超高桥塔高强混凝土性能研究及收缩调控

研究目的:为研究沸石砂砾、粉煤灰陶砂与高吸水树脂(SAP)内养护材料对C60高强混凝土性能的影响,分析单掺及复掺内养护材料对混凝土抗压强度、内部相对湿度及自由收缩的影响规律。研究结论:(1)在单掺形式中,内养护引水量为13.5 kg/m^3时,混凝土减缩效果及力学性能最佳;总引水量为13.5 kg/m^3时,沸石砂砾与高吸水树脂复掺可进一步降低混凝土自由收缩,二者引水质量比为2∶1时,混凝土28 d收缩值仅为基准组混凝土的36.1%;(2)通过不同内养护材料引水量与内部相对湿度关系、自由收缩与内部相对湿度关系,回归得到关键参数,建立内养护混凝土收缩预测模型,可实现收缩调控;(3)结合沪通长江大桥主塔大体积混凝土结构,采用MIDAS FEA软件进行混凝土早期抗裂性分析,复掺沸石砂砾和SAP内养护混凝土塔柱在温度与收缩应力共同作用下,其最易开裂部位的拉应力均小于最大容许拉应力,总体开裂风险较低;(4)本研究结果可为大体积高强混凝土应用提供参考。

Performance and Shrinkage Control of High Strength Concrete for Super High Bridge Tower

Research purposes:In order to study the effect of zeolite gravel,fly ash pottery sand and super absorbent ploymer(SAP)on the performance of C60 high strength concrete,the effects of single-and double-mixed internal curing materials on the compressive strength,internal relative humidity and free shrinkage of concrete were analyzed.Research conclusions:(1)For concrete with single internal curing material,when the water diversion amount from the internal curing materials was 13.5 kg/m^3,the shrinkage reduction effect and mechanical properties of concrete were the best.When the total water diversion amount of the internal curing materials was 13.5 kg/m^3,the double mix of zeolite gravel and SAP can further reduce the free shrinkage value.And the free shrinkage value at 28 d was only 36.1%of the reference group when the water diversion mass ratio of zeolite gravel and SAP was 2∶1.(2)Based on the relationship between the water diversion of different internal curing materials and internal relative humidity,the relationship between free shrinkage and internal relative humidity,the key parameters were obtained,therefore,the shrinkage prediction model of internal curing concrete was established which can realize the control of free shrinkage.(3)Combined with the mass concrete structure of the main tower of Hutong Yangtze river bridge,the crack resistance of concrete in the early stage was analyzed using MIDAS FEA software.Considering the coupled effect of temperature and shrinkage stress,the tensile stress of the most vulnerable cracking position of concrete tower mixed with zeolite gravel and SAP was less than the maximum allowable tensile stress,and the overall cracking risk was relatively low.(4)The research results can provide reference for the application of mass high strength concrete.