Influences and Mechanisms of Nano-C-S-H Gel Addition on Fresh Properties of the Cement-Based Materials with Sucrose as Retarder
Influences and Mechanisms of Nano-C-S-H Gel Addition on Fresh Properties of the Cement-Based Materials with Sucrose as Retarder
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DOI：
10.3390/ma13102345
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发表时间：
2020-05-01
期刊：
影响因子：
3.4
通讯作者：
Sheng, Jiansong
中科院分区：
文献类型：
--
作者：
Kong, Deyu;He, Guangpeng;Sheng, Jiansong
研究了化学合成纳米C-S-H凝胶外加剂对以蔗糖为缓凝剂的水泥基材料新拌性能的影响及其机理。结果表明，随着纳米C-S-H凝胶掺量的增加，新拌水泥浆体的流动值逐渐减小，但略有下降，这是由于纳米C-S-H凝胶具有纤维状且在水和水泥浆体中分散良好的特点。半绝热量热试验结果表明，掺入纳米C-S-H凝胶可以显著缓解蔗糖对水泥水化的缓凝作用。总有机碳表明，纳米C-S-H凝胶的加入有助于减少蔗糖分子在保护层中的吸附，从而使保护层的半渗透性降低较小，这就是为什么纳米C-S-H凝胶的加入可以缓解蔗糖的迟滞作用。通过X射线衍射分析发现，在诱导期开始前，添加纳米C-S-H的浆料中，CH晶体更容易沿尺寸较大的(0001)晶面生长，这是因为C-S-H纳米粒子能够形成3D网络，减缓释放离子的扩散速度，消除浆料中的对流，从而抑制CH晶体的3D成核和生长。X射线衍射分析还表明，蔗糖的加入细化了钙矾石晶体，但纳米C-S-H凝胶的引入没有进一步细化钙矾石晶体，扫描电子显微镜观察也证实了这一点。
Influences and mechanisms of chemically synthesized nano-C-S-H gel addition on fresh properties of the cement-based materials with sucrose as a retarder were investigated in this study. The results showed that the flow value of the fresh cement paste was gradually but slightly reduced with increasing nano-C-S-H gel addition due to its fibrous but well-dispersed characteristic in both water and cement paste. The semi-adiabatic calorimetry testing results verified that incorporation of nano-C-S-H gel could greatly mitigate the retarding effect of sucrose on cement hydration. The total organic carbon (TOC) indicated that the addition of the nano-C-S-H gel helps to reduce adsorption of the sucrose molecules into the protective layer, thus the semi-permeability of the protective layer was less reduced and that is why the addition of the nano-C-S-H gel can mitigate the retardation caused by the sucrose. Through XRD analysis, it was found that the CH crystals are more prone to grow along the (0001) plane with larger size in the paste with nano-C-S-H addition before the induction period starts, because the C-S-H nanoparticles can form 3D network to slow down the diffusion rate of the released ions and eliminate the convection in the paste, thus suppress the 3D nucleation and growth of the CH crystals. The XRD analysis also indicated a refinement of the ettringite crystals in the paste with sucrose addition, but introduction of nano-C-S-H gel did not show further refinement, which was also verified by the SEM observation.