| Inner Mongolia Hetao Irrigation District is located in the arid area of northwest China.The self-compacting concrete used for channel lining suffers from freezing and thawing damage all the year round,and the drought leads to soil salinization,which makes the self-compacting concrete not only damaged by freezing and thawing,but also has sulfate attack.The double factor of corrosion causes the concrete used for the channel lining to be overhauled for a certain period of time and requires a lot of manpower and material resources.It is especially important to improve the durability of concrete by rationally designing the concrete mix ratio to improve its resistance to sulfate attack.This paper is mainly divided into three parts.Firstly,the effect of high-content mineral admixture on the workability,mechanical properties and durability of self-compacting concrete is studied.The amount of cementitious material with better performance of self-compacting concrete is preferred.The influence of specific parameters on the frost resistance of self-compacting concrete under sulfate attack was established.Finally,the freeze-thaw damage model was established based on the results of self-compacting concrete sulfate freeze-thaw test,and the durability of concrete was predicted by model.The specific research results are as follows:(1)The amount of fly ash and the amount of slag have a significant effect on the workability,mechanical properties and impermeability of self-compacting concrete,and there is an interaction between the two,which is optimized by the quadratic general rotation combination design.The amount of cementing material that makes the concrete performance better is: the fly ash is 0~30% of the total amount of the cementing material,and the slag is 10%~30% of the total amount of the cementing material.(2)Selecting the optimized fly ash content and slag content for sulfate freeze-thaw test,the results show that the effect of fly ash content on concrete sulfate freeze-thaw is greater than the effect of slag content on each test;Most of the concrete in the group was destroyed in the 250 th sulphate freeze-thaw cycle.Only one test group could reach 300 freeze-thaw cycles;the data of 250 freeze-thaw cycles showed that with the increase of fly ash content and slag content The damage degree of the concrete first decreases and then increases,and the minimum damage degree of the concrete is 0.098.At this time,the fly ash is 12% of the total amount of the cementitious material,and the slag is the total amount of the cementing material.%.(3)The test results of the concrete sulfate freeze-thaw of the mix ratio parameters(fly ash,slag,coarse aggregate volume ratio,water-cement ratio)show that the test piece did not break when the concrete was frozen and thawed for 300 times.At this time,the effect of fly ash content on concrete sulphate freeze-thaw is greater than slag content,larger than coarse aggregate volume,greater than water-cement ratio,and relative dynamic modulus and damage can be well reflected.The sulphate freeze-thaw condition of concrete;the minimum damage degree of concrete is 0.076,the dosage of fly ash is 106 kg/m3,the dosage of slag is 66 kg/m3,the volume ratio of coarse aggregate is 0.33,water-cement ratio Is 0.3.(4)The damage degree of concrete and the number of freeze-thaw cycles show an exponential change law,and the damage model of the established index form has a high degree of fit;predicting the durability of concrete according to the established damage equation,and theoretically resisting sulfuric acid The concrete mix ratio is better for salt freeze-thaw cycles. |
