古建筑用水硬性石灰的合成及力学性能研究

Research on Preparation and Mechanical Properties of Hydraulic Lime Used for Ancient Buildings

为了合成古建筑修复材料水硬性石灰,以天然姜石为原料,通过煅烧方式制备了水硬性石灰,利用XRD、SEM、伺服万能试验机和白光数字散斑相关方法等测试了水硬性石灰的成分、微观形貌、抗压强度和变形场演化等。结果表明:在900℃煅烧8 h时姜石中CaO、2CaO·SiO_2和2CaO·Al_2O_3·SiO_2的含量与欧洲水硬性石灰NHL5的成分相近;随养护时间的增加,水硬性石灰中CaO和2CaO·SiO_2的含量逐渐降低,CaCO_3和1.5CaO·SiO_2·x H_2O(C-S-H)的含量逐渐增加,而2CaO·Al_2O_3·SiO_2的含量基本不变;养护1~5 d阶段收缩率随养护时间迅速增加,养护6~17 d阶段收缩率随养护时间缓慢增加,养护18 d后收缩率保持恒定;抗压强度随养护时间的增加而增加,养护28 d时抗压强度达到6.75 MPa,达到NHL5的标准;随着载荷的增加,局部区域的应变值逐渐变大,相邻的局部变形区合并成应变局部化带,在峰值载荷处应变局部化带演变成微裂隙,微裂隙扩展成宏观裂纹使试件发生破坏;随养护时间的增加,Ca(OH)_2和2CaO·SiO_2发生反应的数量增加,形成的CaCO_3和C-S-H相互交织构成空间网络结构,水硬性石灰的孔隙率减少,力学强度显著提高。

Hydraulic limes used for restoring ancient buildings were synthetised by calcining loess-doll.The compositions,microstructure,compressive strength and evolution of horizontal strain field of hydraulic limes were analyzed by XRD,SEM,electro hydraulic servo universal tester and white light digital speckle correlation method(DSCM),respectively.The results show that the main components of loess-dolls are CaO,2CaO?Si02 and 2CaO.A1203.Si02 after calcining 8 hours at 900℃,which are similar to that of European hydraulic lime NHL5.The contents of CaC03 and 1.5CaO'Si02;H2 0(C-S-H)increase gradually with curing time,the content of Ca(0H)2 decreases gradually with curing time,and the content of 2CaO12038102 remains constant.Between 1 and 5 d of curing,shrinkage rate increases rapidly with curing time,between 6 and 17 d of curing,shrinkage rate increases slowly with curing time,and after 18 d of curing,shrinkage rate remains constant.Compressive strength of hydraulic lime increases with curing time,and after 28 d of curing the compressive strength of hydraulic lime reaches 6.75 MPa,which meets the standard of NHL5.The deformation field increases along with compressive stress,localization band occurs by the means of merging adjacent deformation regions,and it forms the macro crack that fails the sample.With the increase of curing time,a space network structure is formed by the connection of C-S-H and CaC03 in hydraulic lime,which reduces the porosity and enhances the compressive strength of samples.