The experimental study on microwave-assisted preparation of Ultra-High Performance Geopolymer Concrete (UHPGC).

This paper studied the effects of microwave power and time on microstructure and mechanical properties of Ultra-High Performance Geopolymer Concrete (UHPGC) matrix. Results show that conducting microwave treatment at curing age of 3d is suitable, the optimal microwave power and time are 560 W and 180 s with the 3d compressive strength and flexural strength of 125.4 MPa and 6.0 MPa. The large amount of heat generates in UHPGC matrix under microwave field, which leads to the increase in temperature within the UHPGC matrix. Due to hydration promotion caused by internal temperature rise, the tighter gels accumulation and lower porosity can be observed, which results in the remarkable improvement of compressive strength. However, microwave heating causes higher proportion of large pores and more generation of "melon seed flake" hybrid crosslinking products mainly including N-A-S-H, which will result in the reduction of flexural strength. Moreover, microwave pre-curing is more suitable for preparing UHPGC compared with the oven pre-curing comprehensively considering the early age compressive strength enhancement and energy consumption. • Microwave pre-curing parameters for preparing UHPGC were optimized. • Mechanical properties evolution laws after microwave pre-cured were acquired. • Microstructure evolution mechanism during microwave pre-cured was revealed. [ABSTRACT FROM AUTHOR]