As a matter of fact, AE energy is correlated to fracture energy. However, we have tested several beams including concrete, geopolymer and composite geopolymer concrete. The load-deflection curves is attached herewith. Concrete had a lower toughness compared to the other specimens while it had greater AE total energy. The composite beam (concrete and geoplymer in two layers) showed higher AE energy than pure geopolymer beam. It seems to be somewhat strange why concrete beams with lower toughness had higher value of AE energy and respectively more occurrence of number of AE events. Thank you for your comments.
Dear Arash,
This is an interesting issue. There is of course a relation between AE and fracture toughness but this is not the same for different materials. AE is a small part of the total emitted energy. I have seen the same in a previous study with plain concrete and steel fiber reinf. concrete. Although the toughness of plain concrete was nearly zero compared to the SFRC, it had much higher total energy (accumulated energy for the whole loading up to fracture). Also for the different SFRC types there was still a negative correlation between AE energy and toughness. Please check the attached
(Construction and Building Materials 48 (2013) 1255–1260, Monitoring of the mechanical behavior of concrete with chemically treated steel fibers by acoustic emission)
Dear Prof Aggelis
Thank you for your helpful answer. In fact, in another paper of yours (entitle: Acoustic emission behavior of steel fibre reinforced concrete under bending), the toughness is correlated to AE hits. As toughness increased the AE hits linearly has increased. That test included plain concrete and SFRC and plain concrete had lower number of AE hits since it had lower toughness. In my experiment, both, AE events (Hits) and energy for RC beams were significantly higher than the geopolymer beam. Can we interpret the higher compressive strength of concrete has caused this trend. We had same average amplitude for all specimens but average signal duration and average frequency were considerably higher for concrete beams. The concrete beam was failed in shear while the others failed in flexural. They are all reinforced concrete and as can be seen in load-deflection curves (as attached) they have more and less similar peak load but different post failure deflection (Geopolymer and composite beams were considerably more ductile than concrete beams). I really appreciate your help. Thank you.
Dear Prof Aggelis
Moreover, another challenge risen from the number and space and length of cracks. The total length of crack for geopolymer beam is 120cm while for concrete beam is about 88 cm. I was wondering if the crack length and crack occurrence should affect the number of AE events or not. We expected that when we have longer total length of cracks that should be cause of higher AE events but the results were significantly in contrast. Thank you.
Yes in that paper it was the number of AE hits. In that case the specimens had different fiber volume content. Therefore, the higher the number of fibers, the higher number of pull out events. However, the total energy is higher for the plain concrete even though the total number of events is much smaller. Of course the fracture mode could also be related since the amount of fracture energy may differ. The length of crack is important but also the rate. Maybe concrete due to brittleness of concrete fewer events are needed to create the same crack length.
- Badges
- Science topic