Fly Ash (FA) is one of the waste materials generated from the combustion of solid waste through incinerator and contains hazardous substances. Further treatment to the ash needs to be done to avoid further environmental destruction. As an alternative solution for this problem, FA is used as a replacement material for cement in the mortar. The main objective of this study is to explore the potential use of FA as partial replacement of cement in mortar. The percentage of FA used to replace the cement in this study is 0%, 5%, 10%, 15% and 20%. Several important tests were conducted to identify main properties of the mortar such as compressive strength, water absorption, density and ultra-pulse velocity. Mortar containing 15% of fly ash has the highest of compression strength which is 35 MPa after 28 days. Besides, the mortar containing 5% of fly ash has the highest result of water absorption test and density test whereas mortar containing 20% of fly ash has the highest value for pulse velocity after 28 days. Thus, mortar containing fly ash has good physical and mechanical properties.
