| The relics composed of stone are found in a wide field of site and are present in many types of structure,which shows great significance for us to understand history and social development.A number of factors accelerate the efflorescence rate of stone relics,and some appropriate conservation methods are needed.So,it is important to do some research on the weathering process of stone relics,so as to design a protective material.Based on these,the carbonic stone object situated on Lingyan temple,Jinan,Shandong province were selected as experiment sample,and assembled a design structural of CaC2O4·H2O layer via a controllable synthesis method to slow the efflorescence rate.The research work was mainly carried out from the following four aspects:A field investigation of 9 weathering types(damage,fracture,white crust,man-made pollution,red discoloration,erosion,flake,crack and improper repair)of 475 carbonate stone object from the Tang Dynasty to the late Qing Dynasty in the Lingyan Temple,Changqing,Shandong province was conducted,accompanied with location site and environmental parameters.The results indicate that the most important influence factor of outdoor carbonate stone object is water,and the relationship between weathering feature and factors was also revealed.The weathering process of typical feature(red discoloration,white crust,flake and erosion)was analyzed.Comprehensive evaluation and regional comparison were carried to make a detail description of the formation process of red discoloration.The results of above sample indicated the influence of rainwater on carbonate stone object includes two parts:physical impact and chemical erosion.So,the protective materials should have such advantages of good adhesion,increased film forming ratio and high densification structure.A CaC2O4·H2O bond layer,flexible layer and rigid layer were designed to meet the requirement.(1)The CaC2O4·H2O bond layer was deposited on the surface of white marble via in situ reaction,and chemical agent(NH4)2C2O4 not only form a protective layer,but also increased 25%adhesion strength of the marble surface with product.(2)The CaC2O4·H2O flexible layer was formed on the surface of the bond layer by a colloid solution deposite process.NaOH restrain the hydrolysis of C4H6O4,slow the rate of CaC2O4·H2O precipitation and keep the solution spread on the rough surface to fill the holes in the sample.(3)The CaC2O4·H2O rigid layer was deposit on the surface of the bond layer by a solution deposite process,and the relationship between crystal morphology and growing environment was discussed.It was found that CaC2O4·H2O crystals transformed from irregular particles to square crystals under acidic environment,which met the requirements of particle dense packing theory.Above research provids a reference for the controllable preparation of inorganic protective materials.In order to improve the anti-erosion performance of CaC2O4·H2O film further,bond layer,flexible layer and rigid layer were assembled together by taking full use of the solubility of(NH4)2C2O4?NaOH?HNO3,which was beneficial to reduce the content of residue below the examination limit of FT-IR and Raman spectrum,leading to homogenization of CaC2O4·H2O composite,and formation a densification multilayer on the stone surface.The result of acid rain erosion indicated that the multilayer act as a sacrifice layer and has a long service life.Furthermore,the film not only has excellent barrier properties(stain resistance),but also can be removed and repaired,which provides more guarantees for the practical application.The film can be assembled on a gypsum crust and converted to CaC2O4·H2O owing to the(NH4)2C2O4 agent,which provides a new route for crust cleaning.Above results indicate the film can deposite on the sulfide sample,and hinder the formation of black crust.To test the idea,the multilayer deposite on an efflorescence rock surface and placed it outdoor to test the protective effectiveness.After cold winter,the sample almost not changed,and an integrated CaC2O4·H2O film could be detected.This research lays a foundation for the structural design and stone relic conservation.To sum up,based on the compostion and weathering mechanism of stone object,CaC2O4·H2O multilayer has the advantage of acid rain resistance,pollution resistance,removable and repairable properties was prepared through material selection,controllable synthesis and structural design process.This study would broaden the system of inorganic materials in stone conservation,and also provides a reference for the practical application of this material. |
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