Experimental investigation of heating–cooling effects on the mechanical properties of geopolymer-based high performance concrete heated to elevated temperatures

Abstract

In this study, geopolymer-based high performance concrete (G-HPC) reinforced with steel fibres was utilized to investigate its dynamic behaviour after heating–cooling treatment. A furnace with a heating capacity of 1100 °C was adopted to heat the specimens. The P-wave velocity and quasi-static uniaxial compressive strength of G-HPC after the heating–cooling treatment were obtained and compared with those without the heating–cooling treatment. The experimental findings indicated that the G-HPC specimens suffered different degrees of thermal damage under 250–1000 °C high temperature, while it still remained a good explosive spalling resistance. Moreover, the water cooling regime would cause more serious damage to the G-HPC specimens than the natural cooling. Further, a 50 mm-diameter Split Hopkinson Pressure Bar (SHPB) apparatus was applied to characterize the dynamic behaviour of G-HPC after the heating–cooling treatment, and a high-speed camera was employed to record the failure process. Upon increasing the temperature, the dynamic compressive strength and elastic modulus of G-HPC were deteriorated especially in the temperature range between 250 °C and 750 °C, thereby leading to partial loss of its ability to resist impact loads. However, even after being heated to 1000 °C, the specimens still demonstrated a significant strain rate effect. Besides, the high cooling rate under water was observed to induce a thermal shock, resulting in the secondary damage for the heated specimens.