氯离子掺入方式及偏高岭土对砂浆氯离子结合性能的影响

通过模拟海砂与拌合水将相同含量的氯离子引入砂浆,研究了氯离子掺入方式及偏高岭土对氯离子结合性能的影响。采用能谱仪(EDS)分析了砂浆中氯离子含量分布,使用X射线衍射(XRD)及微商热重法(DTG)分析了水化产物的变化,采用压汞法(MIP)分析了砂浆孔隙结构的变化。结果表明,海砂型氯离子存在从砂粒表面向胶凝材料扩散的过程,而拌合水引入氯离子在砂浆中分布较为均匀。龄期1 d时,砂浆对海砂型氯离子结合性能低于拌合水引入氯离子;龄期28 d时,两种内掺型氯离子结合性能趋于一致。偏高岭土加速早期水泥水化反应,会促进砂浆对拌合水引入氯离子的结合。随偏高岭土掺量的增加,Friedel’s盐及Ca(OH)₂含量逐渐减少。20%与30%(质量分数)偏高岭土掺量下,拌合水引入氯离子对孔隙结构的细化效果更为显著。

Effects of Chloride Introduced Way and Metakaolin on Chloride Binding Capacity of Mortar

The same amount of chloride ions was introduced to mortars by simulated sea sand and mixed water respectively. The effects of chloride introduced way and metakaolin on chloride binding capacity were analyzed. And the corresponding test methods were used to analyze the different aspects: energy disperse spectroscopy (EDS) was conducted to analyze the distribution of chloride content; the change of hydration product was analyzed by X-ray diffraction (XRD) and derivative thermogravimetric method (DTG); the change of pore structure was evaluated by mercury intrusion porosimetry (MIP). The results show that there is a diffusion process of chloride ions from surface of sea sand to cementitious materials, and that chloride ions introduced by mixed water distribute evenly in mortar. The chloride binding capacity in mortar at different ages was discussed. The chloride binding capacity in mortar made with sea sand is lower than that made with mixed water at 1 d age, but these two chloride binding capacities tend to be same at 28 d age. The acceleration of metakaolin on early cement hydration reaction promotes the binding process of chloride ions introduced by mixed water. The content of Friedel’s salt and Ca(OH)₂ decreases with the increase of metakaolin content. The chloride ions introduced by mixed water has a better refinement effect on pore structure at 20% and 30% (mass fraction) metakaolin content.