Shrinkages of C50 concrete at different ages were measured with different experimental devices including condensation,early self-shrinkage(1 d),long term self-shrinkage and drying shrinkage.The effects of water-binder ratio,sand percentage,water content and water reducing agent content on the shrinkage property of C50 box girder concrete were studied systematically,and measures for the preparation of concrete with low shrinkage was proposed.The results show that with increasing water-cement ratio,the self-shrinkage of concrete is reduced,but the condensation and drying shrinkage increase.By reduction of sand percentage and water content,all kinds of shrinkage of concrete,including drying shrinkage,self-shrinkage and condensation can be reduced.The concrete shrinkage can be decreased by optimizing aggregate gradation and controlling flow ability.%采用不同收缩试验装置测试了C50箱梁混凝土的凝缩、早期(1 d)自收缩、长期自收缩和干燥收缩,系统研究了水胶比、砂率、单位用水量及减水剂掺量等混凝土配合比参数对高性能混凝土收缩性能的影响规律,提出了低收缩混凝土的制备要点.研究表明:减小水胶比,C50箱梁混凝土凝缩和干燥收缩减小,但自收缩增大;减小砂率和单位用水量均可显著减小混凝土的凝缩、自收缩和干燥收缩;优化石子级配和适当减小拌和物流动性可显著改善箱梁混凝土的抗收缩性能.
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