Acoustic emission and flexural behaviour of RC beams strengthened with UHPC overlay

Reinforced concrete beams with reinforcement ratios of 0.57%, 0.89% and 1.30% are cast and after subjecting to flexural damage strengthened with ultra high performance concrete (UHPC) overlays of thickness of 10, 15 and 20 mm. The composite retrofitted beams acted monolithically under bending without debonding. The damaged beams were able to regain its origin flexural capacity with 10 mm overlay. The increase in load carrying capacity of beams with 15 mm and 20 mm overlay is 24% and 35% for beams with reinforcement ratio of 0.57%, 11.57% and 18.45% for 0.89% reinforcement ratio and 10.60% and 15.12% for beams with 1.3% reinforcement ratio. During mechanical testing, acoustic emission (AE) parameters are analyzed for five levels of damage, which are formation of hair line crack, visible crack in UHPC overlay, yielding of main bars and finally crushing of composite beams. From parametric studies between rise angle and average frequency, it is found that AE analysis can be successfully used to determine crack movement and classify damage level of retrofitted beams. (C) 2016 Elsevier Ltd. All rights reserved.