The Influence of the Physical and Chemical Properties of Hardened Cement Paste on the Fire-induced Spalling of Concrete

The Influence of the Physical and Chemical Properties of Hardened Cement Paste on the Fire-induced Spalling of Concrete A number of major fire incidents in recent decades, particularly in tunnels and indoor car parks, have increased the awareness among construction designers towards the potential susceptibility of concrete to fire-induced explosive spalling. In some fields of application, this violent breaking-off of concrete layers may reduce the fire resistance time of fire-exposed construction elements. The mechanisms causing explosive spalling are not yet fully understood and discussed controversially among scientists.Fire tests of concrete specimens have shown that the type of cement may have a marked influence on the susceptibility of concrete to explosive spalling. Three common characteristics of those concretes that were found to have an increasedsusceptibility of spalling were identified. For each of the three common characteristics, acorresponding hypothesis describing its possible contribution to the fire-induced concretespalling was proposed. This second part of the article describes the experiments to verify the hypotheses using a dedicated test programme. The evaluation of the tests identified the main mechanisms by which spalling is caused.