Performance Analysis And Replication Of Rammed Earth And Protection Of Stone Materials

With the development of economy and the improvement of people’s awareness of environmental protection,low-carbon and energy-saving rammed earth buildings have been paid more and more attention.Rammed earth building mainly consists of rammed earth wall and stone foundation.It is widely used in rural areas because of its convenient material,heat preservation and energy saving.Therefore,the performance of rammed earth from the ruins of Hangu Pass are measured and analyzed comprehensively.At the same time,the traditional technology is used to replicate the rammed earth.Finally,new nano super-hydrop Hobic protective coatings is proposed to be used in surface protection of common stone materials,and its effects on air permeability and thermal conductivity are analyzed.They have positive reference and Enlightenment for the technology improvement and energy-saving design of modern rammed earth building.The main conclusions are as follows:The samples of rammed earth in Western Han Dynasty are tested and analyzed comprehensively.The results show that the present rammed earth is made of quartz,feldspar,muscovite and calcite,without adding lime and materials containing starch.The average dry density and porosity of rammed earth are 2.02g/cm~3 and 26.2%respectively.The average liquid limit and plastic index of rammed earth are 36.1%and 16.9%respectively,which belong to low liquid limit clay.The proportion of clay,silt,sand and shale grains is about 1:3.6:0.2:0.07.Compared with the local primary loess,the grain composition of rammed earth is very different,and a careful artificial selection is made during the construction.The average peak stress and modulus of elasticity of the present rammed earth reach 3.31 MPa and 227.8 MPa,respectively,indicating better compression performance and engineering stability.High liquid limit silt(R)and low liquid limit clay(M)are selected to replicate the compacted soil,and the characteristics of duplicated rammed earth are studied.The results show that the average dry densities of rammed earth R and M are 1.84g/cm~3 and 1.89g/cm~3respectively,and the average disintegration speed of them are 15.3 g/min and 11 g/min respectively.Both of them have good water stability.The average peak stress of rammed earth R is 3.11 MPa,the average modulus of elasticity is 206.8 MPa,and the peak stress and modulus of elasticity of rammed earth M are 3.18 MPa and 210.9 MPa,respectively.Comparing with rammed earth M,the mechanical properties of rammed earth M are better.By analyzing the particle composition and mineral composition of duplicated rammed earth and rammed earth from Hangu Pass,low liquid limit soil is more suitable for ramming,and mineral composition has greater influence on the engineering properties of rammed earth than particle size content.The rock samples treated with nano-superhydrop Hobic protective coatings(NSHPCs)are tested and analyzed.Results show that the surfaces of rock samples with NSHPCs have an average contact angle of 164°as well as a good acid resistance performance.After coating treatment,the thermal conductivity of sandstone is greatly affected,while that of marble and granite is slightly affected.The effect of coating on gas permeability of stone samples shows attenuation effect in varying degrees.The attenuation order is as follows:granite<marble<sandstone.The order of weatherability of rock samples after coating treatment is as follows:granite>marble>sandstone.