The Effect Of Water Vapor In The Air On The Corrosion Of Statues Or Murals Sound Mechanism And Selection Of Four Common Reinforcing Agents

As an important witness in the long history of mankind,statues/murals have immeasurable value and significance.However,with the baptism and washing of the years,a series of diseases such as soda,herpes,mold and so on will gradually appear in the statues/murals,which will add many problems to the protection of cultural relics.Studies have shown that the main cause of lesions in statues/murals is the migration of water and salt in the ground layer under the influence of the environment,and water vapor in the air is one of the important factors affecting the emergence of diseases.In this paper,it is proposed to carry out research on the influence mechanism of water vapor in the air on the corrosion of statues/murals,and select the reinforcement agent with the best effect on the ground test block under the influence of water vapor,so as to provide technical reference for the restoration and protection of statues or murals in the future:（1）Study on the influence mechanism of water vapor in air on corrosion of ground layer:1)Studies of water vapor penetration in the ground layer have been studied:（1）Under the same salt content,the water vapor permeability and permeation rate of the test block gradually increase with the increase of ambient humidity;（2）Under the same relative humidity,the water vapor permeability of the test block increases with the increase of the salt content of the test block;（3）Under the same humidity condition and constant salt content of the test block,the water vapor permeability of the coarse mud test block is greater than that of the fine mud test block.2)Studies of the water holding capacity of the ground layer have been studied:（1）Under different humidity environments,the water content of the test block gradually decreases with the increase of the total suction.When the total suction is less than 10⁵ kPa,the water content of the coarse mud test block is greater than that of the fine mud test block;（2）The suction of different salt test blocks to water vapor is mainly osmotic suction,and the osmotic suction of the test block increases with the increase of the salt content of the test block;（3）Under the same salt content,the volumetric water content of the test block gradually decreases with the increase of osmotic suction.3)Study on moisture absorption characteristics of ground test block:（1）The study of moisture absorption kinetics shows that under the same salt content and relative humidity,the moisture absorption of the ground test block changes with the moisture absorption time,which conforms to the double exponential model.The moisture absorption kinetic curves of coarse and fine mud test blocks with different salt contents were well fitted with the double exponential model;（2）The study of isothermal equilibrium moisture absorption characteristics shows that the isothermal moisture absorption curve of salt-containing test block belongs to type Ⅱ isothermal moisture absorption curve,and it has a good fitting degree with Polynomial model,Peleg model and DLP model,among which the fitting degree with DLP model is the highest;（3）The moisture content of the same salt content test block gradually increases with the increase of the height and diameter of the test block after the moisture absorption balance of the ground test block at high relative humidity of RH=97.7%.The salt in the test block is mainly NaCl and Na₂SO₄.When the moisture absorption reaches equilibrium,the concentration of Cl^-,SO₄^2-and Na⁺inorganic ions gradually decreases with the increase of the height and diameter of the test block.The ion concentration of the test block in the same height and circle layer increases gradually with the increase of the salt content of the test block;4)Simulated aging cycle tests show that:（1）After each cycle test cycle,with the increase of salt content of the ground test block,the mass increment of the ground test block gradually increases,and the mass increment of the coarse mud test block is greater than that of the fine mud test block;（2）After 20 aging cycle tests,the moisture content of the inner layer of the same salt content is small,the moisture content of the middle layer is the largest,and the moisture content of the outer layer is the smallest.The conductivity,anion and cation of the test block show the imagination of the outer layer being large and the inner layer being small;in the same height and circle layer of the test block,the greater the salt content of the test block,the greater the water content,conductivity and ion concentration of the test block,and the smoother the fine mud test block than the coarse mud test block;（3）The obvious degree of salt damage characteristics of the soil block is gradually obvious with the increase of the salt content of the soil block.When the salt content of the test block is the same,the salt damage degree of the coarse mud test block is greater than that of the fine mud test block.（2）Experimental study on the selection of four common cultural relics reinforcements:1)The water vapor permeation test of the reinforced test block showed that:（1）When the test block reinforcement agent is the same,the water vapor permeability of the reinforced test block increases with the increase of relative humidity;the water vapor permeability of the reinforced test block decreases with the increase of the concentration of the reinforcing agent,that is,when the concentration of the reinforcing agent R is 4%,the four reinforcing agents have the most obvious effect on water vapor barrier;（2）Under the same ambient humidity,the water vapor permeability of different reinforcing agents from large to small is:PVAc>propylene>Silica-modified polypropylene>P B72.2)Reinforced test block simulation aging cycle test（20 cycles）:（1）When the reinforcing agent is the same,the moisture content of the inner,middle and outer layers of the reinforced test block after the simulated aging cycle test is as follows:the moisture content of the inner layer of the ground support test block is small,the moisture content of the middle layer is the largest,and the moisture content of the outer layer is the smallest;after simulating the aging cycle test,the conductivity and ion concentration of the reinforced test block show the phenomenon of high outer layer and low inner laye;（2）The influence of different reinforcing agents on the moisture content of the test block and the mass change of the test block is:PVAc test block>propylene test block>Silica-modified polypropylene test block>P B72 test block.The order of conductivity and ion concentration of test block is opposite to that of water content.（3）According to the apparent morphology of the reinforced test block after the aging cycle test,the reinforcement effect of the four reinforcement agents on the soil block is ranked as PVAc optimal P B72 worst;after reinforcement,the salt damage degree of coarse mud test block is greater than that of fine mud test block.