聚羧酸减水剂对水泥浆结合氯离子性能的影响

从氯离子等温吸附、吸附动力学及吸附热力学3个方面,研究聚羧酸减水剂对水泥浆结合氯离子性能的影响,同时应用XRD微观测试技术研究其作用机理。结果表明:掺入聚羧酸减水剂使水泥浆体结合氯离子能力减弱,且水灰比越小,这种影响作用则越大;掺入聚羧酸减水剂的水泥浆体对氯离子的固化过程,短期内符合准一级动力学方程,表现为物理吸附,长期内符合准二级动力学方程,表现为化学结合,其中随着聚羧酸减水剂掺量的增大,吸附速率逐渐减小;聚羧酸减水剂使水泥浆结合氯离子过程中的自由能变、焓变和熵变都减小,且这个过程是自发、放热的;掺入聚羧酸减水剂主要影响水泥浆体对氯离子的物理吸附,对化学结合没有明显影响。

Influence of polycarboxylate superplasticizer on the chloride binding in cement paste

Through the isothermal adsorption of chloride ion, the adsorption kinetics and the adsorption thermodynamics, the influence of polycarboxylate superplasticizer on the chloride binding in cement paste has been investigated. Besides, the influencing mechanism was examined by the X-ray powder diffractometer(XRD). It has been found that the polycarboxylate superplasticizer reduces the chloride binding, and the smaller the water-cement ratio is, the greater the effect is. Chloride binding onto cement paste with polycarboxylate superplasticizer in a short time conforms to pseudo-first-order kinetic equation, indicating the physical adsorption of chloride ions. In a long time, it conforms to pseudo-second-order kinetic equation, indicating the chemical adsorption of chloride ions. With the increase of content of polycarboxylate superplasticizer, the adsorption rate decreases. The free energy, enthalpy and entropy of chloride binding are decreased with the increase of polycarboxylate superplasticizer, and this process is spontaneous and exothermic. The influence of polycarboxylate superplasticizer on the chloride binding is mainly attributed to the physical adsorption, not chemical combination of chloride ions.