Experimental Study On The Preparation Of Carbon Dioxide Foam Concrete For Mining And The Thermal Insulation Of Roadway Surrounding Rock

The mining of deep coal resources faces the problem of high temperature heat damage,and CO₂ emissions from coal combustion in thermal power plants cause the greenhouse effect.In this thesis,the physical and mechanical properties of different foamed gas foam concrete and the influence of foaming factors on carbon dioxide foam concrete are investigated from the perspective of preparing high ground temperature roadway insulation materials,and the superiority of the performance of carbon dioxide foam concrete is confirmed by using a combination of theoretical analysis,laboratory experiments and numerical simulations.At the same time,the simulation study of thermal insulation of deep high ground temperature surrounding rock was carried out based on the theory of"heat barrier ring".The main research findings are as follows.（1）Foam concrete foaming tests with different gas media were carried out to reveal the influence law of foaming gas on the physical and mechanical properties of foam concrete.It was found that the water absorption,softening coefficient,compressive strength and splitting tensile strength of nitrogen and air foam concrete at the same density level were basically the same,while the relevant properties of carbon dioxide foam concrete were better.For thermal insulation performance,the thermal conductivity of carbon dioxide foam concrete at the same density is the lowest,0.115794～0.196320 W/（m·K）;compared with carbon dioxide foam concrete,the thermal conductivity of nitrogen foam concrete is 21.9%～32.9%higher and air foam concrete is 25.8%～36.6%higher.The analysis of pore structure and hydration product composition shows that carbon dioxide foam concrete has fewer tandem and malformed pores,finer pore structure,and more calcium carbonate in hydration products.（2）The proportioning test of carbon dioxide foam concrete was carried out to obtain the material proportioning suitable for heat insulation of high ground temperature roadway surrounding rock.The effects of foam dosing,water-cement ratio,river sand dosing and polypropylene fiber dosing on the physical and mechanical properties of the material were analyzed.The dry densities of the prepared insulation materials ranged from 973.1 to 1364.0 kg/m³,water absorption rates from 7.5 to 16.4%,softening coefficients from 0.74 to 0.91,compressive strengths from 6.47 to 9.29 MPa,splitting tensile strengths from 0.87 to 1.32 MPa,and thermal conductivity from0.153092 to 0.238466 W/（m·K）.It was found that the foam admixture had the greatest influence on the physical and mechanical properties of the material.Based on the comprehensive consideration of the material cost and the properties,the material ratio applicable to the insulation of the surrounding rock in the high ground temperature roadway was obtained by the analysis of the work efficiency coefficient method.（3）Numerical simulation of the thermal insulation effect of the roadway surrounding rock with carbon dioxide foam concrete.The results show that the size of heat-regulating circle is mainly influenced by the ventilation time,and the radius of heat-regulating circle is less influenced by the entrance air temperature,entrance air speed and thickness of heat-regulating layer,and the increase of heat-regulating layer can effectively reduce the temperature of the roadway.At the same time,appropriately lowering the inlet air temperature and increasing the inlet air speed can effectively improve the heat insulation effect,and the longer the heat insulation tunnel is,the more significant the heat insulation effect is.When the thickness of thermal insulation layer is thicker,the temperature difference between inside and outside of thermal insulation layer is bigger,the effect of heat transfer barrier is higher,and the temperature reduction of wind flow in the tunnel is also bigger,but with the increase of the thickness of thermal insulation layer,the increase of heat transfer barrier effect is weakened continuously.The paper has 69 figures,20 tables and 86 references.