Experimental Investigation on the Bonding Performance of Steel Bars in Desert Sand Concrete After Freeze–Thaw Cycles

Desert sand (DS) serves as a sustainable alternative to river sand in concrete production, delivering environmental and economic benefits. Furthermore, the durability of concrete structures in cold regions is severely affected by freeze-thaw (F-T) cycles. Therefore, this study employed a central pull-out test to examine the bond performance between desert sand concrete (DSC) and steel bars subjected to F-T cycles, considering the effects of the number of F-T cycles, DS replacement ratios (i.e., the replacement ratio of river sand by DS), and the type of reinforcement. The F-T cycle numbers tested were 0, 25, 50, and 75 cycles. The DS replacement ratios were varied at 0%, 20%, 40%, 60%, 80%, and 100%. The plain and threaded steel bars (PSBs and TSBs) were selected for the experiment. The results indicate a decrease in bond strength for both PSB and TSB specimens with increasing F-T cycle numbers. Regarding the DS replacement ratios, bond strength initially decreased, with an increasing replacement rate, then increased, and eventually reduced again. Notably, significantly improved bonding was observed for steel reinforcement in DSC containing 40% or 60% DS compared to plain concrete. Additionally, the bond strengths of PSB specimens were lower than those of TSB specimens under identical conditions. A calculation formula for the bond-slip characteristic was derived using statistical regression, which considered multiple factors. Eventually, a bond-slip constitutive model was developed for the interface between DSC and reinforced steel, showing a high degree of consistency with the experimental data.