To mark 50 years of the Shell Cariphalte range of polymer modified bitumen (PMB), Highways spoke to Professor John Read, general manager for bitumen technology at Shell.
In the UK what is the biggest growth area for the Shell Cariphalte product? Where do you feel it is underused and could prove to be effective?
Highways England's proposal for the Strategic Road Network comes as a response to increasingly highly trafficked infrastructure across the country. The multifunctionality of the Shell Cariphalte range can help provide the solutions necessary to solve the concerns raised in the HE report.
The decades of research and development, as well as application of the latest tools, such as Dynamic Sheet Rheometer (DSR) and Bending Beam Rheometer (BBR) proved that increasing the elasticity of roads reduce the permeant deformation and the rutting of asphalt pavement.
Increased road surface elasticity with Shell’s Cariphalte range of PMBs results in better ability to sustain high traffic volumes, which ultimately prolongs life of busy roads.
In addition, the application of lower temperature PMBs in the asphalt mix can significantly reduce cooling time, enabling roads to reopen up to 90 minutes sooner, reducing congestion.
Finally, Shell Cariphalte used in durable water drainage systems can help provide better water drainage for road surfaces, further reducing the noise impact on neighbouring communities and the environment.
There has recently been a lot of talk about road reinstatements. How can PMB help with solving issues around repaired joints which become the road’s weakest links?
Although the use of PMBs in processes such as trenching can provide a temporary fix, it is important to remember that after trenching has occurred road design becomes severely compromised. As the findings from the ALARM Survey show, opening a road to create a trench can reduce its structural life by up to 30% and the continuing high level of utility openings in England and Wales can have a further detrimental effect.
In practice, the optimum solution is doing everything possible to make sure re-instatement is done to a high enough standard – this is dependent on adequate legislation enforcement from local authorities.
What are the common challenges your tailor-made bitumen is asked to overcome by local authorities? What about Highways England?
Local authorities ask for tailor-made solutions which are designed to help address local challenges such as helping reduce congestion or odours associated with road construction. We’ve listened to these concerns and developed solutions that are better for communities and local authorities. Low temperature PMBs in the design of warm mix asphalt can deliver faster cooling times and ensure roads can be reopened by up to 90 minutes faster than traditional solutions.
Likewise, PMBs with odour-supressing technology like Shell Bitufresh help reduce odour levels by as much as 95-99%. Highly populated roads or city centres will feel the effects of this the most, as odours associated with road maintenance often result in complaints from people and local businesses. With regards to goals set by Highways England, PMBs can be designed to improve workability of asphalt when including RAP. The use of porous asphalt to combat road safety concerns and to reduce noise and water spray is another solution for HE's proposed SRN action plan.
With extreme weather on the rise, could you tell us a bit more about where any specific drainage asphalt is being used and how?
Porous asphalt, with its open textures asphalt design, allows water to ingress and flow away from the surface and base layers, thereby minimising water splashing and making roads safer for use. The inclusion of a PMB such as Shell Cariphalte High Performance in the asphalt mix provides the added benefit of noise reduction.
What are your plans for the next 50 years?
Society needs a mobility network of the future. A road network that can adapt to resolve challenges around climate change and technological progress through roads that can do a lot more than they do today. Road construction in future could be more akin to a service industry. This can include many exciting possibilities such as charging for EVs, capturing solar energy and air pollution particles and allowing for data capture and transfer.
Over the next 50 years we predict an expansion of the Shell Cariphalte range of products to meet upcoming demands, just as we have done in the 50 years up to now, and to help bring about these changes for the benefit of society.
