FIBRE CONCRETE AND ITS AIR PERMEABILITY

A quality of a covercrete (covercrete = cover concrete) up to a depth of 20-50 mm practically decides about the durability of concrete of a structure. The covercrete prevents accessing of acid substances from the atmosphere to steel reinforcement. For evaluation of a state of the covercrete from the durability viewpoint is possible to use a test either of the air or water permeability. Permeability of a thin covercrete depends on its porous structure that forms itself at a process of hydration of cement grains in concrete. The permeability is also influenced by cracks and by others discontinuities in monitored layer which form themselves as early as at setting and in the beginning of hardening due to plastic shrinkage and imperfect compacting of concrete. In this contribution are described some results of measurement of air permeability with a TPT (Torrent Permeability Tester) instrument of selected concretes with different type of fibres and comparative concretes without fibres.