Explosive spalling in R/C structures exposed to fire: key aspects in experimental testing

Explosive spalling in R/C members exposed to fire consists in the violent expulsion of the hottest layers of concrete, due to the combination of compressive stress and vapour pressure, with the consequent reduction of the bearing cross-section and of the structural fire resistance. Experimental tests aimed at assessing concrete spalling sensitivity can be performed at dif-ferent scales, namely small, intermediate and real scale, with increasing time and cost of testing. The correct level of investi-gation must be defined as the right compromise between efficiency and representativeness of the real case. Starting from the comparison among different test setups at different scales, the main parameters to be considered in planning the experi-mental investigations will be described. On the other hand, with regards to the definition of the mix design, it will be shown how the use of different types of fibre can bring remarkable benefits against spalling.