An Experimental Study On The Chloride Diffusion And Electrochmically Accelerated Corrosion Of Ordinary Concrete

Corrosion of reinforcing steel in concrete is the predominant factor in the premature degradation of reinforced concrete structures. Therefore, the study of the chloride diffusivity of and reinforcement corrosion in concrete is of greatly importance for the durability design of reinforced concrete structures. Based on a coastal reclamation project of Zhejiang province, a systematic experimental study on the chloride diffusion and electrochemically accelerated corrosion of ordinary concrete is conducted. The effects of the water/cement ratio, the fiber content, the curing age, the coating type, the number of coating layers, and the dosage of mineral admixtures on the chloride diffusivity of concrete are evaluated. The method for predicting the chloride diffusivity of ordinary concrete is discussed. The effects of the water/cement ratio, the cover depth, and the fiber content on the time to surface cracking of concrete are analyzed. The conclusions of this study are summarized in the following points:(1) The larger the water/cement ratio is, the smaller the chloride diffusivity of concrete is. For a given water/cement ratio, the chloride diffusivity of concrete made with Portland cement for marine projects is smaller than that of ordinary concrete.(2) The larger the fiber content is, the smaller the chloride diffusivity of concrete is.(3) For a given water/cement ratio, the chloride diffusivity of ordinary concrete decreases with the increase of curing age. When the curing age is smaller than 14 days, the rate of change of the chloride diffusivity is larger and when the curing age is larger than 14 days, the rate of change of the chloride diffusivity is smaller.(4) Epoxy resin, PC-40 concrete protective agent, and hexamethyldisiloxane can reduce the chloride diffusivity of ordinary concrete in varying degrees. The effect of epoxy resin is best.(5) The more the number of coating layers is, the smaller of the chloride diffusivity of ordinary concrete is.(6) The larger the dosage of fly ash and mineral powder is, the smaller the chloride diffusivity of ordinary concrete is. Compared with fly ash, the effect of mineral powder on the concrete resistance to chloride ion penetration is better.(7) The method for predicting the chloride diffusivity of ordinary concrete is discussed. The validity of the method is preliminarily verified with experimental results.(8) Under given conditions, the time to surface cracking can be prolonged to various extents with increasing the water/cement ratio, the cover depth, and the fiber content.