Coconut Shell Utilization as a Partial Substitute for Coarse Aggregate and Paddy Husk Ash as Well as Waste Red Brick as a Substitute for Partial Cement to Increase the Quality of Concrete

Abstract

This research investigates the synergistic utilization of three distinct waste streams—coconut shell (CS), paddy husk ash (PHA), and waste red brick (WRB)—to enhance the sustainability and modify the quality of concrete. The study aims to produce a concrete mix where CS serves as a partial substitute for coarse aggregate to reduce density, while PHA and WRB are combined as supplementary cementitious materials (SCMs) to partially substitute cement. An experimental laboratory method was employed, formulating a control mix and several variations with different replacement percentages of these materials. Key properties, including workability, density, compressive strength, and flexural strength, were systematically tested. The results indicate that the inclusion of coconut shell aggregate successfully reduces the unit weight, producing a lightweight concrete. While this substitution tends to decrease compressive strength, the pozzolanic activity from the combined use of paddy husk ash and waste red brick powder contributes to strength development and refines the pore structure. This study identifies an optimal mix proportion that balances reduced density with acceptable mechanical performance, demonstrating the feasibility of using this triple-blend waste composite for sustainable construction, particularly in non-structural or semi-structural applications.