| 摘要: |
| 将水泥砂浆浸泡在pH值为5，9，13的Na2SO4溶液中至330d，采用化学滴定法测定砂浆中Ca2+，OH-的析出量，采用X射线衍射（XRD）仪和差示扫描量热法（DSC）对不同侵蚀龄期下侵蚀产物进行半定量分析，并通过扫描电子显微镜（SEM）对钙硅比和微结构进行了分析.结果表明：溶液pH值越低，Ca2+析出速率越快、析出量越大，且低pH值条件下Ca2+的大量析出有助于其与侵入的SO2-4结合，形成更多低溶解度的CaSO4·2H2O，从而加速Ca2+析出和SO2-4扩散渗入；低pH值环境下大量石膏的形成伴随着Ca(OH)2的大量消耗，且会引起C S H凝胶的脱钙，导致水泥砂浆的胶凝性降低，引起试件的软化和剥落. |
| 关键词: 硅酸盐水泥 硫酸盐侵蚀 pH值 石膏 析钙 |
| DOI：103969/j.issn.1007 9629201902003 |
| 分类号: |
| 基金项目:国家重点研发计划“重点基础材料技术提升与产业化”专项课题（2017YFB0310001）;国家自然科学基金资助项目（51578004,51608004,51778003）;安徽省自然科学基金资助项目（1708085QE102）;安徽高校优秀青年骨干人才国内外访学研修项目（gxgwfx2018048）;高性能土木工程材料国家重点实验室开放基金（2018CEM002） |
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| Effects of pH Value of Sulfate Solution on Calcium Leaching and Products of Cement Mortars |
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LIU Kaiwei, CHENG Xingxing, SUN Daosheng, WANG Aiguo, ZHANG Gaozhan
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Anhui Key Laboratory of Advanced Building Materials, Anhui Jianzhu University, Hefei 230022, China
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| Abstract: |
| Cement mortars were prepared and immersed in Na2SO4solution with different pH values, i.e. 5, 9, and 13, up to 330days. The contents of leached Ca2+ and OH- in solution were analyzed through chemical titration, and products of cement mortars during attack were analyzed by X ray diffraction and differential scanning calorimetry. In addition, scanning electron microscope was further applied to investigate nCa/nSi and microstructures. The results show that the content and rate of calcium leaching in high pH environment are larger than that in the lower pH solution. The leached Ca2+ will continue to react with the diffused SO2-4 to form more CaSO4·2H2O at the lower pH environment. The formation of gypsum in low pH value is accompanied with the consumption of calcium hydroxide, which can cause the decalcification of C S H gel and decrease the gelling property of cement mortar, and result in softening and spalling of the specimens. |
| Key words: Portland cement sulfate attack pH value gypsum calcium leaching |
