Mechanical, microstructural and thermal insulating properties of iron-rich laterite lightweight based geopolymer composite with appropriate coffee husk waste incorporation: A sustainable solution for valuing coffee husk waste

Coffee, one of the most popular hot beverages worldwide, generates substantial quantities of waste by-products during its production, including coffee husk (CH). Disposing of large amounts of CH in landfills poses serious ecological and health risks due to the release of toxic gases during organic decomposition. For the clean environmental disposal, the present work aimed to use CH at varied dosages (0, 2.5, 5.0, 7.5 and 10%) for the production of lightweight laterite-based geopolymer. Results showed that the compressive and flexural strengths decreased from 31.20 to 5.42 MPa and 8.23 to 1.98 MPa with increased CH content up to 10%. Adding CH into geopolymer generated voids weakened the strength development and increased the water absorption and porosity. The thermal conductivity decreased from 0.65 to 0.41 W/mK with increased CH content, making the geopolymer suitable for insulation applications. Water absorption, bulk density, and porosity were characterised according to ASTM C373-88 , and capillary sorption rates using ASTM C1403 . The intended product is a lightweight, geopolymer mortar for thermally insulating non-load-bearing elements, conforming to ASTM and /or EN standards for mortars used in construction.