Experimental Investigation on Waste-Derived Sustainable Concrete Mixes Incorporating Fly Ash, Red Mud, Eggshell Powder, and Construction & Demolition Waste

Abstract

The growing global demand for concrete has intensified concerns regarding the environmental impact of Portland cement production, which contributes significantly to greenhouse gas emissions and the depletion of natural resources. This study presents a systematic experimental evaluation of waste-derived sustainable concrete in which four industrial and agro-industrial by-products — fly ash, red mud, eggshell powder, and construction and demolition waste (C&DW) — were individually incorporated as supplementary cementitious materials (SCMs) in M25-grade concrete at cement replacement levels of 0–20%. Mechanical performance was characterised through compressive, split-tensile, and flexural strength tests at 7, 14, and 28 days, together with workability assessment of all mixes. The comparative evaluation identified optimum replacement levels of 20% for fly ash, 10% for eggshell powder, 10% for red mud, and 15% for C&DW. At these optima, the 28-day compressive strength improved by 12.2%, 8.85%, 6.05%, and 13.83%, respectively, over the control mix, with corresponding gains in split-tensile (up to 12.64%) and flexural strength (up to 11.85%); all mixes retained slump values within IS 456:2000 workability limits. A cost-effectiveness appraisal indicated that C&DW at 15% and fly ash at 20% offer the most economical strength enhancement, as both materials carry negligible acquisition cost. The results demonstrate that single-stream valorisation of locally available wastes can reduce cement consumption, lower CO₂ emissions, and divert substantial waste volumes from landfills without compromising — and in most cases improving — the structural performance of normal-strength concrete.