Strategies for Incorporating High Reclaimed Asphalt Pavement Contents in Asphalt Mixtures
Fawaz Kaseer, Texas A&M UniversityShow Abstract
Akash Bajaj, Texas A&M University
Amy Epps Martin, Texas A&M University
Edith Arambula Mercado, Texas A&M Transportation Institute
Elie Hajj, University of Nevada, Reno
Utilization of high contents of reclaimed asphalt pavement (RAP) has become a common practice to reduce construction costs of asphalt pavements, maintain dwindling natural resources, and improve sustainability. However, this practice poses technical challenges in terms of asphalt mixture production, compaction, and long-term cracking performance. To meet these challenges, mixture component and/or proportioning adjustments are recommended such as employing a softer base binder and/or adding a recycling agent (also called rejuvenator) at a specified dose. In this study, the effect of these adjustments on asphalt mixtures was evaluated via resilient modulus (MR) test, dynamic modulus (|E*|) test, Illinois flexibility index test (I-FIT), disk-shaped compact tension (DCT) test, bending beam rheometer for asphalt mixtures (BBRm) test, uniaxial thermal stress and strain test (UTSST), Hamburg wheel-track test (HWTT), and asphalt pavement analyzer (APA). The effect of these adjustments was also evaluated via the rheological properties of binder blends using the dynamic shear rheometer (DSR) frequency sweep test. Test results showed that only the mixtures/blends with an appropriate dose of recycling agent consistently yielded the best performance among others, after short- and long-term aging conditions.
Effect of Bio Oils on Binder and Mix Properties with High RAP Binder Content
Daba Gedafa, University of North DakotaShow Abstract
Rajib Saha, Florida International University
Daba Gedafa, University of North Dakota
The use of Recycled Asphalt Pavement (RAP) has significantly increased in construction and rehabilitation of flexible pavements to ensure proper utilization of limited natural resources. Bio-oils could act as a rejuvenator and be able to reduce the stiffness of binder and mixes with high RAP content. Two oils, namely Waste Cooking Oil (WCO) and Soy Oil, are potential sources of bio-oils that are abundant and yet to be explored. This study was conducted to explore the effects of the bio-oils on binder and mixture properties that contain high percentage of RAP binder. Two different types of aggregates and two virgin binders were used in the study along with RAP binder that was extracted and modified by the bio-oils in the laboratory. Unaged, Rolling Thin Film Oven (RTFO) aged, and Pressure Aging Vessel (PAV) aged virgin and bio-oil modified RAP binder were tested for both high and low-temperature rheology using Dynamic Shear Rheometer (DSR). Virgin binders were tested as control specimen while 100% RAP binder was used to see the level of modification of RAP binder. These modified binders were further used to make HMA specimens that were tested using Asphalt Pavement Analyzer (APA), Semi-Circular Bending (SCB), and Disk-shaped Compact Tension (DCT) tests to determine the rutting, fatigue cracking, and low-temperature cracking resistance, respectively. Both binder and mix results showed that modified binder with bio-oils, virgin binder, and high RAP binder has maintained/improved the performance of HMA.
Evaluation of Plant-Based Bio Oil and Petroleum-Based Aromatic Oil Rejuvenator Based on Cracking Susceptibility of Hot Mix Asphalt with High RAP Content
Shams Arafat, Louisiana Technological UniversityShow Abstract
Nazimuddin Wasiuddin, Louisiana Technological University
Motivation behind the inclusion of reclaimed asphalt pavement (RAP) in asphalt mix involved environmental benefits and economic savings. Because of highly aged asphalt binder in the RAP, it is a potential source of inferior performance, especially the cracking resistance. Use of rejuvenating agent is one of the approaches to accommodate the RAP in hot mix asphalt. In this study plant-based and petroleum-based rejuvenator were evaluated based on cracking susceptibility of the hot mix asphalt prepared with low (15%) and high (30%) RAP content. Cracking susceptibility of the mix was determined by semi-circular bend test performed at intermediate and low temperature as well as by overlay test which evaluates the resistance to reflective cracking. It was observed that use of rejuvenator can successfully restore the cracking resistance of the mix made of low RAP content. For mix with high RAP content the cracking potential cannot be restored as the control mix but can be improved significantly. Petroleum based rejuvenator performed better to resist cracking at intermediate temperature, but plant-based rejuvenator improves the low temperature cracking properties of the high RAP mix. Plant-based rejuvenator requires lower amount to lower the RAP binder grade to a certain level compared to petroleum based one. Both the types of rejuvenator improve the resistance to moisture induced damage. However, use of maximum amount of rejuvenator should be limited because it can adversely affect the rutting resistance of the mix.
Total Recycled Asphalt Mixes Characteristics and Field Performance
Fazal Safi, University of Illinois, Urbana ChampaignShow Abstract
Imad Al-Qadi, University of Illinois, Urbana Champaign
Kamal Hossain, Memorial University of Newfoundland
Hasan Ozer, University of Illinois, Urbana Champaign
The use of recycled materials in asphalt concrete (AC) pavement has increased significantly for economic and sustainable benefits. However, the use of recycled materials can pose risks to the performance of asphalt pavements. The Illinois Department of Transportation (IDOT) has developed five total recycled asphalt (TRA) mixes in the pursuit of sustainable pavements. These mixes contained up to 60% asphalt binder replacement (ABR) obtained from reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS). Virgin aggregates were replaced by 100% recycled aggregates including RAP, steel slag, and recycled concrete aggregate (RCA). Based on laboratory testing, all mixes offered excellent rutting resistance because of high ABR. The TRA mixes were relatively less compliant and not very sensitive to field aging, whereas indirect tensile strength tests showed indistinguishable results. All mixes have comparable complex modulus |E*| and phase angle (ϕ) values at low temperatures. Plant-mixed lab-compacted (PMLC) mixes had a relatively lower flexibility index (FI) as compared to field cores after construction. The FI values for field cores decreased with aging and/or an increase in recycled materials. An exponential increase in transverse cracking was observed in the field because of relatively high ABR, and/or RCA/steel slag content. The field transverse cracking progression over time and FI values are well-correlated. The 3-D balanced mix design was introduced and was successfully used to distinguish between mixes and is proposed as a tool for better control mix designs for optimum field performance.