多源-多离子耦合作用下水泥胶砂硫酸盐腐蚀机理

Sulfate Corrosion Mechanism of Cement Mortar Under Multi-sources and Multi-ion Coupling Effect

摘要:

硫酸盐渍土地区现浇结构广泛存在多源-多离子耦合腐蚀，利用砂浆内掺Mg²⁺、Cl^-以及SO₄^2-并置于不同的腐蚀环境中，在腐蚀期间分别测定试样的孔隙分布、质量、尺寸以及不同深度硫酸盐浓度的变化，同时测定了抗折、抗压强度的演变规律。采用扫描电镜-能谱分析（SEM-EDS）、X射线衍射（XRD）及热重分析（TG-DTG）等方法观测试样微观结构及矿物成分变化。试验结果表明，内源腐蚀增加了试样的有害孔含量，加速了腐蚀进程；内源腐蚀对试样抗折强度的发展具有明显的不利影响，较无内源腐蚀试样抗折强度降低了50%~67%；内源Mg²⁺严重影响了硫酸盐环境中试样抗折强度的发展，试样的抗折强度仅为无腐蚀组的4.4%；试样表层的Mg²⁺缓解了有害孔隙含量增加趋势，对内部结构具有一定的保护作用。

关键词:现浇结构;硫酸盐腐蚀;多离子腐蚀;内源腐蚀;劣化机理

Abstract:

Multi-source and multi-ion coupling corrosion is widespread in cast-in-situ structures in sulphate saline soil area. By premixing Mg²⁺， Cl^- and SO₄^2- into mortar and placing it in different corrosive environments， the pore distribution， mass， size and sulfate concentration at different depths， as well as the evolution law of flexural and compressive strength of specimens were measured during corrosion period. The microstructure and mineral composition of specimens were observed by scanning electron microscope-energy dispersive spectroscopy analysis （SEM-EDS）， X-ray diffraction （XRD） and thermogravimetric analysis （TG-DTG）. Results show that internal corrosion increased the content of harmful pores and accelerated the corrosion process. Internal corrosion has a significant adverse effect on the development of flexural strength， the strength of the specimens are reduced by 50%~67% compared with that of the specimens without internal corrosion. Internal Mg²⁺ negatively affects the development of the flexural strength of the specimens in the sulfate environment， the flexural strength of the specimens are only 4.4% of that of the non-corrosive specimens. Mg²⁺ in the periphery of specimens alleviates the increasing trend of harmful pore content and has a certain protective effect on the internal structure.

Key words:cast-in-situ structure;sulfate attack;multi ion corrosion;internal corrosion;deterioration mechanism