A new material test method is presented for determining whether or not an actual concrete may suffer from explosive spalling at a specified moisture level. The method takes into account the effect of stresses from hindered thermal expansion at the fire-exposed surface. Cylinders are used, which in many countries serve as standard specimens for testing the compressive strength. Consequently, the method is quick, cheap and easy to use in comparison to the alternative of testing full-scale or semi full-scale structures with correct humidity, load and boundary conditions. A number of concretes have been studied using this method, and it is concluded that sufficient quantities of polypropylene fibres of suitable characteristics may prevent spalling of a concrete even when thermal expansion is restrained.
- Polypropylene fibres