Anti Cracking Design And Evaluation Of Mass Concrete Structure

The rapid development of city to use in the construction of mass concrete structure in the more and more common,but the crack problems is also the subject of much attention.Now mainly taken the cooling pipe measures and reserved construction joints to prevent temperature cracks,during the construction process.People are often not enough attention to the performance of mass concrete.In the mass concrete crack resistance evaluation,most of the crack resistance index is based on the different uses of concrete.It is very important for the design and application of large volume concrete to reasonably evaluate the crack resistance and crack resistance.This article rely on the technology support project of Suzhou District Science "anti crack,anti rust reinforced concrete preparation technology research".Integrated design of mass concrete anti-cracking measures to address large volume concrete crack problem that with the “low temperature rising and shrink” method.Crack resistance described by Wang Tiemeng,is used to predict the cracking of mass concrete.The research results guide the engineering application of mass concrete,this article has the following research:The influences of mineral admixtures on the physical and mechanical properties of concrete,the temperature rise and the durability of the concrete are studied in this article.Test results show that the mineral admixture can reduce the strength and elastic modulus of early concrete,increase the strength and elastic modulus of concrete in the later period?The mixing effect of mineral admixture is better than that of the single mix.Mineral admixture delays the time of the highest temperature in concrete,and reduces the adiabatic temperature rise of concrete.The adiabatic temperature rise of concrete with 40% fly ash is reduced by 24.1%.The disadvantages of large shrinkage of concrete are brought by mineral admixture.UEA expansion agent and polypropylene fiber are chosen to solve the problems of shrinkage of concrete with mineral admixture.UEA expansion agent and polypropylene fiber can improve the splitting tensile strength and elastic modulus of early concrete,and reduce the shrinkage rate of concrete.Experimental results show that the UEA expansive agent and polypropylene fiber can obviously reduce the shrinkage of concrete,polypropylene fiber two experimental groups are shrinkage effect is good in the experimental group mixed UEA expansive agent,but the formercontribution to reduce the adiabatic temperature rise is not.Comprehensive consideration,mix proportion optimization result with double mixing fly ash mineral powder-best UEA expansive agent test group.The crack resistance of concrete was evaluated visually by using the slab restrained cracking and ring shrinkage cracking test.In the slab constraint test,the test results show that cracks appear in the benchmark concrete,the total crack area of the unit area is 29.92mm2/m2,and the crack resistance grade is III grade.No cracking are found in the best mixing ratio test group.In the ring constraint test,no cracking are found in both groups.And compared with the reference concrete,shrinkage strain value of the optimal mix ratio concrete is decreased by 14.7%.Research results were applied successfully on a large commercial and residential projects' raft foundation in Suzhou.The anti crack safety of raft foundation is 1.54.And all the application is successful.The engineering application practice shows that: low temperature rising and shrink made by this method controlled the temperature stress effectively.Crack resistance described by Wang Tiemeng,is accurate and effective to predict the cracking of mass concrete.