The effect of the crumb rubber type and amount on dry process modified asphalt mixture and on low-temperature cracking and high-temperature rutting

Abstract

One of the best examples of circular economy is the application of crumb rubber for asphalt mixture or bitumen modification. The main objective of this study was to determine the effect of crumb rubber type and amount on dry process modified asphalt mixture performance in terms of rutting resistance, water sensitivity, air void content, stiffness, resistance to fatigue and low-temperature cracking. The study shows that the use of untreated crumb rubber increases the air void content by up to 2.7% compared to the reference mixture while the use of treated crumb rubber reduces air void content up to 0.9%. The use of untreated and treated crumb rubber from 0.5% to 3.0% has a negative effect on water sensitivity (strength decreases by 59.5%). The use of crumb rubber up to 1.5% has a positive effect on resistance to rutting, stiffness and resistance to fatigue (proportional rut depth PRDAIR is improved by 0.6–1.1%, stiffness – by 15.4–16.2% and resistance to fatigue – by 24.7–24.9%). This research revealed that the amount up to 3.0% of both types of crumb rubber has a positive effect on the resistance to low-temperature cracking (40.6–52.1%) comparing to the reference mixture with neat bitumen.