The Spalling of Normalweight and Lightweight Concrete on Exposure to Fire

摘要

The immediate reason for setting up, CUR Committee C29 in November 1972 was provided by the results of some fire tests on beams and floors which had been carried out at the request of DSM by the Institute TNO for Building Materials and Building Structures (IBBC-TNO) in 1971. The beams and floor-elements were made of lightweight concrete. The thermal properties of lightweight concrete suggest that a smaller depth of cover than in the case of normal weight concrete can be applied. The test were set up to establish the possible reduction in cover and still to obtain the required fire resistance. However during the tests destructive spalling occurred resulting in a very disappointing fire resistance. Destructive spalling being explosive dislodging of small or large pieces of concrete from the surface. Some further research indicated that the moisture content of the hardened concrete play a very important role for destructive spalling to occur or not. Committee C29 has theoretical and experimental research undertaken for studying the drying process of concrete in relation to the composition of the concrete, the dimensions of the members concerned, and the climate that can be expected to occur in a building. Furthermore, some fire tests on beams and on slab-type specimens were performed at the Committee's request. The results of these tests are presented in this report.