Issue 60

A. Boukhelkhal et alii, Frattura ed Integrità Strutturale, 60 (2022) 89-101; DOI: 10.3221/IGF-ESIS.60.07

Figure 9: T20 and T40 flow times in L-box of SCC mixtures vs MP content.

Figure 10: Dynamic segregation ratio of fresh SCC mixtures vs MP content.

The control mixture has developed the highest resistance to segregation. However, using MP reduced the resistance to segregation. The lower segregation ratio for the control mixture is due to its high viscosity. The increase in the segregation ratio of the other mixtures is attributed to their low viscosity. Compressive strength Fig. 11 shows the compressive strength of SCC mixtures at 7 and 28 days. The compressive strength decreased as the amount of MP increased. This may be attributed to the use of MP, which has no pozzolanic property; therefore, it cannot chemically contribute to the development of the strength at later ages. Also, the low water retention which characterizes the MP induces a significant amount of water in the mixture which contributes through the dilution effect to decrease of the compressive strength. Besides, the reduction of the volume of C 3 S and C 2 S that are responsible for the development of strength, as the cement is partially replaced by MP, decreases also the compressive strength. It has been noted that compressive strength values are between 19-28 MPa at 7 days and 26-37 MPa at 28 days. The mix with 5% of MP developed a similar strength to the reference mix at 28 days. Furthermore, the control mix had the highest strength at all the curing ages due to the high amount of OPC (470 kg/m 3 ). The 20MP mixture with 380 kg/m 3 of OPC had the same compressive strength as conventional concrete with 350 kg/m 3 of OPC which is the most used cement dosage in Algerian construction sites. These results are close to those reported in the literature  30, 40  . However, Tennich et al  15  reported contradictory results. The authors found that the presence of waste fillers from marble in the composition of SCC, at a dosage of 350 kg/m 3 increased the compressive strength by about 6.7% in comparison to ordinary cement vibrated concrete. In recent work, Toubal et al.  41  have shown that wet curing of pastes made with MP leads to higher compressive strength compared to air curing. They also reported that increasing wet curing duration helps to improve the compressive strength by reducing the percentage of water evaporated and the porosity.

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