Experimental investigation on spalling mechanisms in heated concrete

Some recent results obtained during an experimental campaign on concrete spalling in fire conditions are presented in this paper. Since spalling was visually recorded by means of a high-speed camera, the slow-motion sequences provided an insight into the size, shape, and velocity of the spalled-off pieces which made it possible to evaluate the released energy during the acceleration of the concrete chips and to clarify the causes of spalling. The two commonly-accepted theories about the causes of concrete spalling are also recalled, taking advantage of the test results. The roles of the various thermal, mechanical and hydral processes controlling concrete spalling are discussed.