Transport properties in unsaturated cement-based materials - A review

It is certainly true that cement-based materials are rarely saturated in use. Due to their importance to service life prediction and durability assessment of steel reinforced concrete, an increasing attention has been directed to the transport properties in unsaturated cement-based materials over a wide range of water contents in recent years. This review presents recent advances in the understanding of transport properties in unsaturated cement-based materials, including: the experimental approaches, models and modelling for the estimation of ionic diffusivity and gas permeability, the respective influences of water-to-cement (w/c) or water-to-binder (w/b) ratio, chloride binding, supplementary cementitious materials (e.g., silica fume, slag and fly ash), wetting-drying cycles and aggregate-matrix interfacial transition zone (ITZ) on the chloride diffusivity and gas permeability under non-saturated condition. It concludes with a look to the future, including the research needs to be carried out.