Fire Spalling Behavior of Various Polymer Modified Mortars under Ring Restraint

Polymer modified mortar (PMM) is indispensable for repairing and reinforcing concrete structures owing to its excellent adhesion to concrete, compactness, and workability. However, PMM tends to spall when exposed to high temperatures because it contains organic polymers. In this study, a ring-restrained heating test was performed on normal cement mortar and PMM mixed with three types of polymers to investigate the factors that affect fire spalling, such as differences in fire spalling magnitude, restraint stress, and water vapor pressure. Furthermore, a tensile strain failure model based on thermal stress theory was used to evaluate temporal changes in fire spalling depth.