SDA with a cooling effect
With the progressing climate change, heat stress and the number of tropical nights in cities and agglomerations are clearly increasing in Switzerland. In densely built areas, the so-called urban heat island effect intensifies summer heat: Sealed surfaces made of asphalt and concrete store large amounts of heat energy during the day and release it slowly at night. This leads to reduced nighttime cooling and affects the recovery and health of the population.
Since the available space in street areas is limited and greening measures are often only partially implementable, cool road surfaces are gaining increasing importance as a technical adaptation measure. They can help to lower surface temperatures and thus reduce local heat stress.
A central role is played by albedo, which is the reflectivity of a body. By using light aggregates in asphalt – for example, as part of the so-called corner replacement – a larger proportion of incoming solar radiation is reflected rather than absorbed. This leads to lower energy absorption and thus to lower surface temperatures. This effect is particularly beneficial during the hottest hours of the day, but also at night, as less heat is stored and released in the road body.
A particularly interesting example is the SDA surfaces with light corner replacement. They combine the advantages of reduced noise development with those of reduced heating, thus providing a synergy between noise and heat reduction. Since the aggregates are coated with black bitumen during installation, the light stone only becomes visible after a certain amount of wear. This process can be accelerated by targeted surface treatments such as grinding or water jetting.
A.05 Reducing the effect of heat islands with cool road surfaces
Municipality of Köniz - Fact sheet: "cool" road surfaces and "bio-bitumen"