Effect of paste volume on fresh and hardened properties of concrete

Abstract

Water to cement (W/C) ratio has been deemed as one of the most important factors affecting the properties of concrete. However, at constant W/C ratio, cement or cementitious paste volume (CPV) also plays an important role, yet limited research has been done to quantify and unveil the mechanism behind. In this study, the effect of CPV on various performance attributes of concrete at fresh and hardened states was evaluated by varying the CPV from 26% to 32% at two different W/C ratios. Based on the tests results and inter-relationships among them, it was found that decreasing the CPV, i.e., reducing the cement content at constant W/C ratio, would decrease the uncompacted wet density while increase the compacted wet density, increase the strength at all curing ages, increase the Young’s modulus, flexural strength and splitting tensile strength, and improve the quality of concrete, albeit the decrease of workability that could be compensated by increasing the superplasticizer dosage or adding fillers. Moreover, mechanisms behind these phenomena have also been revealed from the perspective of mortar film thickness. The work presented herein should be meaningful in the development of eco-friendly high performance concrete.