Effect of crushed limestone replacement with river gravel on the mechanical properties and economic viability of concrete

Abstract

This research aims to evaluate the technical and economic effects of partially replacing crushed limestone (C) with locally sourced river gravel (G) on the mechanical properties of concrete, under conditions simulating practical field applications where water content is adjusted to achieve suitable workability. The experimental program involved mix designs with river gravel replacement levels of 0%, 50%, 60%, 70%, 80%, 90%, and 100% by weight of coarse aggregate. This adjustment resulted in a decrease in the water-to-cement (W/C) ratio from 0.457 for the 100% crushed stone mix to 0.424 for the 100% river gravel mix. The 28-day test results indicated a systematic decrease in compressive strength as the river gravel content increased, from 278 ksc in the control mix to 188 ksc in the 100% gravel mix, a reduction of approximately 32%. Conversely, the splitting tensile strength exhibited a different behavior, peaking at 29.7 ksc for the mix with 70% river gravel (30C70G), which was 16% higher than the control mix. A techno-economic analysis identified the 50% replacement mix (50C50G) as the optimal balance, achieving a compressive strength of 250 ksc (98% of the design strength) while reducing coarse aggregate costs by approximately 29.7% compared to the mix using only crushed stone. Therefore, the partial replacement of crushed stone with river gravel presents a viable alternative for producing structural concrete in regions where river gravel is an economically advantageous local resource.