Cement is currently the most versatile and widely used material in construction. However, the high carbon emissions and energy consumption associated with the manufacture of cement remains a serious concern. bagasse ash (BA) is a secondary waste product of bagasse-fired power generation. This study investigated the use of BA as a replacement for cement as a means of reducing the environmental impact of concrete-based construction. At 28 days, we measured the water absorption of cement mortar specimens as well as the compressive strength at room-temperature and after heating. Experiments were conducted involving the replacement of various proportions of cement using BA and fly ash (FA), followed by a comparison of the physical properties. Our test results demonstrate the applicability of BA in the production of cement mortar mixtures with high water-binder ratios. It was found that the water-binder ratio determines the optimal proportion of BA when used as a replacement for cement, wherein a higher water-binder ratio means that more of the cement can be replaced with BA. In compressive strength respect, the optimal cement replacement with BA was 15 % to 25 %, whereas the optimal cement replacement with FA was 20 %. BA was shown to have a more pronounced effect in reducing water absorption in cement mortar specimens with high water-binder ratios (0.55 to 0.65). The compactness of specimens with lower water absorption enables them to retain more of their initial compressive strength following exposure to high temperatures.