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超高强混凝土(ultra-high strength concrete,UHSC)的水灰比小于0.25,含有大量的硅灰等微细组分,这有利于颗粒的最优紧密堆积。硅灰的表面化学效应以及较大的表面积使其成为UHSC中最难被分散的组分。由甲基丙烯酸、甲基丙烯酸酯及甲代烯丙基磺酸合成的聚羧酸系超塑化剂能使水泥颗粒被有效润湿,然而烯丙醚-马来酸酐合成的聚羧酸系超塑化剂可以很好地分散硅灰。这2种不同的聚羧酸系超塑化剂的复合可以使其拥有不同的分子结构,从而赋予超高强混凝土很好的流动性。当只加入1种聚羧酸系超塑化剂时其掺量为1%(质量分数,下同),而当加入这种复合聚羧酸系超塑化剂时掺量为0.5%就足够了。这2种类型的聚羧酸系超塑化剂的协同效应是由于它们的选择性吸附:甲基丙烯酸盐基的聚羧酸系超塑化剂主要吸附在水泥颗粒表面,而烯丙醚基聚羧酸系超塑化剂主要吸附在硅灰颗粒表面。实验表明:小分子量的有机酸阴离子(如:柠檬酸盐、葡萄糖酸盐及酒石酸盐中的阴离子)与聚羧酸系超塑化剂之间具有潜在的协同作用。只需加入0.1%的这些阴离子即可显著提高烯丙醚基聚羧酸系超塑化剂的作用效果。这些阴离子可以起到一种辅助作用,它们同时吸附在水泥颗粒表面以及硅灰颗粒表面。水泥颗粒的表面首先由这些阴离子所占据,而硅灰颗粒表面吸附了烯丙醚基聚羧酸系超塑化剂和这些阴离子。这些阴离子起到了一种很强的静电分散效应,使烯丙醚基聚羧酸系超塑化剂的空间位阻效应得到加强。虽然聚羧酸系超塑化剂阴离子具有缓凝作用,但是使用这种复合聚羧酸系仍能制备出高早强混凝土。
The ultra-high strength concrete (UHSC) has a water-cement ratio of less than 0.25 and contains a large amount of fine components such as silica fume, which is beneficial to the optimal compact packing of the particles. The surface chemistry of silica fume and its large surface area make it the hardest component to disperse in the UHSC. Polycarboxylate-based superplasticizers synthesized from methacrylic acid, methacrylates, and methallyl sulfonic acid enable cement particles to be effectively wetted, whereas the polycarboxylic acids synthesized from allyl ether-maleic anhydride Superplasticizer can disperse silica fume well. The combination of these two different polycarboxylate superplasticizers gives them a different molecular structure, giving the ultra-high strength concrete good fluidity. When only one kind of polycarboxylate superplasticizer is added, the content is 1% (mass fraction, the same below), and when 0.5% is added when the composite polycarboxylate superplasticizer is added, it is enough It’s The synergistic effect of these two types of polycarboxylate-based superplasticizers is due to their selective adsorption: the methacrylic-based polycarboxylate-based superplasticizer is mainly adsorbed on the surface of the cement particles while the allyl ether group Polycarboxylate superplasticizer is mainly adsorbed on the surface of silica fume particles. Experiments have shown that small molecular weight organic acid anions (such as: citrate, gluconate and tartrate anions) and polycarboxylate superplasticizer potential synergy. Just add 0.1% of these anions can significantly improve the allyl ether-based polycarboxylate superplasticizer effect. These anions can play a supporting role, they are adsorbed on the surface of cement particles and the surface of silica fume particles. The surface of the cement particles is first occupied by these anions, while allyl ether-based polycarboxylate-based superplasticizers and these anions are adsorbed on the surfaces of the silica fume particles. These anions play a very strong electrostatic dispersion effect, which makes the steric hindrance effect of allyl ether-based polycarboxylate superplasticizer enhanced. Although polycarboxylate superplasticizer anion with retarding effect, but the use of this composite polycarboxylic can still be prepared high early strength concrete.