A Correlation Between Sorptivity Coefficients of Concrete as Calculated from Relationships of Water Uptake with t 0.5 or t 0.25

Sorptivity is a transport parameter widely used for assessing the durable performance of concrete. However, anomalous capillary absorption (or imbibition) is normally reported for cementitious materials, i.e. capillary water uptake evolves non-linearly with t0.5. For decades, different methods of dealing with the anomaly have been adopted in different standards. A novel approach based on the hygroscopic nature of cementitious materials has been recently proposed. A linear relationship of water uptake with t0.25 (instead of t0.5) was proven sound in terms of accurate description of the transport process and fitting with experimental results. For comparative purposes, there is therefore a need for a correlation between the new coefficients and coefficients in the literature computed upon considering an evolution with t0.5. In this manner, the potential of sorptivity in the design for durability of concrete structures, previously hindered by the anomalous behaviour of the material, may be further explored. This paper presents a correlation between sorptivity coefficients of concrete as calculated from relationships of water uptake with t0.5 and t0.25. The data was obtained from the literature and contrasted with own data produced in 6 different laboratories. Samples were pre-dried at 50 °C for a limited period of time. With some limits, the obtained relationship is sound. No particular considerations are required with regard to the features of the concrete mixes (e.g. water-to-cement ratio, type of cement, aggregate type, curing).