Residual fracture properties of concrete subjected to elevated temperatures

Abstract

Investigations on the residual Mode-I fracture behaviors of concrete subjected to elevated temperatures were carried out. Test specimens with the same dimensions, 230 × 200 × 200 mm, were exposed to temperatures varying from 65 to 600°C. The wedge splitting method was employed to obtain the complete load-crack mouth opening displacement curves (P–CMOD) of the post-fire specimens, from which the initial fracture toughness K _ini, the critical fracture toughness K _ic and the fracture energy G _F were calculated. The results demonstrated that K _ini decreased monotonically with increasing heating temperature T _m; K _ic and G _F sustained a hold-increase–decrease tendency with T _m. Furthermore, the characteristic length l _ch, a brittleness parameter, was calculated and it shared the same tendency as K _ic–T _m and G _F–T _m. Thus, any of the three parameters could serve as the index of brittleness for post-fire concrete. The fracture parameters and other material properties of concrete could be closely related to the ultimate weight loss.