Testing procedure for determining the bond-slip law of steel bars in strain hardening cementitious composites

Abstract

In order to advance the use of Strain Hardening Cementitious Composites (SHCC) in structural applications it is essential to understand the mechanics of bond of reinforcement anchored in this type of material. The strength of the cover against splitting as well as the strain development capacity of bars anchored in SHCC are studied in the present experimental study through tests conducted on specially designed tension pullout specimens. Parameter of study was the steel bar diameter and the anchorage length as well as the bar cover. The experimental results obtained from a series of 24 specimens were used to calibrate a mechanistic frictional model for bond along reinforcement anchorages embedded in SHCC. It was shown that the sustained tensile resistance of the SHCC up to large levels of tensile strain was engaged confining the bar-cover interface, thereby preventing through-splitting of the cover as would normally occur in plain concrete matrices. This enabled the contribution of a frictional component to the anchorage strain development capacity that is directly traceable to the deformation capacity of the SHCC matrix. This modelling approach was motivated by the experimental evidence where splitting failures may be mitigated even with short anchorage lengths and relatively small covers (cover thickness = bar diameter) up to large levels of pullout slip of reinforcement.