大吨位混凝土箱梁早期水化热温度场试验研究

Experimental Research on Early Hydration Heat Temperature Field of Large Tonnage Concrete Box Girder

摘要:

大吨位混凝土箱梁在浇筑初期，其水化热现象是引发早期开裂的关键因素。以温州某项目工程中的35 m预制箱梁为实例，进行了早期水化热的跟踪研究。结果显示，35 m箱梁在初期水化热过程中，温度经历了“逐渐升高—高温维持—逐渐降低”的典型变化。水化热引起的最高温度发生在箱梁端部的S1截面右侧腹板芯部，峰值温度达到66.7 ℃，出现在浇筑后第41 h。而混凝土内部与外部的最大温差出现在箱梁端部的S1截面左侧顶腹板芯部与外表层之间，温差高达23.6 ℃，出现在浇筑后第46 h。由于箱梁端部腹板较厚，其内部热量散失较慢，导致该区域降温速率相对较慢。此外，环境温度对箱梁内外温差有显著影响。基于这些发现，提出了预防温度裂缝的有效措施。研究成果对于大吨位箱梁的设计与施工具有重要的参考价值。

Abstract:

In the early stage of pouring large-tonnage concrete box girders, the phenomenon of hydration heat is the key factor causing early cracking. Taking the 35 m precast box girder of a project in Wenzhou as an example, a tracking study on early hydration heat was conducted. The results show that the temperature undergoes a typical change of "gradually increasing - maintaining high temperature - gradually decreasing" during the initial hydration heat process of the 35 m box beam. The highest temperature caused by the hydration heat occurs in the core of the right web of the S1 section at the end of the box beam. The peak temperature reaches 66.7 ℃, which occurs in the 41 st hour after pouring. And the maximum temperature difference between the inside and outside of the concrete occurs between the left top web plate core and the outer surface layer of the S1 section at the end of the box girder, with a temperature difference of up to 23.6 °C, which occurs in the 46 th hour after pouring. Due to the thicker web at the end of the box girder, its internal heat dissipation is slower, resulting in a relatively slow cooling rate in this area. In addition, the ambient temperature has a significant effect on the temperature difference between the inside and outside of the box girder. Based on these findings, the effective measures to prevent temperature cracks are proposed. The research results have important reference value for the design and construction of large-tonnage box girders.