Electric and acoustic activity in notched fiber-reinforced concrete beams under three-point bending

Abstract

An experimental study is presented, aiming to comparatively consider the electric and acoustic activity in fiber-reinforced concrete beams subjected to three-point bending. The study is part of an ongoing project attempting to detect phenomena considered as warning signals of upcoming catastrophic fracture, in case brittle materials are loaded mechanically at levels approaching the critical ones. A mature, well established monitoring tool (Acoustic Emissions) is used, in conjunction with a relatively new sensing technique, which is based on the detection of very weak electric currents (known as Pressure Stimulated Currents) produced during the various damage processes which precede (and lead to) the macroscopic fracture of brittle materials. In this direction, series of three-point bending tests with notched beam-shaped specimens made of concrete (either reinforced with metallic or plastic fibers or without any reinforcing agents) were implemented. It is concluded that, independently of the nature of the reinforcing fibers, both monitoring techniques employed in the experimental protocols (namely, the Acoustic Emissions and the Pressure Stimulated Currents) follow pretty faithfully the respective time evolution of the mechanical quantities and, what is more important, they provide well distinguishable features that can be considered as pre-failure indicators.