Unsaturated Capillary Flow within Alkali Activated Slag Concrete

Abstract

Alkali activated slag concrete (AASC), based on a binder that consists of 100% blast furnace slag that is activated by an alternative alkali to conventional Portland cement, has considerable environmental benefits. Nevertheless, the durability of the exposed surface zone of AASC needs consideration. The ingress of harmful agents is highly influenced by convection-induced effects; e.g., moisture gradients caused by exposure to rainfall or the wetting and drying effects in the splash zone of a marine environment that can lead to high surface concentration of chloride. The convective effects also propagate steel reinforcement corrosion, once initiated, by making available moisture and oxygen for the cathodic reaction at the steel reinforcement, as well as changing the conductivity of the concrete surface zone. This paper reports the behavior of convection-induced uptake of water into AASC and ordinary Portland cement concrete. The sensitivity to “exposed,” “sealed,” and “bath” curing and the resultant pore structure for concrete made with different water/binder is contrasted.