Research On Performance Deteriotation Laws Of Concrete Suffering From Acid Rain And Life Prediction Model

At present,the phenomenon of acid rain is quite common in some parts of our nation.A long-term scour of acid rain to concrete will lead to a serious deterioration of concrete performance.The service life of concrete structure is affected by service environment and material composition,it greatly depends on the chemical constitution of acid rain and the mix proportion of concrete.Concrete structures suffering from a long time acid rain corrosion without protection will have a using function recession and even get an early ending of its service life.Therefore,to solve above problems,this paper investigated the influences of the chemical composition of acid liquor and the material composition of concrete to the deterioration laws of concrete suffering from acid rain.At last,we build up a mathematical prediction model in the establishment of Grey System Theory.Main researches of this paper are followed.?1?The influences of the chemical constitution of acid rain to concrete suffering from acid rain.The laboratory accelerated corrosion experiment was carried out to test the performances of concrete at different erosion period under simulated acid rain environment of different pH value and SO₄^2-concentration.Those performances are weight loss,compressive strength,dynamic modulus,water absorption and acid corrosion depth.We use XRD to analyze the phase composition of corroded and uncorroded area of concrete in different pH solution.The synergy between H⁺and SO₄^2-were discussed.The result shows that:As the pH value increases,it may cause greater damage to concrete;when the pH value was setted at 2.5,as the SO₄^2-concentration value increases,it also can cause greater damage to concrete.There is a synergistic effect between H⁺and SO₄^2-,the existence of SO₄^2-may cause greater damage to concrete.?2?The influences of the material composition to concrete suffering from acid rain.The laboratory accelerated corrosion experiment was carried out to test the performances of concrete at different erosion period to investigate the influence of W/B ratio,the amount of fly ash and the amount of slag powder respectively.The result shows that:The concrete which W/B ratio is between 0.32⁰.37 may get a slow deteration during the corrosion.As the the amount of fly ash increases,it increase the rate of decay of performances of concrete.There is a optimum range of slag powder which is 20%³0%.Chemical composition and microstructure of corroded and uncorroded area of concrete in different amount of fly ash and slag powderwere were investigated.The results show that:Oxide content in concrete can influence the performance recession.We speculate that there is a optimum range of each different oxide content to increase the resistance to acid rain.The microstructure of concrete would change during the corrosion.The density of corroded and uncorroded area can affect corrosion behaviors.When the amount of fly ash and slag powder is very high,it has more unhydrated part and that is useless to the property of concrete.?3?We comparied prediction accuracy of GM?1,1?and MGM?1,2?model for short-term performance degradation by acid rain.To acquire long-term performance data,metabolic MGM?1,2?model was bring in.Through the experimental measurements and fitting a mathematical expression,the formula of acidification rate coefficient with pH value,the amount of fly ash and the amount of slag powderwas were given.Established on the formula of acidification rate coefficient and metabolic MGM?1,2?model,the service life prediction model wsa built.The rest compressive strength rate of concrete suffering from pH=1.5 and pH=2.5 solution was inquired.Because of the limitation of this method,we established a new way to acquire the mechanical property of concrete under limiting condition of durability degradation.