Durability of FRC-Materials

Abstract

AbstractAsbestos cement was the first type of FRC-material that was ever made. It consisted of neat, hardened Portland cement reinforced with asbestos fibres (Vt - 7 vol-%). The most outstanding and valuable property of a high quality asbestos cement was the highly improved durability of this composite material in comparison to what would have been the case, if no fibres had been added or the fibre reinforcement of this extremely brittle matrix had been carried out incorrectly.This paper describes an analysis of the variation in time of the fracture energy, GF, of different types of FRC-material exposed to various climatic conditions.The following types of fibres were examined: steel fibre, ar-glass fibre, synthetic fibre (polypropylene) and natural fibre (sisal fibre and paper pulp cellulose).The climatic exposure conditions were natural out-door weathering or laboratory tests in a special weather-o-meter. Three test series were carried out at the Danish Building Research Institute. The results from these tests have been compared to results from five test series taken from the literature (ar-glass-, steel-, polypropylen-, sisal-fibres and neat concrete).It is concluded that natural and glass fibres are losing strength and ductility in a cementitious matrix. This results in a drastically reduced fracture energy of the composite material over the years. In the worst cases practically no fibre effect is left after some ten years of normal out-door exposure.For the best types of fibres examined (steel fibre, high tenacity, high bond polypropylene and combinations of these two types) the ductility and fracture energy of the composites are increasing significantly even after very long time of exposure.