Preparation And Performance Investigation Of Electromagnetic Wave Absorbing Functional Aggregate Concrete

With the rapid development of science and technology, the electromagnetic radiation caused by electromagnetic radiation is listed as the fourthly environmental pollution following the atmospheric pollution, water pollution and noise pollution. Electromagnetic wave absorbing concrete is a kind of functional building materials which can consume the incident electromagnetic wave as energy of heat or other forms. It has a broad application prospect in the field of protection of electromagnetic interference, secrecy maintaining of electromagnetic information and reduce the harm of electromagnetic wave. Pre-existing absorbing concrete have many problems such as low absorbing efficiency, narrow absorbing frequency range, poor structure and function, high cost which seriously limit its large scale application for electromagnetic protection of buildings.This thesis rely on the National Natural Science Foundation projects. In the traditional absorbing concrete, the aggregate are non-absorbing, which influence the volume and distribution of functional component in the concrete. A research about the design and the preparation method of completely absorbing structure concrete include aggregate is developed. So a new way for the design and research of high performance absorbing concrete is provided.The main research works and achievements are listed as follows:According to the electromagnetic wave absorbing theory, the aggregate with electromagnetic wave absorbing function is designed and prepared, combined with the characteristics of concrete itself, the design idea that absorbing functional aggregate concrete with absorbing properties and mechanical properties is put forward. In matched layer, Perlite is added to improve matching impedance of surface material. In loss layer, absorbing functional aggregates, which evenly distributed in concrete and play a role in absorbing and bearing, and cement paste with absorbing agent constitute absorbing concrete.Absorbing functional aggregate containing TiO2 with excellent performances is prepared through pretreatment of raw material, granulation and calcinations processes, with clay used as pottery basis material and TiO2 powder used as absorbing component. The effects of absorbing agent content and calcination regime on the properties of absorbing functional aggregate are studied, the preparation technology of absorbing function aggregate is determined, the absorbing function aggregate whose absorbing performance and strength performance is in balance is prepared.Absorbing functional aggregate are used to prepare absorbing concrete, and its absorption and strength properties are tested. Results show that the type of aggregate, matched layer and the thickness of specimen have a greater impact on absorbing properties of the concrete. Concrete with absorbing functional aggregate containing 30% TiO2 has the best effect to improve the absorbing properties. In 8~15GHz frequency range, the reflectivity of electromagnetic wave is lower than-8dB when the thickness of double-layer concrete is 20 mm. when the thickness of double-layer concrete is 30 mm, concrete has a better absorbing properties and the minimum reflectivity of the specimen can reach-9.0dB at 18 GHz. The 28 d compressive strength of concrete is 35.5MPa.Combining absorbing functional aggregate containing 30% TiO2 with carbon black, ferrite and nano-TiO2 to prepare absorbing concrete, respectively. Results show that when absorbing functional aggregate is used together with different absorbing agents, the concrete has high absorbing efficiency, wide absorbing frequency range and better strength performance. Especially, when the double-layer concrete containing absorbing functional aggregate and 30% Mn-Zn ferrite has better absorbing properties. In 8~15GHz frequency range, the reflectivity of electromagnetic wave is lower than-10 dB reach to 8.7GHz and the minimum reflectivity of the specimen is-14.7dB when the thickness of double-layer concrete is 20 mm, At the time,the strength of the specimen meet the general requirements of the building on the strength of concrete.