Study On Thermal Properties Of Steel Fiber Graphite Electrothermal Concrete

Electrothermal concrete is prepared by adding conductive materials such as steel fiber and graphite into concrete.It not only meets mechanical properties,but also has electrothermal properties.In view of the thermal properties of the steel fiber graphite electric heating concrete,the theoretical analysis,the experimental exploration,the numerical simulation and the application and popularization series are carried out in order to apply it to the indoor heating and the snow melting and deicing of the pavement,to further promote the multi-function and intelligentization of the concrete such as the traditional building materials and comply with the science and technology.The research content and the main achievements are as follows:(1)Thermal parameters of steel fiber graphite electrothermal concrete.It is found that the porosity ratio of steel fiber reinforced graphite electrothermal concrete reaches 11.7%.Therefore,the steel fiber reinforced graphite electrothermal concrete should be regarded as the four phase composite material of steel fiber,graphite,concrete and air for thermal parameter analysis.The density calculation method and the series thermal resistance network model of composite materials can be used to calculate the density and thermal conductivity of steel fiber graphite electrothermal concrete.In the calculation process,the influence of void ratio should be taken into account,and air as a component is involved in the calculation.(2)Influence of conductive materials on thermal parameters of steel fiber graphite electrothermal concrete.It is found that the density is inversely proportional to the graphite content and the length of steel fiber,and is directly proportional to the amount of steel fiber.The thermal conductivity is directly proportional to the amount of graphite and steel fiber.Among them,the relationship between thermal conductivity and graphite content is more significant.(3)Under different space,the heating test of electric heating concrete plate is carried out with different voltage.It is found that the heat loss of the closed space is faster because of the less heat loss,and the phenomenon is more obvious with the increase of voltage.(4)First,the correctness of the ANSYS finite element model is verified by the experimental results of indoor heating.Then the heating effect of electrothermal concrete under different initial conditions,different mix ratio and different wind speed is analyzed by finite element simulation,and the heat loss of electrothermal concrete is quantified.The results show that when the other conditions are the same,the higher the initial temperature,the more obvious the heating effect of the electrothermal concrete.At the same power,the elevated temperature of electrothermal concrete slab at 3-10 is 3 times higher than that at elevated temperature.With the increase of the temperature of the electrothermal concrete slab,the heat loss in the process of absorption and transmission increases gradually,but the utilization rate of the effective heat increases overall.(5)ANSYS finite element analysis shows that under the same initial conditions,the greater the input power,the faster the temperature rise of the electrothermal concrete.The increase of the temperature of the electrothermal concrete plate under the input power of 2000 W/m2 is 2 times as high as that of the 1000 W/m2,while the heat and the loss of heat absorbed by the electrothermal concrete plate increase,but the higher input power will have a higher efficiency of effective heat utilization.(6)Under the same initial conditions,with the strengthening of the wind,the temperature of the surface of the electrothermal concrete slab is generally decreasing,and most of the heat loss is caused by the convection of the electrothermal concrete plate and the air.(7)The heating,melting and deicing tests of the actual projects were carried out,and the thermal properties of electrothermal concrete boards under different environments were analyzed.After 2 hours of electricity,the surface temperature of the electrothermal concrete slab rises from 1 to 4.5,and the temperature of the cement mortar layer rises from 0.5 to 2.5.The temperature of the pavement and the outdoor environment temperature have been decreasing,but it still reaches the temperature difference at the average of 3 degrees C.The heating effect of the steel fiber graphite electrothermal concrete pavement is obvious,which satisfies the outdoor snow melting.