Each year tens of millions of tons of bamboo are utilized commercially, generating a vast amount of waste. One solution is to calcine this waste and use it as additive in concrete to keep it out of landfills and save money on waste disposal. This research project identifies (1) the optimal calcination condition of bamboo culm ash (BCAsh) and (2) the effect of various cement replacement levels on mortar properties. After considering the amount of energy consumed and the carbon content, burning at 700 °C [1292 °F] for 1.5 h was selected as the optimum condition. Cement replacement levels between 0.5 and 5% were investigated by evaluating the effects on heat of hydration and compressive strength of four mixes of BCAsh mortar. While the BCAsh reduced the strength of the mortar only slightly, it did show a considerable retarding effect on mortar hydration.