A risk-taking public authority renewed a vital road and saved substantial amounts of money with an environment-friendly recycling method.
To pioneer cost and material saving technology in roadbuilding you need a client who is prepared to go out on a limb and share the risk that new ideas might not work out in practice.
Tarmac Heavy Building Materials found such a client in Somerset County Council which needed to totally rebuild 3.5km of its heavily used A3088 link road between the A303 and Yeovil. Somerset was rewarded with a recycling project that was 30% cheaper than conventional carriageway reconstruction using new materials and has a design life of 20 years. At the same time it yielded major environmental advantages in almost eliminating the tipping of waste material and substantially reducing the need to quarry new aggregates.
Temporary closure of the single carriageway road for 35 days enabled the contractor to recover all the original roadbase and surfacing by planing. These arisings were then processed through a crushing and screening plant set up in a depot that was conveniently adjacent to the mid point of the section being rebuilt. Graded material was remixed using Tarmac's cold Foamix process and compacted to form a new road base at a rate of up to 3, 000t of material a day. Finally this was topped by a layer of Tarmac's Masterpave low noise, thin surfacing material.
Somerset CC's achievement on this project is to have avoided the conservative approach to new road technology that is the UK norm. The county pushed ahead with a method that brings together ideas that have been used elsewhere on a job that is not classified as a special experimental section of road but is simply a major maintenance project.
Road recycling using crushed and screened arisings remixed with a cold process to give a fully designed, graded material has been in use in the US and Canada for two decades. Cold mixes have the benefit that they are user friendly for the workforce, avoiding hot polymers that may be a health hazard when inhaled. Tarmac's thin surfacing material, a hybrid between macadam and ashphalt, is one of several products that have become widely used on UK roads over the past two years.
Two different pavement designs were used. The eastbound lane is 265mm of Foamix placed in two layers followed by 65mm thickness of 20mm grade DBM basecourse and 35mm of Masterpave. The westbound is 340mm of Foamix in three layers topped by 40mm of Masterpave.
Somerset County Council
WS Atkins Southwest
Geoff Mountjoy, Asst Area Highway Manager
Tarmac Heavy Building Materials