Contribution of polypropylene fibres melting to permeability change in heated concrete - the fibre amount and length effect

The paper presents the investigations related to concrete permeability change during heating and the contribution of polypropylene fibres melting at the temperature of 163°C to permeability. Permeability is an important parameter governing the occurrence of the explosive behaviour also known as concrete spalling due to fire. To limit the spalling of concrete, the polypropylene fibres are used to act as a fuse and, by melting, reduce gas pressure in concrete pore system. The investigations consisted of testing the permeability change of seven high performance concretes with polypropylene fibres. The permeability was measured after temperature exposure to temperature 140, 160, 180 and 200°C. The results have shown to what extent the fibre length and content affect the permeability when melting. Moreover the results have shown that the addition of polypropylene fibres had the desired impact causing a considerable increase in concrete permeability after fibre melting. (paper)