure 9: Capillary absorption values of different formulations after 72h over time.

Figure 10: Pore size for different formulations after 60 days of immersion in drinking water.

Mathematical approaches between the factors studied In order to make predictive approximations, the analysis of variance (by ANOVA) was performed which gives a pseudo exact estimate of the influence of silica-limestone sand fines on the behavior of sand-based concrete of equal percentage of silica and limestone. The mathematical models offered a preliminary insight that helps the engineer to take decisional measures before making an experimental diagnosis. The calculated slump values were correlated with the fresh densities on the one hand and with the results of the water accessible porosity on the other hand. There is an inverse relationship between subsidence and the corresponding fresh density, and a proportional one between subsidence and porosity. These dependencies have excellent correlation coefficients (R 2 ) equal to 0.975, 0.983 respectively, as shown in Fig. 11. Moreover, a concordant equation of opposition linked the porosity of these different types of concrete at the age of 60 days with the fresh density measured during the making (Fig.12), which has an R 2 of 0.909. From the point of view of the agreement between the mechanical resistance to compression and to bending, we found that the curve shown in Fig. 13 represents an increasing function of the third degree; the values converge towards a correlation coefficient equal to 0.926. These interpretations led us to say that when increasing the substitution rate of

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