Abstract
The use of Reclaimed Asphalt Pavement (RAP) promotes and integrates sustainable solutions into civil engineering practices. Many transportation agencies limit the RAP content to a small percentage. Despite the environmental benefits and cost savings of incorporating RAP into asphalt mixtures, it may result in stiffer mixtures, especially at a higher RAP content, that could be prone to premature cracking. Virgin binder grade adjusting is typically followed to account for the stiffening effect of RAP which may require the use of softer binders. This could increase the cost of Hot Mix Asphalt (HMA) production due to the limited availability of such softer binders in practice. This study examined the use of rejuvenators to improve the performance of asphalt mixtures, with different RAP contents, through a balanced mix design approach to ensure sufficient resistance to cracking and rutting. Rejuvenators have the potential to restore the rheological properties of aged binders. Seven different commercially available rejuvenators were acquired and included in the testing program of this study. The results demonstrated that the use of rejuvenators in asphalt mixtures with RAP is beneficial and could offer environmental benefits and cost savings. However, it is more cost effective to incorporate rejuvenators in asphalt mixtures at high RAP content (e.g., 50 or 70 percent). The cracking performance of mixtures with certain rejuvenators and high RAP content could be comparable to that of the virgin mixture (0 percent RAP) with additional cost savings. The use of tall oil and waste vegetable oil were found effective in improving the cracking resistance and providing cost savings compared to other rejuvenators. The results of this study clearly demonstrated the importance of implementing a balanced mix design approach to optimize the design of asphalt mixtures prepared with RAP and rejuvenators to provide adequate performance in terms of cracking and rutting resistance. The balanced mix design should be supplemented by conducting cost analysis to compare different alternatives that provide acceptable performance. Furthermore, this study evaluated the cracking and rutting performance of 23 different asphalt mixtures produced and used in Idaho. The results demonstrated that these mixtures are expected to exhibit good cracking and rutting performance. In addition, the current practice followed by ITD of using anti stripping agents was found effective in resisting moisture damage.