Water vapour permeability of lightweight concrete prepared with different types of lightweight aggregates

The water vapour permeability of concretes or various building systems is an important parameter when defining the concept of favourable living conditions. Within the scope of the research described in this paper, the water vapour permeability of concretes prepared with different lightweight aggregates (LWA) having an open porosity was compared with that of concretes made with a selected ordinary aggregate. It was found that the coefficient of water vapour permeability μ was, in the case of all the investigated concrete prepared by lightweight aggregates and used water/cement factors, less than 35, whereas in the case of the ordinary concrete it amounted to 84. It is interesting to note that SEM investigations of the interface (transition) zone between the aggregates and the cement matrix did not indicate the occurrence of any densification which could have a negative effect on the water vapour permeability of lightweight concretes (LWAC).