Research On The Reflection And Transmission Performance Of Concrete Support Materials

Concrete is widely used in protection works as one kind of support materials.Because plain concrete's shielding effectiveness to electromagnetic wave is weak,People and electronic equipments inside protection works are easy to be killed,wounded and destoryed under the attack of N-weapons or high-power microwave weapons.Reduced iron powder has good shielding effectiveness as one kind of electromagnetic medias.Compared with hydroxy iron powder,reduced iron powder is cheaper and appropriate for extension and application.Compared with conductive fibers,reduced iron powder is in powder form and can equally distributed in concrete.Steel wire gauzes have good shielding effectiveness to low frequency electromagnetic wave.Working togather with reduced iron powder,Steel wire gauzes can enchance concrete's shielding effectiveness to electromagnetic wave.In this paper,concrete's reflectivity and transmissivity was studied when reduced iron powder and steel wire gauzes were mixed in concrete.The main works include:(1)By mathematical proof,we found that when dielectic constant(magnetic permeability)'s real part is fixed,the larger is the tangent of the loss angle,the better is the wave-absorbing materials' absorbing properties.If the real part of dielectic constant is not certain,the tangent of the loss angle may not correlate positively with absorbing properties.(2)By experimental study,we found that when the mixing amount of reduced iron powder is 200kg/m3,the strength of concrete reaches the peak.The mixing amount of reduced iron powder may not correlate positively with the concrete's strength.When the mixing amount of reduced iron powder is 400kg/m3,the strength is lower than plain concrete.(3)Researched the mxing amount of reduced iron powder,concrete plates' height and base areas and steel wire guazes' effect on concrete paltes' reflectivity and transmissivity.The result shows that when the mixing amount of reduced iron powder is between 0 to 1000kg/m3,with the increase of reduced iron powder's amount,there is little effect on reflectivity.Because the sizes of concrete slabs are limitted,diffuse reflection is exsisted around slabs.Concrete slabs with larger base areas have lower reflectivity than those with smaller base areas.Thickness has little effect on the reflectivity of concrete slabs.(4)Researched plain concrete,steel wire gauzes and concrete with steel wire gauzes' refectivity and transmissivity by simulation.The result shows that the larger is the wire diameter,the higher is the reflectivity and the lower is the transmissivity.The larger is the size of mesh opening,the lower is the reflectivity ang the higher is the transmissivity.With the addition of number of plies,reflectivity gets higher and transmissivity gets lower in most frequency range.Adding steel wire gauzes to concrete,there is little effect on the average value of reflectivity,the transmissivity is lower than plain concrete.The location of steel wire gauzes in concrete will affect resonant,the average value of reflectivity and transmissivity.