An analytical approach to water absorption based in situ test procedures for concrete

There are several procedures that are used to assess empirically the in situ water absorption properties of concretes. All of these are based on complex absorption geometries involving both surface cap and drilled hole sources. In this paper, analyses are presented that show that the absorption from any radially symmetrical source may be described by a polynomial in (time)1/2 in which the sorptivity is the coefficient of the leading term. Application of the analyses thus enables the fundamental measure of water absorption, the sorptivity, to be calculated, so allowing valid and accurate comparisons to be made between data from different materials and also from different test geometries. The analyses can also define the extent to which the simple application of these tests for comparative purposes is acceptable and the cases in which such empirical comparisons may be misleading. Other considerations relating to the in situ testing of cementitious materials generally are considered briefly.