Comparative roles between aragonite and calcite calcium carbonate whiskers in the hydration and strength of cement paste
Comparative roles between aragonite and calcite calcium carbonate whiskers in the hydration and strength of cement paste
复制标题
文石和方解石碳酸钙晶须对水泥净浆水化和强度的作用比较
DOI：
10.1016/j.cemconcomp.2019.103350
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发表时间：
2019-11-01
影响因子：
10.5
通讯作者：
Yin, Hong
中科院分区：
文献类型：
--
作者：
Li, Li;Cao, Mingli;Yin, Hong
文石型碳酸钙晶须（CW）可以改善水泥基复合材料的力学性能。方解石与文石的微观结构不同，但只有少数研究报道了掺入文石和方解石对水泥基复合材料的不同影响。为了充分利用CW作为高性能、低成本的超细纤维，并清楚地了解文石CW和方解石CW之间的不同机理，本研究采用热处理方法将文石CW转化为方解石CW，研究了方解石和文石对CW增强水泥浆体（CWRC）水化和强度的影响，以弥补这一领域的空白。文石和方解石CW在波特兰水泥中表现出全面的物理稀释效应，显著降低了水泥的水化热以及不可蒸发水和Ca（OH）（2）的总量。方解石CW比文石CW具有更显著的成核作用。与文石CWRC相比，方解石CWRC中硅相的水化速度更快，水化放热更高，而铝相的水化速度没有显著差异。Ca（OH）（2）在方解石中的含量高于文石。方解石CW表面水化产物比文石CW表面水化产物多，提高了方解石CW与水泥基体的结合强度。因此，方解石CWRC的抗压强度和抗折强度均高于文石CWRC。对新鲜文石和方解石水泥浆体的流变性试验表明，文石和方解石水泥浆体均显著降低了水泥浆体的流动性，表现出粘度效应。与文石CW相比，方解石CW改善了新拌水泥浆体的流动性，显示了方解石CW的润滑作用。文石和方解石CW呈现与石灰石粉末类似的化学效应，即，波特兰水泥中的铝相与CW中溶解的CO 32-相互作用形成单碳酸盐和半碳酸盐。水泥中Ca（OH）2的取向指数随着水泥基碳纤维的引入而降低。文石和方解石CW也可以用作水泥基复合材料中的微纤维和填料。这些作用改善了水泥石的微观结构，从而提高了水泥石的抗折强度和抗压强度。
Aragonite CaCO3 whisker (CW) could improve the mechanical properties of cementitious composites. The microstructure of calcite is different from that of aragonite, but only a few studies reported different effects in cementitious composites between incorporating aragonite and calcite. In order to fully use CW as high-performance, low-cost microfiber and clearly understand different mechanisms between aragonite and calcite CW, in this study, the heat treatment method was used to convert aragonite CW to calcite CW, and the effect of calcite and aragonite on the hydration and strength of CW reinforced cement paste (CWRC) was studied to bridge the gaps in this area. The aragonite and calcite CWs exhibited the overall physical dilution effect in Portland cement, significantly decreasing the hydration heat of cement and the total amount of non-evaporable water and Ca(OH)(2). Calcite CW presents a more significant nucleation effect than aragonite CW. Compared to aragonite CWRC, the hydration of silicon phase in calcite CWRC is faster and the hydration heat release is higher; however, there is no significant difference in the hydration of aluminum phase. The Ca(OH)(2) content in calcite CWRC was more than that in aragonite CWRC. More hydration products formed on the surface of calcite CW than that on aragonite CW, improving the bonding strength between calcite CW and cement matrix. Hence, both the compressive strength and flexural strength of calcite CWRC are higher than those of aragonite CWRC. The rheological test of fresh aragonite and calcite CWRC proved that both aragonite and calcite CWs significantly decreased the flow of cement paste, presenting viscosity effect. Compared to aragonite CW, calcite CW improved the flowability of fresh cement paste, indicating the lubricant effect of calcite CW. Aragonite and calcite CW present chemical effect similar to limestone powders, i.e., aluminum phase in Portland cement interacted with CO32- dissolved from CW to form mono- and semi- carbonate. The Ca(OH)(2) orientation indexes of cement decreased by the introduction of CWs. Aragonite and calcite CWs can also be used as microfiber and filler in cementitious composites. These effects improved the micro-structure, thus enhanced the flexural and compressive strength of cement paste.