Researchers set out to assess performance of pothole repairs

With the repair bill for cars damaged by the country’s potholes estimated to reach £1bn this year, researchers from Nottingham Trent University and Nottingham University have been awarded funding from the Institution of Civil Engineers (ICE) to undertake a six-month research project into the performance of repair work on potholes.

‘Potholes are a sign of major underlying structural problems — in theory, we should be doing structural rehabilitation — but because of budget and time constraints, there will often have to be patch repairs,’ Dr Mujib Rahman of Nottingham Trent University told The Engineer.

‘The problem with these types of repairs is that everyone tends to use methods based on their own experience — not looking at site conditions, not looking at material types, not looking at the depth of the repair. They don’t have to comply with any sort of design standards.’

The asphalt production and testing facilities at the Nottingham Transportation Engineering Centre (NTEC) at Nottingham University will be used to manufacture trial patching sections, which will be tested under controlled loading, and condition regimes.

Rahman said that the simulated pavement would be analogous to a road eight to 10 years old with a series of potholes that would be subject to shallow repairs, deep repairs and bonded repairs using tack coat bitumen emulsion.

The team will also experiment with hot and cold mixes that have different drawbacks and advantages depending on the time of day and proposed repair type.

The sections will also be subject to non-destructive testing (NDT) techniques such as Impact Echo, radar and ultrasound.

While NDT techniques are increasingly gaining popularity and acceptance in the wider civil engineering community, their application in small-scale maintenance works, such as pothole and patch repairs, is lacking.

This is partly because of the associated cost of NDT but also reflects the lack of importance given to this type of work, Rahman said, adding that they would like to design a portable device if possible.

‘If we can get a way to get some numbers out — stiffness or deflection, say — and use that to inform design specification, so if someone does the repair work they have to maintain that level of stiffness or deflection, that’s the ultimate aim,’ he said.