古建筑修缮中粉化石灰的占比对灰浆性能的影响

Influence of the Ratio of Chalked Lime on the Performance of Pastes in the Restoration of Ancient Buildings

古建筑修缮现场,块状生石灰原材料粉化变质不可避免,实际施工中也难免掺入粉化石灰。为了探究粉化变质石灰的占比对灰浆性能的影响,首先利用X射线衍射(XRD)、X射线荧光光谱(XRF)和热重分析(TG)对块状生石灰及粉化石灰的纯度及变质程度进行了定性及定量分析,然后以相同水灰比、不同粉化石灰占比制样,进行性能对比及机理研究。结果表明:石灰原材料纯度高,块状生石灰未变质,为纯CaO,粉化石灰部分变质,其中CaCO_(3)含量为17.93%。粉化石灰占比增加降低了试样的表面硬度,对养护28 d的试样力学强度影响小,对养护60 d的灰浆试样力学强度有增大趋势,粉化石灰占比达到50%时降低了灰浆的耐水性、抗冻性。干燥表观密度、显气孔率、吸水率、碳化深度及扫描电镜(SEM)结果分析得出性能差异主要是由于粉化石灰胶结性降低,以及制样时粉灰所需水少,相同水灰比条件下剩余游离水多,使得粉灰试样致密度低、孔隙率及吸水率大,从而加快了碳化。工程实际使用中可将粉化石灰占比控制在40%以内。

At the restoration site of ancient building,it is inevitable that the raw material of lumpy quicklime will be chalked and deteriorated,and it is also inevitable to mix chalked lime in the actual construction.In order to explore the influence of the ratio of chalked metamorphic lime on the performance of paste,the purity and metamorphism degree of lumpy quicklime and chalked lime were qualitatively and quantitatively analyzed by X-ray diffraction(XRD),X-ray fluorescence spectrum(XRF)and thermogravimetric analysis(TG).Then samples were prepared with the same water-binder ratio and different proportions of chalked lime for performance comparison and mechanism research.The results show that the raw material lime has high purity,the lumpy quicklime is pure CaO without metamorphism.The chalked lime was partially deteriorated,and the content of CaCO _(3) was 17.93%.The increase in the ratio of chalked lime reduces the surface hardness of the sample,has little effect on the mecha-nical strength of the sample cured for 28 days,and there is a tendency to increase the mechanical strength of the sample after curing for 60 days.When the proportion of chalked lime reaches 50%,the water resistance and freeze-thaw resistance of sample are reduced.According to the analysis of dry apparent density,porosity,water absorption,carbonation depth and scanning electron microscope(SEM)results,it is concluded that the difference in performance is mainly due to the decrease of cementation of chalked lime,less water needed for sample preparation,and more residual free water in the same water-binder ratio,which leads to low density,high porosity and water absorption of samples containing chalked lime,thus accelerating carbonation.In the actual construction,the ratio of chalked lime should be controlled within 40%.