Mechanical properties of steel fiber-reinforced geopolymer concrete after high temperature exposure

Adding a certain amount of steel fibers can overcome the brittleness defects in geopolymer concrete and improve the mechanical properties, which has a broader application prospect. However, the research on the material properties of steel fiber-reinforced geopolymer concrete (SFGPC) after high temperature exposure is still very limited. Therefore, tests on 114 cubes and 57 prisms after exposure to high temperatures were conducted in this paper. The main variables were temperature (20 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, and 800 degrees C), steel fiber volume content (0, 1 %, and 2 %), and concrete type (SFGPC and steel fiber-reinforced ordinary Portland cement concrete (SFOPC)). The results indicated that SFGPC with a steel fiber content of 1 % at 800 degrees C experienced a 53.6 % reduction in compressive strength, a 58 % reduction in splitting tensile strength, a 93.9 % reduction in elastic modulus, a 45.9 % reduction in toughness index, and a 274.5 % increase in peak strain, compared with room temperature. The 1 % fiber content enhanced the compressive strength by 10.3 %-36.5 %, the splitting tensile strength by more than 16 %, the peak strain by 9.6 %-32.7 %, and the toughness index by 24.4 %-64.6 % compared to the absence of fiber content. Based on the room temperature model, a constitutive model of SFGPC under uniaxial compression after high temperatures was developed.