Concrete deterioration detection using distributed sensors

Abstract

The potential for using a distributed fibre optic strain sensor system to detect and quantify localised reinforcement deterioration and explore the failure mechanism of reinforced concrete beams is investigated. The objective is to discover whether distributed fibre optic strain sensors installed either internally or externally can detect pitting corrosion in reinforced concrete beams, and be used to better understand structural behaviour. These sensors enable strain to be measured along the full length of the fibre optic cable, whereas conventional electrical resistance strain gauges offer discrete measurements that may not capture localised strain changes. Axial tension tests on reinforcement bars demonstrate that deterioration detection is possible, but that quantification of deterioration is not necessarily straightforward, depending on the extent of deterioration. Four-point bending tests on reinforced concrete beams illustrate that localised deterioration can be detected and quantified with embedded sensing fibres and that cracks can be detected using externally bonded fibres. The top and bottom reinforcement strain profiles are used to demonstrate that the unexpected ultimate failure loads of the beams are the result of specimens behaving as tied arches at failure. Overall the distributed fibre optic sensor system proves to be effective for detection and quantification of localised deterioration and provides the necessary data to assess the beam failure mechanism.