Mechanical properties of small-diameter rebar grouted sleeve connections after high temperatures

To investigate the mechanical properties of small-diameter rebar grouted sleeve connections after exposure to high temperatures, a total of 24 sets of grouted sleeve connections, 12 sets of grouted sleeve connections with polypropylene fiber (PPF) added to the grout, and 12 sets of grouted sleeve connections with spiral stirrups set at their ends with a length of 0.6 times the anchorage length were designed and manufactured. Then, the uniaxial tensile testswere carried out on the grouted sleeve connections both at room temperature and after high-temperature exposure. The results show that after being subjected to 600 ℃, all three types of grouted sleeve connections experienced bond failure. When exposed to temperatures below 600 ℃, the connections failed due to rebar fracture, with a failure mode similar to that of large-diameter rebar grouted sleeve connections. Due to the high strength and poor deformability of the grout, the confining effect of the spiral reinforcement was weak.This also reduced the amount of grout and increased the risk of grouting defects, leading to a decrease in anchorage performance. The addition of PPF improved the post-high-temperature damage resistance of the grout, slightly increasing both the ultimate load and ultimate elongation after exposure to 600 ℃. The k values for the three types of grouted sleeve connections were calculated, revealing that bond failure can be avoided when k ≥ 2.99, disregarding the influence of grouting defects.