Experimental study of the bonding behavior between coarse aggregate ultra-high performance concrete and steel rebar

Abstract

The shrinkage and cost of ultra-high performance concrete (UHPC) could be effectively controlled by adding coarse aggregate (CA). The bond performance between UHPC and steel rebar was critical to UHPC structures. This paper conducted a pull-out test to investigate the effects of CA strength, size, content (volume fraction), fiber content, cover thickness, and bond length on the bonding behavior of UHPC and steel rebar. The results showed that CA significantly affected the bond strength because it could delay and prevent the expansion of microcracks. Improving the CA strength (106.3 MPa-202.4 MPa) could substantially increase the bond strength. As the CA content increased from 0 to 600 kg/m3, the bond strength increased by 14.49%. The CA size of 5–8 mm improved bond strength better than other sizes. Further, a formula for calculating bond strength and the bond-slip constitutive model was proposed, which agreed with the experimental results.