Sustainable use of rice husk ash in cement-based materials: Environmental evaluation and performance improvement

The feasibility of using agricultural waste of rice husk to prepare highly reactive rice husk ash for sustainable cement-based material was explored through five sets of procedures: optimization of rice husk ash with an improved combustion technique, pozzolanic activity evaluation of the prepared rice husk ash, strength development of mortar with rice husk ash, sulfate attack experiment to investigate the potential durability, and environmental evaluation of rice husk ash utilization. From the results, the optimum rice husk ash using improved combustion technique had high pozzolanic activity, it presented the highest lime-ash compressive strength, a violent pozzolanic reaction heat flow as well as rapid Ca(OH)2 consumption ability among different mineral additives. Compressive strengths of mortars have been enhanced with the increase of rice husk ash contents. The results of sulfate attack indicated that paste with 15% rice husk ash improved sulfate resistance by stabilization of C–S–H and the refinement of pore structure. Sustainability analysis including embodied carbon dioxide emission and energy consumption confirmed the environmental friendliness of rice husk ash utilization. This study verified the feasibility of highly reactive rice husk ash from agricultural waste and the potential utilization of it as sustainable mineral admixture in cement-based materials.