Study On Sulfate Deterioration Damage Of Concrete Under The Strong Corrosive Environment In Northwest China

Concrete is a building material with the highest frequency and maximum usage in modern engineering construction.However,our territory is vast,and our climate environment is very complex,which puts forward severe tests on the durability of concrete structures.Improving the durability and service life of major foundation projects is the top priority in engineering construction and operation.The prediction of durability and service life is of great engineering significance.Therefore,the following researches are carried out in this paper.(1)To simulate the difference between the actual corrosion environment on site,saline soil transported back to the site was used in the test.The specimens were buried in the saline soil transported back to the site in half-buried and full-buried ways,with a 12-day cycle.Na2SO4 solution was added to ensure that the d level was above the soil surface in the first 8 days.After 4 days,no additional water was added and electric fans were used to accelerate the air drying of the water solution on the soil’s surface.The actual erosion situation on site under the action of ecological water transport was simulated.By analyzing the experimental data of the indoor concrete erosion experiment,the corresponding concrete performance deterioration line chart is drawn.Compared with the deterioration law of the actual structure on the site,it can be concluded that the deterioration trend is basically consistent.Therefore,the erosion system adopted in the test can basically reflect the situation on the site.(3)In this paper,the water-cement ratio,the amount and type of the admixture,and the erosion mode are the main influencing factors for the study.The study focuses on the combination of SAP and wollastonite in concrete and the influence of this mixing scheme on the sulfate resistance of concrete.The change of water-cement ratio will lead to the change in the impermeability of concrete so that the rate of sulfate ions penetrating into the concrete will change,and the strength of cement will also change.Therefore,reducing the water-cement ratio will improve the sulfate resistance of concrete.The addition and the change of the dosage of admixture mainly affect the porosity of concrete itself.The admixture suitable for the dosage will reduce the channels for sulfate ions to penetrate into concrete through the effect of volcanic ash,filling effect or internal curing,so as to improve the sulfate resistance of concrete.(4)In this experiment,gravimetric method was used to measure the infiltration of sulfate ions inside concrete under specific erosion cycles,and the specific distribution of sulfate ions inside concrete specimens was determined.By analyzing the test data,it can be concluded that the basic trend of sulfate attack rate is similar in all the concrete specimens with different mix ratios.However,the smaller the porosity is,the lower the water-binder ratio is,and the sulfate ion diffusion rate of the concrete specimens will be slower.Therefore,compared with the concrete specimens with large porosity and high water-binder ratio,its performance deteriorates more slowly in the process of sulfate attack.(5)According to the damage mechanics theory,based on the analysis of the existing test data and referring to the deterioration difference of concrete under different factors,the actual deterioration damage model of mechanical properties of sulfate eroded concrete is proposed.