A Study On The Freeze Injury Of The Exterior Finish System In Heritage Buildings

The types of the heritage buildings' exterior decorated surface which this paper studies mainly are mortar,facing brick and lime sculpture.Mortar represents a significant share and appeared the earliest.Chinese pottery and porcelain were created in ancient times,and they were used for buildings' exterior surface decoration in the early 20 th century.The heritage buildings decorated with lime sculptures in research is also the outcome of the early 20 th century.Long history,however,lead to the damage of different degrees of the excellent cultural relic buildings whose exterior finish are decorated,under the comprehensive affection of its own material properties,regional climate and other factors.Our country has a monsoon climate which is more obvious,and the landscape environment of whom is unique,then forming a feature that has a cold region of wide range,long and cold winter.In 2016 the snow line has reached the most southern Guangdong Province China since 1951,then our country's cold injury scope covers an entire continent.There's a huge amount of heritage buildings with exterior finish in our country,so this article adopts the method of the field survey,investigated six regions,475 cultural relics of the buildings in the cold area,then found that,under the attack of the cold climate,mortar,facing brick and lime sculpture of the exterior finish in the heritage buildings appeared large area of freeze injury.The proportion of the freeze injury degree above severe is 51.6% by assessing the damage form.In order to study the mechanism of freezing damage on the surface of the cultural relic buildings,the author numbers,registers,establishs file of the research sample,then lists,collects statistics and analysis according to the different exterior finish.And then search the law between the position and the form of the freeze injury.The author finaly find that the exterior finish appear crack,crush,fall off as high frequency form of freezing injury no matter the position is different or not.The freeze injury appear more serious where the water flow mark is obvious.The mortar,facing brick and lime sculpture appears different freeze injury form according to different material properties.Integrating the above existing data information and law,the formation of cold damage of the outside facing of historical buildings is an gradual process.The process can be mastered by the form of the freeze injury in heritage buildings.The author find the moisture source and seepage channel of the exterior finish in heritage buildings by consulting document and analyzing data.The author find that the eaves,all around window,plinth,near by drainage system are the weak links of freeze injury by comparing the mortar,facing brick and lime sculpture,precipitation can arrive thesepositions directly or indirectly,water retention is huge.Under the long term effect of temperature under zero degree in cold region,freezing and thawing cycle of water caused the freeze injury of the exterior finish in heritage buildings.To sum up,the thesis base on climate environment and material properties of the cultural relic buildings with veneer decoration to conduct research,through the summary of field survey data information,then find out frost laws between the form and position,and finally obtain the frost formation mechanism and cold weak parts of the historical buildings,The fa?ade of a historical building appears the most serious frost damage where moisture was held up the most,basing on the above study.The author hopes this research can provide corresponding theoretical basis for protection and reparation of the cultural relics of the building exteriors in the future.