九江长江公路大桥索塔高性能清水混凝土耐久性研究

Durability of high-performance fair-faced concrete for cable support tower in Jiujiang Yangtze River highway bridge

九江长江公路大桥索塔施工采用C50高性能粉煤灰混凝土并要求外观达到清水混凝土质量目标。针对索塔混凝土结构施工实践及实际的使用环境,提出索塔高性能清水混凝土的外观质量控制指标及其结构的耐久性设计要求,通过试验研究骨料的碱反应活性及粉煤灰掺量对索塔清水混凝土的抗碳化、抗酸雨侵蚀、抗渗透性、抗冻融等耐久性能的影响。结果表明:选用的砂石骨料不具有碱活性,在索塔混凝土中掺入22.5%粉煤灰能改善其综合耐久性,并满足耐久性设计指标要求。

C50 grade high-performance（HPC） fly ash concrete is used in the cable support tower of Jiujiang Yangtze River highway bridge and the appearance quality is required to meet the standard of fair-faced concrete.Aiming at the engineering practice and actual service environment of the bridge site,we put forward the appearance quality control index and durability design requirements for the cable support tower HPC fair-faced concrete structure,and study the alkali reaction activity of aggregates and the effects of fly ash content on resistances of the cable support tower concretes to carbonation,acid rain,permeability and freezing-thawing through experiment.The results show that the sand and crushed stone used in the engineering construction has no alkali activity,and the comprehensive durability of the cable support tower concrete is improved by 22.5% fly ash as the substitution of portland cement and meets the design index requirements.