Electromagnetic wave absorption characteristics and electrical resistivity of the 2-6 mm thick cement mortar board specimens containing 6-16 mass% of Bincho-charcoal powder were measured by free space method and four probe method, respectively. The 2-4 mm thick specimens containing 8-10% of Bincho-charcoal powder absorbed remarkably the electromagnetic waves with frequencies of 3-8 GHz. Especially about 2.5 mm thick specimen containing 10% of Bincho-charcoal powder absorbed remarkably the electromagnetic wave of 5.8 GHz, which is used for intelligent transportation systems (ITS). It is clarified that these specimens are dielectric absorbers with the electrical resistivities of above 108Ω · cm.
