RESEARCH AND APPLICATION OF ANTI-CRACKING TECHNIQUES FOR DUMBBELL-SHAPED CAP BLOCK CONCRETE
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摘要: 针对武汉新建新河大桥哑铃形大体积承台混凝土的抗裂性问题,采用混凝土浇筑温度控制、水化温升控制、收缩补偿的综合应用,结果表明:拌和水和粗骨料的冷却控温是降低混凝土浇筑温度的关键,通过冷却水管循环水化热调控材料能够显著降低混凝土的水化温升,镁质膨胀剂能够显著补偿大体积混凝土在温降阶段的收缩,但应采用更加严格的保温措施,以免结构里表应变差过大而增加开裂风险。工程实施效果表明,良好且精密的温控措施和有效的补偿收缩是大体积混凝土抗裂的关键。Abstract: The issue of crack resistance of dumbbell-shaped block concrete for caps of the newly built Xinhe Bridge in Wuhan was studied, the comprehensive measures were adopted such as techniques of temperature control casting concrete, temperature rise control for hydration heat and shrinkage compensation. The results showed that the key to reducing the temperature of casting concrete was the temperature control of mixing water and coarse aggregate; the temperature rise of concrete for hydration heat could be significantly reduced through circulating hydration heat regulating materials in cooling water pipes; the shrinkage of block concrete during the drop phase of temperature could be significantly compensated by the magnesian expansion agent, however, more stringent insulation measures should be taken to avoid the excessive surface strain difference between the interior and the surface resulting in increased risk of crack. Practice showed that good and precise control measures of temperature and effective compensation measures for concrete shrinkage were the key to crack resistance of block concrete.
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