When concrete is rapidly heated, material fragments can be ejected from its surface due to the phenomenon of heat-induced spalling, which could result in reinforcement exposure, fire resistance reduction, and the collapse of exposed concrete members. Consequently, significant research has been undertaken aimed at identifying the phenomenon’s influencing parameters allowing the development of effective mitigation strategies. However, the governing mechanisms of spalling are still unclear due to the complex physical processes occurring simultaneously in heated concrete, compounded by material variability.
This research aims to improve the understanding of concrete spalling through a holistic experimental, numerical and stochastic approach. High temperature tests investigated the role of different parameters on concrete’s spalling response and were complemented by the implementation of a state-of-the-art coupled thermo-hygral model for heated concrete. A stochastic analysis was carried out to identify the major sources of uncertainty influencing the model’s hydric response and assess the probabilistic performance of the metamodel’s pore pressure predictions. High-temperature neutron tomography tests enabled a reliability assessment of different pressure measuring systems, with the influence of these instruments on the high-temperature behaviour of concrete also investigated.
The results of this research demonstrate that thermal load and material variability govern different aspects of spalling. Additionally, the intrinsic permeability of the material, followed by its temperature-dependent evolution coefficient were identified as the largest sources of uncertainty significantly affecting the model’s pore pressure predictions. Other thermal and hygral parameters had a secondary influence that diminished over time. The reliability of current probes used for measuring the pore pressures developed in heated concrete was determined to be limited, while embedding pressure probes in concrete significantly affected the material’s high-temperature behaviour, with the effect proportional to probe size.
These findings deepen the understanding of heat-induced concrete spalling and pave the way for the development of effective spalling mitigation strategies.
