Durability of Marine Concrete under Thermal Cycling Loads

Abstract

Data on chloride penetration into concrete exposed to a simulated aggressive marine environment are presented. Concrete specimens, large beams and small cubes, are subjected to 90 complete exposure cycles of wetting and drying plus heating and cooling. The applied exposure condition consists of a drying period of 42 hrs followed by a wetting phase of 6 hrs with salt water containing 5% NaCl. The drying phase itself is a thermal regime characterised by a temperature swing from 20°C to 60°C within a period of 12 hrs. This simulates, with some accelerations, the aggressive marine environmental condition in hot regions with varying daily temperature including direct solar radiation. Totally 315 temperature cycles and 90 cycles of wetting/drying were applied to specimens in this experiment. It was observed that temperature and humidity variations promote chloride penetration into marine concrete significantly. This particular study shows that thermally-induced microcracks increase, but slightly, the permeability of concrete in "restrained" beams compared to the relatively "stress free" small specimens. Effect of two other significant parameters, i.e. type of curing and type of cement, on chloride ingress rate is also investigated.