Development of Excitation Device for Non-Destructive Inspection in Concrete Structures Using Gas Combustion

This paper is concerned with the development of a shock tube suited for nondestructive inspection in concrete structures. The developed shock tube produces shock waves by combustion of propane-air mixture gas in a long cylindrical tube at short intervals. The propane and air mixture are injected into the reaction chamber from the mixing chamber and ignited. A detonation wave goes through the expansion chamber and extends into the atmosphere. The performance of the tube was evaluated by measuring the pressure distribution on a specimen surface and experiments of defect detection for concrete specimens. A triangular wave with a pressure of 4 kPa and a duration of 0.4 ms was obtained at 500 mm distance from the shock tube. In the defect detection, we could detect a defect with a diameter of 200 mm and a depth of 50 mm clearly.