Experimental Study On Durability Of Concrete In Western Saline Soil Area And Life Prediction

Concrete durability has an important impact on the service life of concrete structures and reinforcement in the later stage.Aiming at a series of problems of concrete in Western salted land,such as short service life and high maintenance cost in the later period,this paper relies on the National Natural Science Foundation's“Study On Durability Life Prediction Of Concrete Based On Sulfate Corrosion In Western Salted Land”,Two area with typical saline soil characteristics in Jiuquan and Xi'an were selected for exposure test.At the same time,by analyzing the factors affecting the durability of concrete,combined with the climate characteristics and site environment of the two places,an indoor accelerated test based on exposed test was designed.The relative quality evaluation parameters,the relative dynamic elastic modulus evaluation parameters and the comprehensive evaluation parameters were selected as the evaluation indexes,and the SEM,EDS and XRD method was combined to reveal the corrosion deterioration mechanism of concrete in the western salted area.On this basis,the method of acceleration factor K was used to predict the life of the exposed environment by the indoor and exposed durability change rules,and the following scientific research work was completed and the corresponding results were obtained:?1?Based on the climatic characteristics and corrosive environment of Jiuquan area,the indoor accelerated test is designed,comprehensively considering the influence factors such as dry-wet cycles,ion corrosion and solar radiation.Through the relative quality evaluation parameters,relative dynamic elastic modulus evaluation parameters and comprehensive evaluation parameters,the changes of concrete durability under multi-factor coupling with water-cement ratio of C30,C40and C50 are obtained:The relative quality evaluation parameter?₁,and the relative dynamic elastic modulus evaluation parameter?₂ increased at the initial stage,and then the descending speed rate became faster and faster.The smaller the water-cement ratio is,the better the durability of the concrete is;?2?Expose three strength grade concretes to Jiuquan and Xi'an with typical saline soil characteristics,and conduct non-destructive testing dates on a regular basis,The change rule of concrete durability at both sides is analyzed,and it is obtained that the parameter?₁ and?₂ of concrete in the exposed environment of Jiuquan and Xi'an just change little,and the relative dynamic evaluation parameters of A and B side are quite different.The dynamic elastic parameters rate of where exposed to the air is slower than that in the soil,and the dynamic evaluation parameters of L is smaller than both sides.In the two types of saline soil areas,the durability of Jiuquan area is seriously damaged,and the Xi'an area is relatively light;?3?Based on indoor acceleration test,life prediction is carried out by the method of acceleration factor K of concrete in outdoor exposure environment in Jiuquan and Xi'an,Finally,the result is the expectancy life of C50 concrete is the longest,and the life of C50 and C40 concrete is similar,and the life of C30 concrete is quite different.the smaller the ash ratio is,the better Concrete durability is and the longer the expectancy life of concrete is.It's because that the smaller water-cement ratio concrete got the denser structure and the better corrosion resistance.The service life of concrete in Jiuquan area is significantly lower than that in Xi'an;?4?After all tests,it can be seen by microscopic electron microscopy that many rod-shaped and flaky crystals are formed in the concrete,and we speculate these are ettringite,gypsum,etc,these products reduce the porosity of concrete in the early stage,and performance is enhanced in the macro,later the expansion stress by these products of concrete experiencing is increasing,until the concrete stress limit is exceeded,the original pores of concrete begin to expand.Cracks promote the reaction to occur further,the rate of deterioration continues to accelerate,and finally reaches the failure state.