氢氧化钠对钙矾石的合成及在高温环境下转变的影响  

Effect of NaOH on Synthesis and Transformation of Ettringite Under High Temperature Environment

作　　者：张响 卢晓磊[1,2] 宋建国 贾坚 杨庆春 杜鹏[1,2] 程新[1,2] ZHANG Xiang;LU Xiaole;SONG Jianguo;JIA Jian;YANG Qingchun;DU Peng;CHENG Xin(Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials,University of Jinan,Jinan 250022,China;School of Material Science and Engineering,University of Jinan,Jinan 250022,China)

机构地区：[1]山东省建筑材料制备与测试技术重点实验室,济南大学,济南250022 [2]济南大学材科科学与工程学院,济南250022

出　　处：《硅酸盐学报》2025年第2期428-436,共9页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(52341201,52102020,U22A20126);山东省泰山学者攀登计划。

摘　　要：碱对钙矾石合成及其向单硫型水化硫铝酸钙(AFm)转变具有重要影响。为了探究氢氧化钠(Na OH)对合成钙矾石及其转变的影响规律,通过在溶液法合成钙矾石中添加少量Na OH,详细讨论了高温环境下钙矾石向AFm演变过程。结果表明:添加Na OH的钙矾石样品较纯杂质较少,其形貌由长直粗棒状变为弯曲针棒状,晶胞参数减小,且Na^(+)易取代钙矾石中部分Ca^(2+)格位。此外高温环境下Na OH显著促进了钙矾石向AFm转变,其转变过程可分为3个阶段。首先大部分钙矾石直接转变为AFm相;随后液相中Na^(+)与SO_(4)^(2-)同AFm反应生成中间相U-phase,同时液相中的Ca^(2+)和SO_(4)^(2-)再次与AFm反应形成钙矾石,随后钙矾石又开始转变为中间相U-phase;最终由U-phase全部转变成稳定的AFm。Introduction Ettringite plays an important role in the early strength and volume stability of cement.In a high-concentration sodium sulfate solution,Na^(+)and SO_(4)^(2-)will be embedded between the structural layers of AFm to form a sodium-substituted AFm phase(U-phase).Therefore,the stability of ettringite and AFm under high temperatures and alkaline environments requires attention.Ettringite will not only transform into AFm but also form U-phase in a high-temperature and alkaline environment.However,the specific process of the mutual transformation of ettringite and AFm under the combined action of high temperature and alkalinity is still unclear.The phase transition of hydration products is bound to affect the performance of cement-based materials in high-temperature and high-alkalinity environments.Therefore,it is important and necessary to clarify the transformation process of Ettringite to AFm.Based on this,ettringite was first synthesized by adding a small amount of NaOH to the solution system,and the effect of NaOH on the synthesis and transformation of ettringite was explored,especially the effect on the evolution of the above-mentioned synthesized ettringite to AFm in an environment of 105℃.A detailed discussion was conducted,which provided new understanding of the stability of ettringite in high-alkali and high-temperature environments and also provided theoretical support for the performance degradation of cement-based materials under such conditions.Methods The raw materials Ca(OH)_(2)and Al_(2)(SO_(4))_(3)·18H_(2)O were used to synthesize the ettringite sample by solution method,and the alkaline environment was adjusted by NaOH.Samples were taken at high temperature at designed time intervals to explore the transformation process of ettringite and washed with deionized water and anhydrous ethanol in turn,dried in a vacuum drying oven at40℃,and ground into powder.The phase composition of all samples was tested by the D8 ADVANCE X-ray diffractometer,and the structure of the samples was analyzed

关 键 词：氢氧化钠 高温 钙矾石 单硫型水化硫铝酸钙 转化 

分 类 号：TQ172.1[化学工程—水泥工业]