Experimental Evaluation of Concrete Structural Properties with Recycled Coarse Aggregate and Rice Husk Ash

Abstract

The present work examines the mechanical and structural performance of concrete in which rice husk ash (RHA) partially replaces cement and recycled concrete coarse aggregate (RCA) serves as an alternative to natural coarse aggregate (NCA). Fifteen concrete mixtures were prepared with RCA replacement levels of 0%, 25%, 50%, 75%, and 100% and RHA contents of 0%, 10%, and 20%. Compressive strength was evaluated at 7, 28, and 91 days, while splitting tensile strength was measured at 28 days. Additionally, the structural response of two reinforced concrete beams was assessed under both flexural and shear loading conditions for a reference beam and a beam produced with 100% RCA and 20% RHA. Results showed that increasing RCA content reduced compressive strength by approximately 2–27% and splitting tensile strength by 14.8–37.2% relative to conventional concrete. The incorporation of RHA at 10% and 20% produced similar trends, with compressive strength reductions of about 15% and 27% at 0% and 100% RCA replacement levels, respectively. Although the beam containing 100% RCA and 20% RHA exhibited lower toughness and ductility than the control beam, both beams achieved comparable ultimate load capacities and showed nearly identical responses under shear loading.