Bond behavior of stainless steel (SS) rebar to seawater sea-sand concrete (SSC): Experiments and modeling

The stainless steel (SS) rebar is attractive for reinforcing seawater sea-sand concrete (SSC) due to its desirable corrosion resistance. This study presents a central pull-out test program involving 44 specimens to explore the bond behavior of SS rebar to SSC. Several test parameters, such as concrete type and strength, bar type, anchorage length, concrete cover, and stirrup ratio, were comprehensively discussed to investigate their effects on failure modes, bond-slip responses, and ultimate bond strength. Experimental results show that concrete cover, anchorage length, and concrete strength all play a significant role in failure modes. The bond strength of SS rebar is enhanced with the increase in compressive strength of SSC. Nevertheless, inferior bond strength is detected for SSC specimens compared to the normal concrete (NC) counterparts with the same pre-designed concrete strength regardless of bar type. The average bond strength tends to increase with a decreasing anchorage length and increasing concrete cover. In addition, the use of stirrups can also enhance the bond strength by at least 19.32 % compared to the unstrengthened specimens. By taking into account the similar confinement effect provided by the concrete cover and internal stirrups, a unified confinement coefficient is adopted in the ultimate bond strength model and the design anchorage length. Finally, the bond interface is assumed to consist of unlimited spring and friction elements, and a new bond-slip model is proposed based on stochastic damage theory. The proposed model can reasonably reveal the randomness and nonlinearity of bond-slip responses, and a good agreement is also detected by comparing the theoretical predictions with test results.