Electromagnetic Shielding Properties Of The Waste Tire Steel Wire Cement-based Materials

The electromagnetic shielding materials used in the buildings become a new content of modern architecture design. Cement-based electromagnetic shielding materials have some advantages such as low cost, convenient construction and large protection area, so its market prospect will be very bright in future.The effect of the waste tire steel wire as conductive agent added into the cement paste on the mechanical properties, electrical properties and electromagnetic shielding properties of materials are mainly studied in the paper. The preparation process and work properties of the materials are also researched. The electromagnetic shielding properties of materials made under the different conditions are investigated by taking the coaxial planarspectrum analyzer method, the conditions contain the volume fraction of the waste tire steel wire, curing age, curing condition, adding steel wire and graphite (superconductivity carbon black) and so on, and the conductivity of materials are tested by the four-probe method.The results show that the shielding properties and conductivity of the waste tire steel wire cement-based materials are better than those of the same volume fraction common straight steel fiber cement-based materials. Compared with the steel fiber cement-based materials, the electromagnetic shielding effectiveness of the waste tire steel wire cement-based materials are improved by 51%, which have good conducti-vity and mechanical properties. Increasing the length of the waste tire steel wire properly can improve the electromagnetic shielding properties and conductivity of the cement-based materials, but the dispersion of steel wire in the materials and materials preparation are difficult if the steel wire is too long. The matrix has certain influence on electromagnetic shielding effectiveness of the materials, and the shielding effectiveness of the tire steel wire cement-based paste sample is close to that of the mortar sample when the frequency is lower than 1400 MHz, but compared with the mortar sample the shielding effectiveness of the cement paste sample is obviously improved if the frequency is above 1400 MHz. The shielding effectiveness of the sample is proportional to its thickness. Compared with the 4 mm sample, the shielding effectiveness of the 8 mm sample is improved by 92%. The effect of curing age on electrical conductivity of the materials occur in early periods, and the resistivity of the materials are tended to be stable 21 days later. Compared with the materials added by single conducting medium, the conductivity and electromagnetic shielding properties of the materials are significantly improved when the waste tire steel wire and graphite, steel wire and superconductivity carbon black or steel wire and other medium are added together. The material added by the steel wire and carbon black reaches the maximum shielding effectiveness of 29 dB in the frequency range of 30 kHz—1500 MHz.