Development and Characterization of Sustainable Load-Bearing Masonry Units Incorporating Coconut Shell Ash and Recycled Polyester Fabric

Agricultural and industrial waste have received considerable attention in Sri Lanka as potential raw materials for developing sustainable masonry units. This study investigates the development of high-performance load-bearing masonry units by partially replacing ordinary Portland cement (OPC) with coconut shell ash (CSA) and recycled polyester fabric scraps. CSA was incorporated as a partial cement replacement at levels of 1%, 3%, 5%, 7%, 9%, 11%, 13%, and 15% by weight, while a constant 1% recycled polyester fabric (by weight of binder) was incorporated in all modified mixes. The performance of the masonry units was evaluated in terms of compressive strength, water absorption, and Fourier Transform Infrared (FTIR) spectroscopy to identify the optimum mix composition. The mix containing 7% CSA and 1% polyester fabric achieved the minimum 7-day water absorption of 4.4% and the maximum 28-day compressive strength of 13.9 MPa. FTIR analysis provided clear evidence of pozzolanic activity through the formation of additional Calcium silicate hydrate (C-S-H) gel. The developed masonry units satisfy both ASTM C90 and SLS 855 requirements for load-bearing applications in Sri Lanka. The present study focuses on compressive strength, water absorption, and FTIR characterization of the developed masonry units. Further studies on tensile strength, flexural strength, ductility, and long-term durability are recommended to provide a comprehensive evaluation of the reinforcing effect of recycled polyester fabric.