Eco-efficient structural concrete: Mechanical and durability properties of mixes with cashew nutshell ash and waste foundry sand

The construction industry is facing rising issues related to sustainability and resource depletion, mostly due to the extensive use of conventional materials such as cement and fine aggregates. Cement manufacture emits a substantial amount of carbon, and mining natural aggregates can be harmful to the environment. This study investigates the use of Cashew Nutshell Ash (CNA) and Waste Foundry Sand (WFS) as partial substitutes for cement and fine aggregates in concrete, with the objective of increasing sustainability. In this study, cement was replaced with CNA at varied percentages of 0%, 5%, 10%, 15%, and 20%, while fine aggregate was replaced with WFS at 0%, 10%, 20%, 30%, and 40%. The mechanical, durability, and microstructural properties of the modified concrete were evaluated. The tests involved assessing compressive strength, flexural strength, split tensile strength, acid resistance, water absorption, and chloride ion penetration. The study looked at the combined effect of CNA's pozzolanic activity and WFS's packing efficiency. The results revealed that the combination with 10% CNA and 20% WFS (C10%W20%) had the greatest results, with a 12% improvement in compressive strength, a 15% increase in flexural strength, and a 10.5% increase in split tensile strength compared to the control mix (C0%W0%). Durability tests found that the material is more resistant to acid assaults, has lower water absorption, and has less chloride ion penetration. Finally, the study concludes that CNA and WFS are effective sustainable options for concrete manufacturing, improving both performance and environmental sustainability.