Factors affecting anchorage bond strength in high-performance concrete

The objective of this investigation was to observe the effect of the compressive strength of concrete, reinforcing bar size, thickness of concrete cover, and amount of web reinforcement on the anchorage bond strength and on the bond behavior of reinforced high-performance concrete. For this purpose, eccentric pullout bond tests were conducted under monotonic loading on high-performance concrete specimens. Some of the specimens were reinforced by one and some by two deformed steel bars. The results indicated that the bond strength between reinforcement and concrete increased with increasing concrete strength, cover thickness, and amount of web reinforcement, while it decreased with increasing bar size. Using the test data, the variation in the average bond strength with respect to each of the stated parameters is formulated. The trend of variation for each parameter is compared with the associated trends inherent in the development length expressions of the ACI Building Code and the Eurocode 2. An expression for the required development length, enveloping all the tested specimens, is presented.