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"This study is to evaluate the mechanical and chemical properties of the asphalt concrete (AC) mixture, fine aggregate matrix (FAM), and binder modified by three different rejuvenators and warm mix asphalt (WMA) additive. In this regard, for testing of AC mixtures, the dynamic modulus, dyamic creep, and semicircular bending (SCB) fracture tests were conducted. For testing of FAM mixtures, three types of strain-controlled torsional oscillatory shear tests (i.e., strain sweep, frequency sweep, and time sweep) and the static creep-recovery tests were employed for comparative purposes. For binders, the Fourier transform infrared (FTIR) spectroscopy, saturates-aromatics-resins-asphaltenes (SARA) analysis, dynamic shear rheometer (DSR), and atomic force microscopy (AFM) were used to characterize the physiochemical and mechanical aspects of the asphalt binders. Base on test and analysis results, the rejuvenators can soften the materials, increase the rutting potential and may mitigate moisture damage resistance, while improving cracking and fatigue resistance of the asphaltic mixtures. A comparison between AC mixtures and corresponding FAM mixtures revealed the interrelationships between the two length scales. From the binder tests, it appears that the rejuvenators decrease either carbonyl or sulfoxide of both indices. Addition of rejuvenators to the mixture of recycled asphalt binder and virgin binder led to a decrease in the amount of asphaltenes. Furthermore, rejuvenators improved colloidal instability index (CII), which implies that the aged binder has become more stable due to rejuvenation. The AFM phase images of binders indicated that the softening effect of rejuvenators corresponds to the mechanical test results from DSR" (page ii).
The use of Rejuvenating Agents (RAs), as Recycled Asphalt Pavement (RAP) modifiers, has been increasing over the past years. However, the field performance of asphalt mixtures containing high-RAP materials and modified with RAs has raised some concerns regarding the long-term performance of RAs. This study evaluated the laboratory and field performance of high-RAP mixtures with and without bio-oil RA. Three sets of plant-produced specimens were collected: 1) laboratory-compacted; 2) field-compacted and cored after paving; and 3) field-compacted and cored after one and two years. The Hamburg Wheel Tracking (HWT) test was used to evaluate the specimens' resistance to rutting and moisture damage. The Semi-Circular Bending (SCB) fracture test was performed to examine the specimens' resistance to cracking. The results showed that using the bio-oil RA resulted in an increase in cracking resistance and a decrease in rutting and moisture damage resistance of the RAP-blended mixtures compacted in the laboratory. However, after one and two years of exposure to the environmental conditions and traffic loads, the effect of RA on moisture and rutting susceptibility of the mixtures reduced. The cracking resistance of specimens, estimated by Flexibility Index (FI) and Cracking Resistance Index (CRI), and Tukey's Honestly Significant Difference (HSD) test results implied that the bio-oil RA used in this study could not provide long-term improvement for the RAP-blended mixtures in the laboratory-aging and field-aging conditions. The field performance observations showed that the use of the bio-oil RA in the second layer might have indirectly resulted in more cracks (fatigue and thermal) and ruts in the surface layer.(Page i)
"A previous study by the authors have demonstrated effectiveness of three rejuvenators: R1 (triglyceride/fatty acid: agriculture-tech based), R2 (aromatic extract: petroleum-tech based), and R3 (tall oil: green-tech based) on rejuvenating properties of the aged binder. In that study, it was observed that the rejuvenators made high-RAP mixtures softer and more compliant, which may increase the rutting potential, while they simultaneously improve cracking resistance of the high-RAP materials. Research outcomes and findings from previous study resulted in consequential research needs for more specific investigation of high-RAP mixtures with rejuvenators in order to achieve realistic implementation into future high-RAP paving projects in Nebraska. This study thus aimed to investigate the effects of type, dosage, and treating methods of rejuvenators when they are added in aged asphalt materials. To meet the goal, we used the three rejuvenators (R1, R2, and R3) by conducting various binder-level and mixture-level tests in this study. For the binder-level testing, the performance grading (PG) method was used to primarily determine proper dosages targeting desired binder grades, and two chemical tests (i.e., Fourier Transform Infrared and Saturates-Aromatics-Resins-Asphaltenes analysis) were also conducted to examine chemical characteristics altered by rejuvenation and further aging process. The selected dosage levels from the binder testing were then applied to asphalt concrete (AC) mixture-level performance evaluation by conducting two tests: flow number for rutting and semicircular bending fracture with and without moisture conditioning for cracking. AC mixtures treated with rejuvenators at the dosage levels selected from the binder PG testing showed improved fracture resistance compared to unrejuvenated mixtures. Test-analysis results also indicated that PG binder testing, although it can successfully determine the proper dosage range of rejuvenators, is limited by only assessing the effects of rejuvenators in mechanical properties, which can be better aided by integrating chemical characterization that provides a more in-depth material-specific rejuvenation process. In addition, it appears that rejuvenation methods (e.g., blending and/or curing) can alter performance of aged mixtures. Therefore, the selection of rejuvenators and their implementation into practice should be carried out by considering multiple aspects not only by its PG recovery." (leaf ii).
This book is a printed edition of the Special Issue "Advanced Asphalt Materials and Paving Technologies" that was published in Applied Sciences
This work presents the results of RILEM TC 237-SIB (Testing and characterization of sustainable innovative bituminous materials and systems). The papers have been selected for publication after a rigorous peer review process and will be an invaluable source to outline and clarify the main directions of present and future research and standardization for bituminous materials and pavements. The following topics are covered: - Characterization of binder-aggregate interaction - Innovative testing of bituminous binders, additives and modifiers - Durability and aging of asphalt pavements - Mixture design and compaction analysis - Environmentally sustainable materials and technologies - Advances in laboratory characterization of bituminous materials - Modeling of road materials and pavement performance prediction - Field measurement and in-situ characterization - Innovative materials for reinforcement and interlayer systems - Cracking and damage characterization of asphalt pavements - Recycling and re-use in road pavements This is the proceedings of the RILEM SIB2015 Symposium (Ancona, Italy, October 7-9, 2015).
Asphalt Pavements contains the proceedings of the International Conference on Asphalt Pavements (Raleigh, North Carolina, USA, 1-5 June 2014), and discusses recent advances in theory and practice in asphalt materials and pavements. The contributions cover a wide range of topics:- Environmental protection and socio-economic impacts- Additives and mo
Abstract: The desire to find more sustainable paving practices as well as the dramatically rising binder costs driven by the growing global demand for paved roads, has led to increased interest of the use of reclaimed asphalt pavement (RAP) in very high amounts. So far the major industry trend has been to develop procedures, invest in technologies and build confidence in mixtures with up to 40 % RAP content. However, a few innovators have refined 100 % recycling technologies over the past four decades to a level where routine production of 100 % recycled hot mix asphalt is in clear sight. Rejuvenators are an integral part of 100 % recycled asphalt production and they can also allow to significantly increase the RAP content for conventionally produced asphalt mixtures. An evaluation of the feasibility of production of 100 % recycled hot-mix asphalt was made and the use of rejuvenators is presented in this study. 100 % recycling is discussed by evaluating ten readily available production technologies along with proposing mix design procedures and identifying best RAP management strategies. A total of eleven different products were evaluated for restoring the RAP binder grade with a definite conclusion that achieving target grade (PG or empirical specification) is possible. In addition a rheological, micromechanical and chemical characterization was performed with select rejuvenators and binders from Strategic Highway Research Program (SHRP) library. To further assess the rejuvenators and feasibility of 100 % RAP recycling a series of 100 % mixture tests were performed that indicated significant improvement in low temperature and fatigue cracking resistance while providing a rut resistant mixture. With the use of some rejuvenators a performance equal to that of reference virgin mix was achieved. Based on these findings of rejuvenator effectiveness a methodology for choice of rejuvenator type and dose was proposed. Finally, a cradle-to-gate analysis of environmental effects was performed which indicated 35 % CO2eq savings per ton of produced 100 % RAP asphalt mixture compared to virgin mix while cost analysis showed at least 50 % savings in material related expenses. A short video summarizing the research is available at http://youtu.be/y-rYvdGiEbY.