Nygatan in Stockholm became Sweden’s first asphalt-paved street in 1876. Since then, almost all of the capital’s streets have been asphalted, re-asphalted and repaired. Wear and tear like potholes cause numerous and costly problems. Now a Swedish innovation has made it possible to mitigate upkeep for longer lasting roads. The innovation is a bio-based asphalt that is also favorable for the environment.
Asphalt has been used for thousands of years as a sealant and as a building material. The modern way to manufacture asphalt was developed in the first part of the 1800s. Nowadays, about one ton of asphalt per person per year is manufactured in Sweden.
This is pretty standard in other western European countries where the total volumes of asphalt produced amounts to hundreds of millions of tons per year.
Asphalt consists of stone and bitumen, a petroleum-based binding agent. Stone and bitumen are heated and mixed in an asphalt plant into a thick paste. By varying the stone material, their size and the binder yields asphalt with varying properties.
“Asphalt is a very durable material but heavy transport and temperature fluctuations during the winter can take its toll on roads and streets,” says Thomas Utegård, Marketing at NCC. “Every year, tens of thousands of potholes are repaired and when it comes to the environment and quality, there is a big difference between the materials that fill in the holes. We recently launched BINAB, a new division, to produce NCC Repasfalt which has a much better environmental performance than traditional cold asphalt.”
Bio-based asphalt fixes potholes
“NCC Repasfalt is a cold, self-curing, bio-based and environmentally friendly asphalt mix that offers the same durability and quality as conventional hot asphalt. It can be used on all asphalt surfaces – even on busy highways,” says Utegård. “Every year, one million tons of solvents are spread in the air as a result of repairs with traditional cold asphalt. Each ton of cold asphalt contains 10 to 25 liters of naphtha. With NCC’s Repasfalt, solvent emissions can be completely eliminated.”
The secret of the new asphalt is that the chemical solvents are replaced by a proprietary, bio-based and renewable natural oil. The oil is a waste product from an industrial process that usually gets burned, but NCC Repasfalt has found a better use. After reacting with water, the oil hardens together with the bitumen.
“This type of asphalt is preferred for repairing potholes, large cracks, damage in wells and bridge joints. It is well suited for repairing damage of up to three-square meters and the result is equivalent to conventional cold asphalt and more durable. It can be applied during wet and cold conditions. The coating will not be damaged by rain during or after application and may be used immediately,” concludes Utegård.
Repasfalt is manufactured according to a secret recipe in the small town of Braunau, Austria. NCC has Nordic rights to the material to use it in their service operations. Among the customers who purchase the product are municipalities, private companies with large areas of asphalt, road associations, parking companies and real estate companies. The price is relatively high, which means that Repasfalt cannot replace conventional asphalt in coating entire roads or larger areas.
NCC Green Asphalt®
NCC Green Asphalt® is another example of an environmentally friendly product that NCC has developed in recent years. High process temperature has long been regarded as a prerequisite to obtain strong enough asphalt for use on highways and other areas with heavy traffic. Most of the asphalt produced and placed on Swedish roads is therefore warmly produced, which means that the aggregate and bitumen are heated and mixed at about 160 ° C. The process of traditional asphalt production is both energy-intensive and expensive, but by lowering the temperature to 120 ° C, carbon dioxide emissions can be up to 30 percent lower.
The environmentally friendly method for the production of asphalt is based on first adding water to the binder bitumen and then “blending” the mixture. The process makes the asphalt mix more convenient to handle and manufacturing temperatures can be lowered. The result is a more homogeneously mixed asphalt and the method makes it possible to use harder bitumen thereby creating a more resistant coating. The green asphalt mix is easily packed, has a tight consistent finish and fewer holes – properties that reduce the risk of frost damage and oxidation.
In addition to the reduced emissions of carbon dioxide, carbon monoxide and nitrogen oxides into the environment, the lower process temperatures are also beneficial from a work environment perspective. There is less smoke, dust, and odor that mean that volatile organic contaminants and aromatic hydrocarbons are minimized.
The article was published in August 2014