Experimental Study On Thermal Insulation Performance Of Foamed Cement Banking (FCB) Subgrade Cushion

As a new type of lightweight thermal insulation material,foamed cement banking has many excellent properties.It is not only widely used in housing construction,but also has broad prospects in highway construction,especially in some remote cold regions in China,with poor weather conditions.The geological conditions are complex,and the construction of roads is faced with many problems,such as roadbed diseases such as frost heaving,thaw sinking and tumbling.The foamed cement banking can provide a new scheme and new ideas for highway construction in these areas.This paper studied the influence of different slag and bubble content on the physical and mechanical properties of foamed cement banking,and studied its microstructure,heat conduction.The mechanism of performance and theoretical calculations were analyzed.The structural design and construction of foamed cement banking cushion was carried out in combination with the roadbed engineering diseases coexisting in saline soil and seasonal frozen soil in the Korla region of Xinjiang.The temperature field of the roadbed was monitored and analyzed for a long time.Summarize its engineering application effects.The following main conclusions were obtained:(1)The foaming dose calculated based on the blending formula of the blending ratio is less,and the defoaming under the condition of high speed stirring should be added to the calculation amount 3 times to reach the design requirement.The slag replacement cement content below 60% will increase the strength of foamed cement banking,while the slag content will have little effect on the density,and the water absorption rate will decrease at a certain amount.The increase in the amount of air bubbles will reduce the strength and density,and When the amount of bubbles is less than 300L/m3,the water absorption rate decreases,and when the amount of bubbles exceeds 300L/m3,the water absorption increases.(2)The corrosion resistance of foamed cement banking with slag is improved,and the corrosion resistance is best when the slag content is 10%,but the strength of the foamed cement banking after the immersion in the etching solution is higher than that of the pure soil after fluctuation.Much higher.When the slag-replaced cement content is 50% and the bubble content is 500L/m3,the pore structure is relatively complete,small and uniform,there is basically no through-hole,and the foamed cement banking structure is relatively dense.(3)The heat transfer of foamed cement banking is mainly conducted in the form of heat conduction.The increase of slag content will slightly increase the thermal conductivity,and its effect is less,less than 0.1W/(m·K).The bubble content has a significant effect on the thermal conductivity of foamed cement banking,and the volume of bubbles The thermal conductivity decreases from about 200L/m3 to 500L/m3,which is about 47%,and the relationship between the two is close to a positive proportional relationship.(4)Considering synthetically,when the slag replaces the cement content 50% and the bubble content is 500L/m3,the strength is about 2.4MPa,the thermal conductivity is about 0.48W/(m·K),and other properties are relatively good..It can be used as the mix ratio in the design of the roadbed cushion.(5)When constructing the subgrade cushion under the design mix ratio,it should be set at 50 cm below the ground,and the thickness of the cushion layer can be designed as 1/3 of the subgrade height;The temperature field of foamed cement banking cushion subgrade decreases as the depth increases,the ground under the foamed cement banking cushion is more thermally stable than the foundation under ordinary fillers,which indicates that the foamed cement banking cushion plays a good role in protecting the thermal stability of the ground temperature field.(6)In the long-distance pumping at the project site,the pipeline friction caused a large amount of defoaming,the pumping distance was from 0 to 500 m,and the density,strength and thermal conductivity of foamed cement banking increased by nearly 8%,33% and 11% respectively.