Finite Element Analysis of Steel Fiber-Reinforced Alkali-Activated Slag Concrete Beams Considering Interfacial Bond Behavior

The primary objective of this research was to systematically investigate how bond–slip behavior affects the flexural behavior of alkali-activated slag concrete (AASC) beams reinforced with steel fibers. To this end, a finite element model incorporating the steel–concrete interface bond–slip effect was formulated in Abaqus using a separated modeling approach, grounded in a thorough analysis of established bond–slip constitutive models. Numerical simulations were conducted on both reinforcing bar pull-out specimens and beam members to examine the bond–slip interaction between steel reinforcement and steel fiber-reinforced alkali-activated slag concrete (SFR-AASC), as well as its influence on the flexural behavior of the beams. The results indicate that the bond–slip interaction at the steel–concrete interface can be effectively captured using nonlinear spring elements. The proposed modeling approach is simple to implement and demonstrates stable numerical convergence. For the pull-out specimens, the numerically obtained stress contours along the loading direction, together with the corresponding load–displacement curves, show good agreement with experimental observations. Further comparisons between numerical predictions and experimental results for beam specimens reveal that the prediction errors of the fully bonded model range from 0.2% to 9.7%, whereas those of the model accounting for bond–slip effects are reduced to 0.1–4.7%. The bond–slip model provides more accurate predictions of cracking load, ultimate load, and overall load–displacement behavior, thereby verifying the validity and accuracy of the developed finite element modeling strategy.