An investigation of key mechanical and durability properties of coconut shell concrete with partial replacement of fly ash

This study investigated the effect of adding fly ash on the mechanical and durability characteristics of coconut shell (CS) concrete. Two different mixes were developed, one with CS and the other with conventional aggregate and CS as coarse aggregate. Cement was replaced with Class F fly ash in terms of weight at 0, 10, 20, and 30% in both mixes. Test result showed that the CS concrete with 10% fly ash replacement level exhibited the highest compressive and tensile strength. The addition of fly ash decreased the porosity of CS concrete due to its fineness and increased hydration products in the matrix at later ages. Additionally, it also improved the weak aggregate interfacial transition zone of CS lightweight concrete. Thus, the fly ash addition in CS concrete showed lower values of water absorption, permeable voids, sorptivity, and chloride permeability. Furthermore, the increasing content of fly ash addition improved the durability characteristics of CS concrete considerably.