Bond–slip behavior characterization between ultra-high performance glass sand concrete and high-strength HRB 600 rebar based on acoustic emission monitoring

This study investigates the bonding behavior of high-strength reinforcement of hot-rolled ribbed bar (HRB) 600 in ultra-high performance glass sand concrete (UHPGC) by pull-out and acoustic emission (AE) tests. Fifty-four specimens were designed for the pull-out tests through taking into account the feature parameters including rebar diameters (16, 18, 20, 22 mm), embedded lengths (3d, 4d, 5d, 6d) and curing time (28, 100 and 300 days). The results showed all specimens exhibited splitting pull-out failure (SP) mode. Bond strength decreased by 35% with the embedded length increasing from 3d to 6d; while it decreased by 17% as the rebar diameter increased from 16 to 22 mm. Meanwhile, a good correlation between bond–slip curve and variation of AE parameters was verified and illustrated. The bond–slip process between UHPGC and HRB 600 rebar can be categorized into five main phases based on cumulative AE hits and signal duration. Through the analysis of AE parameters including energy, rise time/peak amplitude (RA)-average frequency (AF) and b-value, it was found that different embedded lengths exhibited distinct failure modes: during the process of damage evolution, the long-embedded model plays a more prominent role in the development of shear cracks. The AE activity and loading force strongly correlate with each other, and various AE signals reflect different active fracture mechanisms.