Effect of Bagasse Ash and Pozzolan on the Flowability and Setting Time of Cement Mortar

Recent advancements in architecture and construction have caused a steady increase in cement consumption. To reduce the dependency on cement resources and minimize waste, various countries have been searching for ways to convert industrial and agricultural wastes into cement substitutes, which could also enhance environmental protection and waste disposal. Bagasse ash is a type of secondary waste from bagasse combustion for power generation. In this study, various amounts of bagasse ash were added to replace a portion of cement materials in making cement mortar. Subsequently, a flowability test was conducted to investigate the flowability of cement mortar at various cement-water ratios and monitoring changes in workability. Under identical conditions, bagasse ash, fly ash, and slag were compared in terms of changes in their workability and setting time. To investigate the effect of the particle structure on the cement mortar flowability, scanning electron microscopy (SEM) was employed to observe the particle structure. Results show that bagasse ash produced from thoroughly washed bagasse did not require any further grinding because the ash particles were smaller than commercial cement or slag powder particles. Thus, the cost of grinding or screening bagasse ash can be minimized by cleaning or ensuring the bagasse is clean before using it to generate power through combustion. Moreover, an uneven surface of bagasse ash was observed in the study, which may be associated with the water retention effect during the blending process. In addition, the particle size of bagasse ash was generally smaller than that of cement. Thus, the bagasse ash reduced the workability of the cement mortar and substantially decreased the initial and final setting time. Therefore, when substituting bagasse ash for a portion of cement, it is recommended to adopt a higher water-colloid ratio (W/B > 0.60).