Bond characteristics of corroding reinforcement in concrete beams

The results of an experimental study of the bond characteristics of reinforced concrete beams subjected to reinforcement corrosion are presented. Beam specimens recommended by the joint RILEM/CEB/FIP Committee were used, which comprised two halves of a reinforced concrete beam rotating about a hinge mechanism. Corrosion was induced at different levels of rebar diameter loss: 0, 0.3, 0.4, 0.5, 1, 2 and 5 percent by impressing direct current of intensity 0.8 and 2.4 mA/cm(2). The specimens were tested under four point bending to induce bond failure and load - free end slip curves were plotted. The tests showed that at up to 0.4% degree of corrosion, no free-end slip occurred in the reinforcement bars until complete breakdown of bond at failure. At higher degrees of reinforcement corrosion, free-end slip commenced immediately upon application of load and increased linearly with increasing load. The free-end slip at maximum load was a function of the degree of reinforcement corrosion. At small degrees of corrosion, the bond strength increased with increasing degree of corrosion, showing a maximum increase of over 25% at 0.4% corrosion. Higher degrees of corrosion led to a sharp decrease in bond strength.