Fractal characterization on pore structure and analysis of fluidity and bleeding of fresh cement paste based on 1H low-field NMR
Fractal characterization on pore structure and analysis of fluidity and bleeding of fresh cement paste based on 1H low-field NMR
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基于1H低场核磁共振的新拌水泥浆体孔隙结构分形表征及流动性和泌水分析
DOI：
10.1016/j.conbuildmat.2017.02.151
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发表时间：
2017-06-01
影响因子：
7.4
通讯作者：
Chen, Chao
中科院分区：
文献类型：
--
作者：
Ji, Yanliang;Sun, Zhenping;Chen, Chao
本文提出了一种基于H-1低场核磁共振谱计算孔结构表面分形维数的新方法。研究了水灰比、水泥比表面积等参数对分形维数的影响。此外，本文还讨论了孔隙结构与流动度和泌水速度的关系。结果表明，新拌水泥浆体的孔结构具有明显的分形特征，在横向弛豫时间（T-2）分布中，孔结构存在分形区域i（2.0 < D-f < 2.2）和分形区域ii（2.6 < D-f< 3.0）。研究发现，Ⅱ区的D-f值对水灰比和水泥比表面积都很敏感。新拌水泥浆体的初始流动度随T-2位置的增加而增加，在相同的T-2位置下，D-f越大，新拌水泥浆体的初始流动度越低。孔隙结构的D-f值越大，排泌速度越低，当T2位置接近时，D-f值可能是排泌水运移的主要因素。(C)2017爱思唯尔有限公司版权所有
In this study, a novel method for calculation of surface fractal dimensions (D-f) of pore structure based on H-1 low-field NMR was proposed. Influencing parameters including water cement ratio and specific areas of cements on the fractal dimensions were investigated. In addition, the relationship between pore structure and fluidity value as well as bleeding velocity was also discussed in this paper. Results confirm that the pore structure of fresh cement paste has a significant fractal feature, and fractal regions, region i (2.0 < D-f < 2.2) and ii (2.6 < D-f< 3.0), are found for the pore structure in the distribution of the transverse relaxation time (T-2). It is found that the D-f for region ii is sensitive to both water cement ratio and specific surface of cements. Moreover, the initial fluidity of fresh cement paste increase with the T-2 position, and with identical T-2 position, fresh cement paste with high D-f can generate a low fluidity. Results also suggest that high D-f of pore structure lead to a low velocity of bleeding, and D-f can be a main factor for migration of the bleeding water when the T-2 positions are close. (C) 2017 Elsevier Ltd. All rights reserved.