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Reuse of polymer asphalt? Sustainability in optima forma
With the high residual value (20 years after construction) of Sealoflex modified asphalt, a new Sealoflex polymer modified binder was developed in extensive cooperation with AsfaltNu to reuse the old polymer modified asphalt. Partly because of this, a PR mixture has been applied to Schiphol Airport's Polderbaan and Aalsmeerbaan that meets the very highest quality requirements.
Of course, this concept is also applicable to public roads. For example, horizontal recycling of ZOAB and SMA granulate can make a significant contribution to achieving the sustainability goals of road authorities within their own acreage without compromising on quality.
In standard AC mixtures, ZOAB/SMA granulate is used sporadically and only in small quantities. However, large batches of ZOAB/SMA granulate are not usable even though the granulate consists of a high-quality crushed stone, filler and bitumen-rich mastic. A higher-grade application of ZOAB/SMA granulate in new ZOAB and SMA overlays thus offers many advantages. Application of more asphalt granulate scores favorably in the context of circular economy, cost savings and lower environmental impact (EQI).
By optimizing the screening process, it is expected to be possible to minimize material loss. This can be done, for example, by sieving all the ZOAB asphalt granulate to 3 mm. How sieving can best be carried out depends on the capabilities at the asphalt plant. A central asphalt plant could be a solution to the availability of suitable ZOAB and SMA asphalt granulate. With proper fractioning and screening, it is also possible to produce ZOAB and SMA overlays with at least 60% PR.
The quality of the binder in a high PR overlay is particularly important. Poor quality will result in a ZOAB/SMA that will soon exhibit fraying before reaching the expected service life. This is caused by the often extreme aging of ZOAB/SMA asphalt granulate. A new binder must therefore have a rejuvenating effect. By also choosing a polymer-modified binder, a long service life can be guaranteed. With customization from the entire chain, reuse is possible with a very high quality.
A product range developed specifically for this customization is Sealoflex® Bio-Recycling (BR). The bio-based rejuvenation additive consists of biological raw materials derived from biological residues, without displacing food crops. As a result, CO2 sequestered without adversely affecting the food supply. In these binders, a bio-based rejuvenation additive is combined with an SBS polymer. The polymer modification ensures long life and the rejuvenation additive upgrades the old bitumen in the PR and also results in better adhesion between the old and freshly added bitumen. Combined with a low temperature (LT) additive, this asphalt can also be produced and processed at up to 30°C lower temperature. These developments ultimately lead to 100% organic binders.
