Research On Moisture-proof And Mildew-proof Technology For The Ground Floor Of Brick-concrete Buildings And The Basements In Jiangnan Area

The Jiangnan Area is plentiful with rainfall,and the groundwater level is about-1m～-2m.The ground floor of the brick-concrete building and the basements are affected by the rising damp for a long time,and the water content of the enclosure structure is relatively high.The high moisture problem leads to an increase in the thermal conductivity of the floor and walls,a decrease in temperature,and condensation on the surface,resulting in higher humidity.Wet walls and floor can easily damage the building structure,furniture and equipment,and at the same time promote the mold growth and endanger human health.The temperature and moisture distribution and fluctuation of the envelope of brickconcrete buildings and the basements are affected by conditions such as air temperature,humidity and soil environment,especially the impact of soil and groundwater on walls and ground is not clear.How to achieve moisture-proof and mildew-proof for the ground floor of brick-concrete buildings and the basements in Jiangnan is an important issue.In the research,a residence and an underground garage in Nanjing were taken as examples,through the methods of field monitoring and numerical simulation,based on the theory of hygrothermal transfer,the research on the causes and influencing factors of condensation on the ground floor of the brickconcrete building and the basements was carried out.The possibility of preventing condensation on the ground floor of the brick-concrete building and the basements by using thermal insulation structures and air-conditioning condensation heat was explored.This research will provide theoretical basis and technical support for the research on moisture-proof and mildew-proof technology of old brick-concrete buildings and underground spaces in Jiangnan Area.The main research conclusions are as follows:(1)Field investigations show that the serious rising damp on the ground floor of brickconcrete buildings is mainly due to the high groundwater level and the rise of capillary water.The condensation in basements mainly occurs in the summer represented by the plum rain season,and the floor is the most serious.The condensation is generally manifested in the surface of non-hygroscopic materials.(2)Field monitoring shows that the groundwater level and underground soil water potential of the residence fluctuate little throughout the year,with an average value of-0.92 m and-10.3k Pa,respectively.With obvious seasonal characteristics,the risk is highest from midJune to mid-July;the ground is most prone to condensation.(3)Combined with the results of field monitoring and numerical simulation,the causes and influencing factors of the dampness in the ground floor of the brick-concrete building were analyzed.The results show that when the groundwater level fluctuates between-1 and-2m,the waterline on the wall is more sensitive to change.When the groundwater level is lower than-2m,the rising damp in the wall is relatively slight.The ventilation and groundwater level have great influence on the condensation on the ground,but the mechanism is different.(4)The causes and influencing factors of basement condensation were analyzed,and the results showed that: air exchange has a greater impact on ground condensation,and the risk of condensation is significantly reduced when the air change rate is greater than 5.0 times/hour;groundwater level has a smaller impact on basement condensation and mainly acts on ground temperature;basement condensation has obvious geographical characteristics.(5)In the ground floor of brick-concrete buildings in the Jiangnan Area,the wall-base ventilation structure has limited moisture-proof and mildew-proof effects,only reducing the condensation risk by 23.0% and mold growth by 10.6%.(6)Based on the actual structure and monitored data,the numerical model of the renovated house was established and validated to evaluate the moisture-proof and mildew-proof effects of ground insulation(5cm thickness)and waterproof renovation.The results show that the average floor temperature in summer increased by 1.0°C,the condensation risk on the floor was reduced by 97.0%,and the mold growth risk on the walls was reduced by 27.3%.(7)Adding thermal insulation layer(≥3cm thick)to the basement floor and walls can prevent condensation(adding 3cm thick thermal insulation board can increase the floor temperature by 1.7℃ in summer).In the cooling season,inputting the hot air of the outdoor unit corresponding to the 83 W power of the air conditioner into each cubic meter of indoor space can increase the floor temperature by 3.7°C and reduce the condensation risk by 99.2%.