Comparison of the effect of different additives on acoustic emission parameters obtained during three-point bending tests of alkali-activated slag composites

摘要

The development of failure in quazi-brittle materials is associated with the formation of micro-cracks, which is followed by the release of energy in the form of elastic ultrasonic waves. The acoustic emission method is an effective non-destructive method for the detection and determination of different damage mechanisms not only in composite materials. This experimental work presents results from the acoustic emission measurements obtained during three-point bending tests without the central notch on alkali-activated materials with various additives. The acoustic emission activity was monitored using piezoelectric sensors, and the way of damage based on parameters of acoustic emission signals was investigated. The preliminary results showed that the addition of carbon black significantly reduced the maximal stress, whereas the addition of graphite increased the brittleness of the alkali-activated material. The higher brittleness is determined by the lower number of overshoots of acoustic emission signals before the fracture of the specimens.