Feasibility of using microwave curing to enhance the compressive strength of mixed recycled aggregate powder based geopolymer

Abstract Geopolymerization technology provides a promising approach for mixed recycled aggregate (MRA). However, the chemical activity of ground MRA powder (MRAP) is generally low, geopolymer binders using MRAP as source material often exhibits less satisfactory performance. This paper investigates the feasibility of using microwave curing method to enhance the compressive strength of MRA based geopolymer paste through an extensive laboratory study. The effect of different parameters, including Metakaolin (MK) addition, microwave curing duration, ambient curing duration before microwave curing, alkali concentration and solid-to-liquid ratio on the efficiency of microwave curing method were examined. Meanwhile, environmental impact and cost-benefit analysis of samples cured by microwave irradiation were performed. The results showed that it is feasible to increase the compressive strength of the MRAP based geopolymer by using microwave curing. Metakaolin addition and higher solid-liquid ratio can improve the efficiency of the microwave curing. A too long microwave irradiation duration may induce a compressive strength degradation of MRAP based geopolymer. The duration of ambient curing before microwave curing is recommended to be shorter than 3 days. In addition, microwave curing can significantly increase the eco-efficiency but greatly reduce the production cost of geopolymers by reducing energy consumption and increasing curing efficiency.