温度影响下混凝土硫酸盐侵蚀行为数值模拟

Numerical Simulation of Concrete Sulfate Attack Behavior under Temperature Influence

摘要:

基于Fick扩散定律和系统吉布斯自由能最小化原理，构建了硫酸盐侵蚀混凝土反应-传输模型.通过Matlab接口程序耦合COMSOL和GEMS软件，实现了该模型的顺序非迭代法数值求解. 研究了温度影响下，考虑钙溶蚀行为的硫酸盐侵蚀混凝土的物相组成、孔隙率、全元素和多离子时空分布规律. 结果表明：混凝土膨胀开裂引起的含S固相损失是导致S元素分布存在峰值的原因；由于膨胀性腐蚀产物的高温稳定性差，靠近混凝土侵蚀表面的孔隙率随着温度的升高而降低；相较于在23 ℃条件下由膨胀开裂所造成的质量损失，混凝土在高温条件下的质量损失主要由孔溶液中初始pH值的降低引起，这一变化导致水化产物发生分解.

Abstract:

A reactive-transport model of concrete under sulfate attack was constructed on the basis of Fick’s diffusion law and the principle of minimum of Gibbs free energy of the system. The numerical solution of the model was achieved using a sequential non-iterative method by coupling COMSOL and GEMS software through Matlab interface program. The space-time distribution patterns of phase composition， porosity， and all elements and multi ion in sulfate-erosion concrete， considering calcium dissolution under the influence of temperature， were investigated. The results show that the loss of S-containing solid phases caused by concrete expansion and cracking is responsible for the existence of peaks in the S element distribution； due to the poor high-temperature stability of expansive corrosion products， the porosity near the concrete erosion surface decreases with increasing temperature； compared to the mass loss caused by expansion and cracking at 23 ℃， the mass loss of concrete under high-temperature conditions is mainly attributed to the decrease in the initial pH of the pore solution， resulting in the decomposition of hydration products.