Fig. 3 Comparison of measured and theoretical weight gains and distances of penetration of water

Consider next the rates of absorption. It can be seen from Fig. 1a that in the first hour of the absorption process, the weight of water absorbed by the 25mm sample with the cut suction surface was 8gm, which is equivalent to an average rate of flow of 2.2×10−9m3/s. Classical permeability theory would suggest that a head of water in excess of 1600m was required to produce this flow through good quality concrete (with an assumed permeability of 10−12m/s). Clearly then permeability is playing no significant part in the mechanism of water absorption observed in these experiments.