基于抑制粘土负作用效果的聚羧酸减水剂的设计合成及机理

Synthesis and Mechanism of Polycarboxylate Superplasticizer Based on the Inhibition of Negative Effects of Clay

混凝土原材料附带的粘土具有劣化作用,给高性能混凝土的推广与应用带来了新的难题。本研究首次报道了基于粘土和聚羧酸分子尺寸计算自主设计合成的聚羧酸减水剂(PCE)对粘土负作用的改善效果,并结合吸附量、热重(TG)分析和X射线衍射(XRD)分析揭示了其对粘土负作用的抑制机理。计算结果表明,粘土层间吸附的不是整个PCE分子而是其功能性的聚醚侧链。因此针对性地合成了一种立体大尺寸分子结构的PCE,并由核磁氢谱(1 H NMR)和凝胶渗透色谱(GPC)证明了预期结构的存在及其分子量特性。性能评价结果表明,该PCE可在含粘土条件下提高22.2%—35.7%的水泥净浆流动度,并且在高粘土掺量下对混凝土1h坍落度也有明显改善。这归因于其大尺寸的立体结构能够产生显著的空间位阻效应,避免大分子上的聚醚侧链被全部吸入粘土层间,从而保障优良的减水分散功效,表现出抑制粘土负作用的效果。

Clay attached in concrete has deterioration effect on the application of high-performance concrete. In this paper, the improvement of polycarboxylate superplasticizer （PCE） synthesized based on the molecular calculation on the negative effect of clay was investigated, and the mechanism was revealed by adsorption, thermal gravimetric （TG） and X-ray diffraction （XRD） measurements. The adsorbed substance between interlayers of clay was side chains rather than the whole PCE, and thus a spatial PCE with large dimension was synthesized followed by 1H nuclear magnetic resonance （ 1H NMR） and gel permeation chromatography （GPC） characterizations. The results showed that in existence of clay, the fluidities of cement pastes containing this PCE increased by 22.2%— 35.7%, but also for the 1 h slump of concrete. This is ascribed to its large-sized structure which can generate steric hindrance effect, and thus its side chains can be prevented from being adsorbed in between interlayers of clay to ensure good dispersing effectiveness, presenting an inhibition of negative effect of clay.