Dynamic propagation behavior of mode I crack in MSF/PVA-MKPC NSCB specimens after high-temperature exposure

In order to improve the high-temperature resistance of engineering cementitious composite (ECC), magnesium potassium phosphate cement (MKPC) was used to replace portland cement, and micro steel fiber (MSF) was used to replace polyvinyl alcohol (PVA) fiber in equal volume. And the fiber-reinforced potassium magnesium phosphate cement matrix composites (MSF/PVA-MKPC) were prepared. The microstructure of the MKPC matrix and the condition of the fibers after subjecting to high temperature were observed by scanning electron microscope (SEM), and the split Hopkinson pressure bar (SHPB) was used to conduct the impact test on notched semi-circular bend (NSCB) specimens after thermal treatment. The dynamic propagation behavior of mode I crack of MSF/PVA-MKPC after heat treatment was studied by crack propagation gauge (CPG) and experimental–numerical method. The results showed that: (1) MSF/PVA-MKPC remained intact after high temperature exposure and did not completely lose the strain hardening and strain softening ability; (2) Dynamic fracture toughness is negatively correlated with crack propagation speed; (3) Dynamic fracture toughness increases with the increase of loading rate and first decreases and then increases with the increase of maximum exposure temperature; (4) Crack arrest exists in the process of crack propagation, and the crack arrest toughness is greater than the initial toughness and the average propagation toughness.