Enhancement of the Durability Properties of Lightweight Coconut Shell Concrete by Incorporating Mineral Admixtures

Introduction Coconut shell concrete (CSC) is a lightweight concrete (LWC) made from waste coconut shells (CSs). CSs have high porosity, which may lead to durability issues. Adding mineral admixtures to LWC can overcome this issue. Hence, this study examined the durability of lightweight CSC that employs fly ash (FA) and silica fume (SF) in lieu of cement. Methods Crushed CSs of 12.5 mm size replaced the conventional coarse aggregate. The effects on water permeability, chloride permeability, capillary water absorption, thermal conductivity, and fire resistance of CSC at varying levels (0%, 5%, and 10%) of FA and SF were evaluated. All the specimens were tested after 28 days of curing. Results The permeability coefficient of CSC at 28 days decreased significantly with 10% SF, ranging from 0.945 × 10-11 to 1.824 × 10-11 m/s. The sorptivity coefficient was reduced below the accepted value of 0.1 mm/min0.5 with mineral admixtures. At 28 days, rapid chloride permeability values improved, varying from 1160 to 1640 Coulombs. The thermal conductivity, measuring between 0.61 and 0.68 W/mK in CSC was influenced more by FA than SF. CSC with 10% SF could withstand a fire attack for nearly 2 hours, making it suitable for Type three building according to the National Building Code standards. Conclusion Adding mineral admixtures enhanced durability by improving the pore structure, with 10% SF demonstrating optimal results. This research underscores the potential of mineral admixtures for enhancing the performance and applicability of lightweight CSC in construction applications.