Abstract:Cementitious grout is the crucial part of the grouted sleeve connection, and its constitutive relationship under loading is the technical support to form the fire safety design method for grouted sleeve connections. The tests with 36 small prism specimens were conducted to study the uniaxial compressive behaviors of heat-damaged cementitious grout under static or dynamic loading strain rates after the specimens were exposed to elevated temperatures up to 600 ℃. It was found that explosive spalling was inhibited by the combined measures of pre-drying temperature with 105 ℃ in 120 min and the heating rate with 5 ℃/min. There were other findings after the specimens being loaded as follows: all specimens were failed to several vertical fractures with full-length along the height, and there were obvious spalling occurring to the specimens under the dynamic strain rate loadings; the compressive strength of heat-damaged specimens under dynamic loading strain rate with 0.067 s^–1 were higher than that under static loading, which was up to 29.6%; the elastic modulus and the peak strains of heat-damaged specimens under the dynamic loading strain rate with 0.001 s^–1 decreased and increased along with the increasing of elevated temperatures, respectively; compared to these of specimens at ambient temperature, the declining range of elastic modulus was up to 57.0% and ascending range of the peak strain was beyond 13.2%; the normalized curves between stress and strain of heat-damaged specimens contained ascending and declining segments, both of which were nonlinear curves; based on the experimental data, a combined static and dynamic uniaxial compression model of heat-damaged cementitious grout was built and used for the finite element simulation of heat-damaged grouted sleeve connections under high-stress cyclic loading. It was found that the peak loads and load-displacement curves from the simulation were consistent with the test results. In addition, the failure pattern of heat-damaged grouted sleeve connections under high-stress cyclic loading with rebar fracture outside the sleeve was firstly demonstrated in the simulation and 400 ℃ was the critical temperature that failure pattern of rebar fracture outside the sleeve converted into the bond-slip failure between cementitious grout and rebar after the connections were exposed to elevated temperatures.