Road surfacing materials containing tar were extensively used in the UK up until the 1980’s and roads that have not had a significant amount of maintenance undertaken on them since that time are highly likely to contain tar. Coal tar has since been classed as carcinogenic and as such must be dealt with as hazardous waste. The cost of disposing of this material is considerable, and in 2018/19 was around £1m, as we are dealing with a contaminated material which must be treated in accordance within guidance and regulations. To establish if the surfacing material contains tar, sample cores of the road surfacing are taken to determine the most appropriate course of action to take to deal with the surplus material.
In 2017 a programme of tar bound recycling was introduced, which involves crushing and re-mixing the waste material to make a product called Ultifoam. This material is permissible to use in the lower layers of carriageway construction in accordance with the Specification for Highway Works. The material must be encapsulated so has to be applied as a binder or road base course.
For the 2017/18 Capital Maintenance Programme this recycling method was successfully used and a balance between the waste being generated, some 5,000 tonnes, and the use of recycled Ultifoam was achieved. In 2018/19, finding this balance had been more of a challenge, as the the programme had more focus on unclassified residential roads, which had a higher possibility of containing tar. Core information indicated a total of 9,500 tonnes of recycled material would be generated, that could potentially be reused on the Highway Network.
The cost of disposing of 9,500 tonnes of tar material to a licensed waste site would cost towards £1m, whereas the overall cost saving associated with recycling and re-using the material is in the region of £500,000 with 230,000Kg of associated carbon savings.
Over the last 12 months, the innovation of using Ultifoam to recycle tar bound material has proven to be a cost-effective solution in dealing with contaminated waste arisings from highway maintenance activities, whilst also having environmental benefits.
Early site surveys, including coring, for the 2019 / 20 road maintenance programme has enabled advanced planning and timely identification of the affected sites to enable the goal of “neutral waste” to be recognized, with minimal tar bound material being sent for disposal.
