Research On Cement-based Multi-functional Composite With Electromagnetic Protection And Microwave Absorbing

Cement-based composites with electromagnetic protection and microwave absorbing (CEMC) are buiding functional materials which can consume electromagnetic wave as energy of other form.lt plays important roles in civilian and military use which are protection of buildings, secrecy maintaining of electromagnetic information and stealth of surface structures. Pre-existing CEMC have many designing problems such as structure, durability and function. They include narrow frequency range, low absorbing efficiency, poor stability, poor suitability to invironment, heavy weight and high cost which seriously limited its application especially for complex geography and climatope conditions.In connection with those problems,new designing concepts have been raised.Through systemic investigation on composition, structure and performances of CEMC and based on spheroidal resonant cavity theory, methods of designing wave absorbing materials hve been studied and explored whose functions are electromagnetic wave absorption, scatterance and spheroidal energy reduction. Relative disciplines of composition, structure and performances were mastered, high-performance cement-based materials were designed and produced that were wave absorption, splitting resistance, heat preservation, durability and environmental protection. Significant basement and theoretical guidance were provided for designing, production and application of the materials.In this article, the main tasks and achievements are as below:Using spheroidal resonant cavity and spheroidal powder ray leigh scattering theory, structural unites with the functions of absorbing, scattering and wearing have been designed and produced which were core-stone and wave-absorbing spheroidal resonant equipments. Furthermore, the ideal structural model CEMC of was proposed. Lots of wave-absorbing spheroidal resonant equipments that functioned as wave-permeating aggregates were evenly distributed in cement-based materials whose performances were improved by assistant cementitious materials, polymer and fiber. Then, the transporting tunnels for wave in materials have been improved, surface reflectance was reduced, resonance loss of wave in materials was increased, wave-absorbing performances of CEMC were greatly enhanced, physical performances of strength, toughness and durability were improved. So, theoretical guidance was offered to production of CEMC.The constitution of microwave absorbing resonator has been fixed. The core of it is ultralight multiaperture wave-permeating aggregate. Through special technique, microwave absorbing resonator can be obtained. According to electromagnetics theories, special model that is microwave absorbing resonator scattering with radius of d has been established. Meanwhile, mathematical formula of microwave absorbing resonator'scattering, absorption and resonant loss has been exactly deduced which offered theoretical guidance to realization efficient absorption and bands'broadening of CEMC electromagnetic wave.Furthermore, through investigation on microwave absorbing resonator materials'structure and performance, the main paramaters of its charge mixture and producing technique have been fixed.Its grain size was 0.6-4.75mm, stacking density was 490 kg·m-3, crushing strength is 2.2 MPa and water absorption during the first 30 minutes was 12.3%. The preparation technology of microwave absorbing resonator with core-stone structure has been mastered. Through mathematical calculations, formula concerning its controlling of thickness was established. The possibilities of designing and controlling were realized to supply designing of CEMC with important functional aggregate.Performances of high-performance CEMC Materials and influence of microwave absorbing resonator on its characters have been systematically studied.Results showed that the cooperated roles of assitant cementitious materials, polymer and fibre on base materials can greatly improve its physical strength and toughness; accompanied with changes of electromagnetic waves of frequency, the influence of base thickness, water to cement ratio, hydration time, absorber and characteristic parameters of particles on wave-absorbing performance of CEMC-based materials changed a lot; through controlling materials'thickness, water to cement ratio and microwave absorbing resonator parameters and connecting technique of adding assitant cementitious materials, polymer and fiber, high-performance and high loss-absorbing CEMC with good physical and mechanical properties have been produced; the main technique parameters of composition of CEMC have been fixed and methods of mix design has been raised.Density and strength were made clear, density and strength formation models of two medium that are high-performance modified base and microwave absorbing resonator have been estabished which showed mechanism of CEMC density and strength formation. Furthermore, connecting durability and function experiments, three-dimensional crossing structure formed by modified polymer and fiber and inner maintenance of microwave absorbing resonator were the essential causes for improvement of durability and anti-crack performance; high rate of blind hole of CEMC ensured low water-absorbing rate and high air-hole rate. It is the main cause for increasing heat preservation performance; what are above functioned together to realize the high performance and multi-fuction.