Study On Weathering Mechanism Of Beijing Marble

Beijing owns a great deal of stone cultural relics, many of which were built by marble.In order to protecting these weathering stone cultural relics, this paper takes the Beijing marble includes Green White stone and white marble as the research objects which are commonly used in many areas, undertake research into their mechanisms through spot reconnaissance and indoor experiments.This paper have done the following works:(1)The minerals, chemical components were respectively tested and analyzed by slice observation under microscope, XRD, XRF; The physical properties and mechanical strength of marble were tested accord the relevant specification. The physical properties include density, porosity, pore diameterdistribution, water absorption, wave velocity. The mechanical strength include uniaxial compressive rock strength, tensile strength of brazil disk split test, flexural strength of under concentrated load.(2)According to the classification come forwarded by ICOMOS-ISCS, the standard of Li Hongsong(2011) and standards issued by Chinese state administration of cultural heritage,the erosion type of Beijing stone cultural relics are crack, exfoliation, disintegration, crusting, dissolved pore, dissolution, missing parts, discoloration, biological parasitism, improper manual repair etc.(3)After 1000 cycles of the alternating of high and low temperature test(-20℃-60℃),the quality loss rate, elasticity wave velocity and dynamic elasticity modulus of fresh marble are gradually decrease and the roughness of fresh marble is increasing; The residual strain of the marble surface can be found after 200 cycles of the alternating of high and low temperature test(20℃-60℃). From marble exfoliation of cultural relics for scanning electron microscopy(SEM) analysis, micro crackswere found between the dolomite mineral crystals and intragranulars.On the basis of that difference in temperature and precipitation is the main factor causing marble weathering.And marble damage and damage mainly caused by the accumulation of residual strain, precipitation caused by the slow dissolution.