Effect of Surface Roughness on the Bond Between Ultrahigh-Performance and Precast Concrete in Bridge Deck Connections

This study investigated the performance of the bond between ultrahigh-performance concrete (UHPC) and precast concrete by the use of three bond test methods: the slant shear test, the third-point flexural bond test, and the pull-off test. The influence of the degree of surface roughness—prepared by sandblasting—on the bond between UHPC and the precast concrete was also studied. The test results showed that the third-point flexural bond test was a convenient and a more realistic test of the bond. The increase in the duration of sandblasting increased the roughness of the precast concrete surface, which was quantified by the sand-spread test. A duration of sandblasting of as short as 10 s was enough to achieve an adequate bond between UHPC and precast concrete at 7 days of age after casting of the UHPC, which was indicated by a failure in the precast concrete part. The ultimate flexural load of those specimens was about the same as the ultimate flexural load of a monolithic precast concrete specimen. Specimens that did not receive any surface roughening (i.e., specimens that were not sandblasted) failed at the bond between UHPC and precast concrete, regardless of the type of precast concrete surface: a sawed surface or a molded surface. The ultimate load carried by these specimens was lower than that carried by monolithic precast concrete specimens. Moreover, the strength of the bond between UHPC and precast concrete cast on an unroughened sawed surface was higher than that between UHPC and precast concrete cast on an unroughened molded surface.