Study On Rising Law And Impact Of Capillary Water In Brick Architectural Heritage Of Wet District

In China,areas around rivers and seas,such as Jiangsu,Shanghai,Tianjin,Zhejiang,Chengdu Plain,Jianghan Plain,Pearl River Delta and other places have shallow groundwater level for about 1-2 meters underground.Therefore,the water content in the walls of the lower floor and basement is high.There are numbers of excellent brick architectural heritage in China,most of which are 1-2 floors.Affected by groundwater,rainwater and perched water,the masonry wall at the bottom is easy to deteriorate and arise degradation of bricks and mortar as powdering,shedding,salting out,strength decay,etc.The environment indoor will also be influenced and appear mold growth,environmental degradation and other phenomena as well.As a result,the safety,durability and livability of historic buildings are threatened.This paper firstly summarizes and analyzes the influence and harm of moisture transfer in walls of brick architectural heritage.For the phenomenon of rising damp in historical buildings in high-humidity areas,the real-scale cavity wall and solid wall are built in the environmental chamber.A comparative study of capillary water rising experiments on cavity wall and solid wall was carried out.At the same time,with regard to the influence of moisture on the heat transfer of historical building walls,the heat transfer experiments of dry and wet walls under different masonry processes were carried out.Finally,combining the experimental results of the two walls,Energyplus was used to analyze the impact of capillary water on the energy consumption of typical southern houses.Through the research above,the main conclusions are as follows:(1)In the research,several detection methods of wall water content and wet front were compared,and a suitable non-destructive test method for wall water content was obtained.The water content of the wall was measured within 9600 hours using the calibrated testo616.(2)In the early stage(within one week),the rising speed of capillary water in Chinese brick wall has a faster velocity,and the capillary water rises about 30 cm in the cavity wall and rises about 24 cm in the solid wall.The law of capillary water rise in two typical brick walls in China accords with the law of H(t)=k*~12.The paper summarizes the water supply of two typical Chinese walls under the influence of shallow groundwater level.The formula provides support for the protection and degradation risk analysis of brick architectural heritage.(3)Experiments have shown that the capillary water in the brick wall(thickness 24 cm)keeps a stable height of about 170 cm,and the capillary water in the brick wall(thickness 24 cm)is about 150 cm.In high-humidity environments,historical buildings in shallow groundwater areas of China are affected by the action of capillary water within this height.(4)Through the real-scale wall experiment,it is found that the average heat transfer coefficient of the cavity wall in the dry state is about 2.13w/m2·k,and the solid wall is about 1.97 W/m2·k.In areas with shallow groundwater level in China,the average heat transfer coefficient of the cavity wall and the solid wall under the influence of capillary water is about 3.61W/m2·k and 3.67 W/m2·k.(5)Based on the measured thermal conductivity of the wall,the simulation shows that the influence of capillary water rise on the overall heating and cooling energy consumption of a typical historic Chinese brick architectural heritage is about 5%.This study aimed at the core of historical building degradation factors–moisture,through the experimental study,both the capillary water law of the typical wall of brick architectural heritage in China and the heat transfer effect of the cavity wall and the solid wall under the action of capillary water are clarified.It provides data support for the analysis of the moist disease mechanism,the prediction of the deterioration,the construction environment control and the energy-saving renovation of the brick architectural heritage in the high-humidity area,and provides a basic research for the preventive conservation and protection measures of the Chinese brick architectural heritage.