软水环境下粉煤灰对水泥净浆溶蚀特性的影响

Influence of fly ash on leaching behavior of cement paste under environment of soft water

为了研究软水环境下掺入粉煤灰对水泥净浆溶蚀特性的影响,该文制备了不同粉煤灰掺量的水泥净浆薄片,进行去离子水中薄片试件浸泡溶蚀实验。通过饱水-干燥称重法、乙二胺四乙酸(EDTA)滴定法、扫描电子显微镜(SEM/EDS)等测试,分析了各试件孔隙率、钙溶出量、钙硅比和微观形貌等随粉煤灰掺量和溶蚀时间的变化规律。结果表明,掺入粉煤灰可增加水泥净浆的初始孔隙率,且试件的溶蚀深度随着粉煤灰掺量的增加而增大,进而导致薄片试件溶蚀进程加快;但掺入粉煤灰可降低水泥浆体中氢氧化钙含量及钙溶出量和溶出速度,且其火山灰反应所生成的致密水化硅酸钙(C-S-H)凝胶可有效填充浆体孔隙,延缓溶蚀过程中试件的孔隙率增长和密实度下降,使薄片试件的溶蚀程度降低。

In order to investigate influence of fly ash on leaching behavior of cement paste in soft water,the cement paste slice specimens with different fly ash content are prepared to perform their leaching experiments in deionized water.By using the saturation-drying weighing method,the ethylene diamine tetraacetic acid(EDTA)titration,and the scanning electron microscope(SEM/EDS)measurement,the changes of porosity,calcium dissolution,Ca-Si ratio and microstructure morphology in the specimens with fly ash content and leaching time are analyzed.Results show that,the addition of fly ash can increase the initial porosity and leaching depth of the slice specimens,and accelerate leaching process of cement pastes.However,the fly ash can also reduce the content of calcium hydroxide and calcium dissolution in the cement paste,and the dense C-S-H gel formed by the pozzolanic reaction can effectively fill the pores in cementpaste resulting in slowing down the increase of porosity and the decrease of compactness in the specimens in its leaching process,so the fly ash can reduce the leaching degree of cement pastes.