Influence of cast and cut concrete surfaces on chloride ingress resistance of concrete in marine splash zone

Abstract

The aim of the study was to investigate the effect of the type of surface on the chloride ingress resistance of concrete. Concrete cylinders with both cut and cast surfaces were exposed to sea water in the tidal zone at Østmarkneset in the Trondheim Fjord in Norway after approx. 1 months of curing. Chloride profiles were determined after 35, 200 days, 1, 2 and 5 years of exposure. Three concretes with water-to-binder ratio 0.45 and with different cements were examined. One concrete was prepared with a coarse Portland cement, the second was prepared with a finely ground Portland cement, and in the third concrete 20% of the Portland cement was replaced by siliceous fly ash. As expected, the samples with cast surfaces exhibited a distinct increase in the chloride content in the outer millimeters of the surface compared to deeper in the concrete. This relates to the higher cement paste content at the cast surface. For the selected concretes, the cast surface lead at all tested ages to a slight increase in the resistance to chloride ingress compared to the cut surfaces.