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随着国家高速铁路客运专线建设发展的加快,铁路客运专线大规模采用后张法预应力混凝土双线整孔简支箱梁作为主型梁,为有效缩短工期,保证施工质量,而采用蒸汽养护这项技术越来越广泛用于客运专线桥梁建设中。采用蒸汽养护可以加速混凝土的水化反应,加快混凝土成熟度,使混凝土提前达到所需的抗拉强度。在蒸汽养护过程中,水泥水化过程中伴随着大量的热量产生,热量在混凝土中不断积蓄,使内部温度升高;由于混凝土导热性比较差,热量传递具有延时性和衰减性,内部水化热不能瞬时传递到表面,开始养护罩内的环境温度比较低,混凝土外层表面通过对流和其他方式与养护罩内的空气和水蒸气混合物进行热量交换,随时间变化将形成内部温度高而外部表层温度低的温度分布状态,即混凝土结构蒸汽养护瞬态温度场,导致混凝土梁体各处温度不均,芯部、表面之间的温差过大,养护质量得不到保证,严重会产生裂缝。蒸汽养护技术既适用于恶略环境、严寒季节,还可以提高预制混凝土箱梁的品质、缩短施工周期;该技术的难点在于严格、准确、实时地控制温度变化。
With the acceleration of the construction and development of national high-speed railway passenger dedicated lines, the large-scale post-tensioned prefabricated concrete double-track full-aperture simple-supported box girder is used as the main beam for large-scale railway passenger dedicated lines. In order to shorten the construction period effectively and ensure the construction quality, This technology is more and more widely used in the construction of passenger dedicated railway bridge. Using steam curing can accelerate the hydration reaction of concrete, accelerate the maturity of concrete, so that the concrete reaches the desired tensile strength in advance. In the steam curing process, cement hydration process is accompanied by a large amount of heat generation, heat accumulates in the concrete, so that the internal temperature increases; due to the relatively poor thermal conductivity of concrete, heat transfer with time delay and decay, the internal water The heat of vaporization can not be instantaneously transmitted to the surface and the ambient temperature at the beginning of the curing of the hood is relatively low. The surface of the concrete is subjected to heat exchange by convection and other means with the air and water vapor mixture in the hood, Low temperature of the outer surface temperature distribution, that is, the steam curing concrete temperature transient field, resulting in uneven temperature throughout the concrete beam, the core, the temperature difference between the surface is too large, the quality of care can not be guaranteed, will produce serious crack. Steam curing technology is not only suitable for harsh environment, cold season, but also can improve the quality of prefabricated concrete box girder, shorten the construction cycle; the difficulty of this technology is strict, accurate and real-time control of temperature changes.