Unravelling the role of a green rejuvenator agent in contrasting the aging effect on bitumen: A dynamics rheology, nuclear magnetic relaxometry and self-diffusion study

The Use of Nuclear Magnetic Resonance Spectroscopy (NMR) to Characterize Bitumen Used in the Road Pavements Industry: A Review

Bitumen, a vital component in road pavement construction, exhibits complex chemo-mechanical properties that necessitate thorough characterization for enhanced understanding and potential modifications. Nuclear Magnetic Resonance (NMR) spectroscopy emerges as a valuable technique for probing the structural and compositional features of bitumen. This review presents an in-depth exploration of the role of NMR spectroscopy in bitumen characterization, highlighting its diverse applications in determining bitumen content, group composition, molecular dynamics, and interaction with additives. Various NMR techniques, including free induction decay (FID), Carr-Purcell-Meilboom-Gill (CPMG), and Pulsed Field Gradient Stimulated Echo (PFGSE), are discussed in the context of their utility in bitumen analysis. Case studies, challenges, and limitations associated with NMR-based bitumen characterization are critically evaluated, offering insights into potential future research directions. Overall, this review provides a comprehensive overview of the current state-of-the-art in NMR-based bitumen characterization and identifies avenues for further advancement in the field.

Plant Waste-Based Bioadditive as an Antioxidant Agent and Rheological Modifier of Bitumen

In recent times, circular economy initiatives in addition to the need for sustainable biomaterials have brought about several attempts at the eco-friendly, eco-sustainable and cost-effective production of asphalt pavements. It is an increasingly common practice in the asphalt industry to improve road pavement performance using additives to enhance the physico-chemical properties of bitumen, which performs the role of the binder in the asphalt mix. This paper evaluated the potential of a bio-based additive derived from olive leaf residue as a modifier and antioxidant agent for bitumen. Samples of neat, aged and doped aged bitumen were analyzed. In this study, the two bio-based additives were characterized in terms of phenol, chlorophyll, lignin and cellulose content, which was correlated with the mechanical properties of the tested samples. The mechanical properties of the neat, modified, aged and unaged samples were evaluated via Dynamic Shear Rheology. The bio-based additives proved to be promising and can improve the properties of bitumen binder and the performance of asphalt pavements in general.

The efficiency of bio-char as bitumen modifier

Improving the mechanical properties of bitumen is an important goal for road pavements design. For this reason, new compounds are now being sought for testing as bitumen modifiers. In this work, the authors studied the effect that two different chars have on two 50/70 bitumens with different chemical and physical characteristics. A complete morphological, surface and bulk characterization of the two additives was carried out. In addition, rheology, Nuclear Magnetic Resonance (NMR) relaxometry and atomic force microscopy were used to analyze the effect that the two additives exert on the properties of the bitumens. According to the results, the char sample with high porosity could be used as a modifier of mechanical properties, while no rejuvenation effects were observed for either of the two additives tested. In addition, the two additives do not give rise to segregation phenomena.

When Physical Chemistry Meets Circular Economy to Solve Environmental Issues: How the ReScA Project Aims at Using Waste Pyrolysis Products to Improve and Rejuvenate Bitumens

Urban waste management is a hard task: more than 30% of the world’s total production of Municipal Solid Wastes (MSW) is not adequately handled, with landfilling remaining as a common practice. Another source of wastes is the road pavement industry: with a service life of about 10–15 years, asphalts become stiff, susceptible to cracks, and therefore no longer adapted for road paving, so they become wastes. To simultaneously solve these problems, a circular economy-based approach is proposed by the ReScA project, suggesting the use of pyrolysis to treat MSW (or its fractions as Refuse Derived Fuels, RDFs), whose residues (oil and char) can be used as added-value ingredients for the asphalt cycle. Char can be used to prepare better performing and durable asphalts, and oil can be used to regenerate exhaust asphalts, avoiding their landfilling. The proposed approach provides a different and more useful pathway in the end-of-waste (EoW) cycle of urban wastes. This proof of concept is suggested by the following two observations: (i) char is made up by carbonaceous particles highly compatible with the organic nature of bitumens, so its addition can reinforce the overall bitumen structure, increasing its mechanical properties and slowing down the molecular kinetics of its aging process; (ii) oil is rich in hydrocarbons, so it can enrich the poor fraction of the maltene phase in exhaust asphalts. These hypotheses have been proved by testing the residues derived from the pyrolysis of RDFs for the improvement of mechanical characteristics of a representative bitumen sample and its regeneration after aging. The proposed approach is suggested by the physico-chemical study of the materials involved, and aims to show how the chemical knowledge of complex systems, like bituminous materials, can help in solving environmental issues. We hope that this approach will be considered as a model method for the future.

Preparation of Asphalt Concretes by Gyratory Compactor: A Case of Study with Rheological and Mechanical Aspects

For asphalt concrete preparation in laboratory mix-design operations, bitumens are usually mixed with micrometer-sized particles (filler), sand and centimeter-sized crushed stones in a gyratory press at a temperature of about 140–155 °C depending on the bitumen viscosity, until adequate homogenization and compaction take place (air voids optimum). This requires energy consumption. To minimize it, the process needs to be optimized and is usually made empirically. The aim of this manuscript is to gain a comprehension of the physico-chemical mechanisms involved in the process by exploring: (i) the rheological properties (viscosity, activation energy) of a neat and RTFOT-aged bitumen, in presence and in absence of a filler, (ii) the volumetric and resistance behavior under the compaction in a standard Gyratory Compactor (GC) of their blends with aggregates and (iii) the mechanical properties (Indirect Tensile Strength, compression and tensile deformation) of the final products. Correlations between activation energy and pre-exponential factor of the viscosity on a side, and between viscosity, workability and final mechanical properties on the other side allowed to provide a rational interpretation of the physico-chemical processes involved in the framework of the physics of complex fluids. The scientific clues will be of help in optimizing the workability in asphalt concretes productions with obvious repercussions in terms of energy savings, useful for economic and environmental issues.