A new method for evaluating (determining) steel bar-concrete adhesion in self compacting concrete: effect of water to binder ratioand type of concrete

Abstract

The resistance to separation of the concrete from its reinforcing steel with which it is in contact is called adhesion. This adhesion constitutes an important property for the use of reinforced concrete. That is why many techniques were developed with the aim of determining this property. Adhesion can be easily found out by standard pullout test machine. However, in this work, the adhesion was measured using Interfacial Indentation test. This technique creates and propagates a crack along the concrete/ steel bar interface and defines the apparent interfacial toughness, which can then be related to the adhesion and mechanical support of the aforementioned interface. Using reinforcing bars, adhesion was measured using Self Compacting Concrete (SCC) and Normal Vibrated Concrete (NVC) specimens. The impact of water-to-binder ratio variations and concrete type on concrete /steel bar adhesion has been the incentive of the present study. Interfacial indentation test on small cylindrical samples have been conducted for 5 SCC and 2 NVC mixtures. Various apparent interfacial toughness have been evaluated. The water-to-binder and concrete type changes seem be better reflected on interfacial toughness, which decrease linearly for higher water content. SCC develops an improved adhesion capacity compared to same strength NVC with similar composition. In this type of studies are rarely those who have tried to characterize the adhesion of matrix/ steel bar reinforcement in Self Compacting Concrete by using the interfacial indentation test as a new methodology. Exclusively, the objective of this research is to fill this gap by characterizing for the first time this concrete/steel bar adhesion by interfacial indentation test and then study the effects of some parameters such as water to binder ratio (w/b) and concrete type on its behavior and on the microstructure of the developed composite material. In conclusion, the indentation test showed clear advantages over the conventional pullout test and shows once again its aptitude to study the adhesion of concrete/ steel bar reinforcement couple.