AERATED CONCRETE MICROWAVE REFLECTION AND TRANSMISSION PROPERTIES IN A WET ENVIRONMENT
Keywords:electromagnetic fields, microwaves, reflection, transmission, aerated concrete, water, wetting
AbstractExcess water content within the building material could greatly alter the interaction of the microwave with the material. In this study aerated concrete (AEROC) block walls (60x60cm) were investigated for their microwave (2.4 GHz) properties under wetting conditions. The spray wetting of the wall was conducted to simulate the environmental processes such as raining or water damage. 50ml/m² water dosage was applied on the surface of the concrete 21 times in 1 min intervals. The results show a noticeable decrease in microwave penetration power through the material after the sample gets enriched with water. As the water content on the surface of the material rises, so does the transmission loss. During the different water content of the aerated concrete, the reflection loss varied from -15.04 dB (dry wall) to -5.03 dB (wet wall’s surface). The transmission loss continues to rise during the entire length of the experiment, from -4.5 dB as a dry sample to -8.3 dB after 441 ml (1035 ml/m² during 23 min) of sprayed water. The variation of reflected microwave power was approximately ten times, which is quite a significant indicator of alteration of microwave propagation. The results demonstrate wetting process as an considerable factor in assessing microwave propagation in near the sources, such as mobile phone base station antennas, industrial microwave heaters and ovens etc.
Sutton, W.H., Microwave processing of ceramic materials. Am. Ceram. Soc. Bull. 1989, 68, 376–386.
Thostenson, E.T., Chou, T.-W., Microwave processing: fundamentals and applications. Compos. Part A Appl. Sci. Manuf. 1999, 30, 1055–1071.
Clark, D.E., Folz, D.C., West, J.K., Processing materials with microwave energy. Mater. Sci. Eng. A 2000, 287, 153–158.
Das, S., Mukhopadhyay, A., Datta, S., Basu, D., Prospects of microwave processing: An overview. Bull. Mater. Sci. 2009, 32, 1–13.
Sbartai ZM, Laurens S, Balayssac JP, Ballivy G, Arliguie G. Effect of concrete moisture on radar signal amplitude. ACI materials journal. 2006 Nov 1;103(6):419
Laurens, S.; Balayssac, J.-P.; Rhazi, J.; and Arliguie, G., “Influence of Concrete Moisture Upon Radar Waveform,” Materials and Structures, V. 35, No. 248, May 2002, pp. 198-203.
Bungey, J. H., “Sub-Surface Radar Testing of Concrete: A Review,”Construction and Building Materials, V. 18, 2004, pp. 1-8.
Halabe, U. B.; Bhandarkar, V.; Chen , H.-L.; and Sami, Z., “Detection of Sub-Surface Anomalies in Concrete Br idge Decks Using Ground Penetrating Radar,” ACI Materials Journal, V. 94, No. 5, Sept.-Oct. 1997, pp. 396-408.
Soutsos, M. N.; Bungey, J. H.; Millard, S. G.; Shaw, M. R.; and Patterson, A., “Dielectric Properties of Concrete and their Influence on Radar Testing,” NDT&E International, V. 34, 2001, pp. 419-425.
Rhim, H. C., and Büyüköztürk, O., “Electromagnetic Properties of Concrete at Microwave Frequency Range,” ACI Materials Journal, V. 95, No. 3, May-June 1998, pp. 262-271.
Robert, A., “Dielectric Permitti vity of Concrete Between 50 MHZand 1 GHz and GPR Measurements for Building Materials Evaluation,” Journal of Applied Geophysics, V. 40, 1998, pp. 89-94