Main content | back to top
A cooler way to lay roads
Millions of kilometres of asphalt-paved roads across the world provide essential routes for transport. Construction firms lay more every day. Mixing and laying asphalt traditionally uses a lot of energy and produces carbon dioxide (CO2). A Shell-patented process lets companies do this at lower temperatures, saving energy and reducing CO2.
Road-building companies traditionally heat bitumen – the residue from crude-oil refining – and mix it with hot sand and gravel to make asphalt. The high temperature needed to make these mixtures consumes a lot of energy, resulting in CO2 emissions. An advanced Shell process enables companies to mix and lay asphalt at lower temperatures. This brings environmental benefits to road building – such as 25-35% lower CO2 emissions – at every step.
Preparation
Conventional asphalt: To soften the bitumen for mixing, the asphalt ingredients have to be heated to between 160°C and 190°C – the temperature range for cooking a turkey.
Shell WAM* Foam asphalt: Soft bitumen coats the sand and gravel at temperatures 50°-60°C cooler than conventional bitumen. A type of hard bitumen is then frothed up with water – like milk at an espresso bar. In its bubbly state, the hard bitumen blends readily into the asphalt mixture.
Heat and CO2
Conventional asphalt: Fuel is burned to heat the asphalt ingredients before mixing. This produces CO2 emissions.
Shell WAM* Foam asphalt: The lower preparation temperature means that 25-35% less energy is used at the mixing plant, resulting in lower CO2 emissions.
Dust and fumes
Conventional asphalt: The hot bitumen emits fumes. The mixing sand and gravel generate a lot of dust.
Shell WAM* Foam asphalt: Lower-temperature mixing gives off far less dust and fumes.
Road surface
Conventional asphalt: Dump trucks deliver the hot asphalt to the work site, where a paver spreads it and a roller compacts it.
Shell WAM* Foam asphalt: Conventional pavers and rollers easily spread and compact the asphalt, even at lower temperatures. The dash of hard bitumen added to the mix strengthens the soft bitumen, making the asphalt as hard-wearing as conventional asphalt.
The Shell WAM Foam process blends a runny soft bitumen and a frothy hard bitumen. This is done at lower temperatures than the conventional asphalt-mixing process, saving energy and reducing CO2 emissions.
A Dutch company has recently adapted the WAM process to include recycled asphalt, bringing even greater environmental benefits.
* WAM, which stands for “warm asphalt mix”, is a registered trade mark of Shell Brands International AG.
Page Tools
