This study investigates the mechanisms and efficacy of recycling agents on the structural and mechanical recovery of binders and asphalt mixtures containing high levels of Reclaimed Asphalt Pavement (RAP). Three commercial recycling agents, two biomass-derived and one petroleum-based, were characterized and evaluated through a multi-scale experimental approach combining rheological, chemical (Saturates, Aromatics, Resins - Asphaltenes Determinator - SAR-AD™), thermal (Temperature-Modulated Differential Scanning Calorimetry - TMDSC), and structural (Small Angle X-ray Scattering - SAXS) analyses. Results indicate that all recycling agents exhibited softening effects governed by simple rheological laws, with no clear evidence of compatibilizing action on asphaltene clusters within the investigated dosages and the sensitivity of the applied methods. While SAXS/USAXS did not reveal detectable changes in nanostructural features within the investigated q-range/length scales and conditioning history, thermomechanical performance, including viscoelastic transition (TVET) and relaxation (Tm=0.3, Thermal Stress Restrained Specimen Test - TSRST), improved proportionally with recycling agent dosage. Notably, the petroleum-derived recycling agent achieved greater low-temperature relaxation, though all recycling agents supported partial property restoration toward 35/50 reference binders. At the asphalt mix scale, modulus predictions using |G*|15°C,10 Hz-based criteria closely aligned with experimental outcomes. The study underscores the importance of tuning recycling agent selection and dosage based on binder rheology and RAP characteristics, while emphasizing the need to distinguish between softening and compatibilization effects to optimize long-term pavement performance.

An increase in use of reclaimed asphalt pavement (RAP) materials was observed for the last few years. These materials are composed of aged asphalt which can cause implementation issues due to its high viscosity. This work suggests a new way to explain a part of this problematic by tribological analysis and to assess the lubricating ability of aged asphalt. The influence of asphalt aging is investigated on the frictional properties using two 35/50 asphalt penetration graded specimens and a third one extracted from RAP. Short and long-term as well as natural effects of aging are examined on penetration grade, ring and ball temperature, infrared indices, and asphaltene content to demonstrate a physical hardening of the studied asphalts. The influence of natural or thermal aging are also studied by tribological measurements on lubricating properties. A ball on a three-plate equipment are used to evaluate the coefficient of friction (CoF) as a function of sliding velocity (Stribeck Curve) from 120 degrees C to 80 degrees C. The increase in asphaltene content after oxidation increases the frictional coefficient in the hydrodynamic regime. These observations were confirmed by tribological analysis performed on asphalts with controlled asphaltene contents (0, 15, 20 wt%). In addition of the physical hardening, asphalt oxidation causes a decrease of the lubricant properties. The evaluation of frictional coefficient can be added to the other well-known parameters to explain workability issues in presence of aged materials.

Fluxing agents (or flux oils) are oil products added to bitumen in order to decrease the viscosity of the binder hence allowing spraying, coating and paving applications more efficiently. Following the application on the road substrate, the flux oil evaporates to recover original binder's properties.In 2015, Solvay and Eurovia have associated their own expertise in chemicals and road construction respectively, to design a new versatile fluxing agent for the road industry. This new flux oil has an outstanding safety profile (no labelling, and high flash point). It is partly bio-sourced (45% of its carbons are bio-sourced), the other part being a side-product of Solvay's plant production, and fully biodegradable. Because of its unique properties this new flux oil needs less concentration (-20 to 45%) than other fluxing agents to decrease the viscosity of bitumen hence minimizing the use of volatile compounds. Moreover, it enables a quicker cohesion build-up of fluxed bituminous products.The fluxed binders are devoted to various types of application including surface dressing, micro-surfacing, cold mixes and storable mixes used in maintenance.This paper aims to describe the numerous technical and other advantages of this new product based on laboratory and jobsite results.

The current challenge is to produce asphalt mixtures incorporating higher rates (>50%) of Reclaimed Asphalt (RA) while controlling the quality of the final mix. During the service life of a pavement properties change, mainly due to oxidation and need to be restored. The resulting mix must exhibit at least equivalent performances regarding the mechanical and durability properties compared to that from a mix without RA. Hence, recycling agents are sometimes employed to “rejuvenate” aged bitumen. In this study, three recycling agents were used on both RA and neat bitumens, displaying different compositions. The effects on unaged and aged blends were assessed through rheology tests using Dynamic Shear (DSR) and Bending Beam (BBR) Rheometers. Data from DSR obtained with 4 mm and 8 mm parallel plates allowed to calculate the Glover-Rowe criteria and to determine the crossover parameters whilst BBR measurements yield Tm, Ts and ΔTc parameters. The blends resulting from the two bitumens displayed a similar evolution of behavior. This outcome suggests that these tests cannot discriminate the origin of the rejuvenation phenomenon since they only highlight the softening effect of the recycling agent and not its impact at the molecular level, i.e. on asphaltene and maltene compounds.

This study focuses on the mechanisms of bitumen emulsification and on the impact of the formulation, when emulsification is carried out in the area of high internal phase ratio (0.9). Kinetics of emulsification were determined using systemic rheology coupled with optical microscopy observations. Microscopic observations revealed a catastrophic phase inversion with formation of abnormal multiple emulsions, occurring very quickly after contacting the bitumen with the aqueous phase containing the surfactant. The direct emulsion thus obtained is then refined during a subsequent agitation step. The viscosity follow-up during the emulsification highlights four steps in the kinetic of catastrophic phase inversion, which have been related to morphological characteristics of the dispersions observed by optical microscopy. (C) 2014 Elsevier B.V. All rights reserved.

Variways, eco-comparator for road variants 4 Variways is a design and decision-making tool that helps clients choose between different road and motorway variants for a given project. It aims to propose a design approach that minimizes greenhouse gas (GHG) emissions and energy consumption generated by traffic using the road. More than just a tool for comparing conventional costs, Variways offers a sustainable development ranking of variants for all vehicle types using the infrastructure. Eric Locquet, Mireille Lattuati

In Europe, Eurovia and MeadWestvaco have been working together since 2006 in the development and promotion of warm mix asphalt (WMA). Since then, nearly one million tones of WMA have been manufactured and applied on different types of roads, under different climates, and with various types of aggregates and asphalt binders. This article describes one of the most challenging achievements realized thus far: use WMA in the construction of the three base courses on the highway A35, around the city of Strasbourg, France, near German border. The mix design incorporated 10% RAP - reclaimed asphalt pavement - materials with a 35/50 pen virgin binder. The average manufacturing temperature of the WMA was around 115°C, more than 50°C below the HMA reference. Construction of the WMA pavements began in November 2009, when ambient daily high temperatures were around 10°C. Job materials and mix properties are described. Production details, construction operations, and pavement performance characteristics are also presented. A comparison between the performance of the mix on the and in the laboratory is also discussed in conjunction with comparative performances of the HMA reference.