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工程调查显示,部分大体积混凝土桥墩发生开裂的特点是,裂纹在浇筑后7 d拆模时即出现在承台以上实心结构的中间位置,呈上下走向,并且在桥墩两面对称出现,判断裂纹主要是由于施工中内降温和外保温措施不充分造成的;试验研究显示,掺合料替代水泥的比例越高,降低水化热的作用越显著,粉煤灰降低水化热的作用略高于矿渣粉,将粉煤灰与矿渣粉复合后替代40%的水泥,即能够保证工程的混凝土强度设计要求,又能够显著降低水化热;同时,建议施工时在钢模板内衬织物来提高外保温效果。
Engineering survey shows that the cracking of some large-volume concrete piers is characterized by the fact that the cracks appear in the middle position of the solid structure above the abutment when the die is demolded at 7 days after pouring, and appear up and down directionally and appear symmetrically on both sides of the pier to judge the main crack Is due to the construction of the internal cooling and external insulation measures inadequate caused; experimental studies show that the proportion of admixtures instead of cement the higher the role of reducing the heat of hydration is more significant, the role of fly ash to reduce heat of hydration slightly higher than Slag powder, the fly ash and slag powder composite instead of 40% of the cement, that is, to ensure that the concrete strength of the project design requirements, but also significantly reduce the heat of hydration; the same time, it is recommended that the construction of steel stencil lined fabric to improve outside Insulation effect.