ACOUSTIC AND ELECTROMAGNETIC EMISSION OF LIGHTWEIGHT CONCRETE WITH POLYPROPYLENE FIBERS

This paper is focused on failure monitoring in lightweight concrete (special high-performance concrete that contains porous aggregate with a low bulk density) with high-strength polypropylene fibers under mechanical loading. The aim was to determine how the cracks' generation intensity in the tested concrete samples depends on the fibers' length and quantity. Our diagnostic method is based on a measurement of the acoustic and electromagnetic emission signals, which occur when solid dielectric materials are mechanically stressed. Several groups of lightweight concrete samples with various types and concentrations of high-strength polypropylene fibers were prepared for our experiment. We made two-channel measurements of the concrete samples from each group for defined loading conditions. The first channel was electromagnetic emission (EME) and the second was acoustic emission (AE). The electromagnetic emission and acoustic emission methods are promising methods to study the generation and behavior of cracks. The main advantage of EME and AE is their ability to be detected already in the stressed stage, which prevents macroscopic deterioration in solids. From the obtained results it can be concluded that the generated cracks' intensity is significantly affected by the presence of polypropylene fibers and by their length and dosage.