Characterizing and modelling the bond-slip behaviour of steel bars in 3D printed engineered cementitious composites

Embedding rebars in 3D printed engineered cementitious composites (3DP-ECC) promises to improve the structural toughness and loading capacity, while a robust bond between them is critical for digital construction with reinforcements. This paper presents a series of pull-out tests on the bond behaviour between rebars and 3DP-ECC to investigate the effects of variable rebar arrangement direction, diameter and anchorage length. Results indicate that the failure patterns mainly showed pull-out failure due to the lower probability of interlayer splitting failure caused by the improved interlayer fracture resistance capacity in 3DP-ECC compared to ordinary 3D printed concrete. The rebar direction most significantly affected the slip stage in the bond stress-slip curve, whereas the rebar diameter and anchorage length had almost no effect on the curves. The bond strength of the printed specimens in the parallel direction enhanced by 2.9%–10.5 % than that in the vertical direction, while it declined by 27.4%–27.6 % as the rebar diameter increased from 8 to 14 mm. Moreover, a bond-slip constitutive model for steel bar reinforced 3DP-ECC was established to predict the bond behaviour as a function of the rebar location and physical characteristics. The exploration of the bond behaviour and constitutive relationships of steel bar reinforced 3DP-ECC provides a basis for integrated performance evaluation in practical application.