水硬性石灰合成及拉破坏特性试验研究

水硬性石灰在欧洲石质文物修复和加固中获得了很大成功。我国的石质文物主要是砂岩,水硬性石灰的修复效果不好。为满足我国石质文物修复和加固的需求,本文以石灰石和黏土为原料,在950℃煅烧不同时间,制备出水硬性石,对试样的成分、微观形貌、收缩率、抗拉强度和拉破坏过程等进行了研究。结果表明:(1)试样中含有水硬性成分2CaO·SiO2(C2S);煅烧8h时,成分与欧洲水硬性石灰NHL5接近;1.5CaO·SiO2·xH2O(C-S-H)和CaCO3的含量随龄期的增加逐渐增加。(2)龄期1~3d,收缩率较小;龄期4~6d,收缩率以线性规律增加;7d以后,收缩率趋于稳定。(3)局部变形区随拉应力的增加而变大,邻近局部变形区逐渐合并,形成面积更大的应变局部化带;载荷超过峰值后,产生微裂隙;随载荷进一步增加,微裂隙扩展,贯穿整个试件,发展成宏观裂隙,使试件破坏。(4)抗拉强度随龄期的增加而增加,水硬性石灰中C-S-H、CaCO3等相互交织,构成空间致密体,使试件力学强度提高。合成的水硬性石灰物理力学性能与欧洲水硬性石灰NHL5相近,并且成分均匀、可控,在石质文物修复和加固工程中具有良好应用前景。

Experimental study on synthesis and tensile failure characteristics of hydraulic lime

Hydraulic limes are considered as an appropriate material for restoration and reinforcement of stone historical relics in Europe.However,they have poor performance for the restoration of sandstone historical relics in China.The synthesis mechanism and tensile failure characteristics of hydraulic limes are studied by calcination of limestone and clay for different durations at 950℃in order to explore appropriate restoration and reinforcement materials for stone historical relics in China.Compositions of hydraulic limes with different burning time and curing ages,microscopic morphology,shrinkage rate and tensile strength are analyzed.The results show that hydraulic limes contain hydraulic components 2 CaO·SiO2(C2S).The components of hydraulic lime are similar to those of the European hydraulic lime NHL5 after calcining for 8 hours.1.5 CaO·SiO2·H2O(C-S-H)and CaCO3 appear in hydraulic limes as the curing ages increase.At early ages(between 1 and 3 days),the shrinkage rate increases slowly with ages;At middle ages(between 4 and 6 days),the shrinkage rate increases quickly with ages;And the shrinkage rate remains constant after 7 days.At early stages of loading,the area of deformation zones increases with tensile stress.Localized bands appear by merging adjacent deformation zones,and after the peak load,it develops into the macro-crack that destroys the sample.As the curing ages increase,the tensile strength of hydraulic limes increases,and a network structure is formed by overlapping of C-S-H and CaCO3 in hydraulic limes,which enhances the mechanical strength of the samples.The physical and mechanical properties of synthesized samples are similar to those of European hydraulic lime NHL5.The samples with homogeneous and controllable compositions have great applications in restoration and reinforcement projects of stone historical relics in China.