Nahabwe Isaac2025-04-292025-04-292025-04-16https://hdl.handle.net/20.500.12311/2606UndergraduateThis study explores the suitability of using water hyacinth ash (WHA) as a partial replacement of cement in mortar to improve its properties for application in damp-prone environments. Laboratory testing was conducted to determine the chemical composition of water hyacinth ash and compare mortar compressive strength, workability and water absorption effects. WHA was incorporated at 0%, 2.5%, 5.0%, 7.5%, and 10%, replacing cement by weight. The XRF analysis results revealed that silica is predominate in WHA (SiO₂ – 51.65%) and alumina (Al₂O₃ – 23.24%), exhibiting good pozzolanic properties. Compressive strength improved with addition of WHA up to 7.5% partial replacement of cement (to 21.6 MPa for 28 days). The workability of mortar also improved with addition of WHA and the peak was 5.0% replacement. The incorporation of WHA resulted into reduced water absorption characteristics, with the lowest value recorded at 7.5% replacement (at 3.8%), indicating enhanced resistance to water ingress and proving its suitability for damp-prone construction applications.enThesis