Relationship between sorptivity and capillary coefficient for water absorption of cement-based materials: theory analysis and experiment

The durability of cement-based materials depends on the property of water absorption. In this work, a technique of X-ray CT combined with CsCl enhancing was used to continuously monitor the dynamic process of water uptake in cement-based materials and the gravimetric method was used to measure the amount of water absorption. The relationship between the capillary coefficient (k) and sorptivity (S) was firstly established based on theory analysis and well verified by the experiment results. In accordance with theory analysis and experiment results, it is found that the ratio of sorptivity to capillary coefficient equals the porosity (phi) of materials, i.e. S/k = phi. This model provides a simple method for obtaining the capillary coefficient of porous materials from the measurement of sorptivity and porosity.