Research On Uniformity Control And Cracking Resistance Of Large Mobility Concrete

With the rapid development of China's economy,the government invested heavily in infrastructure projects,so the demand for concrete increased year by year.In order to pumping construction,modern high performance concrete to improve mobility.However,large mobility concrete cracking phenomenon is a big problem,this is puzzling experts engineering and technicians.Most of this people try to reduce the cracking tendency of concrete by reducing the shrinkage of concrete and use steel reinforcement bars,but the affect wasn't distinct,the problem has not been solved well.The uniformity is mainly the degree of aggregate distribution in concrete,it is an important factor affecting the crack resistance of concrete,this paper studies the method of detection and characterization of high fluidity concrete uniformity,the concrete segregation rate,density difference between inside and outside the concrete,coarse aggregate difference between inside and outside of concrete to characterize the quality of fresh concrete uniformity,using ultrasonic characteriese hardened concrete uniformity,the homogeneity of concrete structure can also be described by image processing.Raw material quality is one of the factor that affecting the uniformity of concrete,such as aggregate gradation.Concrete mix parameters is another factor,such as water binder ratio,sand ratio and water reducing admixture,workability of concrete,such as flowability,water retention and cohesiveness.Construction control and vibration time affect the uniformity of concrete.The key factor is the concrete fluidity and vibration time.The concrete with poor uniformity shows the characteristics of mortar or slurry,and the compressive strength decreases,the shrinkage increases and the crack resistance decreases obviously.In this paper,it is proposed that the inhomogeneity of concrete ultrasonic velocity can be used to judge the heterogeneity of concrete,the smaller the degree of uniformity,the better the uniformity of concrete,the lower the dry shrinkage of concrete,the crack resistance and chloride ion permeability be better.There are many factors that influence the homogeneity of concrete,such as flowability,sand ratio,water binder ratio and vibration time,on the premise of not changing other conditions,according to the results of the homogeneity of concrete,the influence of the homogeneity of concrete on the strength and durability of concrete is studied.By improving the workability to enhance the homogeneity of concrete,improve the workability of concrete is mainly from two aspects,on the one hand,control the quality of raw materials and optimize the mix proportion of concrete,on the other hand,in the process of concrete construction,the density of the ingredients to strictly control the accuracy,mixing and molding,the flow and vibration time are key factors.In this paper,the reasons of large area concrete cracking is analyzed,the anti cracking performance of concrete surface can be improved greatly by adding the crack resistant accessories.Choose the corresponding crack accessories for different strength grade of concrete,the crack resistance can be improved by 95%.For high strength concrete with low water binder ratio and high self-constriction,the application of the technology of light particles in the maintenance,the maintenance effect is obvious,the strength of concrete is improved,the shrinkage of concrete is reduced,the concrete crack resistance and sulfate resistance is improved.