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Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening.
This volume highlights the latest advances, innovations, and applications in the field of asphalt pavement technology, as presented by leading international researchers and engineers at the 5th International Symposium on Asphalt Pavements & Environment (ISAP 2019 APE Symposium), held in Padua, Italy on September 11-13, 2019. It covers a diverse range of topics concerning materials and technologies for asphalt pavements, designed for sustainability and environmental compatibility: sustainable pavement materials, marginal materials for asphalt pavements, pavement structures, testing methods and performance, maintenance and management methods, urban heat island mitigation, energy harvesting, and Life Cycle Assessment. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster multidisciplinary collaboration among different specialists.
Warm mix asphalt (WMA) has generated a lot of interest worldwide based on the potential to realize environmental benefits related to lower production temperature and safe disposal of crumb rubber (tires). However, barriers to complete implementation of WMA technology still exist because of the lack of understanding of how different additives affect the performance of crumb rubber modified (CRM) binders. This paper investigates the effects of three WMA additives and crumb rubber concentration on the low-temperature performance of the CRM binders. The WMA additives used in this study were Sasobit, RH, and Advera, and the ambient 40 mesh tire rubber at different concentrations of 10 %, 15 %, 20 %, and 25 % by the weight of asphalt binder were applied in this paper. Burgers model was used to describe the relationship between deformation and time for rubberized WMA binder. The models parameters such as relaxation time, delay time, creep stiffness, m-value and m/S(t)-ratio were applied to evaluate the low-temperature performance of the rubberized WMA binders. Furthermore, the statistical analysis of variance (ANOVA) technique was applied to quantify the effects of different WMA additives and crumb rubber concentrations on the rubberized asphalt binders' low-temperature performance. It was found that Advera could be used to enhance the low-temperature performance by enhancing the stress relaxation, whereas RH and Sasobit did not exhibit this ability, thereby weakening the low-temperature performance of the CRM binders. The crumb rubber concentration could significantly increase the rubberized WMA binders' low-temperature performance by influencing the flexural creep stiffness of the control binders.
The proceedings of the 2013 Airfield & Highway Pavement Conference: Sustainable and Efficient Pavements, held in Los Angeles, California, June 9-12, 2013 contains 123 peer-reviewed papers that focus on the latest developments and cutting-edge technological improvements in pavements and pavement sustainability. Topics include: advanced modeling, design, and analysis of pavements; construction and rehabilitation techniques; asphalt characterization and testing; recycling materials in pavements; pavement quality control/quality assurance; pavement sustainability and life-cycle assessment; nondestructive testing and evaluation; pavement management systems; and airfield and pavement case studies. This proceedings will be of interest to researchers, designers, project/construction managers, and contractors.
Sustainable road construction and maintenance could be supported when excellent warm-mix additives are employed in the modification of asphalt. These warm-mix additives provide remedies for today's requirements such as fatigue cracking resistance, durability, thermal cracking resistance, rutting resistance and resistance to moisture damage. Warm-mix additives are based on waxes and surfactants which reduce energy consumption and carbon dioxide emissions significantly during the construction phase of the pavement. In this study, the effects of two warm mix additives, siloxane and oxidised polyethylene wax, on roofing asphalt flux (RAF) and asphalt modified with waste engine oil (655-7) were investigated to evaluate the rheological, aging and failure properties of the asphalt binders. In terms of the properties of these two different asphalts, RAF has proved to be superior quality asphalt whereas 655-7 is poor quality asphalt. The properties of the modified asphalt samples were measured by Superpave(TM) tests such as Dynamic Shear Rheometer (DSR) test and Bending Beam Rheometer (BBR) test as well as modified protocols such as the extended BBR (eBBR) test (LS-308) and the Double-Edge-Notched Tension (DENT) test (LS-299) after laboratory aging. In addition, the Avrami theory was used to gain an insight on the crystallization of asphalt or the waxes within the asphalt binder. This study has however shown that the eBBR and DENT tests are better tools for providing accurate specification tests to curb thermal and fatigue cracking in contemporary asphalt pavements.
Rubberized asphalt has been used to improve the mechanical characteristics (e.g., rutting resistance, fatigue life, friction, and skid resistance) of hot mix asphalt mixtures. The objective of this research was to investigate the rheological characteristics of the rubberized asphalt binders after various long-term aging procedures, using the penetration index, the dynamic shear rheometer, the bending beam rheometer, and high pressure-gel permeation chromatographic testing. The experimental design included the use of three binder sources, three binder grades (PG 64-22, PG 64-22+10 %-40 ambient rubber, and PG 76-22) and three aging states, i.e., virgin, rolling thin film oven, and pressurized aged vessel [four test temperatures (65, 80, 100, and 110°C) and five aging durations (15, 20, 40, 80, and 144 h) under the pressure of 2070 kPa]. The test results show that, as expected, the use of crumb rubber can effectively improve the PG grade and aging resistance of the virgin asphalt binder. A series of rheological properties (e.g., penetration, stiffness, m-value, and percentages of large and small molecular sizes) illustrate that the PG 64-22 binder, mixed with 10 %-40 ambient rubber, yields similar or improved rheological properties in comparison with PG 76-22 using 3 % styrene-butadiene-styrene polymer after various long-term aging procedures.