The effect of fibres on steel bar corrosion and flexural behaviour of corroded RC beams

Abstract

This paper reports the results of an experimental programme aimed at investigating the influence of fibre reinforcement on the corrosion process of conventional steel rebar embedded in cracked concrete and on the flexural behaviour of reinforced concrete beams. Un-and pre-cracked reinforced concrete beams were subjected to natural corrosion through cyclic exposure to a 10% chloride solution for a period of three years. Subsequently, flexural tests were carried out under three-point bending configuration. Gravimetric measurements showed higher corrosion levels for bars in plain concrete compared to fibre reinforced concrete, and visual inspection of the bars revealed that fibres promoted a more distributed corrosion pattern. From detailed examination of the bars through 3D laser scanning technique, the main parameter controlling the local corrosion level of individual pits appears to be the local interfacial conditions; grater loads during pre-cracking and repeated load cycles yielded greater cross-sectional losses. Moreover, there was a tendency for more localized corrosion in beams with open cracks, indicating a possible impact of crack width on the extension of corrosion. The results from the flexural tests showed a consistent increase of load capacity for fibre reinforced beams compared to their plain concrete counterparts but only a marginal influence of the fibres on the rotation capacity. Furthermore, the rotation capacity of the beams was found to decrease several times faster than the load capacity with increasing loss of rebar cross-sectional area.

Correlation between concrete cracks and corrosion characteristics of steel reinforcement in pre-cracked plain and fibre-reinforced concrete beams

“…A small improvement (in terms of delayed corrosion initiation) was observed when fibres were added. In the subsequent study [19], the flexural behaviour of corroded plain RC and FRC beams (among the specimens in [18]) was examined. FRC beams were found to display higher residual load capacity at reinforcement yielding than plain RC beams, whereas the relative loss of load capacity (the loss of load normalised by the load on reference beams) as a function of the maximum local corrosion level was similar to that seen in plain RC beams [19].…”

“…In the subsequent study [19], the flexural behaviour of corroded plain RC and FRC beams (among the specimens in [18]) was examined. FRC beams were found to display higher residual load capacity at reinforcement yielding than plain RC beams, whereas the relative loss of load capacity (the loss of load normalised by the load on reference beams) as a function of the maximum local corrosion level was similar to that seen in plain RC beams [19]. However, the relative contribution of the fibres to the residual capacity of FRC beams and mechanical behaviour of corroded rebars could not be investigated specifically, as it was not possible to evaluate the mechanical behaviour of those rebars accurately after the flexural capacity tests.…”

“…However, the relative contribution of the fibres to the residual capacity of FRC beams and mechanical behaviour of corroded rebars could not be investigated specifically, as it was not possible to evaluate the mechanical behaviour of those rebars accurately after the flexural capacity tests. Following the tests, the corrosion level of critical rebar segments was evaluated using 3D-scanning [19]. However, no clear trend was identified in maximum local corrosion levels regarding (1) fibre addition, (2) targeted crack widths of 0.2 and 0.3 mm and (3) loading type.…”

Influence of Cracking on Oxygen Transport in UHPFRC Using Stainless Steel Sensors

“…One of the few studies performed on FRC in micro-cracked state [14] reports that FRC improves the durability in load levels between 30 and 50% of the ultimate strength, which reduces the permeability to water and delaying corrosion initiation, with more delay with higher contents of fibers. Similarly, it has also been reported [15] that the presence of fibers contributes to a more generalized corrosion on rebars instead of pitting corrosion, which produces a fast section loss in the pitting zone.…”

The influence of simultaneous action of the aggressive environment and loading on strength of RC beams

“…The corrosion of the reinforcing bars was avoided in order to exclude its impact on the stressstrain state of the beams. This effect is more complex and requires a separate study [5,9]. At achievement by experimental samples of ULS the reinforcing ratio made for a series 3 (212) -1.93-1.99%, for a series 1 (214) -2.6-2.8 %, for a series 4 (216) -3.43-3.54%.…”