Evaluation of damage in cellulose fiber reinforced concrete using acoustic emission.

摘要

The objectives of the research program were to evaluate the damage effect of moisture and fatigue loading regarding the performance of Cellulose Fiber Reinforced Concrete (CFRC) and to develop a reliable inspection methodology using acoustic emission (AE) to identify the failure mechanism.;ASTM third-point bending tests were conducted on CFRC beams; both monotonic and fatigue loading. The AE data were collected and compared using visual observations from a Scanning Electronic Microscope to identify the failure mechanisms at various damage levels. The failure mechanisms were determined to be matrix cracking, fiber/matrix debonding and fiber breakage. These fracture mechanisms were found to associate with low, middle and high amplitudes, respectively.;The knowledge of fracture mechanisms was then applied to identify the effect of various moisture conditions towards CFRC's properties and the material's fatigue property. ASTM three-edge-bearing tests were performed on pipe sections with AE.;Data analysis involved correlating mechanical properties and AE results. Various methods were used to interpret the AE signals. Analysis of conventional AE parameters including hits, counts, energy and signal strength show that AE can provide real-time inspection of internal damage, both minor and visible. Methods of AE amplitude distribution, AE cumulative amplitude distribution and b-value are powerful tools to discern the fracture mechanism. Duration versus amplitude, on the other hand, proved to be useful in interpreting the quality of AE data and distinguishing friction data from valid data.;In summary, the fracture mechanism, moisture effects and fatigue properties of CFRC were studied. The AE analysis methodology developed in this research program are believed to be reliable for future inspection of structures made with CFRC materials.