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The sorptivity is an easily measured material property which characterizes the tendency of a porous material to absorb and transmit water by capillarity. Its theoretical basis in unsaturated flow theory is reviewed, together with methods of measurement suitable for cement-based materials. Available data on mortars and concretes are included. The dependence of the sorptivity on initial water content, temperature and fluid properties is also described. Other test methods (the initial surface absorption, the Figg water absorption and the Covercrete absorption tests) are discussed in terms of the sorptivity.

Fired-clay materials such as brick, tile and ceramic artefacts are found widely in archaeological deposits. The slow progressive chemical recombination of ceramics with environmental moisture (rehydroxylation) provides the basis for archaeological dating. Rehydroxylation rates are described by a (time) 1/4 power law. A ceramic sample may be dated by first heating it to determine its lifetime water mass gain, and then exposing it to water vapour to measure its mass gain rate and hence its individual rehydroxylation kinetic constant. The kinetic constant depends on temperature. Mean lifetime temperatures are estimated from historical meteorological data. Calculated ages of samples of established provenance from Roman to modern dates agree excellently with assigned (known) ages. This agreement shows that the power law holds precisely on millennial time scales. The power law exponent is accurately 1 / 4 , consistent with the theory of fractional (anomalous) 'single-file' diffusion.

The precision of methods used for the determination of hygric properties of porous building materials was investigated. The study was performed in the framework of the EU-initiated HAMSTAD-project. Six laboratories measured the selected hygric properties of three porous building materials. While the most measured properties show acceptable agreement, yet, it was found that some of the existing standards or commonly accepted measurement methods need improvement. Most striking were large variations in the results of the vapour transmission tests performed in accordance to the existing European Standard.

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