Study On Evaluation System Of Waterproof Material Of Sandstone Cultural Relics

Among the stone cultural relics preserved in the open,sandstone cultural relics are large in number and rich in types,which have extremely high historical and artistic value.Most sandstone cultural relics are immovable historical relics of high porosity and thus sandstone cultural relics are often threatened by various environmental factors such as rainwater,air pollution,soluble salt,and organisms.Among the many factors affecting the protection of sandstone cultural relics,the involvement of water is particularly critical.The application of water-repellent materials on the stone surface has been a common conservation measures for sandstone cultural relics.At present,there are many waterproof products for historic stone conservation,ranging from traditional acrylic polymers to the latest nanocomposite materials.So it is an important task to evaluate and select the appropriate waterproof materials for sandstone cultural relics.The difference of materials and environments has led to different weathering mechanism and degrees of damage.Therefore,the evaluation of protective materials has always been a difficult task in the conservation of cultural relics.Previous research shows that that the focus and main difficulty of the evaluation of waterproof materials are in the following three aspects:1.The selection of evaluation indicators: The evaluation of cultural relics protection materials aims to reveal the protection effect of application,which is different from the assessment of general functional materials.The selection of evaluation index should not only consider the principle of cultural relic protection,but also truly reflect the protection effect of the material.2.Testing methods of evaluation indicators: Many technical and industry standards are used to test the performance of waterproof materials,but some of them set a high standard for operating skills or equipments,which is hard to apply to cultural relics.3.The evaluation of testing result: By the experimental tests of long core,all indexes of water proof materials are obtained,how to evaluate the protection capability of the materials is the next important task of the evaluation research of cultural relics protection materials.Nevertheless,research on this part is very scarce.In summary,at present,there is no widely approved evaluation system specifically for evaluating the applicability of waterproof material of sandstone cultural relics.Present researches on the evaluation of waterproof materials for cultural relics mostly discuss a specific material,while one can find various kinds of the evaluation indicators and technical methods in different research.In order to make the evaluation work of waterproof materials normalizable and scientific,this paper makes a comprehensive analysis on literature and experiment to systematically study the evaluation indexes,index testing methods and evaluation criteria of waterproof material,design a evaluation system for the application of waterproof materials on sandstone cultural relics.Finally,the evaluation system is applied to the evaluation research of waterproof material of Yungang Grottoes,proving the feasibility and validity of the system.It is hoped that this research can offer references for historic stone conservation and for the study on protection materials.