Enhancing the Properties of Laterite Bricks with Coconut Coir Fibre and Kaolin Powder for Building Application

Abstract

Portland cement is widely used, but its cost and environmental impact have prompted interest in alternative materials for producing low-cost masonry units, including laterite bricks. The aim of this study is to investigate engineering properties of laterite bricks incorporating coconut coir fibre (CCF) and kaolin powder (KP). Four modified formulations containing 0.5% CCF and 5%, 10%, 15% or 20% KP by mass of laterite were compared with an unmodified control. Specimens were assessed after 7, 28, 56 and 90 days of curing, as applicable to each property. At 90 days, the control recorded a compressive strength of 1.017 N/mm², whereas the modified mixtures ranged from 1.100 to 1.198 N/mm²; the 5% KP–0.5% CCF formulation performed best among the modified mixtures. Splitting tensile strength at 90 days was 0.135 N/mm² for the control and 0.095–0.130 N/mm² for the modified mixtures. At 28 days, water absorption was lower in all modified formulations (2.41–2.50%) than in the control (2.57%). At 90 days, the modified mixtures recorded higher absorption (1.20–1.79%) than the control (0.44%). The 90-day density of the modified mixtures ranged from 1,482.62 to 1,575.00 kg/m³, compared with 1,586.19 kg/m³ for the control. Abrasion measurements varied across mixtures and curing ages, but their interpretation requires clarification of the reporting unit and the direction of the coefficient. These results suggest that the 5% KP–0.5% CCF formulation offers the highest compressive strength among the modified mixtures, exceeded the control. The measured strengths do not establish suitability for load-bearing walls. Non-load-bearing applications may be considered only after verification against the relevant construction requirements. Further investigation of longer-term durability, microstructure, thermal behaviour and life-cycle performance is warranted.