With the UK's draft Climate Change Bill set to become law, every industry is under the spotlight to sign up for sustainability and to make long term commitments towards cutting their carbon footprint. Recycling old materials and process improvements are a step in the right direction for the asphalt industry but their contribution is still small.



The concept of preserving asphalt surfaces may be relatively new in the UK but the timing is perfect for its move into the mainstream. The preservative has just secured HAPAS approval, it's a green alternative to resurfacing and preventative maintenance is the only practical, cost effective way to stop the road network deteriorating.

Asphalt preservative is a cold spray-applied surface treatment suitable for all asphalt, macadam and surface dressings. The treatment has been widely used for over 40 years in the US and around 12 years in the Czech Republic to prevent new and existing surfaces from deteriorating but it is still relatively unheard of in the UK.

The preservative, marketed globally under the Rhinophalt brand name, contains predominantly Gilsonite: an extremely hard (>2 pen), naturally occurring and readily soluble resinous hydrocarbon. The solution can be easily and quickly spray applied at recommended dosages of 0.5 l/m2, followed by a 2.mm down silica aggregate coating at 0.5 kg/m2. The treated area can be re-trafficked within one to three hours of application, depending on the ambient temperature. Areas of up to 40,000 m2 can be sprayed in

a single shift with three operatives and a purpose built vehicle; the process is also virtually silent making it ideal for off-peak treatment of highways and trunk roads. The treatment can also be applied by a lance on smaller roads, kerb lines and areas with

restricted vehicular access.

Asphalt preservative works by penetrating into the road surface to chemically re-engineer the binder, forming a flexible membrane around the aggregate within 10 mm of the surface and to seal in essential oils and resins. As these are ?locked in?, the re-engineered

bitumen remains flexible rather than becoming brittle. The treatment prevents the ingress of surface water and protects against oxidisation but without affecting the polished stone value (PSV), the skid resistance or adding to the road surface level.

Although asphalt preservative has only just secured HAPAS/BBA certification (number

07/H125), following extensive trials on sections of the M40, it has a long track record from the UK's road maintenance sector to draw on. For years, the preservative has been an integral part of the Rhinopatch infra red road repair process to protect joint free reinstated areas from any future degradation. With the oldest patch on the Buckingham

bypass (A421) coming up for 11 years old and still appearing in good condition, even a single application of the preservative is extremely effective.

Rhinophalt has also been used on many larger scale preventative maintenance programmes too, including treatment of the taxiways at Glasgow Airport and RAF Brize Norton plus many trunk and urban roads, footpaths and car parks across the UK.

Herefordshire County Council was one of the earliest adopters in preserving a five year old thin surfacing in need of repair. Steven Thompson from the Council has said that the treatment, following a programme of patching, has given seven years of additional life to the surface course and the surface ?still looks as good as when it was first done?.

Following the recent HAPAS approval, North Ayrshire Council is the first authority to adopt a mainstream policy for preventative maintenance. Ronnie Small, Head of

Roads, is enthusiastic about the preservative's potential saying, ?If we can stop the surface from cracking then we'll cut the need for much more costly reactive maintenance years down the line which has got to be good and welcome news for taxpayers and for motorists.?

In addition, following the initial trials for HAPAS accreditation, the M40 has placed a further order and several other DBFO contractors are now actively considering preservation as the answer to a costly problem dogging many projects. Although technically thin surfacings should last 10 to 12 years, in practice some authorities are having to fund unexpected repairs or, worse still, face the prospect of total resurfacing much sooner than this. By immediately halting the ageing process, asphalt preservative can help authorities avoid massive unexpected costs as a direct result of the premature ageing of thin surfacings.

With councils and contractors in England and Wales alone treating over one million potholes annually, as well as facing a ten year backlog and considerable budgetary pressures, the case for pre-serving every major road in a bid to stem the pothole ?crisis? seems logical.

Being green and clean

Asphalt preservative has been likened to ?wood preservative for blacktop?; an analogy that is clearly helpful in explaining its protective role. No one would dream of installing a wooden post and rail fencing without giving it a regular coat of preservative. The highways sector, airport owners and other stakeholders already have a preservation culture for their lamp columns, crash barriers and bridges and are fast realizing that they need to manage their asphalt assets in a similar manner. Given the mounting legislative and market pressures to go green, the argument will increasingly be driven by environmental concerns and the need to preserve and protect.

The road maintenance sector can play a major role in helping the UK meet its aggressive CO2 reduction targets but, until recently, the sector's potential contribution was virtually unknown. In March of this year Best Foot Forward (BFF), an independent UK based sustainability consultancy, published a carbon footprint audit looking at a number of areas including preservation versus resurfacing. Although there is no overall record of how much resurfacing is done, the estimated figure of 100 million m2 was used to model the UK situation. On that basis, resurfacing alone contributes around 5.2 million tonnes (Mt) of CO2 annually ? equivalent to the annual output of around 1.5 million cars - whereas one application of preservative every five years could cut that figure by 94%.

The opportunity to significantly cut emissions, manage their properties in a more cost effective manner and to invest for the long term rather than in reactive maintenance is encouraging more asset managers to sign up for preservation. Of course it will not be warmly welcomed by an asphalt sector already witnessing falling sales: the number of new major infrastructure projects is slowing and maintenance budgets are either not keeping pace or are being increasingly absorbed by the rising costs of emergency works, traffic management and liability claims. But the industry has a choice: to get on board and support preservation as a way ahead or battle against a market urgently looking for practical, lower cost answers for a greener, cleaner and more sustainable world by claiming only ?dig up and replace? will do.