Kent County Council (KCC) and its partners at Amey have been working in collaboration with the Nottingham Transportation Engineering Centre at the University of Nottingham to understand the challenges, properties, and the feasibility of using Gipave to repair and resurface the county’s pavements.
This research forms part of the £22.9m Association of Directors of Environment, Economy, Planning & Transport (ADEPT) SMART Places Live Labs programme and builds on the Gipave trial KCC and Amey undertook in July 2020, where core samples from the Gipave asphalt carriageway showed improvements in many structural factors, including fracture toughness, stiffness modulus and fatigue (Amey set to trial sustainable graphene asphalt on Kent roads).
Gipave is a graphene-enhanced asphalt supermodifier that involves melting pellets (containing graphene and recycled plastics) into the aggregate mix when the stone is mixed with bitumen. The resulting product has been shown to extend expected surface lifetime by approximately 2.5 times over its non-Gipave alternative – expecting to last up to 25 years.
Kent County Council Strategic Asset Manager, Alan Casson, said: “Given KCC’s strong pledge to reduce carbon and the challenges the highways sector continues to face, we are committed to finding ways to reduce the environmental impact of our road maintenance works and to extend the lifespan of our roads. We are therefore delighted to be part of this encouraging trial with Amey, Iterchimica, the University of Nottingham and GW Highways (resurfacing contractor).”
To better estimate the longevity of Gipave when used to build or repair pavements, the University of Nottingham carried out Pavement Design Analysis (PDA) that looked to model the structural performance that Gipave could exhibit in the real world across a range of different road types and surfacing materials.
Working in collaboration with Amey’s Kent highways team and KCC, four recently resurfaced roads with different construction types were identified, core sample results provided and the University of Nottingham carried out a set of comparative Pavement Design Analyses (PDAs) for each site. The PDAs looked at Gipave vs Stone Mastic Asphalt (SMA), Gipave vs Asphalt Concrete (AC) and Gipave vs Polymer modified Bitumen (PMB).
Modelling from the PDAs concluded that all of the sites would show some improvement in lifetime extension through the use of Gipave, with one site lasting more than four times longer with Gipave than SMA before top-down cracks started appearing. It also indicated that the scale of that lifetime extension was limited by the quality of the base and binder course below the Gipave surface. However, the performance of a Gipave asphalt mix - like any asphalt layer - is dependent on the pavement's structural characteristics.
Professor Nick Thom from the University of Nottingham, adds: “Two cases have been identified where Gipave is likely to provide significant benefit. The first is the case of SMA surface and binder course over a hydraulically-bound (e.g. cemented) or cold-mix asphalt base; the second is a thick asphalt pavement including SMA surface and binder course. In both these cases the benefit derived from Gipave additive in terms of life extension prior to significant maintenance is predicted to be a factor of 2.5 to 3.”
Using the outputs from the PDA, Amey’s team have worked with KCC to produce an Asset Lifecycle Model that provides estimates for the cost and carbon saving using the Gipave product, showing that over a 65-year asset life, carbon savings of 23kg CO2/m2 could be achieved on a scheme such as East Hill, Dartford (covering 2,700m2), as well as over 1.5 tonnes of waste plastic that would be recycled into the asphalt surface. Although the material is more expensive to lay in the first place, modelling has estimated a 32% reduction in cost over its lifetime.
Sunita Dulai, Head of Business Improvement for Transport Infrastructure at Amey, added: “We are delighted to present and publish the results of the University of Nottingham’s Pavement Design Analyses and encourage people to read the full paper. Working in collaboration with the University of Nottingham we’re able to show the science behind live research trials and provide statistical evidence to our client of the benefits of introducing new, environmental products to traditional repair and maintenance works.”
As a result of the research from University of Nottingham, KCC is proceeding cautiously with Gipave with plans to undertake works on three other schemes in the later part of 2022 to trial the material in a wider range of locations and road types. These trials will seek to replicate test results from the East Hill Dartford trial, and also test the commercial viability of Gipave. Depending on the results of these further trials, KCC is considering using Gipave to resurface some of the highest-trafficked roads so as to minimise disruption at the most sensitive sites over the years - reducing the need to come back after 15 years to resurface again.
Giles Perkins, Live Labs Programme Director said: “It is very exciting to see the practical role that graphene can play in helping deliver improved local roads and better outcomes for customers. With Live Labs 2 having been announced with its focus on net-zero highways, we hope to see more innovations in this space helping the sector to reduce its whole life impacts.”
To find out more about the research undertaken, visit https://www.nottingham.ac.uk/research/groups/ntec/documents/design-of-pavements-incorporating-gipave-oct-2021.pdf
The ADEPT SMART Places Live Labs programme is a two-year £22.9 million project funded by the Department for Transport and supported by project partners SNC-Lavalin’s Atkins business, EY, Kier, 02, Ringway and WSP.
Nine local authorities are working on projects to introduce digital innovation across SMART mobility, transport, highways, maintenance, data, energy and communications. Live Labs is part of ADEPT’s SMART Places programme to support the use of digital technology in place-based services.
Contextual notes for editors:
Gipave, which has been developed by Iterchimica, is a patented Graphene Plus-enhanced asphalt concrete supermodifier which is used to build and/or resurface roads in a more environmentally responsible manner, while ensuring an improved road surface lifecycle. The product is the result of a six-year research program in collaboration with Directa Plus – producer and supplier of Graphene Plus, G.Eco and the University of Milan – Bicocca.
Graphene Plus, a pure form of graphene produced by Directa Plus through a sustainable process, is certified as safe for humans and the environment. As well as using waste plastics which would not normally be recycled, the asphalt containing Gipave can be entirely recycled.
To date, Gipave has also been used in several trials in Italy and in the UK including a number of roads and airport taxiways. All tests conducted by universities and laboratories have shown excellent results in terms of increased pavement performances, extending the service life of the surface which minimises maintenance costs.
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