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The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP. [ABSTRACT FROM AUTHOR]

Asphalt pavement is under different climatic conditions throughout its service life, which means that fatigue cracking does not occur at a specific temperature, but at a temperature range. The main objective of this paper is to evaluate the influence of different temperatures in the fatigue life of two asphalt binders: a non-modified binder (penetration grade 30/45) and a highly polymermodified binder (HPMB). The fatigue resistance characterization was performed by means of a linear amplitude sweep (LAS) test at the temperatures of 10, 15, 20, 25, and 30°C using a dynamic shear rheometer (DSR). From the dynamic shear modulus (|G*|) results, adhesion loss was observed between the binder and the rheometer parallel plate at the lower temperature of 10°C,while at higher temperatures (25 and 30°C) plastic flow was observed rather than fatigue damage. Therefore, considering that the actual test procedure does not specify the testing temperature, the evaluation of failure mechanism is essential to validate test results, because the random selection of test temperature might lead to inconsistent data.

The addition of polymers on asphalt binders aims to enhance their performance, especially at high temperatures, which correspond to rutting resistance. The Superpave rutting parameter (|G*|/sinδ) has been considered to be inadequate to characterize the performance of modified materials, therefore the Multiple Stress Creep and Recovery (MSCR) test was developed, providing the parameter non-recoverable compliance (Jnr). This research has the main objective of correlating asphalt binders performance-based characterization with rutting resistance of asphalt mixtures, and presents results obtained for one conventional (50/70 penetration grade) and two modified asphalt binders (2.1% RET and 1.9% RET) regarding their rheological characteristics. With the use of the dynamic shear rheometer (DSR), master curves and MSCR results were obtained for the three binders. In addition, permanent deformation tests were performed on the asphalt mixtures by means of laboratory traffic simulation. The rutting characterization indicated higher permanent deformation resistance for the modified binders for the asphalt binder and the asphalt mixture testing. The main conclusions were that the use of modified binder reduced in approximately 50% the Jnr values and the rut depth; also, the asphalt binders’ characteristics were able to predict the asphalt mixtures rutting resistance.

Cold recycled asphalt mixtures (CRAMs) may present a compressive resilient modulus dependent on the stress state. Currently, there is no widespread consensus on a triaxial resilient modulus (TxRM) model for CRAM analysis. A widely accepted TxRM model would favour the analysis of CRAM's layered pavement systems. This paper assessed the adequacy of different TxRM models of CRAM's specimens with different compositions, aggregate gradation and physical characteristics. Based on the literature, three different TxRM models were selected. The models' non-linear estimation was performed through Levenberg–Marquardt algorithm. Model selection analysis was based on residuals square sum root (RSSR) assessment. Ni et al.'s model was found to be the most adequate for CRAM's TxRM modelling based on RSSR analysis. The model selection was done regardless of aggregate gradation, binder type/content, air void content, RAP content, TxRM values range, active filler type and curing time of the tested specimens. [ABSTRACT FROM AUTHOR]

This research evaluated recycled asphalt mixtures (RAMs) for application as wearing course in heavy traffic highways. The main objectives were to investigate the effect of different RAP contents and the effect of a recycling agent (RA) on the mechanical properties of RAMs. Recycled asphalt mixtures with low (10, 20 and 25%) and high (35, 50 and 65%) RAP contents were evaluated. Two of these mixtures (25 and 50% RAP content) were also evaluated after the addition of the RA. The results indicate that conditioning the RAP during the production of RAMs influences the RAP binder activation and the mechanical behaviour of the mixtures. RAMs with high RAP contents presented better resistance to permanent deformation and resulted in satisfactory resistance to fatigue cracking due to the activation of the RAP asphalt binder. Finally, the addition of the RA improved fatigue resistance for higher amounts of RAP without reducing rutting resistance. [ABSTRACT FROM AUTHOR]

There is limited information on the characteristics and performance of paving mixtures made with 100% bio-binders. Moisture damage resistance of this type of mixture is a concern since the components of the bio-binder may have a higher affinity with water than asphalt binders. In this context, this paper presents a moisture damage susceptibility evaluation of wood-based bio-binder-aggregate interfaces in terms of energy parameters calculated from surface free energy components. The bio-binder was used as a total replacement for asphalt binders, and the responses were compared to a neat- and a highly modified-asphalt binder, considering different aggregate sources. Results suggest the bio-binder has similar moisture damage resistance to the neat asphalt binder and higher resistance than the highly modified asphalt binder, providing a first indication for the potential use of this bio-binder as 100% asphalt binder replacement. However, additional research is still required to validate these findings at the mixture level. [ABSTRACT FROM AUTHOR]

Recycling techniques are important tools for rehabilitation of old and deteriorated asphalt pavements. The production of cold recycled mixes using reclaimed asphalt pavement as aggregates provides economic benefits as it decreases transportation costs, energy consumption, and gas emissions. Despite that, there is no internationally accepted methodology to design this type of mix. The present research evaluated the design of cold recycled mixes through different compaction methods and varying asphalt emulsion and cement contents. Different curing temperatures and periods were analyzed to propose a faster and more practical method for mix design in the laboratory. Mechanical tests performed indicated that specimens compacted by the Marshall hammer provide similar results when varying asphalt emulsion and cement contents, while the Proctor hammer compaction was able to better capture the influence of these materials. The temperature of 60°C associated with shorter curing time is believed to be good for design purposes. Key words: cold recycled mixes design, compaction methods, mechanical behavior, curing processes. Les techniques de recyclage sont d'importants outils en matiere de remise en etat des vieux revetements asphaltiques deteriores. La fabrication d'enrobes recycles a froid en utilisant les revetements asphaltiques recuperes comme agregats offre des avantages economiques, car les couts de transport, la consommation d'energie et les emissions de gaz sont moindres. Malgre cela, il n'y a pas de methodologie acceptee mondialement en matiere de conception de ce type d'enrobe. La presente recherche a evalue la conception d'enrobes recycles a froid en utilisant differentes methodes de compactage ainsi que des teneurs en emulsion bitumineuse et en ciment variees. On a analyse differentes temperatures et periodes de traitement afin de proposer une methode plus rapide et pratique de concevoir les enrobes en laboratoire. Les essais mecaniques effectues ont indique que les specimens compactes a l'aide du marteau Marshall produisent des resultats semblables lorsqu'on varie les teneurs en emulsion bitumineuse et en ciment, tandis que le marteau compacteur Proctor a ete en mesure de mieux refleter l'effet de ces materiaux. On croit que la temperature de 60°C liee a un temps de traitement plus court s'avere favorable aux fins de conception. [Traduit par la Redaction] Mots-cles : conception d'enrobes recycles fi froid, methodes de compactage, comportement mecanique, procede de durcissement., Introduction In the past few decades, cold recycling of asphalt mixes has become an important technique to be used for the rehabilitation of old deteriorated asphalt pavements. Many researchers have [...]