钙矾石形貌调控及其机理研究

发布时间：2018-04-24 14:45

  本文选题：钙矾石 + 合成条件　； 参考：《中国建筑材料科学研究总院》2017年硕士论文

【摘要】：钙矾石是硫铝酸盐水泥水化的主要产物,决定着硫铝酸盐水泥的性能,且在硅酸盐水泥混凝土中其影响也非常重要。钙矾石的形成条件决定了其形貌,其形成时间影响着水泥和混凝土的性能。钙矾石形成和形貌的研究,对水泥混凝土性能的改善具有重要的意义。本文采用铝酸三钙和二水石膏、硫铝酸钙和二水石膏、氢氧化钙和硫酸铝三组原材料,在溶液中合成了纯的钙矾石。采用电子扫描电镜(SEM)、X射线衍射(XRD)、热分析(TG-DSC)、红外光谱(IR)等测试技术,研究了合成时间、原材料、合成温度、p H值、不同掺量的硼酸、碳酸锂、聚羧酸减水剂等对钙矾石形成和形貌的影响。1.不同原材料合成的钙矾石形貌显著不同且长宽比差异显著,以C3A和二水石膏为原材料合成的钙矾石尺寸远小于其他两组原材料合成的钙矾石,长宽比约为其他两组长宽比的1/10;在100℃合成温度下,钙矾石不能稳定存在,在较短的时间后就会转化为单硫型水化硫铝酸钙;随着液相p H值的增加,钙矾石的长宽比逐渐减小,且钙矾石形貌由长杆状向细小的针状转变。溶液中钙矾石的形成机理为:既可直接生成钙矾石,又可先形成单硫型水化硫铝酸钙,而后单硫型水化硫铝酸钙和SO42 、Ca2+反应形成钙矾石。2.硼酸能够抑制钙矾石的生长,随着硼酸掺量的增加,钙矾石的长宽比逐渐减小,尺寸变短,当硼酸掺量提高到10%、20%时,出现了较多的扁柱状的钙矾石;碳酸锂通过吸附在钙矾石晶体的侧面,抑制钙矾石晶体宽度的生长,碳酸锂可以加快钙矾石的形成速度;聚羧酸减水剂对钙矾石晶体宽度上的生长起到抑制作用,使得钙矾石晶体变长变细,长宽比明显增加,但对钙矾石成核起到促进作用。3.提出了钙矾石形貌调控的方案。通过掺加碳酸锂和聚羧酸减水剂均可获得长杆状钙矾石;调节p H值为12.5以上时,可以获得细针状钙矾石;掺加硼酸可以获得短柱状钙矾石;硼酸与聚羧酸减水剂复合掺加,可以获得又短又细的钙矾石。
[Abstract]:Ettringite is the main product of sulphoaluminate cement hydration, which determines the performance of sulphoaluminate cement, and its influence in Portland cement concrete is also very important. The morphology of ettringite is determined by the formation conditions of ettringite, and the formation time of ettringite affects the properties of cement and concrete. The formation and morphology of ettringite are of great significance to the improvement of cement concrete performance. In this paper, pure ettringite was synthesized in solution from three groups of raw materials such as tricalcium aluminate and gypsum dihydrate, calcium sulphoaluminate and gypsum dihydrate, calcium hydroxide and aluminum sulfate. The synthesis time, raw materials, synthesis temperature, boric acid and lithium carbonate were studied by means of electron scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal analysis (TG-DSCN) and IR (IR). Effects of polycarboxylic acid superplasticizer on the formation and morphology of ettringite. The morphology and aspect ratio of ettringite synthesized from different raw materials are significantly different. The size of ettringite synthesized from C3A and gypsum dihydrate is much smaller than that from other two groups of raw materials. The aspect ratio is about 1 / 10 of the other two groups. Ettringite can not exist stably at 100 鈩，

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