Comparison of Bond Strength of Steel Bars in Normal- and High-Strength Concrete

A comparative analytical study of the average bond strength at failure of reinforcing bars embedded in unconfined normal-strength concrete (NSC) and high-strength concrete (HSC) is undertaken. The analysis makes use of an experimentally derived local bond stress-slip model and considers the progressive bond deterioration along the development/splice length with the increase in bar force. Results of the average bond strength (or development/splice strength) predicted by the analysis showed excellent agreement with experimental data for both NSC and HSC. The analysis predicted a highly nonuniform bond stress distribution at bond failure along the development/splice length, particularly for HSC. Below a certain limit of the development/splice length (about 15–20db), the average bond strength at failure, normalized to fcʹ1/2is larger for HSC as compared to NSC. However, as the development length increases beyond this limit, the normalized bond strength of HSC becomes progressively smaller than that of NSC. While normalization of the average bond strength to fc1/4 may underestimate the effect of fcʹon the bond strength for short development/splice lengths, it leads to almost identical normalized bond strength results for NSC and HSC within the practical range of development/splice lengths (in excess of 17–20db).