Rebar corrosion in coral aggregate concrete: Determination of chloride threshold by LPR

Chloride threshold is a significant index to judge the initial corrosion of rebar in concrete structures, and a key parameter for durability analysis and service life design of reinforced concrete structures. In the present wok, the corrosion rate of rebar embedded in coral aggregate concrete and the chloride ion diffusion law of coral aggregate concrete was studied by the linear polarization resistance method and two-dimensional chloride diffusion model, respectively. Depending on the relationship between the surface free chloride content of rebar and its corrosion rate, the chloride threshold values of different rebar in coral aggregate concrete were finally determined. The results indicate that the corrosion rate of rebar in coral aggregate concrete gradually decreases with the increase of concrete strength grade and cover thickness, and the order of anti-corrosion performance of reinforcements from high to low is: epoxy resin coated steel, 2205 duplex stainless steel, 316 L stainless steel, organic coated steel and ordinary steel. The chloride threshold values (% by weight of concrete) of these reinforcements in coral aggregate concrete were determined and ranked from small to large as follows: ordinary steel (< 0.15%), organic coated steel (< 0.21%), 316 L stainless steel (0.33% similar to 0.41%), 2205 duplex stainless steel (> 0.46%) and epoxy resin coated steel (> 0.49%). Additionally, there is a remarkable regression relation of corrosion rate between surface free chloride contents and cover thickness of reinforcement, which has a great significance of the research of steel corrosion in coral aggregate concrete.