A new test method to study the influence of pore pressure on fracture behaviour of concrete during heating

Fracture behaviour of concrete at high temperature is one of the factors governing explosive spalling, namely the expulsion of chunks due to both pressure build-up in the pores and stress induced by thermal gradients and external loads. In this context, a special experimental setup has been developed aimed at performing simple indirect-tension tests under different levels of sustained pore pressure. A cubic specimen is heated on two opposite faces, whereas the lateral sides are sealed and thermally insulated, so as to instate a mono-dimensional thermo-hygral transient field. In the splitting test, fracture develops along the symmetry plane, where both temperature and pressure are monitored by means of a customized probe. The results show that pore pressure has a significant influence on the mechanical response of heated concrete, though the concurrent contribution of external load and thermal strain is required for triggering explosive spalling.