Interfacial Indentation Test for the Study of Reinforcement bar/concrete matrix Adhesion in High Performance Self Compacting Concretes

The interfacial indentation test is experimented for the first time in order to characterize the adhesion between the concrete and its steel reinforcement. This technique, developed to estimate the adhesion of thick coatings (thermal barrier, plasma torch deposits, etc.), is used here to create and propagate a crack along the concrete/reinforcement interface. The length of this crack makes it possible to calculate an apparent interfacial toughness which can then be linked to the concrete/reinforcement adhesion, and therefore to the resistance of the elaborate structure. The mechanical properties, hardness and Young s modulus of the various constituents were determined from indentation tests, and micro cracks at the concrete/reinforcement interface are generated by Vickers macro-hardness tests using indentation loads ranging from 300 to 1200 N. The properties of three concretes are compared: a high-performance vibrated concrete HPVC (VC54) and two high-performance self-compacting concretes HPSCCs (SCC54 and SCC62), both developed in the laboratory. The adhesion in terms of apparent interfacial toughness of (SCC54) was found to be greater by 9.17 % than that of (VC54) with the same compressive strength. This improvement in bond behavior of SCC against that of vibrated concrete (VC) can be attributed to the higher amount of fine aggregates and higher workability, which results in a better containment of the reinforcement bars. The results obtained by this test are in agreement with those of conventional pull-outs tests while being easier to realize, and we propose its use in order to characterize the adhesion between the concrete and its metallic reinforcement.