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首页> 外文会议>Tenth international conference on superplasticizers and other chemical admixtures 2012 >The Role of Non-Adsorbed PCE Molecules in Cement Dispersion: Experimental Evidence for a New Dispersion Mechanism
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The Role of Non-Adsorbed PCE Molecules in Cement Dispersion: Experimental Evidence for a New Dispersion Mechanism

机译：未吸附的PCE分子在水泥分散中的作用：新的分散机理的实验证据

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摘要

The working mechanism for cement dispersion of an isoprenyloxy ether-based polycarboxylate superplasticizer (PCE-A) and of several PCEs based on MPEG-ester (PCE-B0, PCE-B1, PCE-B2) or APEG-ether monomers (PCE-C) was investigated via cement paste flow testing and measurement of hydrodynamic radius of solved PCE molecules, adsorption isotherm, adsorption rate and zeta potential. Using "mini slump" test method it was found that the isoprenyloxy ether - acrylic acid copolymer (PCE-A) exhibits the highest water reduction, followed by the methacrylic acid - MPEG - 1100 - methac-rylate copolymer (PCE-B2), whereas the methacrylic acid - MPEG - 250 - methacrylate copolymer (PCE-B0) required a very high dosage. Further experiments revealed that in cement pore solution, the conformation of PCE-A is star-like; while PCE-B0, PCE-B1 and PCE-B2 show a worm like conformation with flexible backbone and PCE-C exhibits a rod like structure possessing high rigidity. PCE-B2 disperses cement mainly via strong steric repulsion instigated by the long side chain. Based on adsorption and zeta potential data obtained it is proposed that PCE-A, PCE-B0, PCE-B1 and PCE-C disperse cement not only by steric repulsion originating from adsorbed PCE, but also by electrostatic and/or steric repulsion owed to non-adsorbed PCE molecules present in the pore solution. Especially PCE-B0 was found to require a dosage substantially beyond its saturation adsorption. This suggests that free PCE dissolved in the pore solution may provide the main contribution to cement dispersion. Consequently, a new type of dispersion mechanism which originates from dissolved PCE molecules exercising a "lubricating" effect between cement particles is postulated for PCE-B0.
机译：异戊二烯氧基醚基聚羧酸盐高效减水剂（PCE-A）和几种基于MPEG-酯（PCE-B0，PCE-B1，PCE-B2）或APEG-醚单体（PCE-C）的PCE水泥分散的工作机理通过水泥浆流动测试和测量溶解的PCE分子的流体动力学半径，吸附等温线，吸附速率和Zeta电位进行了研究。使用“小坍落度”测试方法发现，异戊二烯氧基醚-丙烯酸共聚物（PCE-A）表现出最高的减水率，其次是甲基丙烯酸-MPEG-1100-甲基丙烯酸酯共聚物（PCE-B2），而甲基丙烯酸-MPEG-250-甲基丙烯酸酯共聚物（PCE-B0）需要很高的剂量。进一步的实验表明，在水泥孔隙溶液中，PCE-A的构型呈星状。 PCE-B0，PCE-B1和PCE-B2显示出具有柔性骨架的蠕虫状构象，PCE-C显示出具有高刚性的杆状结构。 PCE-B2主要通过长侧链引起的强空间排斥力来分散水泥。根据获得的吸附和ζ电势数据，提出PCE-A，PCE-B0，PCE-B1和PCE-C不仅通过吸附的PCE产生的空间排斥，还通过由于产生的静电和/或空间排斥来分散水泥孔溶液中存在非吸附的PCE分子。特别是发现PCE-B0需要的剂量大大超过其饱和吸附量。这表明溶解在孔隙溶液中的游离PCE可能对水泥的分散起主要作用。因此，对于PCE-B0，假定了一种新型的分散机制，其起源于在水泥颗粒之间发挥“润滑”作用的溶解的PCE分子。

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