Study On Crack Resistance Promotional Technology Of Subway Lining Concrete

As one of the important traffic projects in the city,the subway project is particularly important for its safety and durability.For the concrete used in the construction of subway projects,the strength grade is high,and the stability of performance is affected by many factors such as raw material quality,cement dosage and construction conditions.In addition,for the coastal environment in which a city is under construction,the concrete used is also affected by seawater erosion with high concentrations of corrosive ions.For example,cracks in the reinforced concrete structure itself will cause corrosion of the steel bars,seriously affecting the overall structure.Safety and use.Therefore,in order to improve the crack resistance of concrete,and in combination with the needs of subway construction,the system’s crack resistance performance of the subway lining concrete is studied.The main research contents are as follows:（1）In view of the cracking problem of the lining concrete used in the subway construction under construction,some sites of a city subway line were tested and investigated in the field,including:performance testing of concrete raw materials,data statistics of cracked areas,and original mix ratio of lining concrete.Performance verification and analysis of the cause of cracking.（2）According to the technical requirements of the crack resistance of mass concrete,this paper adopts the method of mixing minerals with large amount of minerals.Under different cementitious material systems,the reference mix ratio of subway lining concrete is calculated according to the linear regression equation between the compressive strength of concrete 28d and the amount of cementing material and the ratio of glue,and based on the analysis of raw material cost in a certain city area.The best mix ratio of low cost and excellent performance is the recommended mix ratio of subway lining concrete.（3）Based on the obtained recommended ratio of subway lining concrete,the crack resistance performance was studied,including:hydration heat test analysis,dry shrinkage performance and early crack resistance test,and chloride ion penetration resistance test.Compared with the original mix ratio of subway lining concrete,the shrinkage performance and crack resistance of the recommended mix ratio are significantly improved.The maximum shrinkage of concrete specimens when it reaches 60d curing age is lower than 3×10^-4,flat cracking.The test specimens used in the test showed no cracks during the curing period of 9 days,and the impermeability was also good.After the on-site inspection and investigation of the recommended mix ratio of subway lining concrete,it was found that the concrete rebound strength all meet the requirements of strength grade,the number of cracks in concrete decreased by 85%and the average width of cracks decreased by 65%.The use of the recommended mix ratio significantly improves the crack resistance of the concrete.The recommended ratio of high crack resistance subway lining concrete proposed in this paper has good engineering application effect,and also meets the durability and safety of subway engineering.It has great use value for subway construction.