Experimental Study On The Durability Of High Performance Concrete In Marine Environment

Concrete structures corrode easily in marine environment. According to the different role of the marine environment on the structures, the marine environment is often divided into the atmosphere zone, splash zone, tidal zone and water zone, the corrosion conditions, corrosion character and corrosion rate of these areas varies. The structures in the splash zone and tidal zone area erode most seriously, which are the most critical areas to control the service life of structures. In this paper, the durability of high performance concrete (HPC) in splash zone and tidal zone was studied, the freeze-thaw cycle, capillary water absorption and chloride ion penetration test of HPC with different admixtures were developed to analyze the influence of water-cement ratio, silica fume and fiber to the durability of concrete, as well as influence of coating on frost-resistant durability of concrete. These studies provide a reference to improve the durability of marine concrete structures. The main researches include:(1) The durability of C30 and C60 HPC with different admixtures in marine environment was researched, and the research findings are references for concrete mix design of concrete structures in splash zone and tidal zone. The test results show that, the incorporation of silica fume can improve the performance of freezing-thawing durability, anti-capillary water absorption and chloride penetration resistance of HPC. The incorporation of polypropylene fibers can improve the frost resistance of HPC, but had no obvious improvement on anti-capillary water absorption and chloride permeability resistance.(2) The high performance concrete was coated, and the freezing-thawing durability in marine environment was studied. The experimental results show that the coating can significantly improve the performance of freeze-thaw resistance of concrete, and also show that the epoxy polyamide coating and acrylic polyurethane coating is superior to aluminum powder coating and chlorinated rubber coating to improve this capacity.(3) The resistance to chloride ion penetration of concrete before and after freeze-thaw cycles was studied; the test results indicate that concrete deterioration due to freeze-thaw cycles plays an important role on chloride permeability. The chloride diffusion coefficient increases with the raise of freeze-thaw cycles.(4) Chloride-induced corrosion of steel bars in reinforced concrete structures exposed to marine environments has become the major cause of resistance deterioration. Chloride ion diffusion process in concrete was described by improved Fick Second Law of diffusion, and starting corrosive time of reinforcement in concrete was predicted. The results show that the admixtures and the cover thickness of concrete take great parts in the durability life of concrete structures.