Study And Evaluation Of Concrete Durability In The Action Of Carbonization-Sulfate Attack-Dry-Wet Cycle

In recent years,concrete materials have been widely used in civil engineering.Affected by the service environment of concrete,many concrete structures which have not reached the design life length are damaged by the environment.In Northwest China arid pumping irrigation area,affected by climate,geography and so on over a long period of time,a large number of hydraulic concrete structures appear different degrees of erosion damage,which greatly threatened the safe operation of irrigation area water conservancy project.There are many researches on the mechanism and rule of concrete durability deterioration under single factor.However,under many factors of erosion,the mechanism of concrete durability deterioration is not clear.The rule of deterioration process is fuzzy and the durability evaluation is not perfectly available.Therefore,the research and evaluation of concrete durability under the combined action of multiple factors will have more practical significance and application value.In this paper,combined with the project of "the research on the durability of the concrete structure based on multi field coupling in the irrigation district",which is supported by the scientific and technological innovation talent support program in Henan province.This paper takes concrete buildings in Jingtaichuan electrical irrigated area(hereinafter referred to as "JD irrigation area")as the research object.Based on the analysis of water samples,soil samples and spelling residues in the working environment of water conservancy concrete structure in irrigation area,the main erosion effect and erosion medium will be revealed.Design concrete with different water binder ratio,fly ash content and air entraining agent,then carry out indoor accelerated deterioration test,then the durability deterioration of concrete is revealed.Based on the grey relational theory and extension theory,the concrete durability of each test group in different erosion stages was evaluated quantitatively and qualitatively,the following conclusions can be drawn:(1)Under the action of carbonation sulfate erosion and drying and watering cycle,the durability deterioration of concrete with different mixing ratio has experienced three stages: slightly increased-stable(slow descent)-rapid descent.The influence of water binder ratio on the durability of concrete is relatively remarkable.The smaller the water binder ratio is,the stronger the durability is and the slower the degradation process is.Obviously the addition of fly ash can improve the durability of concrete.The durability of concrete with 20% fly ash is the best.The use of air entraining agent can improve the durability of concrete.(2)Based on the correlation value,the concrete durability grade can be divided into five grades: good,preferably,medium,sub-standard and poor.In the early stage of experiment,the durability of concrete in each test group was higher than the "preferably" level with associate 0.75,and the durability was in a strong state.In the later stage of experiment,the durability of concrete in each test group was below the "sub-standard" level with associate 0.45,and the durability was in a weak state.Through concrete durability test under carbonation-sulfate attack-drying and watering cycle,combined with durability deterioration rules and overall merit,provide reference for the durability design of dry pumping irrigation area of hydraulic concrete structure and the basis for the operation and maintenance of existing concrete buildings.