Optimization of discharge condition for recycling aggregate by pulsed discharge inside of concrete

The development of a new recycling technology for waste concrete scraps becomes a big issue in Japan due to the increase of the scraps and the decrease of the natural coarse aggregates. In the present work, a new technology of concrete aggregates recycling using pulsed discharges was performed. A Marx generator was used as a pulsed power source and a point to hemisphere mesh configuration electrode was immersed in water. The pulsed voltages were applied to the concrete scraps which placed on hemisphere mesh and the discharges passes were occurred inside of concrete scraps as the result of the electrical breakdown. Immediately after the breakdown, the concrete scraps were broken by the shockwave due to the volumetric thermal expansion of the discharge pass. After the repetitive discharge treatments, the recycled coarse aggregates were evaluated. From our previous results, the quality of the recycled coarse aggregates such as the oven-dry density, the water absorption ratio, and the fineness modulus were controlled by the energy consumption of discharge treatments. In this work, the effects of the gap distance between high voltage point electrode and concrete surface was discussed. The results showed that the optimum condition was obtained in case that the high voltage point electrode always comes in contact with the target concrete.