Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate
Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate
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DOI：
10.1111/jace.16467
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发表时间：
2019-10-01
影响因子：
3.9
通讯作者：
Kumar, Aditya
中科院分区：
文献类型：
--
作者：
Lapeyre, Jonathan;Ma, Hongyan;Kumar, Aditya
研究了偏高岭土（MK）的粒度分布对硅酸三钙（C3 S-T-1）浆体水化动力学的影响。利用物理实验和相边界成核和生长（pBNG）模拟进行了调查。[C3S分别研究了8%（质量分数）和30%（质量分数）MK制备的[+ MK]浆料。使用三种不同的MK PSD：细MK，颗粒尺寸为32 μ m。结果表明，MK颗粒的比表面积（SSA）与C3 S水化行为在前72小时内的变化之间存在非线性和非单调的相关性。在C3 S的低取代度（即，8%（质量））下，细MK和在一定程度上粗MK充当填料，并且促进硅酸钙水合物（C-S-H）的额外成核和生长。当C_3S取代量增加到30%（质量分数）时，细颗粒和粗颗粒MK的填充效应发生逆转，导致C-S-H成核和生长受到抑制。在中间体MK的情况下也观察到这种填料效应的逆转;但与其他PSD不同的是，中间体MK在低和高置换水平下都显示出逆转。这是由于中间MK快速溶解的能力-与粗MK和细MK相比具有更快的动力学-这导致溶液中铝酸盐[Al（OH）（4）（-）]离子的更快释放。铝酸盐离子吸附在C3 S和MK颗粒上，通过阻断C3 S溶解位点和衬底表面上的C-S-H成核位点并抑制C-S-H的后成核生长来抑制C3 S水合。总体而言，结果表明，基于研磨的增强在SSA的MK颗粒不一定增强早期水合的C3 S。
The focus of this study is to elucidate the role of particle size distribution (PSD) of metakaolin (MK) on hydration kinetics of tricalcium silicate (C3S-T-1) pastes. Investigations were carried out utilizing both physical experiments and phase boundary nucleation and growth (pBNG) simulations. [C3S + MK] pastes, prepared using 8%(mass) or 30%(mass) MK, were investigated. Three different PSDs of MK were used: fine MK, with particulate sizes 32 mu m. Results show that the correlation between specific surface area (SSA) of MK's particulates and the consequent alteration in hydration behavior of C3S in first 72 hours is nonlinear and nonmonotonic. At low replacement of C3S (ie, at 8% (mass)), fine MK, and, to some extent, coarse MK act as fillers, and facilitate additional nucleation and growth of calcium silicate hydrate (C-S-H). When C3S replacement increases to 30% (mass), the filler effects of both fine and coarse MK are reversed, leading to suppression of C-S-H nucleation and growth. Such reversal of filler effect is also observed in the case of intermediate MK; but unlike the other PSDs, the intermediate MK shows reversal at both low and high replacement levels. This is due to the ability of intermediate MK to dissolve rapidly-with faster kinetics compared to both coarse and fine MK-which results in faster release of aluminate [Al(OH)(4)(-)] ions in the solution. The aluminate ions adsorb onto C3S and MK particulates and suppress C3S hydration by blocking C3S dissolution sites and C-S-H nucleation sites on the substrates' surfaces and suppressing the post-nucleation growth of C-S-H. Overall, the results suggest that grinding-based enhancement in SSA of MK particulates does not necessarily enhance early-age hydration of C3S.