Identification of the failure mode of corroding steel rebars in a viaduct in service through hardness measurements

Abstract

In the present work, rebars extracted from a reinforced concrete viaduct that had to be demolished has been studied because they broke in service with an unusual tilted pattern for the rebars without reduction in diameter. The structure was a bridge suffering alkali-silica reaction and reinforcement corrosion. The determination of rebar's in service failure mode is very complex due, among other causes, to their high degree of degradation by corrosion. In this work it has been shown that by performing hardness measurements along a diameter in the cross section of the bars it is possible to determine their failure mode, tensile or fatigue. The results show a similar probability of in service fatigue or tensile plastic collapse failure. In both cases, a brittle fracture has occurred. The corrugations of the rebars generate a stress concentration that explains the observed tilted appearance of the fracture surface. The influence of different corrugation patterns, as for example B 500SD, in service fracture appearance should be studied to extend the conclusions reached in the present work. (172).

Keywords

• Tilted fracture
• Rebar
• Integrity
• Ductility
• Corrosion