High Amount Of Reclaimed Asphalt Pavement Research Articles

Influence of bio-based and refined rejuvenators on asphalt mixture with cold RAP

ABSTRACT In the recent years, research on the effects of rejuvenation on hot mix asphalt (HMA) with a high amount of RAP (Reclaimed Asphalt Pavement) has intensified. However, the vast majority of scientists focus on the technology of preheated RAP addition (e.g. in the parallel dryer). It was decided to investigate the effect of rejuvenators on asphalt mixtures containing non-preheated RAP (RAP cold addition into the mixer). Different types of rejuvenators were used in the research. The tests were carried out for the binder course and the base course. The optimal amount of cold RAP in the mixtures was determined and based on the initial tests of stiffness modulus and air void content, the amount of rejuvenators was adjusted for later tests. Tests of air void content, stiffness, resistance to water and frost and rutting resistance were carried out in the laboratory. Afterwards tests in the asphalt mixing plant were conducted for the rejuvenator with the best results for the base course. The results obtained confirmed the potential of using rejuvenators for mixtures with cold RAP addition into the mixer. It has been shown that bio-based rejuvenators are suitable for the use in different types of asphalt mixtures.

Assessment of performance characteristics of pavement base course incorporating reclaimed asphalt pavement and asphaltenes

Asphalt pavement is demolished and milled at the end of its service life, resulting in an enormous amount of waste material known as reclaimed asphalt pavement (RAP). Using cold recycling techniques, it is possible to reuse RAP for base course construction. However, using a high amount of RAP could have negative effects on the mechanical properties and durability of the base course. In this study, to improve the performance of asphalt emulsion recycled base course prepared with RAP, asphaltenes derived from Alberta oil-sands bitumen was added to the mixture. The performance properties of the selected mixtures were investigated at high, intermediate, and low temperatures. Testing results and statistical analysis revealed that asphaltenes enhances the high and intermediate temperature performance of the modified mixes significantly. The low-temperature creep compliance of asphaltenes-modified mixtures was slightly lower than the unmodified mixtures, however, the low-temperature properties of the modified mixes were not significantly affected.

Effect of Bitumen Production Process and Mix Heating Temperature on the Rheological Properties of Hot Recycled Mix Asphalt

Heavy traffic loads require the replacement of damaged pavements, so a huge amount of reclaimed asphalt pavement (RAP) material is now available and must be recycled in order to avoid landfill and to achieve both environmental and economic benefits. The most common and profitable solution to reuse RAP is associated with the hot recycling technique, as it allows recovering both solid and binding components of RAP. Several factors influence the performance of hot recycled mix asphalt (HRMA). Among those, this paper focuses on the role played by the origin of the virgin bitumen, i.e. the oil-distillation process, and by the mixing temperature adopted during HRMA production. The objective was to evaluate the rheological properties of mixtures produced using a high amount of RAP (50%), two different rejuvenators, two mixing temperatures (140 °C or 170 °C) and two neat bitumen types derived from different distillation processes (visbreaker and straight-run). The results showed that the addition of RAP led to an increase in the dynamic modulus and a decrease in the phase angle, while the use of rejuvenators partly tended to rebalance these characteristics. The visbreaker bitumen showed a higher sensitivity to short-term aging than the straight-run, determining higher mix stiffness and lower viscous features. The higher mixing temperature also determined an increase in the complex modulus and a reduction in the phase angle as a result of the higher mobilization of the aged bitumen from the RAP.

Evaluation of a biofuel residue-derived recycling agent with a low carbon footprint

Protecting environment, conserving natural resources by recycling and replacing non-renewable materials with renewable ones, reducing material cost, and utilizing sustainable processes are actively pursued by asphalt industry. Consistent with those efforts, Recycling Agents (RAg) with different technologies have been introduced which allow using high amounts of Reclaimed Asphalt Pavement (RAP) in construction of new pavements. RAgs, depending on their type and chemical composition, affect the mechanical properties of the asphalt binders differently. This study was undertaken to characterize effectiveness of using a relatively new plant-based RAg produced from biofuel residue in a low-carbon footprint process when used in asphalt binder blends containing a high amount of RAP. Effects of using different amounts of RAg, namely 0, 4, 6, and 8% (by binder weight) incorporated in a blend of a PG 58-28 containing 30% laboratory-simulated RAP binder (RAPsb) on binder blends’ rheological properties were studied by testing them in a dynamic shear rheometer and a bending beam rheometer and by conducting Multiple Stress Creep Recovery (MSCR) tests. In addition, effect of using RAg by its optimum dosage in a blend of PG 58-28 binder containing 30% RAPsb on its adhesion with granite and quartzite aggregates and moisture-induced damage was characterized. As a result, a Superpave grade of PG 58-34 was found to be achievable by incorporating 4% RAg in a blend of PG 58-28 and 30% RAPsb. Also, incorporating 4% RAg in a blend of PG 58-28 and 30% RAPsb improved the fatigue resistance of the RAPsb-laden binder to an extent which exceeded that of the neat PG 58-28. Furthermore, an elastic recovery response significantly higher than and a non-recoverable creep response equivalent to those observed in neat PG 58-28 were achieved by incorporating 4% RAg in a blend of PG 58-28 and 30% RAPsb, both having an MSCR grade of PG 58S. Finally, an overall improvement in resistance to moisture damage in PG 58-28 binder containing 30% RAPsb with granite and quartzite was observed as a result of incorporating 4% RAg in the blend.