Experimental Research On The Durability Of Concrete Exposed To Different Parts Of Marine Environment

The scale of infrastructures in China has exceeded the number of other countries. While China has extended coastline, the penetration of chloride in these areas is serious. The buildings often damage easily, which threaten the safety of people's lives and property. Therefore, how to design buildings in marine environment and how to extend their service life have become a hot topic among designers and engineers.On the basis of above-mentioned problems, in order to give reference to the researches in the future, the thesis studies chloride diffusion in three different parts of marine environment, i.e. submerge area, splash area and atmospheric area.To begin with, the experiment were carried out to simulate submerge area. In this part, the specimens with three different water-cement ratio were placed into various chloride salts. The purpose of this experiment was to study the effect of water-cement ratio and the associated cation ions on chloride diffusion. The results showed chloride diffusion coefficient increased along with water-cement ratio and the source of chloride ions had an influence on the amount of chloride ion in concrete.The following part focused on the penetration of chloride in splash area. The influence of wetting and drying cycles on chloride diffusion were studied and the corrosion liquids were mixed with NaCl, MgCl2, CaCl2. Besides, the specimens, which were placed into wetting and drying condition, were compared with submerge specimens to analyze the effect of wetting and drying condition on chloride diffusion. Furthermore, when specimens were exposed into these two different conditions to some certain days, they were tested to investigate the changes of their compressive strengths. The results showed that the chloride diffusion coefficients in both submerge and wetting and drying condition were decreased with time and the diffusion coefficients in wetting and drying condition were about 1.5 to 2 times larger than submerge condition. After being immersed in corrosion liquids, the compressive strengths of specimens were higher, when compared with 28d compressive strengths.At last, the combination of chloride and carbonation were proposed to study the corrosion in atmospheric area. The single penetration of chloride and carbonation were also investigated. The results illustrated that the combined penetration affected the carbonation of the specimens and chloride concentration along the penetration depth was no longer coincident with monotone decreasing. In addition, the combined condition would decrease the resistance of chloride diffusion.