Bond characteristics of carbon and stainless steel flat rebars with an alternate rib pattern

The good performance of reinforced concrete depends on the appropriate transfer of forces between reinforcing rebars and concrete, which relies on the bond interaction between the two materials. At an uncracked section, both materials work together by means of the bond forces; however, if the tensile strength of the concrete is reached at a certain part of the structure, a crack will appear and the steel will be the only active element at the cracked section. At increasing loads, the crack will continue opening and large crack openings may lead to a failure of the rebar and to the collapse of the whole structure. A new idea to positively influence the cracking behaviour has emerged, which is based on the combination of smooth and rib zones within the same reinforcing rebar. Furthermore, use of stainless steel flat reinforcement has been considered as an option to optimize the reinforcing of shallow slabs. This paper presents bond tests performed on carbon and stainless steel flat reinforcements embedded in concrete and with different alternate rib configurations. Test results are presented in terms of bond strength and force transfer stiffness, as well as in terms of bond stress–slip relationship. Results show no differences between the bond capacity of carbon and stainless steel rebars if other parameters are kept constant. The use of an alternate surface configuration combining smooth and ribbed zones within the bond length, does affect the bond capacity of the rebar, and the position of the smooth zone within the bond length plays an important role.