受酸腐蚀砂岩的物理化学性质及反应动力学模型研究

Physico-Chemical Properties and a Reaction Kinetic Model of Acid-Corroded Sandstone

目的研究受酸腐蚀砂岩的物理化学性质,建立酸岩反应动力学模型,为酸性环境下的工程耐久性评价提供参考.方法通过室内长期加速腐蚀试验,监测不同浸泡时段岩样的质量变化和浸泡溶液的pH值及Na+、K+、Mg2+、Ca2+等阳离子浓度的变化.结果反应初期(0~90 d)阳离子的溶蚀速率较高,随着腐蚀时间的延长,化学反应速率降低,阳离子的溶蚀速率延缓,反应后期溶蚀速率又逐渐增大;随着腐蚀时间的延长,烘干岩样的质量损失率不断增大,而湿岩样的质量增长率呈先增大而后减小的趋势;各阶段硫酸溶液pH值总体呈增大趋势.结论受酸腐蚀岩样质量、浸泡溶液pH值以及阳离子浓度的变化具有明显的阶段性劣化特征;反应由扩散和化学反应共同作用,其中化学反应为烘干岩样主导作用,扩散作用为湿岩样前期主导作用,后期化学反应和内扩散共同主导;酸岩反应动力学模型较准确地表达了硫酸溶液腐蚀下岩样质量与时间的变化关系.

In this paper,the physico-chemical properties of the acid-corroded sandstone are studied,and an acid-rock reaction kinetic model is established,which can provide a reference for engineering durability evaluation in an acidic environment.Based on the long-term accelerated corrosion tests,the mass of the dried and wet sandstone samples,changes of the pH value and the concentration of Na+、K+、Mg2+、Ca2+ of the soaking solution were obtained at every period of time.The test results indicate that the dissolution rate of the aforementioned cations is fast in the initial periods(0~90 d).The chemical reaction rate decreases with increasing time,yet it increases gradually in the later periods.With increasing the soaking time,mass loss of the dried samples increases continuously,while it increases first and then decrease for the wet samples.The pH values of the acid solution take an increasing trend.The mass of the acid corroded samples,the pH value and the concentration of cations in the soaking solution hold obvious damage characteristics.The acid-rock reaction is dominated by diffusion and chemical action.For the dried rock sample,the chemical reaction is dominant.For the wet rock sample,the early period is dominated by diffusion,and the later period is dominated by diffusion and chemical reaction.The acid-rock reaction kinetic model can express the mass variation of the acid corroded rock accurately.