Effect Of Temperature And Moisture On The Strength Of Restoration Materials For Cultural Relic Sandstone

China is rich in numerous sandstone cliff Buddha statues,distributed throughout the country,with strong cultural heritage and historical significance.Numerous sandstone cultural relics in China have a long history,but due to their long-term exposure to the natural environment,the main body of the cultural relics will undergo different degrees of weathering,which is prone to deterioration such as cracks,rock mass detachment,and deliquescence.Therefore,the restoration of cultural relics has become particularly important.In order to find a suitable restoration material for the protection of sandstone cultural relics,this article takes two commonly used restoration materials in the field of cultural relics restoration as the research object,and studies the changes in mechanical strength after being affected by temperature and humidity.Two repair materials,natural hydraulic lime(NHL2)and hydraulic lime with a 12% cement content(CHL12),were selected,both referred to as NHL2 and CHL12 in the text.By controlling its physical conditions,the mechanical properties and durability are investigated.Secondly,hydraulic lime(CHL5)with a 5% cement content as the repair material was used to bond the cultural relic sandstone with CHL12,and mechanical strength tests were conducted to provide reference for actual repair projects.The main research work and achievements of this article are as follows:1.Mechanical strength tests were conducted on repair materials NHL2 and CHL12,and the tests found that the tensile strength,internal friction angle,and cohesion of NHL2 were higher than those of CHL12,indicating good mechanical properties.2.NHL2 and CHL12 were subjected to high temperature,low temperature and freeze-thaw cycles to study their mechanical properties under the influence of different temperatures.Through mechanical strength testing,it was found that the tensile strength and shear strength indicators of the two repair materials decreased to varying degrees under the influence of constant temperature,and high temperature had a significant impact on the repair materials.Secondly,through freeze-thaw cycling tests,a reasonable temperature cycling range was set by fully considering the temperature changes in the area where sandstone cultural relics are located.It was found that the tensile strength and shear strength indexes of the two repair materials showed different degrees of reduction after freeze-thaw cycles compared to the room temperature condition,while the difference between the strength values of 5 freeze-thaw cycles and10 freeze-thaw cycles was not significant,and the trend of gradual stabilization could be seen.3.Study the changes in mechanical properties of NHL2 and CHL12 under different humidity effects at saturation rates of 100% and 80%.The tensile strength values and shear strength indexes of the two repair material specimen bodies were reduced to different degrees after they were full of water.Among them,the complete saturation treatment has a significant impact on the tensile strength and shear strength indicators of the two repair materials.4.Mechanical strength testing was conducted on the cultural relic sandstone bonded with the repaired material CHL5 and CHL12.The experiment showed that in actual restoration work,CHL12 has good mechanical strength properties and can be restored to the original rock to a higher degree.5.Using the finite element software ABAQUS,numerical simulations were conducted on two types of repair materials.By establishing the Brazilian splitting failure model and the direct shear failure model,the mechanical failure process of the two brittle materials was studied,taking into account the damage caused by temperature and humidity to the mechanical model.In this paper,we investigate the strength of NHL2 and CHL12 by controlling the objective physical conditions of different temperatures and humidity.The mechanical strength of the heritage sandstone was also studied by bonding it using CHL5 and CHL12.It was shown that the mechanical properties of CHL12 are better than those of CHL5,while the mechanical strength properties of NHL2 are better compared with those of NHL2,but the durability of CHL12 is better and it is less affected by temperature and humidity,which makes it more suitable for application in the restoration work of sandstone quality artifacts.