Utilization of Agricultural Waste as Aggregates and Pozzolans in Lightweight Concrete – A Review
1 *Abdulganiyu H. O., 2 Odeyemi S. O., 3 Giwa Z.T.
1,2,3Department of Civil Engineering, Kwara State University Malete, Nigeria
DOI: 10.36108/laujoces/6202.61.0201
Abstract
Agricultural wastes are increasingly being investigated as sustainable substitutes for conventional aggregates and supplementary cementitious materials in lightweight concrete. This review synthesizes studies on rice husk ash, coconut shell, palm kernel shell, cassava peel ash, sawdust ash, groundnut shell ash, corn cob ash, and related agro-wastes, focusing on their effects on density, strength, durability, thermal performance, and microstructure. The reviewed studies show that these materials can reduce concrete density to about 800 to 2100 kg/m³, while compressive strength commonly ranges from below 10 MPa for highly porous insulation mixes to about 30 to 40 MPa for optimized structural or semi-structural lightweight concrete mixes. Optimal cement replacement levels are generally around 5 to 20 percent for ashes such as rice husk ash, cassava peel ash, sawdust ash, and groundnut shell ash, while aggregate replacement levels of 10 to 25 percent are often more suitable for coconut shell and palm kernel shell concretes. Properly processed agro-wastes can also improve water absorption resistance, shrinkage control, thermal insulation, and, in some cases, sulfate and chloride resistance, although excessive replacement usually reduces strength and workability. What distinguishes this review from earlier ones is its combined focus on both aggregates and pozzolans in lightweight concrete, its comparison of performance trends across different agricultural wastes as well as its identification of application-specific optimum ranges rather than a purely descriptive summary. It also highlights the limited number of studies on self-compacting, high performance and field-scale lightweight concrete as well as the scarcity of standardized mix design procedures, long-term durability data and lifecycle assessment frameworks. Overall, agricultural wastes offer a practical route to lower-cost, lower-carbon lightweight concrete but broader adoption will depend on standardization, durability verification, and performance based mix design.
Keywords Agricultural waste; Lightweight concrete; Pozzolans; Mechanical properties; Durability; Microstructural properties