Potholes. What is the long-term solution?
Every 60 minutes RAC patrols attend a pothole-related breakdown. The inevitable colder conditions with Winter drawing close will trigger even more potholes. There is no doubt that potholes are causing many motorists and cyclists increasing distress during their journeys, damaging their vehicles and creating treacherous road conditions. But is just filling them in going to solve the problem in the long term? Or is there an underlying issue?
The UK highways market has been obsessed with high profile press coverage of successful pothole repairs responding to the short term demands of public opinion. Consequently, highways authorities have concentrated on a reactive maintenance approach to pothole management.
The DfT pothole funding mechanism appeared to support this strategy however in 2017 it was evident that the organisation wished to move away from good news stories to a much longer-term approach encouraging an alternative approach and the use of innovation in adopting preventative maintenance.
More recently a DfT representative in answering a query on the recent 2020 budget clarified that the £2.5bn Pothole Fund was for highways authorities to both repair potholes or to stop them forming in the first place. They were endorsing the observations made in 2017 emphasising that the funding was to be awarded based on undertaking both reactive and preventative actions.
The underlying issue
Cracks in the wearing surface and subsequent penetration of water are a significant cause of potholes. Still, as the cracks appear at the surface, the assumption is often made that this is the pavement level at which all cracks commence and can be treated on the surface and necessarily replaced.
Due consideration is not given to reflective cracking caused by failures in the lower levels and penetrating up through the various pavement layers with resultant surface cracks and pothole development.
When it comes to asphalt pavement, true sustainability is all about finding solutions that maximise the quality and durability of the pavement surface. To extend the asphalt pavement’s useful life, while optimising the use of materials and reducing the complexity and length of the maintenance process – all while working within strict budgetary limits.
The longer-term solution
The installation of interlayers/SAMIs/reinforcement grids within the pavement layers during resurfacing performs in several ways to prevent reflective cracks and extend the life of the pavement enhanced by placement as deep as possible during the works.
The systems operate initially as a barrier to absorb cracks and deflecting the built-up stress across the interlayer preventing cracks penetrating to the upper layers of the pavement. Ideally, by placing at the base/binder interface, the binder and subsequent surfacing layers are prevented from cracking.
Most importantly for highway engineers, as the wearing surface suffers from normal wear, subsequent treatments, and resurfacing can take place safely in the knowledge that such an investment can be placed on a crack-free binder layer, enhancing the overall pavement life.
Choice of type and grid strength provides a variety of means to extend pavement life. Grids provide an anchor for the next layer aggregate skeleton, added structural strength, prevention of asphalt elongation to cracking levels and where incorporating a bitumen bond coat acts as a water barrier.
An excellent solution is the GlasGrid® Reinforcement Systems family of products, available from the Asphalt Group.
GlasGrid’s® innovative design sets it apart from other reinforcement products by significantly reducing shearing within the fibres to maintain integral strength.
Low elongation is an essential factor in manufactured products that absorb stress. GlasGrid® has been rigorously tested in the laboratory and in the field – in independent studies, GlasGrid® has provided outstanding results. Its excellent bonding capabilities, high tensile strength and the ability to provide an effective moisture barrier mean that GlasGrid® is the performance product of choice for demanding applications.
Designing and Specifying Asphalt Reinforcement for Road Maintenance
The Asphalt Group, in conjunction with LCRIG, is holding a free CPD accredited coffee break webinar entitled Designing and Specifying Asphalt Reinforcement for Road Maintenance. On 4 December 2020 at 10.30 am. Delivered by Gerald Byrne, National Specification Manager at the Asphalt Group.
The webinar will give guidance and training on how to design and specify asphalt reinforcement in the most effective way to control cracking failure.
The 30 min webinar will refer to the publishing of Clause 936 and how to use this guide to specify generically and prescriptively crack controlling systems and the bond coats, which form an integral part of the system.
Attendees will also leave the webinar with a thorough understanding on how asphalt reinforcement can support designs that join new to existing construction such as in smart motorway projects on the HE Network and where developers are joining their pavements to local authority infrastructure.