Evaluation of the optimal concrete mix design with coconut shell ash as a partial cement replacement

Concrete is a major construction material with a significant environmental impact. Among other materials, coconut shell ash could be used as a partial replacement of cement to produce sustainable concrete. This study aimed to investigate the use of coconut shell ash as a partial cement replacement to reduce the environmental impact whilst achieving the predefined structural performance of concrete. The fresh, hardened and microstructural properties were investigated, and a life cycle assessment within the product stage was conducted in this study. When considering 15%, 20%, 25% and 30% replacement level concrete mixes, compressive strength was 27.31 MPa, 26.94 MPa, 25.60 MPa and 21.40 MPa at 28 days and environmental impact reduction in global warming potential were over 10%, 15%, 20% and 25% respectively. Based on the structural performance and environmental impact, 20% was the optimal replacement level. Therefore, cement can be replaced by coconut shell ash up to 20% to achieve the average target compressive strength as 25 MPa by reducing the environmental impact in global warming potential over 15%.