Paving the roads of the future

Author Giulia Squadrin

The number of vehicles on the road globally is likely to double in the next 30 years.

This will increase the pressure on already crumbling road systems in many cash-strapped European countries, including the UK

Motorists demand higher performance roads that stand the test of time, while governments look to keep budgets under tight control.

Concerns over the environmental impact of road projects and paving materials also need to be taken into account.

Meanwhile, bitumen and asphalt suppliers continue to hope for an increase in spending on maintenance and projects to support demand for their road paving products.

Speciality modified bitumen, such as polymer modified bitumen (PMB) and polymer modified asphalt mixtures (PMAs), could well fill the gaps.

The market has been growing significantly in recent years and offers numerous benefits, allowing for longer periods of time between repair work, greater intensity of use and reductions in noise and pollution.

Work is being done across the globe to improve the quality of paving materials to cope with the challenges posed by climate change, population growth, and ever rising standards required for road and highway performance.

To sustain the weight of the increased number of vehicles and reduce the likelihood of traffic backlogs, European governments focus on improving road quality and bitumen performance, investing in new technologies and increasingly promoting the use of polymers and additives in asphalt mixtures.

These elements increase the durability of road surfaces by at least one third, consequently reducing rehabilitation and maintenance costs.

Polymers, rejuvenators and additives also significantly reduce greenhouse emissions and energy consumption, cutting manufacturing temperatures and promoting the application of technologies with a lower environmental impact.

New road projects — especially for highways — have higher performance and standard requirements, which can only be met by employing new technologies, such as PMB and PMAs.

Both can be equally effective, but are slightly different in terms of production and logistics.

Polymer modified bitumen is obtained through wet process, meaning polymers — mainly styrene–butadiene–styrene (SBS), styrene–isoprene–styrene (SIS) and styrene–ethylene/butylene–styrene (SEBS) — are added to bitumen in the production phase at the refinery.

Combinations of the various polymers generate different PMB grades — such as 25-55/55 for binders and 45-80/65 for the upper layer — which are traded at different prices, and are traded at a sizeable premium to standard bitumen grades.

In the past five years, requirements of polymer-modified bitumen have grown by 5pc in Poland, reaching an overall market share of 20pc, while demand for PMB in Germany is 30pc of total market share, Onico general bitumen manager Tomas Borodziej said during the Argus European Bitumen and Asphalt conference in Porto, Portugal.

Russia is one of the main sources of PMB and bitumen emulsions for central European markets, with Gazpromneft being one of the key PMB producers and exporters in the country. Serbian, Hungarian, Polish and Bulgarian refiners are also producing various grades of polymer-modified bitumen to meet regional demand.

Polymer modified asphalt mixtures are obtained through dry process, meaning that polymers and additives are added to the asphalt mixture in the asphalt pug mill, after the production phase is completed.

PMAs are used extensively in many parts of the world, but especially in north Africa and Latin America where warm temperatures increase the risk of asphalt rutting.

Large portions of Italian highways and up to 1,000km of roads in Romania have also been built with PMAs, using additives supplied by Italian firm Iterchimica, one of a number of leading innovators in the field of asphalt additives, also explained at the Porto conference.

Pavements with polymer additions exhibit greater resistance to deformation, less fatigue damage, less thermal cracking and less temperature susceptibility. PMB and PMAs offer higher rigidity and durability and have better resistance to cracks, rutting and stripping, ensuring high performance standards even in extreme weather conditions.

The downside to these niche products is a higher initial price, although suppliers stress this can be repaid by the longer life and the lower environmental impact of such grades.

Refiners and road contractors seem to believe that PMB and modified asphalt mixtures are the way forward. Will these new technologies reshape the concept of road performance and sustainability for the car of the future? 

"Eventually, all cars are going to be autonomous," American businessman Steve Jurvetson said. Autonomous or not, cars will still need roads to drive on.

 

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