水化热引起的大体积混凝土墙温度分析

Analysis of hydration heat induced temperature rise in massive concrete walls

根据已提出的考虑混凝土化学反应速率的热传导方程新理论 ,分析了水化热引起的大体积混凝土墙的温度场 ,给出了该问题非线性热传导方程的解析迭代公式 .研究中 ,绝热温升采用了基于Arrhenius理论的有效时间的函数 ,从而导致求解非线性热传导方程 .从计算结果得出如下结论 :(a)浇筑温度对大体积混凝土墙的最高温升有显著影响 .浇筑温度越高 ,混凝土墙的内外最大温差越大 .(b)由于混凝土的导热系数低 ,墙中心的温度高于其表面温度 ,这将导致混凝土墙横断面上不同位置在不同时刻具有不同的水化热化学反应速率 .(c)水化热化学反应速率随温度升高而加快 ,从而使混凝土硬化速率加快 ,初凝和最终凝固时间缩短 .因此 ,在炎热气候条件下宜采用低热水泥 .

On the basis of the new theory of heat conduction equation considering the chemical reaction rate of concrete, the temperature field caused by hydration heat in massive concrete walls is analyzed, and the analytical iterative solution to the nonlinear heat conduction equation is presented. In the analysis, the adiabatic temperature rise is taken as a function of effective time based on the Arrhenius theory, resulting in a non-linear differential equation. Then 180 nonlinear equations are solved by the iteration method, and the following conclusions are drawn: (1) placement temperature has a great effect on the maximum temperature rise in massive concrete walls, and the higher the placement temperature, the larger the maximum temperature difference between the inside and the surface of a concrete wall; (2) owing to the low thermal conductivity of concrete, the temperature at the center of a concrete wall is higher than that of the surface, resulting in different chemical reaction rates of hydration heat and different effective time at different points of the cross section of a concrete wall; (3) the increase of chemical reaction rate with temperature leads to the acceleration of hardening of concrete and the reduction of its initial and final setting time, so low heat cement is preferred under hot weather conditions.