腐蚀介质对硬化水泥浆体溶蚀特性的影响

Influence of corrosion solution on calcium leaching behavior of hardened cement pastes

为了获得腐蚀介质对水泥浆体溶蚀特性的影响规律,采用去离子水和6 M NH_4Cl溶液作为腐蚀介质,分别开展室温(25℃)环境下水灰比为0.45的硬化水泥净浆薄片试件的常规和加速溶蚀,并通过饱水干燥称重法、扫描电子显微镜(SEM/EDS)、X射线衍射法(XRD)等测试,分析了2种腐蚀介质中硬化水泥浆体的孔隙率、钙硅比及其物相组成和微结构的演变规律。结果表明,在25℃室温环境下,同去离子水相比,氯化铵溶液中水泥净浆试件孔隙率增加和钙硅比降低的速率均显著提高,而氯化铵溶液中溶蚀9 d后的试件微观形貌与去离子水浸泡360 d的微结构形貌基本一致,且溶蚀后的物相组成也基本相同;氯化铵溶液显著提高了硬化水泥浆体的溶蚀进程,并可较短的时间内获得其溶蚀特性,但并未改变溶蚀过程中硬化水泥浆体的物相组成和微结构特性,可作为混凝土等水泥基材料的加速溶蚀介质。

In order to obtain the influence of corrosion solution on calcium leaching behavior of hardened cement pastes, the deionized water and 6 M NH4C1 solution were used as corrosion mediums to carry out conventional and accelerated leaching experiments on the cement paste slice specimens with the water-cement ratio of 0.45 at room temperature（25 ℃ ）, respectively. By using the saturation-drying weighing, scanning electron microscopy with energy dispersive spectrometer （SEM/EDS） and X-ray diffraction （XRD）, the porosity, microstructure morphology, calcium-silicon mass ratio （Ca/Si） and phase composition of the specimens immersed in two corrosion solutions have been analyzed. Results show that when the room temperature is 25 ℃ , compared to the leaching behavior of cement paste slice specimens in deionized water, the leaching rate, characterized by the increasing porosity and the decreasing Ca/Si ratio, of cement paste slice specimens immersed in 6 M NH4C1 solution has a significant increase. The morphology of the slice specimens after 9-day leaching in 6 M NH4C1 solution is similar with that of the slice specimen immersed in deionized water for 360 days, while there are basically the same phase compositions of specimens immersed in two corrosion solutions. Thus, 6 M NH4C1 solution can greatly accelerate the leaching process of hardened cement paste without any alteration to its phase composition and microstructure characteristics during leaching process, and the same leaching characteristics of hardened cement pastes in the deionized water in a relatively short period of time can be obtained. This indicates that NH4C1 solution can be used as a corrosion medium for accelerating the leaching experiment of cement-based materials.