Project Summary
Crumb rubber (CR) modified asphalt pavements: As part of a major research effort funded by the Michigan Department of Environmental Quality (MDEQ), we have been working towards finding feasible methods of using scrap-tire rubber (i.e., crumb rubber (CR)) in asphalt pavements in Michigan. We (in collaboration with the Ingham County) constructed seven different test sections in and around Lansing, MI. We conducted extensive laboratory testing to better understand the compatibility of various CR modified asphalt technologies (e.g., wet process, preswollen and polymer coated CR methods) with the local aggregates and binders. While working on the different technologies, we developed our own technology called the CR-hybrid, a hybrid CR modified mixture using both Terminally Blend and Dry technologies. The test section with the CR-Hybrid has been performing well. Furthermore, MDEQ funding also allowed us to perform fundamental research on CR modified asphalt pavements. For example, we developed methods (based on micromechanics) of back-calculating the dynamic shear modulus (|G*|) of swollen rubber within asphalt the crumb rubber modified asphalt binders. Validation of this method was done through 3D X-ray Computed Micro-Tomography (Micro-CT) imaging and 3D Finite Element Modeling using the real 3D X-ray Micro-CT images of CR-modified binders.
Impact
This project is anticipated to increase the market demand for scrap tire usage in Michigan. The design specifications for CR modified asphalt pavements as well as their performance data that will be obtained in this research will encourage design engineers to utilize CR modified asphalt pavements, which are shown in other States to work better and cost less. Some of the advantages of crumb rubber modified asphalt include: (i) Improved cracking and rutting resistance, (ii) reduced aging (oxidation) because of the anti-oxidants in the scrap tire rubber, (iii) improved skid resistance, (iv) decreased tire/pavement noise levels and (v) beneficial reuse of 1000-2000 scrap tires per lane mile (depending on the technology).
Acknowledgements
Funding for this project has been provided by the Michigan Department of Environmental Quality (MDEQ), Scrap Tire Market Development Grant. This support is greatly appreciated.