A meso-level investigation into the explosive spalling mechanism of high-performance concrete under fire exposure

High-performance concrete (HPC) is prone to spalling under fire conditions. However, few quantitative theoretical studies on the spalling mechanism are available in the literature and the spalling mechanism has not been well interpreted. In this paper, the spalling behavior of cubic specimens is numerically modeled and the spalling mechanism is investigated at a meso-level. In modeling, the temperature field, the thermal decomposition of cement paste, the build-up vapor pressure, the moisture transport, and the distribution and evolution of thermal stresses in concrete are analyzed in a quantitative manner. Based on the numerical results, the spalling mechanism is interpreted from different angles. It is concluded that the explosive spalling of HPC specimens under fire exposure is mainly attributed to the temperature gradient-induced thermal stress.