Study of Robustness of Self-Compacting Concretes Made with Low Fines Content

Viscosity-modifying admixtures (VMAs) are often used to increase the robustness of self-compacting concretes (SCCs); however, concretes produced in this way require a higher cement or additions content than those made with additional limestone filler and thus are less attractive from the point of view of economics and sustainability. In light of this, the objective of this paper was to study the robustness of a SCC made with VMAs and low filler content and to determine whether it was comparable to a commercial SCC, with high limestone filler content and less cement. Three types of SCCs with water/cement (w/c) = 0.6 were produced with water contents varying between -7.5% and +7.5%. A linear regression model was constructed from the experimental data for each of the properties analyzed so as to provide an easy method of calculating the acceptable percentage of water-content variation in concrete that satisfies certain robustness requirements. This model provides a comparison of the different types of SCCs and thus assists the concrete producer to select the appropriate mixes. The results show that variations in flowability and compressive strength due to changes in water content were very similar in the three concrete types considered in this study. However, when filler was replaced by VMA, the material's cohesive properties (viscosity and segregation resistance) showed improvement. In the SCC made with additional limestone fines, slump flow spread time T 50 and V-funnel time were the properties that contributed the most to reducing the material robustness. It was also observed that segregation resistance and compressive strength do not play a significant role in the robustness of SCCs under consideration. DOI: 10.1061/(ASCE)MT.1943-5533.0000609. (C) 2013 American Society of Civil Engineers.