碳化环境混凝土结构的耐久性定量分析模型

Quantitative Durability Analysis Models of Concrete Structures under Carbonation Environment

为了准确分析混凝土的碳化深度,研究建立了碳化环境下混凝土结构的耐久性定量分析模型。首先根据水泥水化和混凝土碳化的物理化学反应过程,结合混凝土中二氧化碳、氢氧化钙和水化硅酸钙的物质的量守恒定律,研究建立了混凝土碳化多场耦合数值分析模型的控制方程及其初始条件和边界条件;然后基于混凝土的碳化机理,结合混凝土碳化反应与水泥水化反应的化学物质平衡关系,确定了混凝土中氢氧化钙和水化硅酸钙的初始浓度、氢氧化钙和水化硅酸钙的碳化反应速率系数、二氧化碳扩散系数等模型参数;最后结合64组标准碳化环境下的混凝土碳化试验数据,定量分析了时间步长、空间步长、矿物掺合料二次水化反应程度系数的取值对碳化分析模型的计算精度和计算效率的影响规律。

In order to analyze the concrete carbonation depth accurately,a quantitative durability analysis model of concrete structure under carbonation environment was established.According to the physical and chemical reaction process of cement hydration and concrete carbonation,the governing equations as well as initial and boundary conditions of the multi-field coupling numerical analysis model of concrete carbonation was developed first by taking into account the conservation law of carbon dioxide,calcium hydroxide and calcium silicate hydrate in concrete.Then the model parameters such as the initial concentration of calcium hydroxide and calcium silicate hydrate in concrete,the carbonation reaction rate coefficient of calcium hydroxide and calcium silicate hydrate,carbon dioxide diffusion coefficient were determined based on the carbonation mechanism of concrete and the chemical balance relationship between concrete carbonation reaction and cement hydration reaction.Finally,the influence of time step,space step and coefficients of secondary hydration reaction degree of mineral admixtures on the accuracy and efficiency of the proposed model was investigated based on 64 sets of carbonation test data of concrete under standard carbonation environment.