Evaluating the impact of fly ash as a sand substitute on concrete performance

Abstract

Urbanisation and infrastructure development are increasing the demand for concrete, endangering ecology and straining natural resources. However, without compromising quality, concrete can be made more environmentally friendly by incorporating recycled components. The physical properties of an ecologically friendly concrete – using fly ash (FA) as a fine aggregate substitute for sand – were examined in this study. Both destructive and non-destructive testing techniques were used to evaluate the concrete properties. After creating concrete mixtures with 10–50% substitutions of FA for sand, the workability, compressive strength and split tensile strength were evaluated and compared with conventional concrete. The results showed that replacing 40% of sand with FA increased the split tensile strength by 15.45%, increased the compressive strength by 29.94% and reduced the workability by 28%. The optimum blend produced a rebound number of 42.4 and a notable improvement (26.90%) in ultrasonic pulse velocity (UPV). Regression analysis confirmed a strong link between compressive strength, UPV and rebound number. Using 40% FA as a replacement for sand improved the physical properties of the concrete and lowered costs, while demonstrating environmentally friendly building methods.