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Abstract
Acoustic emission (AE) waveform is generated by dislocation, microcracking and other
irreversible changes in a concrete material. Based on the AE technique (AET), this
paper focuses on strain rate effect on physical mechanisms of hydraulic concrete specimens
during the entire fracture process of three point bending (TPB) flexural tests at
quasi-static levels. More emphasis is placed on the influence of strain rate on AE
hit rate and AE source location around peak stress. Under low strain rates, namely
0.77×10(-7)s(-1), 1×10(-7)s(-1) to 1×10(-6)s(-1) respectively, the results show that
the tensile strength increases as the strain rate increases while the peak AE hit
rate decreases. Meanwhile, the specimen under a relatively higher strain rate shows
a relatively wider intrinsic process zone in a more diffuser manner, lots of distributed
microcracks relatively decrease stress intensity, thus delay both microcracking localization
and macrocrack propagation. These phenomena can be attributed to Stéfan effect. In
addition, further tests, namely the combination of AE monitoring and strain measuring
systems was designed to understand the correlation between AE event activity and microfracture
(i.e., microcracking and microcracking localization). The relative variation trend
of cumulative AE events accords well with that of the load-deformation curve.