Experimental Study On The Basic Performance And Durability Of Foamed Mixture Lightweight Soil As Core Layer

In recent years,with the national vigorous promotion of green building and energy-saving building,the development and application of new wall materials have provided unprecedented opportunities,among which light steel keel composite self-insulating wall is the most widely used.And the foamed mixture lightweight soil has attracted much attention in the engineering and highway fields because of its good heat and sound insulation,high fluidity and self-supporting after curing.Based on the material characteristics of foamed mixture lightweight soil,combining it with light steel keel composite wall and using foamed mixture lightweight soil as light insulation material to fill inside the composite wall will not only have material cost saving,easy construction and good heat insulation and sound insulation effect,but also will be important for the development of foamed mixture lightweight soil to be applied to other directions of civil engineering.In order to develop the foamed mixture lightweight soil that can be used as the core layer of light steel keel composite wall,this paper prepares foamed mixture lightweight soil with different composition ratios,and explores the influence of raw material soil,fly ash and bubble content on the properties of foamed mixture lightweight soil and the degree of change by studying its basic physical properties,mechanical properties and durability change law.The main research contents and results obtained in this paper are as follows:(1)The basic physical and mechanical properties of foamed mixture lightweight soils with different composition ratios were tested by wet capacity test,fluidity test,compressive strength test and dry density test,and the variation of the effects of different amounts of raw materials on the properties of foamed mixture lightweight soils were analyzed.The test results show that the amount of raw materials,the ratio of fly ash to raw materials and the amount of air bubbles have different effects on the properties of foamed mixture lightweight soil.(2)Based on the thermal conductivity test and the theory of calculating the thermal performance of light steel keel composite walls,the heat transfer coefficients of different wall thicknesses are calculated and the applicable building types and regions of composite walls of different thicknesses from 100 mm to 370 mm are explored in comparison with the heat transfer coefficient limits for different building categories and different climatic regions in the current energy conservation design codes in China.(3)The seepage resistance of foamed mixture lightweight soils with different composition ratios was investigated by water table drop height test and water absorption rate test.By analyzing the formulae of mass water absorption rate and volume water absorption rate,it was concluded that the volume water absorption rate better reflects the seepage resistance performance of the material than the mass water absorption rate.The test results were also compared with most of the existing specifications for lightweight wall materials in China.The test results show that the test results of water level drop height of each specimen and water absorption rate test results are about the same.The water absorption rate of foamed mixture lightweight soil is influenced by the amount of raw material soil,and the water absorption rate of foamed mixture lightweight soil tends to decrease with the increase of fly ash mixture ratio.Except for individual ratios,the water absorption rate of foamed mixture lightweight soil in all ratios can meet the requirements of light weight wall material specification.(4)The weight and compressive strength of foamed mixture lightweight soils with different composition ratios after 15 complete freeze-thaw cycles were studied through the freezing performance test,and the weight loss rate and compressive strength loss rate were calculated.The test results show that the freeze-thaw resistance of foamed mixture lightweight soil decreases with the increase of raw material soil mixture,and fly ash can significantly improve the freeze-thaw resistance of foamed mixture lightweight soil.At the same time,the frost resistance of foamed mixture lightweight soil is obviously affected by the amount of air bubbles,and there exists an optimal value of air bubbles.(5)The carbonation coefficients of foamed mixture lightweight soils mixed with bubbles of different composition ratios and their carbonation depths with time were studied by artificial rapid carbonation tests.And based on the relationship between natural conditions and the carbonation rate coefficient in the rapid carbonation test,the carbonation depth of foamed mixture lightweight soil under natural conditions was deduced from the carbonation results obtained from the carbonation test,and then the carbonation life of foamed mixture lightweight soil and composite wall was predicted.The test results show that the amount of raw material soil,the ratio of fly ash to raw material soil and the bubble content have obvious effects on the carbonization performance of the foamed mixture lightweight soil,and the carbonization depth shows a linear increasing relationship with the longer carbonization age.By optimizing the design ratio,coating the outer surface of the composite wall with air-tight finishing materials and improving the maintenance environment,the service life of the foamed mixture lightweight soil and its composite wall can meet the design requirements.The research results of this paper provide some experimental basis and reference for the effective use of foamed mixture lightweight soil in light steel keel composite walls.