When winter maintenance gets raised around this time each year everyone usually immediately thinks about gritting or salt spreading on our roads, which although beneficial on one hand is also unfriendly towards asphalt roads.
The salt can over time penetrate into the asphalt and weaken the material acting as a precursor for pot-holes being formed.
So if we accept we need to continue to spread salt and grit onto our roads to alleviate the risk of driving on ice then we should also accept that we need to prioritise sealing our roads beforehand to help stop both water and salt penetrating into the asphalt.
By not adopting a preventative maintenance approach and sealing our roads while they are still in reasonable condition we risk shortening the service life of our most valuable asset resulting in a higher maintenance spend further down the track.
One proven method for sealing our roads is to use surface dressing, a treatment now into its second century of use which involves spraying a bitumen emulsion binder onto the prepared road surface then dressing the binder with chippings. Sounds simple but getting it right is best left to qualified experienced contractors as with any process it requires close control throughout to get it right first time.
Surface dressing imparts both road surface texture and therefore improved skidding resistance but also seals the road surface inhibiting water ingress. If water is unable to penetrate the road surface it cannot then act to undermine the integrity of the asphalt. Surface dressing is however a seasonal treatment and best used between April and September. So in effect sealing our roads during the summer months is a most valuable form of winter preparation because it counters potholing and road deterioration thereby saving more significant future maintenance costs.
Authorities should also be aware that nowadays there are other complimentary treatments available that can be used both during and outside the surface dressing season. These are often known as asphalt preservation treatments and involve the spray application of special proprietary bituminous binders onto the road surface.
So this process does not restore skidding resistance but it does seal the road surface and helps to keep water and salt out during the winter thereby extending the life of the road surface. Whereas surface dressing is best used when the road is just starting to show signs of deterioration, preservation treatments are best used on roads that are in generally good condition. So in effect they represent a good investment by helping to extend the service life of the better parts of the network so they don’t slip into the amber category of requiring more costly maintenance.
Another critical issue regarding preparing our roads well in advance of the harsh winter months involves patching. Often authorities do their patching far too late driven by funding constraints. The best advice is to get your patching done during warmer months to allow time for the patch to become trafficked and bedded in during the summer and hence better able to survive the colder winter months.
Patching during the spring/summer period is also best practice if the road is to be surface dressed the following year. This provides ample time for the patch to stabilise under traffic, resulting in a denser surface, which in turn ensures the surface dressing binder when sprayed, isn’t absorbed into the patched area resulting in less binder on the road surface to bond the chippings.
Patched areas in a road are much weaker than the surrounding road surface because it is very difficult to compact a patch to the same density as the surrounding road surface. They are in effect localised weak spots on the road surface which is why patched areas can sometimes fail within a few months and need to be re-done.
Sector Scheme 23 for small scale pavement repairs is currently being established and aims to regulate the quality, and in particular the workmanship, involved in carrying out patching. When it is launched next year all highway authorities should look to employ contractors who are registered against this new quality scheme.
It is of course well known that funding patterns drive a great deal of road maintenance to be undertaken during the worst six months of each year between September and March when the weather is colder, wetter and daylight shorter all of which only hinders the delivery of good quality durable treatments and repairs.
This in turn ultimately results in increased costs over shorter maintenance cycles so the sooner we have more stable regular funding this can only help to provide better value for the public purse.
Dr Howard Robinson is chief executive and company secretary of the Road Surface Treatments Association (RSTA).
For more information and to register for the UK's leading winter maintenance conference and exhibition, Cold Comfort 2014, click here.
