Strength and Durability Studies on Concrete using Cashew Nut Shell Ash (CNSA) waste as Supplementary Materials

As the world population is expected to increase significantly, there is a greater need for housing and, as a result, building materials. Conventional manufacturing methods for materials such as concrete involve substantial energy usage and substantial release of carbon emissions, which contribute to environmental deterioration. This study investigates the incorporation of Cashew Nut Shell Ash (CNSA) as a partial replacement for Ordinary Portland Cement (OPC) as primary cement, while CNSA formed binary blends. The study examined various water-to-binder ratios (0.55, 0.50, and 0.45) and a total binder content of 310 kg/m³, with replacement levels at 0%, 10%, 20%, 30%, and 40%. Compressive strength tests were performed at 2, 7, 28, and 90 days, shows a consistent increase in strength over time. Optimal CNSA content (10-30%) enhanced long-term strength due to its pozzolanic activity. Additionally, the elastic modulus was tested, indicating improved stiffness in mixes containing CNSA in comparison with the conventional concrete systems. Durability tests such as Rapid Chloride Permeability Test and carbonation depth analysis showed that CNSA addition generally decreased chloride conductivity, thereby enhancing durability. However, replacement levels (beyond 40%) exhibited diminishing returns. The results suggest that CNSA is a viable partial replacement for cement, improving concrete's workability, density, and long-term strength while enhancing durability against chloride penetration and carbonation. These findings support CNSA's potential in creating sustainable and resilient concrete systems.