Pull-Out Behavior of High Yield Strength Steel Deformed Bars Embedded in High Strength Concrete

In this paper, the authors present results of an experimental program carried out to study the pull-out behavior of a new type of high yield strength steel deformed reinforcing bars (f sub y = 830 MPa) embedded in high strength concrete (f sub c = 100 MPa). Influence of embedded length, concrete strength and yield steel strength on bond strength has been investigated by means of pull-out tests. The final aim of this research program is to define design and specification requirements for this new material. Variations of the average ultimate bond strength with embedded length, for concretes with compressive strength from 40 MPa to 100 MPa, produce horizontal curves, which indicates that the mean ultimate bond stress is an appropriate bond strength indicator. Ultimate bond strength increases proportionally with both the increase of tensile strength and compressive strength of concrete. No significant effect of the yield steel strength of reinforcement on the value of the mean ultimate bond stress has been observed. In the case of a pull-out failure, the relationships between the ultimate mean bond stress and the main characteristics of the bond between steel and concrete (embedded length, mechanical strengths of concrete and yield steel strength) are similar to the ones of standard deformed reinforcement (f sub y = 500 MPa).