Experimental investigation of the transfer properties of ribbed and round steel rebars concrete interfaces under shear loading and after unloading

The assessment of the transfer properties evolution along the steel-concrete interface (SCI) subjected to various shear loadings is vital for ensuring the durability of reinforced concrete (RC) structures. This program explores the mechanical behaviours of RC specimens under push-in tests and analyses gas transfer properties of the SCI at various shear loadings. Concrete specimens, reinforced with ribbed and round smooth steel rebars were prone to mechanical and transfer properties tests. Real time and residual gas transfer properties tests were performed during the push-in tests and after unloading, respectively. The apparent transfer properties are calculated using Darcy’s law for compressive fluids and the applicability of the Klinkenberg approach was limited to a specific set of inlet gas pressures. Analysis of the apparent transfer properties to determine a purely viscous transfer property is performed using Klinkenberg approach for different loading states. The initial transfer properties were found alike for RC specimens with ribbed or round smooth steel rebar, equal on average to 4.95 × 10 − 17 m 2 . Results for ribbed steel concrete specimens show a significant increase in transfer properties up to a factor of 11 in the pre-peak phase. The transfer property evolution is then described by a plateau in the post-peak phase. On contrary, for the round smooth steel concrete specimens, only a slight increase in the viscous transfer property, compared to RC specimens with ribbed steel, namely in the pre-peak phase, is observed. Generally, transfer properties of the SCI were not affected when subjected to shear stresses up to 2.85 MPa. Average crack openings were evaluated by applying an inverse analysis based on modified Poiseuille’s law. Results indicate that crack openings reached at maximum 45 µm for concrete with ribbed steel due to shear whereas it was around 30 µm for concrete with smooth round rebar. Finally, for all flow measurements , the transfer properties under loading and after unloading were found of the same order of magnitude. • Transfer properties at the steel rebar – concrete interface under shear loadings and after unloading are assessed. • This paper has led to original permeability measurements for various shear loadings at the steel-concrete interfaces. • Two types of steel reinforcement are studied, ribbed and smooth steel rebars . • Flow values and apparent transfer properties are analyzed to determine viscous ones. • Local crack openings are estimated by applying an inverse analysis.