HAPAS Approval For Stirling Lloyd's Crack Sealing Systems
With funding throughout the public sector being cut including £683 million from the transport budget (The Times), Local Authorities are having to be more astute with their spending. If that wasn’t enough, after being hit by the coldest winter for thirty one years the UK’s asphalt pavements are in a poor state, resulting in an estimated pothole repair backlog of eleven years.
Whilst highway repairs may be seen by politicians as an easy target for reducing public spending,
pavement engineers are only too aware of the need for timely maintenance interventions in the short term to avoid costly resurfacing liabilities in the medium term. With the finance for resurfacing works being unavailable and as the postponing of safety critical maintenance work is not an option, the industry needs to find maintenance solutions which give as much value for money as possible.
In addition to this financial dilemma, our responsibility to the environment also has to be considered; waste production and CO2 generation from highway repairs and surfacing needs to be minimised over the long term, giving another reason why deferring maintenance is not a sensible option.
Repairing Defects
The mechanisms of asphalt pavement degradation, caused by water ingress, are well understood and has been discussed by many academics, commentators and appears in TRL’s Road Note 42 (“Best Practice Guide for Durability of Asphalt Pavements”). Water can enter the layers of the asphalt pavement through cracks and defects in the surface causing degradation and decay by freeze thaw and hydraulic action.
Consequently we need to be addressing the cause of the problem – that of water ingress, rather than reacting to the resultant damage.
Overbanding techniques using bitumen based products which were originally designed to prevent water penetration have fallen from grace over the last few years. Many pavement engineers consider it to be a cost effective technique for sealing cracks in asphalt and to stop the decay but safety concerns have caused many to stop using it. However it’s not the idea which is at fault.
In the right circumstances bitumen is a good product but, as with any material, it is not suitable for all applications, crack repair being one of them. Under trafficking and heat thermoplastic materials spread while aggregate cast into the material is easily plucked out creating shiny surfaces which are potential fatal skid hazards.
Currently, one of the biggest risks to our pavements in the UK is joints between asphalt mats opening up to become ‘fretted joints’. This problem has been exacerbated by the decline in overbanding, changing weather and a preference for thin surfacing, which is more prone to joint degradation. Traditional methods of repair require a wide section to be planed out and asphalt reapplied. However this creates two unsealed joints where previously there was only one. Issues of compaction and water ingress into the two joints then cause worse decay. When joints on heavily trafficked roads, where asphalt mats meet under the white line, require repairing not only do excavation methods create two joints but these have to be formed further into the carriageway under the wheels of traffic, which aggravates the decay.
The need for maintaining the road network has been recognised; HAPAS approvals which assess a product’s suitability for particular applications aims to raise the quality of road repairs and help improve safety.
BBA HAPAS Certification
Since 2003 the HAPAS certification has recognised overbanding and crack repair as a system for repairing asphalt pavements. The BBA’s ‘Guidelines Document for the Assessment and Certification of Crack Sealing Systems for Highways’ recognises four types of cracks for which systems can be approved to remedy:
- Overband - for cracks less than 5mm, which have a maximum band width of 40mm
- Fill and overband – for cracks up to 40mm which have a maximum band width of 200m
- Inlaid single crack – an excavation method for a single crack
- Inlaid multiple cracks – an excavation method for multiple cracks
Despite these efforts to bring some quality to the marketplace, since its inception few products have been submitted for approval under this guidance, perhaps an indictment on the materials hitherto being used for these applications with no material previously passing in the overband category.
All Bases Covered
Stirling Lloyd’s systems address the issues raised; utilising their advanced resin technology they have introduced a range of crack sealing products that have been awarded HAPAS approval. Instead of using bitumen based materials Stirling Lloyd use cold applied reactive resin technology. Where other potential resins are hard, brittle materials and therefore clearly unsuitable for the repair of flexible pavements, Stirling Lloyd have matched the characteristics of their base resin technology to that of the asphalt to create a compatible repair.
The thermoset products developed ensure that even under trafficking and in warmer weather the repair does not spread and aggregate isn’t plucked from the material, consequently specified skid resistance values (SRVs) are maintained and do not cause a skid hazard for road users, particularly motorcyclists. Having won the Prince Michael International Road Safety Award for Motorcycle Safety in 2009, in a joint application with Saint Gobain and Bristol City Council, Stirling Lloyd understand well the importance of reducing skid risks on the road network.
The cold application is another benefit, both to the client and to the public. Eliminating the use of hot materials means that safety risks are dramatically reduced and carbon generation is minimised, providing a more eco-friendly solution.
Having full HAPAS approval to deal with the four types of cracks shows that these claims of increased safety, maintained srvs and the elimination of ‘spreading’ have third party verification; allowing local authorities and utility companies to have confidence when repairing the road.
The three systems approved under Certificate Number: 10/H160 are:
Safetrack® Overbanding – for cracks up to 5mm wide with a band width maximum of 40mm. Applied in the same way as traditional systems Safetrack Overbanding seals the joint to stop water ingress while its thermoset properties mean that it does not spread or lose aggregate. Consequently when Safetrack Overbanding is applied at 40mm wide it will always be 40mm wide, and with aggregate throughout the mass of the material, not just as an overscatter, it maintains its skid resistance throughout its life. View the certificate.
Safetrack® Crack Infill – for cracks up to 40mm wide with a band width maximum of 200mm. Addressing the key limitations of traditional fretted joint repair methods, Safetrack Crack Infill is a cost effective, long lasting system that is faster to install than using planeing out techniques, resulting in less disruption to the travelling public, lower traffic management costs and greater availability of pavements. With less waste being produced this system also has added environmental benefits and, like Safetrack Overbanding, its thermoset properties means that it does not become a skid hazard. By sealing the joint, which stops subsequent water ingress, and supporting the edges of the asphalt the decay is arrested. View the certificate.
Ultrajoint® – for inlaid single and multiple cracks. Developed in conjunction with LMS Highways, the Ultrajoint system offers a solution to repair of fretted joints and multiple cracks where planeing is favoured. Whilst Stirling Lloyd’s primary approach has been to repair cracks and fretted joints in asphalt by applying material to the existing profile of the road surface, specialist contractor LMS Highways have developed a micro-milling technique in order to recess a crack repair product into the road surface for optimum road quality. Unlike traditional plane out alternatives LMS Highways’ system is more accurate and works at much shallower depths to reduce waste generation. Its faster output leads to shorter possession times of the road and a quicker return to service. The milled out surface is then repaired with Stirling Lloyd’s material, offering the same long-term, environmental and thermoset benefits. View the certificate.
Commenting on the certification Stirling Lloyd’s Development Director, Mike Harper, commented “repairing and maintaining our roads is essential but many of the materials available for doing this, to date, appear to create unacceptable safety risks; so the strategy often adopted is to do nothing. Last winter took its toll on our roads because of water ingress and repeated freeze thaw cycles, for which we will pay the price for for many years to come. The answer is to seal the cracks to stop the decay at the first opportunity. With solutions now available for all types of cracks in asphalt pavements that are HAPAS approved means that roads no longer need to be left to degrade on the grounds of safety.”
Long Term Solutions
The UK highway industry has a great challenge in just trying to maintain our network to the required standard and keep all user groups safe, improve journey times and reduce disruption. This coupled with the issue of CO2 and the squeezing constraints of the budget cuts makes it a difficult job to do. However HAPAS approved Safetrack Overbanding, Safetrack Crack Infill and Ultrajoint provide cost effective solutions which give better value for money and address the cause of pavement degradation at source thus improving the long term condition of the network.
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