Effect of interfacial treatments on wet joints performance in steel-UHTCC composite bridge decks

Abstract

Using Ultra-High Toughness Cementitious Composite (UHTCC) to the wet joints of composite bridge decks (CBDs) is a new solution to the cracking issue under hogging moments. Interfacial treatments and reinforcement details play a critical role in enhancing the crack resistance performance of wet joints in CBDs, while the quantitative impact of these factors on wet joints utilizing UHTCC materials remains uncertain. In this study, three different wet joint interfacial treatments (surface roughening, smearing epoxy adhesive, applying both) were proposed and the crack resistance performance were investigated through hogging moment tests on CBDs. During the tests, failure modes, flexural capacity, deformation behavior, force mechanism, crack propagation process and strain development of the CBD specimens with different wet joint details were discussed. To investigate the crack resistance performance of different wet joint interfaces, theoretical model for calculating nominal UHTCC tensile stress considering steel/UHTCC interfacial slip was constructed. Subsequently, the development curves of maximum crack width with nominal UHTCC tensile stress at wet joint interfaces were plotted. Test results indicated that interfacial treatment methods exert a distinct influence on the crack resistance performance of wet joints in steel-UHTCC CBDs. For reinforcement-enhanced wet joints, wet joint interfaces can be treated only with surface roughening, and the crack resistance performance was comparable to that treated with the combination of surface roughening and epoxy adhesive. Wet joint interfaces treated with the combination of surface roughening and epoxy adhesive exhibit a smaller value and growth rate of maximum crack width compared to those treated only with epoxy adhesive, and the cracking stresses σ0.05, σ0.1, and σ0.2 at wet joint interfaces were improved by 41.1%, 35.7%, and 232.6%, respectively. The wet joint interfaces in conventional wet joints are recommended to be treated with a combination of surface roughening and epoxy adhesive, resulting in smaller growth rates of interfacial maximum crack width. Moreover, the cracking stresses σ0.1 and σ0.2 at these interfaces were respectively improved by 577.4% and 400% compared to those treated only with surface roughening.