Use of ground palm oil fuel ash to improve strength, sulfate resistance, and water permeability of concrete containing high amount of recycled concrete aggregates

This study proposes the use of ground palm oil fuel ash (POFA) with high fineness to improve the mechanical properties and durability of concrete containing high amount of recycled concrete aggregates. The mixture proportions of the recycled aggregate concretes were separated into two groups; the first group was composed of 100% coarse recycled aggregate and natural river sand, while the second group was composed of 100% both coarse and fine recycled aggregates. A portion of ordinary Portland cement type I (OPC) was replaced by ground POFA at 20%, 35%, and 50% by weight of binder for both recycled aggregate concrete groups. The results showed that ground POFA could improve the compressive strength and reduce the water permeability of recycled aggregate concretes. With 20% replacement of OPC by ground POFA, the compressive strength of recycled aggregate concretes was only 7% lower than that of the conventional concrete. The modulus of elasticity of recycled aggregate concrete with and without ground POFA was lower than that of the conventional concrete by approximately 25%. Finally, ground POFA could be used effectively to reduce the expansion of recycled aggregate concrete. As the replacement of ground POFA in concrete is increased, the expansion of recycled aggregate concrete due to sodium sulfate attack decreased.