Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)
Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)
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DOI：
10.1016/j.cemconres.2012.08.013
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发表时间：
2012-11-01
影响因子：
11.4
通讯作者：
Plank, J.
中科院分区：
文献类型：
--
作者：
Schroefl, Ch.;Gruber, M.;Plank, J.
当使用MPEG型和APEG型PCE的混合物时，UHPC的流态化效果特别好。在这里，对这种行为的机制进行了研究。对单个水泥和微细二氧化硅浆体的测试表明，mEg-PCE对水泥的分散效果好于二氧化硅，而APEG-PCE对二氧化硅的流态化效果尤其好。这一行为可以用APEG-PCE在二氧化硅上的优先吸附来解释，而mpeg-PCE对水泥和二氧化硅表现出更平衡的亲和力。将从单个水泥和微型硅胶浆体获得的吸附数据与含有水泥/硅胶混合物的全配方超高性能混凝土的吸附数据进行了比较。在UHPC配方中，两种PCE仍然表现出优先和选择性的吸附，就像在单独的水泥和硅胶浆料中观察到的那样。PCE的优先吸附是由于它们不同的立体化学，即羧酸基必须与位于水泥水合物或二氧化硅表面的钙离子/原子的空间位置相匹配。(C)2012爱思唯尔有限公司。保留所有权利。
UHPC is fluidized particularly well when a blend of MPEG- and APEG-type PCEs is applied. Here, the mechanism for this behavior was investigated. Testing individual cement and micro silica pastes revealed that the MPEG-PCE disperses cement better than silica whereas the APEG-PCE fluidizes silica particularly well. This behavior is explained by preferential adsorption of APEG-PCE on silica while MPEG-PCEs exhibit a more balanced affinity to both cement and silica. Adsorption data obtained from individual cement and micro silica pastes were compared with those found for the fully formulated UHPC containing a cement/silica blend. In the UHPC formulation, both PCEs still exhibit preferential and selective adsorption similar as was observed for individual cement and silica pastes. Preferential adsorption of PCEs is explained by their different stereochemistry whereby the carboxylate groups have to match with the steric position of calcium ions/atoms situated at the surfaces of cement hydrates or silica. (C) 2012 Elsevier Ltd. All rights reserved.