Experimental investigation on mechanical properties of lightweight reactive powder concrete using lightweight expanded clay sand

Abstract

This study investigates the mechanical properties of lightweight reactive powder concrete (LWRPC) under normal curing conditions, with a focus on grades M70, M80, and M90. The research was conducted in two phases. In the first phase, conventional reactive powder concrete (RPC) was formulated using quartz sand and 0–30% supplementary cementitious materials (microsilica and alccofine), guided by the Elkem Material Mix Analyzer (EMMA) and the modified Andreassen model. In the second phase, lightweight expanded clay sand (LECS) was incorporated to develop LWRPC, and its mechanical properties were assessed. The study developed mix proportions for the specified grades and identified 10% microsilica and 20% alccofine as an effective blend for improving strength and workability, while LECS contributed to a more than 20% reduction in density. The developed LWRPC grades achieved 86–90% of its 28-day compressive strength within 7 days, with an average density of 1893 kg/m³, 22% lower than corresponding normal high-strength concrete (NHSC) grades, resulting in a 35% increase in structural efficiency. The modulus of elasticity of LWRPC was found to be 10% higher than high-strength lightweight concrete (HSLWC) in the literature. Additionally, flexural and splitting tensile strengths revealed improvements of 24% and 63%, respectively, compared to HSLWC, and 11% and 22% relative to NHSC grades. Although LWRPC has a higher cost ($239/m³) approximately three times that of NHSC, the results demonstrate that it offers superior structural performance, positioning it as a high-performance lightweight concrete.