Sustainable warm mix asphalt – driving efficiency and reducing carbon on on the A350

The A350 Westbury road condition was poor, resulting from the underlying ground conditions that are prevalent in this part of Wiltshire. The road reconstruction would require a 24/7 road closure, diverting HGV traffic onto the Highways England network, which was already at capacity and other traffic onto lengthy diversions on other local roads. The scheme was originally planned to commence on 16 September and complete on 11 October. The scheme was to be undertaken in sections with planed areas to be laid with two layers of 60mm AC 20 HDM Binder with a 200KN geogrid in between and 50 surface course of 10mm ULTILAYER S. Each reconstruction section was to take 1.5 days sections including ancillary works. The total scheme was costed at £470k.

Wiltshire and Tarmac Contracting collaboratively reviewed the programme and found that using warm temperature asphalt would provide very significant efficiency savings. The use of warm temperature asphalt for all of the construction layers enabled the work to be undertaken in a more efficient manner. The lower binder course was completed quicker providing the optimum temperature for the installation of the geogrid much sooner. This time saving then enabled the upper binder course layer to be installed in the same shift. This also enabled the team to complete ancillary works on other sections during the shift, providing a 0.5 day saving on each programmed 1.5 day section. The earlier finishes during the contract period allowed access for residents to their houses and the town centre.

The scheme was completed seven days earlier than programmed, providing a saving on the overall cost of £70k, principally from traffic management, whilst allowing for 25% more work to be completed. The early completion reduced the diversion period and disruption for through traffic and the local community. Public appreciation was expressed in a complimentary letter published in the Wiltshire Times. The emphasis on sustainability may have helped Wiltshire Council to be named the most climate-friendly council in England and Wales by Friends of the Earth when assessing local authorities’ energy, transport and recycling plans. ‘’My approach to warm temperature asphalt is, why wouldn’t you. This asphalt provides sustainability benefits, improves site safety and as the A350 Westbury site demonstrates,gives the opportunity to adopt a more efficient way of working in delivering schemes.” Diane Ware - Principal Technical Officer - Highways.