Study On The Performance Of Polypropylene Fiber Reinforced Concrete Resistance To Chloridion Erosion

The corrosion of steel bar caused by chloride ion erosion leads to the failure oreven destruction of concrete structure, leading to huge economic losses, so thedurability of concrete structures in chloride-erosion environment was concerned byengineering community. Therefore, It’s meaningful on the study of the diffusionproperties of the chloride ion in concrete which aimed at delay of the time thechloride ions reaching the surface of steel.This article studied the impact of four types of factor levels on the relativelydynamic modulus of elasticity, relative mass loss and concrete water-soluble chlorideion concentration that was tested by long-term immersion and drying-weting cyclesmethods. The four types of factor levels are strength grade of concrete (C30, C50,C60, C70), polypropylene fiber content (0,0.06%,0.08%,0.1%), fly ash mixed cover(0,15%,25%,35%), and the concentration of chlorine salt solution (0,3%,5%,7%).Meanwhile, the distribution of the chloride ion diffusion in concrete is processed intotwo-dimensional numerical simulation.The quality of specimens and dynanic modulus of elasticity measured in the ageof30d,60d,90d,180d, and360d have little difference in long-term immersion anddrying-weting cycles. It indicates that the diffusion of chloride ion in the plainconcrete does not cause damaging effects yet, and thus the influence on the relativemass loss and relative dynamic modulus of elasticity is very small.It is found that the erosion depth of chloride ions in the concrete within20mm,and the water-soluble chloride ion concentration measured at the same depth in the group of drying-weting cycles is greater. In a depth of0~5mm the higher theconcentration of external salt solution, the influnce is more significant. With a furtherincrease of the depth of erosion the concrete internal density is greater due to thecement hydration reaction. Moreover, chloride ions was absorbed by C-S-H wnichwas generated in the cement hydration reaction, so that diffusion of chloride ions willbe blocked effectively. In this case, the impact of concrete strength on theconcentration of chloride ions in the concrete gradually becomes more significant.When the strength grade of concrete is C50or C60, and the content of polypropylenefiber is0.06%or0.08%, the concentration of water-soluble chloride ion in concrete isrelatively low compared with that of plain concrete.Based on Fick’s second law, the influences of temperature, humidity, timedependence of chloride ion diffusion and other factors on the diffusion of chloride ionare taken into consideration in this paper. And after a integrated chloride diffusionmodel in different chloride binding mechanism is bulit, the value of each parameter isdiscussed. Meanwhile the influence of strength grade of concrete, polypropylene fibercontent, fly ash mixed cover and the concentration of chlorine salt solution areanalyzed. These four factors affect the decay of chloride diffusion coefficient overtime.According to the changing condition of the concentration of chloride ions withthe the change of erosion depth and the two-dimensional transport properties of thechloride ion in concrete, a two-dimensional diffusion model of chloride ion intrusionof concrete is built based on Fick’s second law as base model of diffusion, andcorresponding numerical simulation is realized by ANSYS.