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首页> 外文会议>International Conference on Superplasticizers and Other Chemical Admixtures in Concrete >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：非吸附PCCE分子在水泥分散中的作用：新分散机制的实验证据

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The working mechanism for cement dispersion of an isoprenyloxy ether-based polycarboxylate superplasticizer (PCErA) and of several PCEs based on MPEG-ester (PCE-BO, 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-BO) required a very high dosage. Further experiments revealed that in cement pore solution, the conformation of PCE-A is star-like; while PCE-BO, 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-BO, PCE-B 1 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-BO 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-BO.
机译：用于isoprenyloxy醚系聚羧酸酯的超增塑剂（PCErA）的水泥分散性和基于MPEG-酯（PCE-BO，PCE-B1，PCE-B2）或APEG-醚单体几个的PCE的（PCE-C）的工作机制是通过水泥膏流检测和解决PCE分子的流体动力学半径，吸附等温线，吸附率和ζ电势的测量的影响。使用“微型坍落度”试验方法，发现了isoprenyloxy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 - methac-rylate共聚物（PCE-B2），而所述甲基丙烯酸 - MPEG - 250 - 丙烯酸甲酯共​​聚物（PCE-BO）所需要的非常高的剂量。进一步的实验表明，在水泥孔溶液中，PCE-A的构象是恒星状的;而PCE-BO，PCE-B1和PCE-B2显示像柔性主链和构象的蜗杆PCE-C显示状结构的杆具有较高的刚性。 PCE-B2主要通过长侧链唤醒的强空间排斥来分散水泥。基于吸附和ζ电位数据得到的提出，PCE-A，PCE-BO，PCE-B 1和PCE-C分散水泥不仅通过从吸附PCE空间排斥始发，还通过静电和/或空间位阻斥力欠到未吸附分子PCE存在于孔隙溶液。尤其PCE-BO发现需要基本上剂量超过其饱和吸附。这表明溶解在孔隙溶液中的游离PCE可以为水泥分散提供主要贡献。因此，一种新的类型的分散机构，该机构由溶解PCE分子行使水泥颗粒之间的“润滑”效应源自假定为PCE-BO。

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