The permeability and mechanical properties of the blast furnace slag concretes made of neutral (CaO/SiO2≈1) and low alumina content (Al2O3≈8.5%) slags have been investigated. As in Part 1, three concretes were compared with each other, namely PC concrete, blended cement concrete and alkali-activated slag concrete. Theoretical models, e.g. a carbonation estimation model, were introduced and examined. The influence of the type of the cementing materials on the mechanical properties was investigated. Attention was paid to the effect of the microcracks in the alkali-activated slag concrete on the mechanical properties of concrete. In addition, the effects of the specimen size on the strength values of different kinds of concretes were studied.