Accelerated Corrosion Test And Life Assessment Of Reinforced Concrete In Saline Soil

SO₄^2-,Cl^-,Mg²⁺and other strong corrosive ions were found in the soil inthe western saline soil region of China,together with the special service environment such as strong wind sand,dry environment and strong ultraviolet,le ading to the local reinforced concrete structure cracking,corrosion and other durability problems,greatly reduced the service life.Although scholars at home and abroad have carried out some research on the corrosion damage of reinforced concrete under the action of harsh environment,there were still some shortcomings in the current accelerated test method of reinforced concrete indoor consta nt current,and the corrosion mechanism was not clear and targeted.Therefore,the research on the process and mechanism of corrosion damage was carried out in the Western saline soil area.In view of this,the constant current accelerated corrosion test o f reinforced concrete was carried out under different current densit ies,different thicknesses of protective layer and active mineral admixture.Taking corrosion current density,maximum crack width,relative dynamic elastic modulus,relative mass and chlo ride ion content as evaluation indexes of durability degradation,a comprehensive evaluation system of durability degradation rule in saline soil environment was established.Combined with the damage evolution process of reinforced concrete macroscopic,mesoscopic and microscopic structure,the corrosion degradation rule under different test conditions was analyzed.Based on the probability distribution function,the deterioration model of durability of reinforced concrete accelerated by constant current in saline soil environment in Western China was established and its life was evaluated.The main conclusions of this paper are as follows:（1）The degradation rule of the constant current accelerated corrosion test of reinforced concrete in saline soil environment is as follows:at the early stage of the constant current accelerated test,the corrosive ions in saline soil does not reach the surface of the reinforcement,and the external current alone led to the corrosion of the reinforcement,and the corrosion degradation rate of the reinforced concrete was slow;at the middle stage of the constant current accelerated test,the chloride ions gradually reached the surface of the reinforcement under the superposition effect of free diffusion and electromigration,at the later stage of constant current accelerated test,the corrosion products accumulated and expanded,resulting in cracks in reinforced concrete,which provides a channel for the entry of corrosion ions,and the corrosion rate of reinforced concrete is faster.（2）In this paper,the constant current density conditions of 182μA/cm²,364μA/cm² and 546μA/cm² are set.The results show that under the condition of 364μA/cm²,the acceleration efficiency of reinforced concrete is the maximu m;under the condition of 182μA/cm²,the corrosion degradation rate of reinforced concrete is the slowest;under the condition of 546μA/cm²,the corrosion degradation rate of reinforced concrete is in the medium proportion.The corrosion degradation rate does not increase with the increase of current density,but there is a turning point.（3）In this paper,25mm and 50mm concrete Protective layer conditions are set.The research shows that the thickness of the Protective layer is closely related to the durability of reinforced concrete under the constant current accelerated corrosion condition in saline soil environment.The thicker the protective layer,the smaller the degradation rate and the longer the test life.（4）In this paper,four concrete mix proportions are set,which are ordinary,fly ash,mineral powder and fly ash-mineral powder reinforced concrete.The results show that 30%fly ash is the fastest to degrade and the acceleration efficiency is the largest;15%fly ash and 15%mineral powder are the second;30%mineral powder is the lowest;ordinary reinforced concrete is the slowest to degrade and the acceleration efficiency is the smallest.