Capillary Shape: Influence on Water Transport within Unsaturated Alkali Activated Slag Concrete

Abstract

Cementitious binders consisting of ground granulated iron slag and an alkaline activator (alkali activated slag) have considerable environmental benefits when used as an alternative to conventional 100% ordinary portland cement binders. The objective of this paper is to demonstrate the effect of pore cross section shape on unsaturated flow and to contrast the laboratory and numerical predictions of alkali activated slag binders and 100% portland cement binders. Convection-based uptake of water within capillary pores is modeled using pore size distribution data; however, most existing predictive models are based on the assumption of a circular cross section. This model allows for changeable capillary cross-sectional shape by employing ellipses ranging in shape from circular to slit. By applying a shape factor that accounts for departure from circularity of the pore cross section, the prediction model shows reasonable agreement with water sorptivity test data. As well as different binder types, the predictive model is assessed over a range of concrete ages and curing conditions.