Title:
Evaluating Bond Quality at Interface between Reinforcing Bars and Concrete Using Impact-Echo Method
Author(s):
Yu-Feng Lin, Yiching Lin, and Bo-Yau Tsai
Publication:
Materials Journal
Volume:
101
Issue:
2
Appears on pages(s):
154-161
Keywords:
bar; bond strength; test.
DOI:
10.14359/13064
Date:
3/1/2004
Abstract:
This paper investigates the feasibility of using the impact-echo method for evaluating the bond quality at the interface between reinforcing bars and concrete. Five reinforced concrete beams were constructed as specimens. One specimen containing normal reinforcing bars was used as a reference beam. Two specimens containing reinforcing bars smeared with epoxy and oil, respectively, were used to study the different degrees of bond loss at the interface. In addition, two specimens containing normal reinforcing bars were vibrated severely on a self-made shaking table shortly after initial setting of concrete to simulate the bond damage in fresh reinforced concrete beams due to unexpected vibration or impact. First, the impact-echo tests were performed on the five specimens to nondestructively evaluate the bond quality at the bar-concrete interface. Subsequently, the bond strengths of all the specimens were determined by loading tests. Experimental results show that a significant difference in the impact-echo responses between the reference specimen and the specimens containing abnormal reinforcing bar-concrete interfaces. The results obtained from loading tests show a bond strength reduction of 10 and 17% for the specimens containing epoxy-coated and oil-smeared bars, respectively. The reduction in bond strength of the vibrated specimen can reach as high as 23%. It is demonstrated that the impact-echo technique is capable of qualitatively detecting damage at bar-concrete interfaces.