Chloride Transport In RC Flexural Beams And Time-dependent Reinforcement Corrosion Under Chloride Action

Most of real structures subject to the external loads in the marine environment.Thus,chloride transport in concrete is not only affected by environmental factors,but also related to the forms of external loads.Reinforcement corrosion in reinforced concrete(RC)structures will be accelerated under coupling flexural loads and chloride action,which may result in cracks of concrete and reduction of structural capacity,and further affect the service life of RC structures.In this research,based on Fick's second law and basic calculation principles of concrete members with flexural loads,the calculation methods for the apparent chloride diffusion coefficients and chloride concentrations in concrete of different stress zones of RC beams under flexural loads were proposed.The time dependency of apparent chloride diffusion coefficient and the influence of flexural load levels on chloride diffusivity of RC beams in different stress zones were analyzed.Moreover,based on the two test methods(i.e.weighing method and three-dimensional laser scanning technique),under different exposure environments and flexural loads,the uniform corrosion rate and randomness of corrosion non-uniformity of corroded tensile reinforcements in concrete with different water-to-cement(w/c)ratios were studied.In addition,under different exposure conditions,the predicted values of time to corrosion initiation of tensile reinforcement in RC beams were calculated,and the probability distribution forms of critical chloride concentrations were also analyzed.The main contents in this paper are as follows:1.The time-dependent model of apparent chloride diffusion coefficients in concrete which considering the effect of stress state at different depths of concrete under flexural loads was established.Then,comparing with the simplified time-dependentmodel of chloride diffusion and existing measured data,the viability of time-dependent prediction model proposed in this paper was confirmed.2.Based on the time-dependent prediction model of chloride diffusivity which considering the effect of stress state at different depths of concrete,as well as the long-term exposure test of RC beams in the natural tidal environment,the effect of flexural loads on chloride transport in different stress zones of concrete was studied.Moreover,the critical compressive stress of accelerating chloride transport in concrete under coupling flexural loads and chloride action was also analyzed.3.The time-dependent corrosion process and randomness of non-uniform corrosion of tensile reinforcements were analyzed,based on the long-term exposure test of RC flexural beams in the simulated tidal environment.4.According to the time-dependent model of mass corrosion rates of tensile reinforcements,the times to corrosion initiation of tensile reinforcement in RC beams under different w/c ratios,flexural loads and exposure environments were predicted.Moreover,the probability distribution forms of critical chloride concentrations of tensile reinforcement corrosion initiation under different exposure conditions were compared.