Experimental Study On Durability Of Exposed Concrete And Life Prediction Based On Wiener Method

There are many salt lakes,alkali beaches and swamps in western China,and the environmental conditions are harsh.It is the area with the most distribution of saline soil in China.The aggressive natural environment makes the durability of the concrete structure in this area deteriorate seriously,which is far less than the average service life of the national concrete structure.With the steady advancement of the national strategy “The Belt and Road”,the active and effective participation of the western region in the national strategy has led to a new round of construction in the western region.Therefore,studying the durability deterioration law of concrete structures in this area and predicting its reliability life has great theoretical significance and practical application value for the construction of this area.This research is supported by National Natural Science Foundation of “study on durability prediction of concrete based on sulfate corrosion in Western Saline Soil region of China”.In view of the serious damage to concrete materials in western salty soil areas,the key factors affecting the service life of concrete structures in this area are selected,and three different durability tests were designed.The concrete specimens with different mix ratios were studied,the deterioration law and corrosion mechanism of concrete structure were analyzed.The relative mass and relative dynamic elastic modulus were selected as the degradation index,using Wiener distribution model to predict the service life of concrete structures under different environmental factors.This experiment completed the following research work and achieved corresponding results:1.Based on the real natural environment and climate characteristics of Geermu area,accelerated deterioration test of concrete in the environment of the area was designed.The plan considerd the long time of sunshine,strong ultraviolet radiation and corrosive ion concentration in Geermu area.Various factors such as high corrosive ion concentration,the relative quality evaluation parameters,the relative dynamic elastic modulus evaluation parameters,and the comprehensive damage evaluation parameters were used to analyze the durability deterioration of concrete specimens in the simulated Geermu natural environment,and the mechanical properties and microstructure of the specimens were combined.The change and the corrosion process and mechanism of the concrete specimen were obtained.The results show that under the erosion of corrosive ions,the main corrosion products inside the concrete are gypsum and ettringite.2.Different mix proportion of concrete specimens are buried in Geermu City,Qinghai Province,in typical heavy-salted soil areas.From the non-destructive testing,the relative quality evaluation parameters,relative dynamic elastic modulus evaluation parameters and comprehensive damage evaluation parameters are used to evaluate deterioration of concrete specimens.The deterioration regularity of concrete specimens in this area is obtained,and the change of flexural strength and compressive strength of specimens is combined with microscopic image.The deterioration mechanism of concrete structure is analyzed,and the resistance of concrete with different strength grades is compared.It is concluded that as the concrete strength grade increases,its corrosion resistance is stronger,and under the exposed conditions of the site,the corrosion of the concrete specimen embedded end is more serious.3.The concrete specimens with different proportions are buried in Tianshui City,Gansu Province.The quality loss and ultrasonic wave velocity of concrete specimens are collected by non-destructive testing.Relative quality evaluation parameters,relative dynamic elastic modal evaluation parameters and comprehensive damage evaluation parameters are selected to evaluate the deterioration of concrete specimens under the exposure conditions.The mechanical properties of the test specimens before and after the test were compared with the SEM and XRD images.The deterioration mechanism of the concrete structure was analyzed.It is found that the deterioration of concrete performance has a greater impact on flexural strength.4.The relative mass and relative dynamic elastic modulus were selected as the degradation index,and the Wiener probability distribution was used to model the degradation process of the specimen.The reliability curves of the concrete specimen under different conditions were obtained,and their life expectancy was predicted.The Prediction results shows that the relative dynamic modulus is a more sensitive index than the relative quality.