Development of an environmental-friendly durable self-compacting concrete

In this experimental study on self-compacting concrete (SCC), the Manufactured sand (M-sand) and Fly ash (FA) were utilised for partial replacement of Natural sand (N-sand) and Ordinary Portland Cement (OPC), respectively. N-sand was partially replaced by M-sand at various percentage levels, after the dose of FA in the mix was optimised. In terms of compressive strength, the optimum replacement level of OPC by FA was 20%, whilst for replacement of N-sand by M-sand it was 50%. Two types of mixes were prepared to compare the macro and micro level properties of SCC, i.e., SCC-I (100%OPC + 100%N-sand) and SCC-II (80%OPC + 20%FA + 50%N-sand + 50%M-sand). The characteristics of fresh concrete mixes were determined using Slump flow, T50 time, V-funnel, L-box, U-box, and J-ring tests. After 28 days of curing in tap water, both types of specimens were exposed to a solution of ammonium sulphate [(NH4)2SO4] containing sulphate salt concentration of 2.0 g/l for 360 days to test their durability. Loss in compressive strength, weight change, sorptivity, and micro-structural changes (XRD, SEM, and EDS) all were evaluated for up to 360 days. It was found that the use of FA and M-sand in concrete makes it more environmental-friendly and durable, as well as have better performance in a sulphate environment.