地下水对混凝土侵蚀性的热力学研究

Thermodynamic Study on Concrete Corroded by Underground Water

采用化学热力学方法分析地下水对混凝土的碳酸型、硫酸盐型及硫氢酸型侵蚀。以新建渝怀线圆梁山隧道为实例,对隧道内地下水取样进行全分析,依据水质分析结果设计了五个化学反应方程式,利用德拜-休克尔极限公式及反应平衡常数与吉布斯自由能间的关系式进行活度和热力学计算,得到三组二氧化碳分压对数值和二组反应进行方向判据数值,继而依据创建的二氧化碳分压与反应进行方向的两组判据进行判别分析。分析结果表明,圆梁山隧道地下水对混凝土具有弱碳酸型侵蚀,不存在硫酸盐型侵蚀;由于逸出天然气中的H2S的溶解度较小,可不考虑H2S作用的硫氢酸侵蚀。

The carbonation, sulfation and sulfureted hydrogen acid corrosion of underground water on concrete are analyzed by chemical thermodynamics. As the sample of Yuanliangshan Tunnel in Chongqing-Huaihua Railway, based on the full analysis of underground water specimens, five chemical equations are designed. With the use of the Deby-Huckel Equation of coefficient of activity and the relation of equilibrium constant and Gibbs free energy, the activity and thermomechanics are calculated and obtains three groups of values of carbon dioxide pressure and two groups of criterion values of reaction direction. According to the two criterion of partial pressure of carbon dioxide and reaction direction, the calcaulatoin shows that the underground water has weak in carbonation corrosion to concrete. As calculated value of density being less than the value of limit-density, it has no sulfation corrosion effect on concrete. Sulfureted hydrogen acid corrosion has not been taken into account, becaue of the low solubility of H2S of the released natural gas in the underground water.