Investigation on the use of a novel chemical bitumen additive with reclaimed asphalt and at lower mix production and construction temperatures: a case study

New regulations on bitumen fumes and aerosols, along with increasing traffic and climatic loads on highways, demand innovative construction materials. In this investigation, a novel isocyanate-based bitumen additive was used to pave 0.5 km of an asphalt binder layer with 50% reclaimed asphalt at 20-30°C below hot mix asphalt (HMA) temperatures, in Germany. During construction, bitumen fumes and aerosols were measured for both reference and modified asphalt mixtures. The reference mixture was paved using a similar mixture but with standard polymer modified bitumen, at standard HMA temperatures. For the investigation, a bitumen 70/100 was modified with 2.0% by wt with this novel isocyanate-based additive in an in-line procedure directly at an asphalt mixing plant without affecting production times. Bitumen and asphalt tests were conducted in the laboratory, on asphalt gathered from the construction site. Due to the temperature reduction, the emissions could be considerably reduced, while maintaining comparable asphalt performance..