A Street with a New Function
Recipe for a road with a new, additional function. The ingredients:
Quartz powder and quartz sand
Both aggregates are used to increase the strength of concrete. Quartz sand forms the bulk of the concrete, while quartz powder acts as a filler. The substances are among the main components of the granulate.
Under UV light, TiO2 acts as a catalyst to accelerate the conversion of nitrogen oxides into harmless, water-soluble nitrates. The TiO2 particles are not consumed during the reaction.
Cement serves as a binder and is the main component of the innovative asphalt. It produces strength-forming CSH phases through the hydration of cement clinker (e.g., C3S, C2S) with tempering water.
The synthetic aggregate for ClAir® Asphalt consists of crushed ultra-high-performance concrete (UHPC) mixed with titanium dioxide and other materials. The raw UHPC has a TiO2 content of about five percent. For the aggregate, the UHPC is crushed to a 1/3 mm grain size (TiO2 content <1%). It can be used for all load classes. In the road paving process, about one kilogramme of the granulate is sprinkled directly into the hot asphalt per one square metre of road. Under UV light, the material accelerates the conversion of air pollutants such as nitrogen oxides into harmless nitrates. It also reduces the rolling noise of vehicles travelling on the road.
In this project, STRABAG not only developed the recipe and the installation process, but also optimised the machine and processing technology as well as the sensors for monitoring the temperature and distribution of the mix. The project was managed by PSS in Bad Hersfeld.
Here you can see how the new building material and the paving technique are tested in a construction project (and on a test stretch) on the Federal Highway 1 in Geltow near Potsdam.
Installation of the road surface
1. The paver-mounted spreader
The spreader is mounted to the paver directly behind the screed. Through an electrical coupling, the spreader adapts to the speed of the paver, keeping the spread rate even during installation. Only a small amount of the aggregate is necessary for full-surface coverage – about 1.3 kg/m².
The spreading width is between 2.5 and 5 m; with attachments, the paver-mounted spreader can be extended up to 8 m. The spread rate is 300 to 3,000 grams per square metre.
2. The innovation bunker
The charging concept fills the paver-mounted spreader continuously with the aggregate. The innovation hopper consists of an asphalt bunker and an aggregate bunker. It is also equipped with temperature and level sensors. A hydraulic flap on the aggregate bunker allows for a separate filling of asphalt mix and aggregate. The aggregate is transported by means of a conveyor belt to the spreader behind the screed. The asphalt bunker holds about 27 tonnes of material. The capacity of the aggregate bunker is up to 2 tonnes.