Enhancing the performance of metakaolin blended cement mortar through in-situ production of nano to sub-micro calcium carbonate particles
Enhancing the performance of metakaolin blended cement mortar through in-situ production of nano to sub-micro calcium carbonate particles
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DOI：
10.1016/j.conbuildmat.2018.11.134
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发表时间：
2019-01-30
影响因子：
7.4
通讯作者：
Fang, Yi
中科院分区：
文献类型：
--
作者：
Qian, Xin;Wang, Jialai;Fang, Yi
偏高岭土因其具有较高的火山灰活性和比表面积，已成为一种受欢迎的替代普通硅酸盐水泥（OPC）的补充胶凝材料。本研究提出了一种新的方法——预碳化法，利用偏高岭土水泥与碳酸钙之间的协同作用，进一步提高水泥砂浆的性能。这种新方法是在熟石灰浆中通过鼓泡二氧化碳原位制备纳米至亚微碳酸钙颗粒。然后将制成的碳化浆与砂浆的其他成分混合。原位制备的纳米至亚微碳酸钙颗粒由于具有较高的比表面积，因此具有较高的反应活性，使得水泥与碳酸钙之间的反应更快、更完全。试验研究表明，采用该方法可提高偏高岭土混合砂浆的力学性能和耐久性。量热分析结果表明，由于碳酸钙纳米至亚微米颗粒提供了额外的异质成核位点，碳化石灰浆可以加速偏高岭土水泥的水化。TGA/XRD结果表明，预碳化的熟石灰浆在砂浆/混凝土中产生了更多的钙矾石，水化产物的总体积增加，导致砂浆/混凝土的微观结构更加致密。以上结果表明，原位制备纳米至亚微碳酸钙颗粒为提高偏高岭土水泥性能提供了一条可行的途径。(C) 2018 Elsevier Ltd.版权所有。
Metakaolin has emerged as a popular supplementary cementitious material to partially replace ordinary Portland cement (OPC) due to its high pozzolanic reactivity and surface area. In this study, a new method, pre-carbonation method, is proposed to exploit the synergistic effect between the metakaolin blended cement and calcium carbonate so that the performance of the cement mortar can be further improved. This new method in-situ produces nano to sub-micro calcium carbonate particles in a slaked lime slurry through bubbling carbon dioxide. The produced carbonated slurry is then mixed with other ingredients of the mortar. The in-situ produced nano to sub-micro calcium carbonate particles possess high reactivity due to their high surface area, leading to faster and more complete reaction between the cement and the calcium carbonate. Experimental studies show both the mechanical properties and durability of the metakaolin blended mortar have been improved by the proposed method. The calorimetry results show that the carbonated slaked lime slurry can accelerate the hydration of the metakaolin blended cement due to the extra heterogenous nucleation sites provided by the calcium carbonate nano to sub-micro particles. TGA/XRD results suggest that more ettringite is produced in the mortar/concrete with pre-carbonated slaked lime slurry, which increases the total volume of the hydration products, leading to a denser microstructure of the mortar/concrete. All these findings suggest that in-situ production of nano to submicro calcium carbonate particles provides a viable way to improve the performance of metakaolin blended cement. (C) 2018 Elsevier Ltd. All rights reserved.