Study On Sulfate Corrosion Resistance Of Recycled Coarse Aggregate Concrete

Due to the continuous growth of China's building industry,the consumption of concrete materials is increasing.At the same time,the demolition of houses,the renovation and renovation of roads will produce a large amount of waste concrete,which brings problems of resources and environment.In the case of serious shortage of concrete raw materials,solving the problem of recycling of waste concrete will be related to the healthier and more sustainable development of the construction industry and the whole society.The research on recycled concrete has become a hot topic in the civil engineering field.The research on the durability of recycled concrete has great theoretical and practical significance for its application in concrete structural engineering.Concrete sulfate attack is a serious erosion damage,and it is also the most complicated and destructive environmental water erosion.Therefore,research on recycled concrete sulfuric acid Salt erosion has important application value and significance for the design of recycled concrete.In the test of the resistance to sulfate attack of coarse aggregate concrete naturally immersed in a single sodium sulfate solution and a single magnesium sulfate solution,it is obtained from the analysis of the apparent phenomenon of corrosion,the change of ultrasonic sound velocity and the rate of mass change.When the concentration of the solution increases,the rate of sulfate attack increases;at the same concentration,with the increase of the replacement ratio of the recycled coarse aggregate,the sulfate resistance of the recycled concrete is reduced,and the concrete with 100% substitution rate is compared with the sound velocity without the mixed group.Decreased by about 5%,but in the 5% sodium sulfate solution,the rate of decline in sound velocity increased to 7.138% in the later stage of corrosion;And the ultrasonic sound velocity of the test piece with the replacement rate of recycled coarse aggregate is less than 30%.Compared with natural concrete,the ultrasonic sound velocity is only about 2.50%,which has good resistance to sulfate attack,but the substitution rate exceeds 50%.Sulfate erosion performance has suddenly decreased.The effect of sodium chloride on the sulfate attack resistance of recycled coarse aggregate concrete was studied by adding a certain amount of sodium chloride to sodium sulfate and magnesium sulfate solution.It was found that the ultrasonic sound velocity of the recycled concrete with the chloride salt was corroded.The growth rate in the early stage is much smaller than that in the single sodium sulfate solution.At 30 days,the chlorine salt content is 5%,and the concrete sound speed of 50% substitution rate only increases by 1.795%,but the non-mixing group increases by 3.003%;The descending speed is also small,and the decreasing speed with the increase of chlorine salt content is smaller.The speed of sound drop of the non-mixed test block is about twice that of the 5% salt test group;the chlorine salt can be seen for recycled concrete.The anti-sodium sulfate attack has a good inhibitory effect,and the greater the chlorine salt content,the better the inhibition effect;the recycled coarse aggregate concrete in sodium chloride-magnesium sulfate solution has three aspects: apparent phenomenon,ultrasonic sound velocity and quality change.It shows that the corrosion damage phenomenon is more serious than the test piece in a single magnesium sulfate solution,and even the phenomenon that the corrosion damage is more serious with the increase of the chlorine salt content,indicating that the chlorine salt is resistant to sulfur by the recycled coarse aggregate concrete.No effect of suppressing the corrosion of magnesium,chloride ions can be effectively suppressed sulfate corrosion,erosion is suppressed but not magnesium ions.In the study of the sulfate erosion damage of recycled coarse aggregate concrete under natural immersion,the simple composite function was used to fit the sulfate attack damage of the recycled coarse aggregate concrete under natural immersion,and the different sulphates under natural immersion were obtained by fitting.The corrosion damage evolution equation of recycled coarse aggregate concrete in solution describes the influence of the replacement ratio of the coarse aggregate,sodium sulfate concentration,magnesium sulfate concentration and chloride salt concentration on the damage process of recycled coarse aggregate concrete.The paper has pictures 44;Tables 45;Referenrences 93.