Developments in Near-Surface Testing of Covercrete

Abstract

The work presented details a testing methodology whereby a range of properties of cover-zone concrete can be determined, these properties being ultimately linked to the long-term performance of concrete. Emphasis is place on the application of a surface-applied, water absorption method in conjunction with electrical measurements taken within the cover zone. In the current work, the influence of cyclic wetting and drying of normal portland cement concretes, with and without blast-furnace slag replacement, were studied. Samples were subjected to both water and chloride solution. The study shows that the depth and rate of water penetration during absorption can be evaluated; when these data are combined with volumetric gain, the effective porosity of concrete in the cover region can be estimated. Conductivity profiles taken over cycles of wetting and drying can be used to provide information on the zone of influence of drying action (convective zone), on-going hydration effects, and ionic ingress.