偏高岭土在人造水硬性石灰修复砂浆中的应用研究

Application of Metakaolin in Artificial Hydraulic Lime Repair Mortar

为研制一种适用于历史建筑修复的绿色无机修复材料,本文基于青岛多栋砖砌体结构历史建筑黏结材料的XRD测试结果,通过掺偏高岭土制备了基于人造水硬性石灰的修复砂浆,测试了人造水硬性石灰砂浆的流动度、凝结时间、质量损失率、干燥收缩率以及力学性能等指标,研究了偏高岭土对人造水硬性石灰砂浆的影响。结果表明:偏高岭土可降低人造水硬性石灰砂浆的流动度,缩短凝结时间,降低收缩率,提高抗压强度及黏结强度。当掺量为5.0%和7.5%(质量分数)时,人造水硬性石灰砂浆的56 d抗压强度分别提升了66.8%和94.3%,黏结强度分别提升了22.2%和25.9%。采用XRD和SEM对材料的微观结构进行测试分析发现,偏高岭土能使人造水硬性石灰砂浆性能提升的主要原因是偏高岭土中的活性SiO_(2)和Al_(2)O_(3)与石灰发生直接反应并消耗Ca(OH)_(2),促进了水泥水化,增强了水化产物与骨料间的黏结力。

In order to prepare a green inorganic restoration material that is suitable for the restoration of historical buildings,based on the XRD test results of the bonding materials of several historical brick masonry buildings in Qingdao,an artificial hydraulic lime repair mortar was prepared by mixing metakaolin.The influence of metakaolin on the artificial hydraulic lime mortar was studied by testing the fluidity,setting time,mass loss rate,dring shrinkage rate and mechanical properties.The results show that metakaolin can reduce the fluidity,shorten the setting time,reduce the dring shrinkage rate and improve the compressive strength and bonding strength of artificial hydraulic lime mortar.When the content is 5.0%and 7.5%(mass fraction),the 56 d compressive strength of artificial hydraulic lime mortar increases by 66.8%and 94.3%,and the bond strength increases by 22.2%and 25.9%.Finally,XRD and SEM were used to test and analyze the microstructure of the materials.The results show that the main reason for the improvement of the performance of the artificial hydraulic lime mortar by metakaolin is that the active SiO_(2)and Al_(2)O_(3)in metakaolin react directly with the lime,and consume Ca(OH)_(2),which promotes the hydration of cement and enhances the bonding force between the hydrated products and the aggregate.