Further steps have already taken place. In the cantons of Jura and Vaud, Weibel AG built two test sections on cantonal roads using rubber granulate asphalt. "A rough asphalt on a road with a medium load," explains Samuel Probst, "and a surface asphalt on a road with a relatively high load. After all, they were supposed to be real endurance tests."
Unlike previous experiences with the "wet" production process, the paving went "absolutely smoothly," according to the manager in charge. On site, the workers did not have to endure any odors from heated rubber, and the consistency and workability of the asphalt was comparable to a polymer-modified asphalt. Admittedly, it will only show its true character after years. Paving took place last summer; the pavement is thus still in its infancy.
Just like another test asphalt, which was laid as top layer at a heavily used intersection in Zurich. Its laboratory values were not beyond doubt: When the bitumen was hardness tested with a penetrating needle, the results fluctuated wildly and were sometimes well above the target values. "That suggests it might be too soft," says pavement specialist Martin Horat of the civil engineering office of the city of Zurich. "Let's see if there are deformations when it gets hot in summer."
Hans-Peter Beyeler, director at the "Eurobitume" association in Switzerland, is not particularly worried, though. "I already heard about that. I wouldn't worry about it for the time being," says the expert, who previously worked for almost 13 years as a pavement specialist at the Federal Roads Office (Astra). When rubber and bitumen are mixed, a new material is created; its behavior no longer corresponds to the original ingredients. His assessment: "The needle test may simply not provide useful information."
From his own experience, Beyeler understands that there is also resistance in the industry to asphalt as a "garbage chute" for recycled materials and skepticism about rubber in the road. Some 15 years ago, he witnessed how a test on the A1 in the canton of Aargau with rubber-modified bitumen, added as granules, went thoroughly wrong: The material was insufficiently dissolved in the mix; lumps formed in the asphalt. In the pavement, they spread on the surface; they had to be drilled out and filled with mastic asphalt.