A new frontier in rubberized asphalt technology has been achieved with the new innovative product called Reacted and Activated Rubber (RAR). As introduced in AR2012 international conference and in the 2013 TRB annual meeting, RAR is composed of neat soft bitumen, fine grinded crumb tire rubber, and a siliceous Activated Mineral Binder Stabilizer (AMBS), at optimized proportions. RAR is produced by a simple low-energy process to form a dried granulated activated rubber. It can be added, directly to the pugmill, for producing any type of Hot Mix Asphalt (HMA) – Dense, Open Graded, Gap graded, SMA, etc., for replacing part of the asphalt cement (bitumen) at different proportions.
As reported, RAR modifies the neat bitumen by increasing its PG grading, while modifying also the resilience, and recovery properties. When added to HMA mixes, RAR showed much better Stability, Rutting & Fatigue resistance and low draindown in SMA mixes (without the fibers), under attractive cost/benefit and environmental conditions.
This paper summarized further successful R&D effort in the laboratory and in the field, where actual three Road Tests were performed and monitored in Israel, using RAR HMA mixes under hot climatic conditions. The RAR HMA mixes (Dense and Superpave "S" graded) were produced in conventional batch asphalt plants with the use of the regular SMA fiber-feeder for feeding the RAR directly to the pugmill without any additional heating or setting. The road tests included a residential street and highly trafficked industrial road in the city of Tel Aviv, and an access road to a very busy aggregate quarry. The performance and results so far (after more than two years of service from the first road test) have clearly strengthen the advantages of RAR Asphalt Rubber mixes achieved in the first phase of the research, leading to actual paving jobs, and new modified specifications for asphalt rubber in Israel.