Development of high-strength self-compacting concrete with low fineness modulus sand

Abstract

Self-compacting concrete is a highly flowing concrete that compact under self-weight without any vibration effort. The high workability of concrete mixtures is achieved by the reduction in coarse aggregate content while increasing fines aggregate volume. Usually, coarse quartz sands with fineness modulus more than 2.5 are used as fine aggregate. The use of low fineness modulus sands, characterized by high intergranular porosity and high specific surface area, as a fine aggregate, leads to an increase in the concrete mixture water demand and a decrease in its flowability. In such conditions, to obtain high-workability and high-strength concrete, increased cement consumption is required. The purpose of this study was to develop high-strength self-compacting concrete with reduced cement consumption and using low fineness modulus sand. To achieve this purpose, we optimized aggregates consumption in concrete composition, which achieves minimum aggregate mixture intergranular porosity, best concrete mixture workability without segregation, and maximum concrete strength. It has been established that silica fume and superplasticizer using allows obtaining high-strength self-compacting concrete of strength class B60 with low-quality fine sand and reduced cement consumption of 360 kg/m3. With increasing mixtures retention time before concrete placing, there was an insignificant increase in the flowability of obtained self-compacting concrete mixture and an improvement in the physical and mechanical properties of concrete. Remixing of concrete mixtures and concrete placing after 90 minutes from concrete mix preparation moment allowed to increase concrete strength to 17%, increase its density to 15 kg/m3, and reduce porosity to 25%.