This week’s extraordinary spell of hot weather is causing roads across the UK to soften and stick to tyres. The bitumen, also known asphalt and used in road construction; softens and loses its strength when the temperature is too high, and will harden back again when temperatures fall, according to expert Howard Robinson, chief executive of the Road Surface Treatments Association based in Wolverhampton.
This calls for a little extra caution while driving on the roads, until the weather improves and the roads are properly repaired. It is especially better to exercise caution if there are heavy vehicles on the road or typically use it. The larger weight of the vehicles can cause the road to bend in to unnatural bumps and ridges- which in turn can cause nasty surprises in the form of sudden and violent jerks while driving. This is doubly important should there be a toddler on board.
This was the hottest June on record since 1995, and is expected to also be the longest spell of hot weather since. Councils across the UK- including Cambridgeshire and Norfolk are using road gritters, normally used in the winter to spread salt, to spread granite dust or sand and stabilise the bitumen, making the road safe again for vehicles. This is a standard best practice during hot temperatures according to Robinson. He likened the asphalt to chocolate- its strength and hardness go up and down depending on the temperature.
However, he termed the melting of the roads in the summer as ‘not surprising’ during a heatwave and said that the roads could be quickly treated and be back to normal when the temperatures reduce.
The asphalt is used to bind the gravel and sand used in the construction of the road. Essentially it acts as the glue that sticks everything together. At around 50 degrees Celsius, the asphalt begins to soften and rise. The result being that the road becomes quite literally ‘unglued’ from its constituent components.
With outside temperatures hovering at 31 degrees for the past week, the black surface of the road seems to have absorbed enough heat to reach its ‘melting point’.
This could be prevented by using asphalt produced using a new specification introduced after the heatwave in 1995. By using polymer modified binders with hot rolled asphalt, the melting temperature of the road goes up to approximately 80 degrees Celsius. However, the downside is that it is more expensive to use than the standard asphalt.
Robinson put the percentage of roads using the modern technology at around 5 percent in the UK. This is largely due to cost considerations as the more expensive asphalt only makes financial sense on roads expected to carry heavy traffic. Other products that usually include polymer modified binders such as thin surface courses as well as surface dressings used to improve skid resistance and seal road surfaces can also help prevent melted roads during extreme weather.