| In hot summer and cold winter region of China,the outdoor air is with relatively high humidity and the average monthly relative humidity?RH?is about 80%.The building envelop has always been in a humid environment for high outdoor humidity.It has great impacts on human daily life including thermal comfort,building structure safety,building energy consumption and preservation of interior items.Therefore,it is significant to control indoor RH for the industry of chemical,food,medicine and equipment maintenance.The hygroscopic material is a passive method to control indoor RH.It has attracted wide attention of researchers from all over the world,for its diverse forms,complex structure and nonlinear of the hygroscopic process.Based on the theory of capillary condensation,this paper conducts experiment on the microstructure,adsorption property,mechanical and thermal performance of raw materials.A new composite hygroscopic mortar is proposed in the paper and the results shows that it can be widly used in hot and humid region.In addition,the equation of equilibrium moisture content is established and analyzed on the basis of Kelvin theory.The main work of this paper includes the following parts:?1?Based on the performance test of traditional hygroscopic materials,some raw hygroscopic materials with combined properties of heat preservation and strength are chosen to form the new composite hygroscopic mortar,which is energy efficient and cheap.The environmental Scanning Electron Microscope?SEM?is used to observe the morphology characteristics of materials.The aperture analyzer with automatic specific surface area is used to analyze the pore structure and pore size distribution of materials.Some aggregates including wood fiber,sepiolite and expanded perlite are chosen for further ratio test analysis to make the composite hygroscopic mortar with good shape and high stir performance.The microscopic properties of the new composite hygroscopic mortar including pore structure and pore size are analyzed.The relationship between microscopic property and the adsorption performance of composite hygroscopic mortar is analyzed.?2?According to the theory of capillary condensation,the traditional Kelvin equation is modified and the equilibrium moisture content of composite hygroscopic mortar is established.The adsorption of micropores in porous materials is incorporated into the theory of effective radius of adsorption.The effective radius is calculated by the hole model instead of the traditional cylindrical model.The combination of micropores and the mesopores is put forward,namely the“V”model,which strengthern the effect of micropores in the traditional adsorption analysis.Based on the relationship between pore volume and effective radius,pressure and temperature in Kelvin equation,a prediction model between the moisture content and the ambient temperature,humidity and material structure is established with the dimensional analysis method.In addition,according to the moisture bufferring theory,the moisture bufferring simulation test is carried out in a closed box,and the results of the Moisture bufferring performance(MBVpractical)are compared with the dimensional analysis results.The relationship between the composite hygroscopic mortar and the moisture absorption performance is established for the first time,which provides the theoretical basis for the research and application of the composite hygroscopic mortar.?3?The effects of composite hygroscopic mortar on indoor thermal environment of residential buildings are analyzed.A comparison experiment is carried out between a room with traditional brick wall?cement mortar-porous brick-cement mortar?and the other room with hygroscopic brick wall?cement mortar-porous brick-composite hygroscopic mortar?in residential apartment.The impact of composite hygroscopic mortar on the temperature and RH of test room in Changsha is evaluated in January?typical wet and cold climate?and April?back to south climate?.The field tests of acoustic insulation and pollutant adsorption are conducted to provide the actual data for the practical application of composite hygroscopic mortar.The experimental results show that the composite hygroscopic mortar does not only have high hygroscopic performance,but also performances well on sound insulation and pollutant adsorption.?4?The influence of moisture content of composite hygroscopic mortar on mold risk in building envelops is studied.The evaluation model of mold growth analysis based on transient temperature and humidity is used to analyze the mold risk of the inner wall and indoor air in Changsha.Combined the analysis of experiment and simulation,it is found that the heat preservation performance in the room with composite hygroscopic mortar is better than the traditional mortar room,and the time of annual RH is higher than the critical value of mold growth,and the mold risk index is also smaller than the traditional mortar room.?5?The influence of the moisture content and the insulation layer thickness on the whole life cycle energy consumption of composite hygroscopic mortar is analyzed by Matlab software.The lowest energy consumption of the combination of traditional mortar and composite hygroscopic mortar is studied by considering the total energy consumption of building material production stage and operation stage based on the requirement of structure and application.The heat transfer energy consumption of composite hygroscopic mortar room in winter is 20-40%higher than that of traditional mortar room when ignoring the impact of moisture content on the thermal conductivity of building envelop.Considering the influence of moisture content,the thermal conductivity of composite hygroscopic mortar in winter is up to 0.25 W/?m K?,which is more than the thermal conductivity?0.12 W/?m K??and is still 1/4of the thermal conductivity?0.93 W/?m K??under the standard condition of traditional mortarr.When considering the impact of moisture content,the actual energy consumption of composite hygroscopic mortar room in winter is 10-20%higher than that traditional mortar room.Meanwhile,the heat transfer energy consumption of composite hygroscopic mortar room is still 10-20%lower than that of traditional mortar room under the standard condition.?6?Numerical simulation study of energy consumption and RH in both heating and cooling period of composite hygroscopic mortar and traditional mortar is carried out by the HAMT model of EnergyPlus software.The results show that the RH of the room with composite hygroscopic mortar can be controlled in the range of 50-70%along with small fluctuation and the annual energy consumption per unit of construction is 20%lower than that of traditional mortar in the hot summer and cold winter area.As for cold areas,the moisture absorption effect of the composite hygroscopic mortar in winter is not obvious and there is little variation of the humidity difference between day and night in summer.But the indoor RH is better than the traditional room,and the energy consumption per unit area of the whole year is 17%lower than that of traditional mortar.For the hot summer and warm winter area,the RH of the room with composite hygroscopic mortar decreases by 9.6%in the case of no heating.While in the case of summer cooling,the room with composite hygroscopic mortar has small fluctuation of RH and the RH can be controlled in the range of 55-70%,and the energy consumption per unit area of the whole year is 17.5%lower than the room withtraditional mortar.This paper proposes a systematical method of making the composite hygroscopic mortar based on selection of testing materials,analysis of pore structure,adsorption property,strength and thermal properties on selected aggregates and sample of the new composite hygroscopic mortar.The practical application performances including the mold growth risk and building energy consumption of the composite hygroscopic mortar are evaluated.This paper provides theoretical support and technical support for the production of high-performance hygroscopic materials,building materials performance evaluation,the mold risk assessment of building materials and the design of building energy efficiency.It is an effective supplement and improvement for the research methods and achievements of existing hygroscopic materials. |
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