New asphalt likes a sip of rainwater

What is Drainphalt? Inge: "A permeable asphalt, specially developed for laying on parking lots, driveways and roadways around buildings. The innovative paving was developed because of the many requests from customers to bring something similar to the market. In 2017, plans to develop Drainphalt became concrete after we participated in Willemen Groep's innovation competition."

Unprecedented water drainage properties
Willemen Infra has started laying test sections to perfect the composition of the special asphalt. "The final result is impressive. The asphalt is permeable to water and has a large storage capacity. The grain size is a maximum of 32 mm; the asphalt therefore has 30 % cavities. This not only gives Drainphalt perfect permeability properties, but also gives water ample time to seep through to the underlying layers. This is how it eventually reaches the groundwater," explains Inge.

Drainphalt also acts as a storage buffer for the water. The buffer capacity can be called very impressive: "This asphalt can buffer 300 liters per m³. Drainphalt also retains its properties in the event of frost. Of the well-known problem with ZOAB , freezing to pieces, Drainphalt does not suffer."

Production and processing
The all-new asphalt is produced at Willemen's asphalt plants at 135˚ to 140˚ Celsius. Inge explains, "This ensures less CO₂-emissions and makes it more pleasant for the road worker during placement. For installation, one needs a permeable foundation and subsoil that is sufficiently load-bearing. In other words, an unbound foundation and sandy soil."

On the parking spaces, 20 cm of Drainphalt will be applied on top of the foundation. The roadways between the bays will first receive 16 cm of Drainphalt and then a 4 cm closed top layer. "The drainage from the driving lane goes towards the Drainphalt on the parking spaces, after which the water is absorbed into the Drainphalt. Because the layer of Drainphalt under the closed top layer is in direct contact with the Drainphalt on the parking lot, it therefore also buffers water under the roadway."

Tom Willemen, CEO of the Willemen Group, officially opened the event.

Spectacular demonstration
The influential audience on Nov. 27 included members of the press and media in the morning, and professionals from road construction and government agencies in the afternoon. Tom Willemen, CEO of the Willemen Groep, officially opened the event in the morning. To top it off, the public was treated to spectacular demonstrations that day, on the parking lot of Flanders Expo in Ghent. Willemen Infra had installed a test section with Drainphalt and rained down a month's worth of water on it, via an artificial cloud. No less than 1,400 liters of water on 20 m² fell down on the Drainphalt, resulting in ... dry feet. Drainphalt did exactly what it was designed to do and neatly drained the downpour.

In conclusion, Inge says, "We are first concentrating on the Belgian market with Drainphalt and will offer it from Willemen Groep itself, but other road builders can also collect it from our asphalt plants. Eventually we will move to a situation where Drainphalt is produced worldwide under license."