Electrohydraulic shock wave generation as a mean to increase intrinsic permeability of concrete

The objective of this article is to present an experimental study of pulsed arc electrohydraulic discharges (PAED) in water. The aim is to produce dynamic shock waves in order to increase the intrinsic permeability of mortar specimens which are immersed in water. The experimental set up allows the switching of high pulsed energy up to 100kJ in order to develop high amplitude shock waves in water. A relationship between the peak pressure, the energy remaining at breakdown time and the distance from the channel discharge to the mortar specimen allows the control of the peak pressure applied to cylindrical mortar specimens. The maximum applied pressure is 250 MPa. The evolution of damage due to dynamic mechanical loads is correlated with the intrinsic permeability of the mortar. The behaviour of the intrinsic permeability versus applied dynamic pressure is studied in single shock. A threshold of pressure is highlighted. Indeed, no modification of the intrinsic permeability is measured for dynamic pressure level lower than 90 MPa. From this value, the permeability increases linearly on a log-log plot. The influence of shock number on permeability is also presented for a constant applied pressure of 90 MPa. A good correlation between qualitative results of the image analysis (tomography and micro CT) and gas permeability is observed.