Spalling, which is often defined as a material thermal instability, occurs in concrete members shortly after exposure to fire (Mindeguia et al. 2013). As a result, many physical and chemical reactions including evaporation of free water, dehydration of cement gel and decomposition of Calcium Silicate Hydrate (CSH) happen inside the concrete (Bazant & Kaplan 1996). These phenomena result in the generation of pore pressure and thermal gradient inside the concrete initially causing micro cracks both within and on the surface of the concrete member. As time lapses, thermal stresses result in wider cracks and eventual dislodgement of some larger pieces of concrete from exposed surfaces. Referring to the heating rate and specifications of the concrete, even explosive spalling might happen which exposes steel reinforcements, with low thermal strength, to high temperature and hence threatening the integrity of the concrete member (Tian 2011; Zhang & Davie 2013; Guerrieri & Fragomeni 2013).