Three-dimensional electrical tomography for imaging large concrete members

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Concrete structures are ubiquitous and critical components of UK and international civil infrastructure, cityscapes, waste containment facilities, and much more. Now, more than ever, we demand more from our concrete structures, from safety, durability, economy, and environmental perspectives. For example, in the UK alone, there are approximately 67,400 highway bridges carrying heavy goods vehicles and over 70% are reinforced concrete, prestressed concrete, or concrete culvert bridges. Of these, nearly 70% were built between 1960 and 1990. Given this information, the cost of replacing or remediating ageing national bridges in the UK alone is huge. For example, the total maintenance backlog for council-managed (in Great Britain) road bridges has been estimated to be £6.7bn. This indicates that council-managed concrete bridges in Great Britain are currently in a £4.7bn maintenance backlog. The costs associated with deconstructing and reconstructing these bridges can be estimated as a figure approximately two orders of magnitude larger than the current maintenance backlog. Therefore, feasibly addressing contemporary concrete infrastructure challenges requires more than a monetary solution, it requires technical innovation. To begin addressing the demands of an ageing concrete infrastructure, we must first be able reliably assess the condition of concrete structures during their lifespan in order to, e.g., rehabilitate them before replacement or discontinuing service before failure. At present, however, many non-destructive testing/structural health monitoring (NDT/SHM) imaging methods offer limited information regarding the internal condition of concrete structures. This project responds to this issue by determining the feasibility of a new 3D approach (electrical tomography) for use in assessing the condition and health of concrete structural members, such as beams, slabs, and columns. Outcomes from the project have the potential to enable (i) experimental studies of the fundamental behaviour of reinforced concrete members by allowing researchers to quantifiably "see" inside members exposed to extreme environmental and/or loading conditions and (ii) quantitative 3D condition monitoring of constructed concrete structures. From an asset management perspective, this non-destructive technology would allow maintainers to "see" inside concrete structures. In doing this, maintainers can detect internal damage, such as cracking and reinforcement corrosion, and repair/replace individual members before they jeopardise safety or give rise to expensive systematic problems requiring replacement of the entire structure.