Assessment of bond-slip behavior of hybrid fiber reinforced engineered cementitious composites (ECC) and deformed rebar via AE monitoring

Abstract

This paper investigates the efficiency of acoustic emission (AE) technique for monitoring and assessing the bond-slip behavior and damage characteristics of deformed rebar embedded in hybrid fiber reinforced engineered cementitious composites (ECC). A series of pull-out tests were conducted on 48 prism samples with variable rebar diameters (14 mm, 20 mm, and 25 mm), embedded length (3d, 4d and 5d), and cover thickness (2.5d, 4d, 5d and 6d). Two AE sensors, attached on ECC surface and rebar surface respectively, were utilized to critically monitor the AE activity emitted from the ECC matrix and the interface between ECC and rebar throughout the tests. The bond-slip behavior of ECC-rebar presented a more ductile performance than conventional concrete (CC)-rebar because of fiber bridging effect. The damage classification and damage characteristics were clarified by measuring AE activity. The debonding process of ECC-rebar could be divided into four main stages based on the slope changes of cumulative AE hits, and further refined into several substages based on the sudden rises of AE energy. Besides AE cumulative parameters, the Ib-values calculated from AE signals of ECC matrix and ECC-rebar interface were analyzed and compared, which behaved more effectively in identifying the development of cracks and distinguishing the maximum bond stress. Also, the AE intensity analysis was implemented to identify the micro-mechanism transformation during different bonding stages. Moreover, the AE intensity results of CC-rebar obtained from previous research and ECC-rebar in this study were compared.