Research On Comprehensive Control Of Shrinkage For High-strength Concrete In Cable-stayed Bridge Tower

The concrete of the cable-stayed bridge tower concrete has the characteristics of high strength,large hydration heat,and poor maintenance environment.Under strong constraints,the cracking risk of high-strength volume concrete is outstanding.How to effectively maintain concrete in this service environment,reduce its shrinkage,and reduce the risk of cracking has become a key problem to be solved by the project.Based on this,this paper selects the C60 high-strength concrete actually used in the bridge tower,and uses SAP(superabsorbent resin),zeolite gravel,fly ash pottery sand,and zeolite powder to study the internal curing materials for concrete at different dosages.On the basis of this,the influence of SAP and zeolite powder,fly ash ceramsite and zeolite powder on the performance of concrete was studied,and the shrinkage control method was proposed.Combining with the main tower structure and the construction technology of Hutong Yangtze River Bridge(330 m in height and thickness of most of the tower wall exceeds 1.5 m,It is typical high-strength volume concrete structure under strong constraints)explores the effect of internal and external collaborative maintenance on concrete and provides a basis for evaluating the internal and external collaborative maintenance methods.The research results can provide a reference for engineering applications.The main work and conclusions of the paper are as follows:(1)The influence of four internal curing materials on the mechanical properties of concrete,cement hydration process,shrinkage performance and internal relative humidity under different dosages was studied.The shrinkage effect and shrinkage mechanism of internal curing were analyzed.The results show that the mechanical properties,cement hydration process,and self-shrinkage are used as evaluation indicators to evaluate the internal curing effect of different internal curing materials.With the increase in the amount of internal curing materials,the shrinking effect of concrete continues to increase.The amount should not exceed 10%,20%,20% and 15%,respectively,and use this to determine the optimal amount of internal curing material and the optimal amount of internal curing water.(2)Considering the different water release sequence of the three internal curing materials in concrete,SAP and zeolite powder,fly ash ceramic sand and zeolite powder were matched with each other,and the performance of concrete with different internal curing materials on the performance of concrete was studied.influences.The results show that the compressive strength and self-shrinkage are used as evaluation indicators to study the influence of internal curing on the volume stability of concrete,and to analyze the internal curing effect and its mechanism.Through the relative humidity test,the change curve of the internal relative humidity of the concrete is obtained,the theoretical calculation is carried out,and the mechanism of the matching internal curing material to adjust the internal relative humidity is discussed.Proposed integrated control technology for internal maintenance.(3)The effects of different curing methods on the mechanical properties,crack resistance and internal relative humidity of internal curing concrete were studied,the mechanism of internal and external cooperative maintenance was analyzed,and an integrated internal and external curing method was proposed.Based on the determined compounding ratio of the compound and internal curing material,the mechanical properties,free shrinkage strain,anti-cracking performance,etc.are used as the evaluation indicators to comprehensively evaluate the internal and external collaborative maintenance effect,and provide reference for engineering applications.