Valorisation Of Agricultural Waste Ash For Sustainable Concrete

Abstract

The construction industry's dependence on ordinary Portland cement (OPC) has raised serious environmental 
concerns owing to the large carbon dioxide emissions and energy consumption associated with clinker 
production. Simultaneously, agricultural activities generate enormous volumes of biomass residues such as rice 
husk, sugarcane bagasse, palm oil waste, corn cob, and wheat straw, which are often disposed of through open 
burning or landfilling, creating additional ecological burden. Converting these residues into pozzolanic ashes for 
partial replacement of cement offers a dual solution reducing clinker demand while valorising agro-waste. This 
review paper critically synthesises past experimental and analytical studies on the effect of agricultural waste ash 
(AWA) on the fresh and hardened properties of concrete, including workability, setting time, bulk density, 
compressive strength, split tensile strength, flexural strength, and durability indicators such as water absorption, 
chloride penetration, and sulphate resistance. The review draws upon rice husk ash (RHA), sugarcane bagasse 
ash (SCBA), palm oil fuel ash (POFA), corn cob ash (CCA), and wheat/straw ashes as representative agro-wastes. 
Findings across the literature consistently indicate that ash fineness, silica content, and optimum replacement 
dosage (typically 10–20%) govern performance, with excessive replacement beyond 25–30% generally reducing 
workability and strength due to increased water demand and unreacted residue. The paper further presents a 
meta-analytical comparison of reported strength trends, identifies methodological inconsistencies across studies, 
and highlights research gaps concerning standardisation, long-term durability, and machine-learning-based 
prediction models. The review concludes that agricultural waste ash is a technically viable and environmentally 
beneficial supplementary cementitious material (SCM), provided its physicochemical variability is properly 
characterised and controlled.