What if we could cut the carbon emissions associated with a road surface by reducing the carbon footprint of the material itself and by extending the life of that surface, while cutting overall lifetime costs? That is what National Highways is investigating with the latest UK trial of GiPave, an additive for asphalt mixes that combines recycled plastics with graphene.
Eurovia UK produced and installed asphalt containing GiPave on a 1km stretch of the A12 northbound between Hatfield Peveral and Witham in August this year. The mix also contained 40% reclaimed asphalt planings (RAP).
GiPave, which was developed by Italian additive specialist Iterchimica, is made from a polymer modifier, derived from hard waste plastics that would not normally be recycled and graphite nano platelets, supplied by Directa Plus. It was first laid on the Via Ardeatina outside Rome in 2018.
In conducting the trial with GiPave, National Highways is following the lead of local authorities in Oxfordshire, Kent, Staffordshire and Essex. The A12 trial contains the highest proportion of RAP that has been used with a mix containing GiPave in the UK, although it has been used with high percentages of RAP in other countries.
Currently polymer modified bitumens (PMBs) are often used for roads that have high volumes of traffic because they improve an asphalt’s strength and flexibility, boosting resistance to both rutting and cracking. GiPave, does the same thing as a PMB, even better, according to Iterchimica. Tests conducted on behalf of Oxfordshire County Council, which conducted it first GiPave trial back in 2019, have indicated that a road surface containing GiPave would last for 40 years compared to 15 years for a standard mix.
There are also carbon savings to be had from deploying GiPave. Calculations by the University of Milan-Biocca showed that GiPave had a 92% lower carbon footprint than an SBS polymer modifier. Looking over the whole life of a road, using GiPave gives a 70% reduction in carbon emissions compared to a standard mix, whereas SBS-modified bitumen gives a 30% saving, according to the University.
Since GiPave is still at the trial stage, it is not yet clear how much more it would cost compared to a mix containing PMB. Iterchimica has indicated that material costs are around 15 to 20% higher than for an SBS PMB – which equates to an uplift of around 10% in overall paving costs. But, it says, cost savings would start to kick in after eight years and rising to 25% over 20 years.
The National Highways trial is part of a research programme which is looking at several low carbon asphalt technologies. It is being conducted with Eurovia, Jean Lefebvre (UK), AtkinsRéalis, Iterchimica and Directa Plus. The performance of the road surface will be monitored and tested, in comparison to a stretch paved using PMB.
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Sources:
AtkinsRéalis joins National Highways in trial of high performance, low carbon asphalt – AtkinsRéalis (atkinsrealis.com)