Prediction of convective transport within unsaturated concrete utilizing pore size distribution data

The durability of concrete structures is often compromised by physical and chemical interaction with the external environment that leads to ongoing maintenance and, in the worst cases, can lead to reduced structural integrity and consequent asset replacement. Concrete is a porous material and most field-exposed concrete is partially saturated with water. Where the concrete is unsaturated and there is no external water pressure acting on a concrete surface, the primary mechanisms of transport into concrete are convective-diffusion ingress (i.e. uptake of water and water-borne agents due to capillary attraction). This paper assesses capillarity and outlines a predictive model of the uptake of water by concrete based on analysis of the pore size distribution. It is acknowledged that concrete has a multitude of internal pores with a broad range of lengths and cross-sectional shapes, surface roughness, tortuosities, random meeting and divergence with adjacent pores, microcracks and fractures, and variable pore-water chemical composition, however the prediction model shows reasonable agreement with water sorptivity test data