Study On Migration Mechanism Of Water And Salt In Deliquesous Diseases Of Statues/Murals

Statues/murals are important references for us to explore the characteristics of the times,and the occurrence of statues/murals diseases seriously endangers the preservation of statues/murals and other cultural relics.Water and salt migration is one of the main reasons for the deliquescence of statues/murals.Therefore,this paper takes the ground layer of statues/murals as the research object,and carries out water and salt migration cycle experiments and water vapor deliquescence experiments in the environment to explore the influence of water and salt migration of gaseous water and liquid water on the deliquescence of ground layer.Through the analysis of relevant experimental data,the following main conclusions are obtained:1.The statue/mural backing layer saltwater migration cycle experiment shows:(1)After the capillary water migration cycle experiment,the water content decreased first and then increased with the increase of the height of the ground test block,and the conductivity and the concentration of anions and cations increased slowly and then increased rapidly,which indicated that the salt migrated to the top of the ground test block with the migration solution.(2)After the water and salt migration cycle experiment under different concentrations of single salt solution,the water content and conductivity of the ground test block decreased first and then increased with the increase of the height of the ground test block.The ion content carried by the migration liquid showed a trend of high at both ends and low in the middle.Although the ion content contained in the ground test block itself increased with the increase of the height of the ground test block,the overall growth was small,that is,the salt in the external solution played a leading role in the deliquescence disease of the statue/mural.(3)After the water-salt migration cycle experiment under different concentrations of mixed salt migration solution,due to the drying effect,the water content,conductivity and anion and cation concentration of the ground test block generally showed a trend of high at the top and bottom and low in the middle.(4)The water-salt migration cycle experiment showed that the higher the concentration of the migration solution,the greater the surface tension,the faster the migration rate,the higher the top conductivity,the more salt it enriched,and the more prone to deliquescence.The type of ground test block has little effect on the migration of soluble salt.With the continuous progress of the experiment,the water and salt in the salt solution repeatedly eroded the ground test block,causing irreversible damage such as cracking and crisping inside,surface and top of the test block.2.The water vapor deliquescence experiment in the environment shows:(1)The study of moisture absorption kinetics shows that the moisture absorption and moisture absorption rate of the ground test block increase with the increase of relative humidity and dry density.The moisture absorption kinetics curves of different dry density samples are most consistent with the double exponential model(R~2>0.99).(2)The water vapor deliquescence experiment of different dry densities of the ground test block under dry-wet alternation shows that the moisture absorption period of the ground test block is longer than the moisture release period,and the moisture absorption amount is greater than the moisture release amount;the greater the dry density,the greater the moisture absorption and desorption.After moisture absorption and desorption,the water content in the ground test block increases first and then decreases with the increase of the height of the ground test block,and the conductivity,anion and cation concentrations increase with the increase of the height of the ground test block.The water content and salt increment at the top increased with the increase of dry density of the test block.After absorption-desorption,there will be water left in the ground test block,which will drive the salt in the ground test block to migrate,and repeated dissolution-crystallization will occur,which will aggravate the deliquescence disease of the statue/mural.In view of the above results,we can reduce the impact of deliquescence on cultural relics such as statues/murals by controlling water,salt and migration.