Characterisation and microstructure of high-performance concretes reinforced with metal fibres ripened in seawater.

High-performance concretes reinforced with metal fibres (SFRHPC) have multiple advantages when they are used in the marine environment. These materials provide high strengths at the young age that permit faster formwork stripping, resistance to hydrostatic thrusts due to the tides, structural elements sections' reduction, as well as weight reduction of the structure, and the increase of the abrasion resistance to sand or gravel. The maritime works are exposed to specific seawater aggressions. Seawater contains aggressive salts, which damage the concrete and the steel that it may contain. These salts are mainly chlorides and sulphates. This study investigated the ripening of steel fibre-reinforced high-performance concrete, with 15% substitution of cement by blast furnace slag, in Rance (France's seawater). This experimental study analysed the effect of 6 and 24 months of ripening of the sample, in aggressive water, on the characterisation of the concrete and the microstructure of the cement's matrix and its fibres. Also, in this study, after two years of concrete conservation, we carried out the chemical and mineralogical composition of the seawater. The results showed that there is no significant alteration of concrete kept in seawater and the steel fibres were not altered. In other words, it stayed passivated even after two years of ripening. [ABSTRACT FROM AUTHOR]