Study Of Reproduction And Modification Of Rammed Earth And Thermal Performance As Building Envelope

China is one of the famous ancient civilizations,leaving many exquisite traditional skills during the long history.For the development of modern architectural technology,it is of great significance to actively seek inspiration and explore China’s traditional construction technology.This is also promising to inherit traditional culture and enhance cultural confidence.Therefore,inspired by the rammed earth of Hangu Pass in the Western Han Dynasty,this work was carried out to reproduce the rammed earth based on the ancient Chinese construction technique using typical silt clay as main materials.Then the rammed earth was modified by adding quicklime and straw fiber,and the corresponding mechanical properties,salt corrosion resistance and thermal properties of reproduced rammed earths were tested and analyzed.Finally,the feasibility,suitability and energy-saving performance of rammed earths as parts of the envelope of modern rural residential buildings were analyzed.The main work and results are as follows:High liquid-limit soils and low liquid-limit soils from different areas were selected for the reproduction of rammed earths.The results showed that the average dry density of reproduced rammed earths with low liquid-limit was higher than the case of high liquid limit.For the silty clay with low liquid limit,the clay content had a greater influence on the quality of rammed earth,and its proper range was 20-30%.The more clay content of rammed earth,the worse the mechanical properties,and the better the water resistance.For the high liquid-limit soils,although the mechanical strength is acceptable,its water resistance performance was not as good as that of low liquid limit soils.Adding quicklime and straw fiber can improve the performance of rammed earth.Among them,adding a proper amount of quicklime can improve the water resistance and salt corrosion resistance of the replica rammed earth,and strengthen its mechanical properties to a certain extent.It was found that the compression strength and shear strength of rammed earths increased firstly and then decrease with the increase of the lime content.The optimal lime content ranged from 6 to 8%,and for the case of the clay content exceeding 30%,the modification was not recommended.Compared with the quicklime,the addition of straw fiber can improve the salt-corrosion resistance,compression strength and shear strength of rammed earths to a greater extent.The optimal fiber content ranged from1 to 1.5%.The thermal performance of rammed earths was tested and simulated.The results showed that the addition of quicklime and straw fiber can reduce the thermal conductivity of rammed earths.The typical value of the thermal conductivity of rammed earths ranged from 0.5 to 0.7 W/(m·K).Finally,the thermal performance of rammed earths as parts of the envelope of rural residential buildings was analyzed,and the analysis of energy consumption of buildings was carried out based on simulation.The results showed that the indoor thermal environment of rammed earth buildings was more stable and comfortable than that of brick-concrete buildings with the same structure,and the total load of the building was lower.The increase in the thickness of rammed earth walls and insulation layers can further reduce the cooling and heating load of buildings.In cold areas,it was recommended that the thickness of the rammed earth layer should be 600～800mm and the optimal thickness of insulation layer should be 70 mm.