Influence of rice husk–bark ash on mechanical properties of concrete containing high amount of recycled aggregates

In this study, ground rice husk–bark ash (RHBA) was used as a pozzolanic material in concrete containing high amount of recycled aggregates. The concretes were prepared by using 100% of recycled coarse aggregate (RCA), then river sand was replaced by recycled fine aggregate (RFA) at 0%, 50%, and 100% by weight of the fine aggregate (river sand plus recycled fine aggregate). The results revealed that recycled aggregate concretes had lower compressive strength than that of the conventional concrete (concrete made from normal aggregates). In addition, the use of ground RHBA in recycled aggregate concrete gave higher compressive strength than the recycled aggregate concrete without ground RHBA even though it increased the slump loss of concrete. The splitting tensile strength of the recycled aggregate concrete was 8.15% of the compressive strength. Finally, the modulus of elasticity of recycled aggregate concrete was lower than that of the conventional concrete and was about 4% lower than the value predicted by ACI 318.