Researchers set out to assess performance of pothole repairs
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A new project is to study the performance of pothole repairs on a simulated road in an effort to create best-practice maintenance guidelines.
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.
Readers' comments (8)
Malcolm | 16 Dec 2011 2:42 pm
Has anybody analysed the type of wheels and tyre combinatons that are damaged by dropping in a pothole? Personally I think the problem is low profile tyres on alloy wheels. There's no give in the tyres and no impact strength in the wheels and I don't think we should pay for the replacement of highly expensive wheels. It's a road, not a billiard table.
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Mike Allen | 18 Dec 2011 2:29 pm
M27 between junctions 2 and 3 has developed longitudinal potholes between sucessive laying strips. Why not repair these using varying mixes and inspect/photograph at intervals ? It will be fairly obvious which methods work and which don't with real traffic. Then do the costing.
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john | 19 Dec 2011 0:34 am
Please do all your tests using a fully loaded forty tonne articulated truck and then an agricultural tractor and trailor , the trailor on the agricultural tractor will have lttle if no suspension, which knocks the death out of roads.
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anthony ball | 3 Jan 2012 6:06 pm
today 3rd jan we were about to leave the motorway at junction 3 m27 when bang we hit a large pothole we had a flat tyre and it bent the wheel after the AA came out thay advised us to get the car checked out by the garage because our car did not sound right and the stearing did not feel right there was no sign post warning us of potholes.
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Anonymous | 4 Jan 2012 4:27 pm
Can you buy a new car without alloy wheels? Who invented these fragile replacements for pressed steel? One small and unseen crack can cause a leak, with tubeless tyres.
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A Cyclist | 6 Jan 2012 2:19 pm
A lot of pot holes are at the join between two layings of tarmac.
They don't seem to apply any sealing to these joins allowing moisture to get in, freeze and thaw, and suffer the hydraulic impact as vehicles pass over.
A reason for not applying the sealing is apparently it leaves a slippery section that is of risk to cyclists and motorcyclists.
As a cyclist, the linear groves that open up are more dangerous, being like tram lines, and I am always nervous when near painted lines.
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Anonymous | 9 Jan 2012 4:51 pm
For reasons that will follow I wish to remain anonymous.
In Manchester there are plenty of roads made up of 50 mm of ashphalt over stone setts (cobbles).
The road to our works breaks up due to heavy wagons, particulary where they turn. The council repairs do not last, a drop of cold ashphalt and a tamper (punner) to compact the fill to nearly level the road.
We now carry out or own repairs with great success, a tack coat to seal the edges, the hot ashphalt and a wacker plate and some time spent ensuring a level smooth surface.
How long have we had roads? Surely the civils should already be on top of this by now.
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Anonymous | 17 Jan 2012 7:59 pm
Comming from an Australian background (Civil Engineer) and working with an Asphalt contractor in the UK I feel I'm partially qualified to comment.
I've been appauled at what passes for UK workmanship basically. To repair a pot hole (assuming no shoving of the subgrade) you first need to tack coat it liberally, then place the Asphalt mix (a PMB modified with 0.3%SBS is best although more expensive) and most importantly COMPACT IT.
In the UK, this is often attempted with a plate compactor which does nothing more than tighten up the surface which is fine for unbound granular pavements with no clay but will not get to the bottom of any cohesive material (like Asphalt). If the layer is more than about 20mm thick then it needs actual compactive effort with a wacker packer (trench rammer for the UK crowd) - as this will ram the material home and compact it from the base of the layer. If done properly, on a concrete subgrade, there is no reason it shouldn't last - especially given the baby sized trucks that are used over here.
Importantly, you have to keep the water out - this is where the PMB comes in. It is more expensive but it is highly elastic - research from Aus (AAPA & Austroads) show that PMB - fully networked - will resist rutting even by Type 2 road trains. Personal experience of using PMB spray seals on roads with highly expansive subgrades have certainly shown that they can accommodate large deflections.
However, as with all things - they won't last forever and often it is a case of the surface reaching the end of its life and needing replacement rather than patching.
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