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Because of the aged binder properties, high Reclaimed Asphalt Pavement (RAP) content asphalt mixtures are more susceptible to cracking failures than virgin mixtures. Thus the production of recycled...

In this study, the mechanical and physico-chemical properties of a new kind of modified bitumen are presented. The bituminous binders have been modified in order to understand the effect on the structural properties of several compounds such as a Polymer elastomer as Styrene Butadiene Rubber (SBR), Polymer thermoplastic polypropylene (PP) and a waste plastic (Waste PP). Laboratory tests have been focused on the characterization of bitumen modified with single product and their binary combinations compared with pristine binder as a reference. Characterization has been conducted by using conventional as well as advanced methods on bitumens. Fundamental rheological tests, based on dynamic shear rheometer in the temperature range from -30 °C to +160 °C have been performed and the structure of a bitumens and modified bitumens has been analysed by the mobility of the oily maltene by self-diffusion Pulsed field gradient spin-echo (PGSE) FT-NMR experiments.

ILT is particularly useful when the signal is characterized by multi-exponential decay, for example in spin relaxation or in the dephasing of the NMR spin echo signal associated with sopra molecular aggregation under the influence of pulsed magnetic or internal field gradients. As novel approach to observe the real rejuvenating effect of the potential additive, an Inverse Laplace Transform of the NMR spin-echo decay (T2) was applied. The potentialities of a new, non-toxic and eco-friendly biocompatible additive on aged bitumen are explored for the first time as bitumen rejuvenator, by means of advanced rheological and Relaxometry-NMR measurements. Pristine, aged, and doped aged bitumen morphology have been investigated by SEM. The new rejuvenator helps to rearrange the structure of the aged bitumen (aiming at the original one), and this mechanism can be observed by ILTNMR analysis.

Nowadays, many different materials are known to function, using different test methods, as rejuvenating agent when introduced into recycled asphalt pavements. However, it should be noticed that, an additive, which has a complete rejuvenating function, enables the chemical structure reorganization of the aged bitumen, otherwise not achieved by traditional methods. This rearrangement brings back the aged bitumen structure to the condition of the original one, restoring the elasticity and workability of the binder. In this study, two non-toxic and eco-friendly biocompatible additives have been tested to work as rejuvenators on an aged bitumen binder by means of Powder X-Ray Diffraction (PXRD) measurements and Nuclear Magnetic Spectroscopy (NMR). Powder X-ray diffraction (PXRD) analysis has been proved to be a very useful technique for assessing the structure of virgin, aged, and rejuvenating agent-added bitumen and for figuring out the chemical action of the additive in bitumen. All the test results were also supported by T2-NMR spectroscopy, which proves the validity of this method in chemical analysis.

Over the years, the need for the synthesis of biodegradable materials has facilitated the drift of the asphalt industry towards eco-sustainable and cost-effective production of road pavements. The principal additives in the asphalt industry to improve the performance of road pavements and increase its lifespan are majorly rheological modifiers, adhesion promoters and anti-oxidant agents. Rheological modifiers increase physico-chemical properties such as transition temperature of asphalt binder (bitumen), adhesion promoters increase the affinity between binder and stone aggregates while anti-oxidant agents reduce the effects of oxidation caused by exposure to air, water and other natural elements during the production of asphalt pavements. In this study, we tested the effectiveness of a food grade bio-additive on these three aforementioned properties. We also sought to hypothesize the mechanisms by which the additive confers these desired features on bitumen. We present this study to evaluate the effects of turmeric, a food-based additive, on bitumen. The study was conducted through dynamic shear rheology (DSR), atomic force microscopy, scanning electron microscopy (SEM) and boiling test analysis.

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&ndash, 155 &deg, 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.

The stones used for the construction of road surfaces have a complex mineralogical and hence chemical composition. They are made up of several types of minerals put together. This generates a significant difference in adhesion with the bituminous binder. The aim of this study is to create a mathematical model able to predict the adhesion between bitumen and stone on the basis of contact angle measurements made on different pure minerals. The mathematical model used was developed keeping in mind the exponential bond that the minerals have with the corresponding bond angle. This model also confirmed the established fact that the lower the value of Δ, the better the adhesion between the bitumen and the aggregate.

Asphalt concretes are materials used worldwide. It is well-known that in such materials the minor component, the bitumen, plays the most important role since it binds the high fraction (>95%) of inorganic macrometer-sized particles ensuring a coherent material fit for uses in road pavement. Additives can be used to increase the overall rheological properties, with high benefits in terms of resistance to mechanical stress and to ageing. Among these, nanoparticles have recently been considered as very effective additives in increasing the overall performance, increasing the viscosity, the rutting parameter and the recovery from deformation. However, they are expensive, so a delicate equilibrium between costs and benefits must be found for large-scale uses. In this framework, we furnish our critical analysis of the state-of-the art technologies used for improving the bitumen performances by means of nanoparticles with an eye to eventual added-values (like anti-oxidant effect, antistripping properties, or UV radiation screening which avoids radiation-induced ageing…). We will critically consider the costs involved in their use and we will give our opinion about vanguard techniques which can be fit for the analysis of nanoparticles-containing bitumens and asphalts. Interesting perspectives will be also given for future research and applications.

Asphalt concretes are biphasic systems, with a predominant phase (c.a. 93-96% w/w) made by the macro-meter sized inorganic aggregates hold together by small amounts of a viscoelastic binding bitumen (c.a. 5%). Even if the bitumen is in minor amount, it plays an important role dictating all the desired properties: rheological performances, resistance to aging etc. What happens if nanoparticles are used as additive in such materials? They usually confer enhanced resistance under mechanical stress and give sometimes interesting added-values properties so, despite the high costs of their production, nanoparticles are interesting materials which are being monitored for large scales applications. This work introduces the reader to the properties of nanoparticles in an easy to review their use in bitumen and asphalt preparation. Silica, ceramic, clay, other oxides and inorganic nanoparticles are presented and critically discussed in the framework of their use in bitumen and asphalt preparation for various scopes. Organic and functionalized nanoparticles are likewise discussed. Perspectives and cost analysis are also given for a more complete view of the problematic, hoping this could help researchers in their piloted design of material for road pavements with ever-increasing performances.

This paper evaluated the potentialities of a green and biocompatible rejuvenator agent (HR) in conferring an appreciable resistance against the effects caused by artificial aging on a given bitumen. Both neat and aged bitumens were analyzed and compared to analogous samples modified with HR. Control samples containing a vegetable oil as softening agent were also tested for comparison. The tested samples were subjected to a second aging cycle. Structural differences between the samples were carried out through an inverse Laplace transform of the NMR spin-echo decay (T2) and self-diffusion measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE-NMR) spectroscopy. In addition, dynamic rheological analyses were conducted to determine the dependence of the gel-sol transition temperature on both the type of additive and ageing process. The present study clearly highlighted the fact that artificial ageing, realized here by the rolling thin film oven test (RTFOT) and the pressure ageing vessel (PAV) test, induced important structural modifications. The analysis of relaxation times and self-diffusion coefficients indicated that ageing promoted the formation of molecular populations characterized by a shift of the distribution toward higher molecular weights compared to unaged bitumen. Diffusion data showed also an Arrhenius-like temperature dependence. A correlation between all the data was attempted to understand the role of the investigated additives. The eco-friendly biocompatible rejuvenator helped not only to restore the structure of the aged bitumen, but even slowed down the processes of a second aging (aiming at the first aged sample).

The asphalt industry’s incentive to reduce greenhouse gas emissions has increased since the 1990s due to growing concerns on environmental issues such as global warming and carbon footprint. This has stimulated the introduction of Warm Mix Asphalt (WMA) and its technologies which serve the purpose of reducing greenhouse gas emissions by reducing the mixing and compaction temperatures of asphalt mix. WMA gained popularity due to the environmental benefit it offers without compromising the properties, performance and quality of the asphalt mix. WMA is produced at significantly lower temperatures (slightly above 100 °C) and thus results in less energy consumption, fewer emissions, reduced ageing, lower mixing and compaction temperatures, cool weather paving and better workability of the mix. The latter of these benefits is attributed to the incorporation of additives into WMA. These additives can also confer even better performance of WMA in comparison to conventional Hot Mix Asphalt (HMA) methods. Even though there are recommended dosages of several WMA additives, there is no general standardized mixture design procedure and this makes it challenging to characterize the mechanism(s) of action of these additives in the warm mix. The effects of the addition of additives into WMA are known to a reasonable extent but not so much is known about the underlying interactions and phenomena which bring about the mechanism(s) by which these additives confer beneficial features into the warm mix. Additives in a certain way are being used to bridge the gap and minimize or even nullify the effect of the mixing temperature deficit involved in WMA processes while improving the general properties of the mix. This review presents WMA technologies such as wax, chemical additives and foaming processes and the mechanisms by which they function to confer desired characteristics and improve the durability of the mix. Hybrid techniques are also briefly mentioned in this paper in addition to a detailed description of the specific modes of action of popular WMA technologies such as Sasobit, Evotherm and Advera. This paper highlights the environmental and technical advantages of WMA over the conventional HMA methods and also comprehensively analyzes the mechanism(s) of action of additives in conferring desirable characteristics on WMA, which ultimately improves its durability.

Tuning the rheological properties of bitumens is extremely important for applicative purposes. This can be achieved by the use of chemical additives tuning the asphaltene-asphaltene and asphaltene-maltene interactions. We propose the use of an epoxy-resin to give more rigid and thermally stable bitumens on the basis of its tendency to form polymeric networks which would bridge asphaltene clusters. Rheometry confirmed this hypothesis and showed that a load of epoxy-resin as low as 0.1% gives the highest rigidity. Atomic Force Microscopy highlighted the structural changes at the basis of the observed effects. The small amount of epoxy resin needed and its low-cost are elements deserving monitoring.

Bitumen is a complex material used for road pavement throughout the world. During paving and pavement service life loss of more volatile compounds and oxidization takes place. Hence, asphaltene micelles become larger so that the fluidity of the system is reduced; the material becomes rigid, stiff and brittle so needing replacement. Once removed, it can be processed to restore its original properties and used for Reclaimed Asphalt Pavement (RAP). For such a process, additives called “rejuvenators” are used: they act on the chemical structure of aged bitumen to restore its physical properties to a state very similar to virgin bitumen. Alternatively, softening agents can be used to restore only the physical properties. An additive conferring regenerating characteristic on the asphalt mix increases the longevity of asphalt pavements due to the fact that it brings the bitumen back to its initial state; on the other hand, softening agents render the aged bitumen more workable but road pavements remain rigid and eventually break in the course of use. At the moment, methods that can distinguish a regenerating effect from a fluxing effect are not known. This study aims at evaluating the different effects of the additives on aged bitumen. For this purpose, we used a commercial additive (tritolyl poly phosphate, TPI) working as rejuvenator and a softening agent (soy oil) which is a well-known fluxing agent. The effects of the additives on aged bitumen have been investigated through Dynamic Shear Rheometer, Atomic Force Microscopy, Optical Microscopy and Infrared Spectroscopy.

Thanks to greater attention to the environment and the depletion of non-renewable resources, the sustainability and the circular economy have become crucial topics. The current trend of pavement engineering is to reduce the use of standard bitumen by replacing it with more sustainable materials such as industrial residues and by-products. In this regard, the present study aims to characterize innovative extended bitumen using recycled materials. Due to promising preliminary results as bitumen modifiers, the powdered rubber from end-of-life tires and the re-refined engine oil bottom (REOB) have been investigated as feasible components of bitumen extenders. Nevertheless, several variables strongly affect the performance of the resulting binder, which cannot be neglected. Hence, this research focuses on the rubber&ndash, REOB interaction in order to evaluate their optimum ratio, which may maximize the use and advantages of both recycled materials as suitable partial replacements for bitumen. Various rubber&ndash, REOB ratios were considered and investigated by means of low and high frequency nuclear magnetic resonance (NMR) spectrometers and scanning electron microscope (SEM).

To date, few methods allow distinguishing a fluxing effect of an additive for bitumen from a regenerating effect. This research aims at identifying a method to accurately establish whether an oxidized bitumen has been regenerated or has simply been fluxed by a softener. Oxidized bitumens, simulating the aging process that results in road pavement lifetime, were prepared by the Rolling thin film oven test (RTFOT) procedure for 225 min and the Pressure Aging Vessel (PAV) procedure. Their asphaltene parts were extracted and analyzed by calorimetry (Differential Scanning Calorimetry DSC), and the results were compared with the presence and absence of a fluxing agent and real rejuvenators. The self-consistent results showed that the thermal properties of the asphaltene fractions is a sound probe to monitor the effect of rejuvenation clearly distinguishable from the mere fluxing effect. This preliminary study might allow the creation of standard protocols capable of identifying a priori the rejuvenating effect of an additive in the future. Furthermore, given the widespread use of calorimetry for the characterization, it tends to become a widely accessible and useful tool for this purpose in material characterization laboratories.

The performances of a modified bitumen as a function of the concentration of an added organosilane modifier was examined in terms of its consistency, adhesion and rheological properties. In particular, the modifier guarantees excellent performance at 0.01 wt% loading, and almost complete resistance to water at 0.03 wt% loading. A quantitative evaluation of the modified bitumen’s performance was carried out by a contact angle test. Moreover, SEM/EDS analysis showed that the organosilane modifier was able to penetrate the surface of the stone, thus aiding anchoring of the binder to the surface.

This review aims to explore the state of the knowledge and the state-of-the-art regarding bitumen rejuvenation. In particular, attention was paid to clear things up about the rejuvenator mechanism of action. Frequently, the terms rejuvenator and flux oil, or oil (i.e., softening agent) are used as if they were synonymous. According to our knowledge, these two terms refer to substances producing different modifications to the aged bitumen: they can decrease the viscosity (softening agents), or, in addition to this, restore the original microstructure (real rejuvenators). In order to deal with the argument in its entirety, the bitumen is investigated in terms of chemical structure and microstructural features. Proper investigating tools are, therefore, needed to distinguish the different mechanisms of action of the various types of bitumen, so attention is focused on recent research and the use of different investigation techniques to distinguish between various additives. Methods based on organic synthesis can also be used to prepare ad-hoc rejuvenating molecules with higher performances. The interplay of chemical interaction, structural changes and overall effect of the additive is then presented in terms of the modern concepts of complex systems, which furnishes valid arguments to suggest X-ray scattering and Nuclear Magnetic Resonance relaxometry experiments as vanguard and forefront tools to study bitumen. Far from being a standard review, this work represents a critical analysis of the state-of-the-art taking into account for the molecular basis at the origin of the observed behavior. Furnishing a novel viewpoint for the study of bitumen based on the concepts of the complex systems in physics, it constitutes a novel approach for the study of these systems.

In the asphalt industry, bituminous emulsions are widely used in road pavement operations and in building/construction processes such as cold mix asphalt and waterproofing processes, respectively. A very important fact to keep in mind is that not all types of bitumen are suitable for the realization of bituminous emulsions. This is largely due to the variation in their chemical nature and the different cracking processes carried out on the bitumen during the fractional distillation process in the petroleum industry. The objective of this study is to identify the underlying causes of the non-emulsionability of bitumen using Nuclear Magnetic Resonance (NMR) and Dynamic Shear Rheology (DSR) analysis. NMR analysis aims at identifying the fundamental chemical components that are responsible for the emulsionability of the bitumen binder and how important their role is in this phenomenon. On the other hand, the DSR analysis is aimed at determining if the rheological (viscoelastic) behavior of bitumen is implicated in its emulsionability. The indications gotten from the data produced by these techniques, enable us as soon as the analyzed bitumen is deemed non-emulsionable to identify what type of additive can be used to modify the bitumen and alleviate its non-emulsionability until a point where its chemical components become ideal for the realization of bituminous emulsions. In this research work, a model bitumen (labelled as Cimar) which is known for its excellently high emulsionability in the production of anionic bituminous emulsions was used as the reference sample. Two bitumens (labelled as Adriatica and Alma) which from preliminary testing were deemed non-emulsionable were alongside the additives selected and subjected to the aforementioned techniques for analysis on their emulsionability. The NMR data obtained allowed the identification of the chemical nature of the components of the analyzed bitumens and the design of the right additive which improves the bitumen and makes it suitable for the preparation of emulsions. In addition to these, a largely uncommon however effective method of acid number determination of bitumen gave indications on an underlying factor which largely influences the emulsionability of bitumen. An aliphatic and an aromatic surfactant were identified thanks to the spectroscopic findings in this study.

This paper deals with the fundamental differences between industrial and paving-grade bituminous binders. The paper is presented in two main sections: 1) a review of the materials’ colloidal structure and the required properties for the industrial and paving applications; 2) a wide range of experimental tests with which the bituminous binders were studied and compared. In this research, a 160/220 industrial bitumen was studied and compared to a paving-grade bitumen with the same penetration and with a lower penetration, 70/100 one. The research consisted of physical, chemical, thermal, microstructural, and rheological analysis to provide a comprehensive understanding of these bituminous binders of diverse applications. Overall, the comparison of the tests’ results indicated that while the asphaltene content and its characteristics have a great influence on the bitumen’s properties, it is not the only fundamental factor. During the study of the chemical structures via Atomic Force Microscopy (AFM), it was found that the Peri phase (attributed to the resins) also plays an important role, defining the bitumen’s physical visco-elastic properties. In fact, from a microstructural point of view using AFM a significant difference was notified between the industrial bitumen and the paving-grade ones. These differences allow the paving-grade bitumens to be more elastic and ductile compared to the industrial bitumen.

Road pavement is principally made of mineral aggregates and a bitumen binder. Aggregates, due to their mineralogical nature, have complex chemical compositions and physical properties, which are strongly dependent on the minerals that constitute the stones. In pavement technology, bitumen/aggregate affinity is of paramount importance. Moisture damage in hot mix asphalt (HMA) is one of the major concerns in durability of flexible pavements, to improve the adhesion between the bitumen and the stones and increase the life of the road pavements often it is necessary using additives as the antistripping agents. Currently, there are several techniques such as the Boiling Test, the Rolling Bottle Test (RBT), etc., which evaluate the adhesion between the bitumen and the stones, however, most of them are based on a subjective evaluation. In the present paper, several types of mineral aggregates are characterized in detail by optical microscopy (OM) and X-ray powder diffraction (XRPD) in order to correlate the Boiling Test and the contact angle method to investigate the level of bitumen/aggregate affinity. For this reason, a single type of modified bitumen and two adhesion promoters were studied. The obtained results show the reliability of the technique used. However, there are still some limitations regarding the use of a contact angle test in assessing bitumen/aggregate affinity.

In the past three decades, several conventional methods have been employed for characterizing the bitumen ageing phenomenon, such as rheological testing, ultraviolet testing, gel permeation chromatography (GPC), gas chromatography (GC), atomic force microscopy (AFM), X-ray scattering, and Fourier transform infrared spectroscopy (FTIR). Nevertheless, these techniques can provide only limited observations of the structural micro-modifications occurring during bitumen ageing. In this study, Fourier transform nuclear magnetic resonance self-diffusion coefficient (FT-NMR-SDC) spectroscopy, as a novel method, was employed to investigate and compare the microstructural changes between virgin bitumen (pristine bitumen) and aged bitumen. The virgin bitumen was aged artificially using two standard ageing tests: Rolling Thin-Film Oven Test (RTFOT) and Pressure Ageing Vessel (PAV). For a comprehensive comparison and an assessment of the validity of this method, the generated samples were studied using various methods: rheological test, atomic force microscopy, and optical microscopy. Significant differences were obtained between the structure and ageing patterns of virgin and aged bitumen. The results indicate that the modification of maltenes to asphaltenes is responsible for the ageing character. When compared with the other methods&rsquo, findings, FT-NMR-SDC observations confirm that the asphaltene content increases during ageing processes.

The functionality of a green additive, acting as bitumen rejuvenator was considered in the presented experimental work. The additive’s effects on aged bitumen have been investigated through advanced rheological and NMR-relaxometry measurements. Bitumen ageing encompasses volatilization and oxidation which enable changes in the material molecular structure. Volatilization occurs mainly at high temperatures during production, transport and laying of the asphalt concrete. The oxidation, also caused by atmospheric oxygen and UV radiation, leads to an increased fragility and development of cracks in the asphalt layer. Fresh, aged, and doped recycled bitumens were tested. Rheology and NMR have been used to assess the structural differences between the bitumens and to understand the role of the proposed additive. A real rejuvenator helps to rearrange the colloidal structure of the oxidized bitumen, thus recreating one similar to the fresh bitumen. As a novel approach to bitumen characterisation, an inverse Laplace transform of the NMR spin-echo decay (T2) was here applied.

Bitumen aging is the major factor which contributes to the deterioration of the road pavement. Oxidation and volatilization are generally considered as the most important phenomena affecting aging in asphalt paving mixtures. The present study was carried to investigate whether various antioxidants provided by natural resources such as phospholipids, ascorbic acid as well as lignin from rice husk, could be used to reduce age hardening in asphalt binders. A selected bituminous material was modified by adding 2 % w/w of the anti-aging natural additives and subjected to accelerated oxidative aging regimes according to the Rolling Thin Film Oven Test (RTFOT) method. The effects of aging were evaluated based on changes in sol-gel transition temperature of modified bitumens measured through Dynamic Shear Rheology (DSR). Moreover, changes of Electron Paramagnetic Resonance (EPR) spectra were monitored on the bituminous fractions asphaltene and maltene separated by solvent extraction upon oxidative aging. The phospholipids-treated binder exhibited the highest resistance to oxidation and the lowest age-hardening effect compared to the other tested anti-oxidants. The combination of EPR and DSR techniques represents a promising method for elucidating the changes in associated complex properties of bitumen fractions promoted by addition of free radical scavengers borrowed by green resources.

Bitumen has unique chemo-mechanical properties, and for this reason, it is today one of the main constituents of many industrial products beside its common use in highway pavements construction. While the excellent rheological properties of bitumens have been investigated by means of different techniques, much remains to be known about the intrinsic properties of this complex material. It is therefore important to investigate its structure and properties from a closer point of view, towards possible useful modifications of the neat material. The present research developed a technique to investigate the composition of bitumens using Thin Layer Chromatography (TLC) to separate the different fractions, and Nuclear Magnetic Resonance (NMR) spectroscopy to assess and quantify the aliphatic hydrogen part with respect to the aromatic part. To achieve a comprehensive understanding of the chemical composition of the materials, Proton Nuclear Magnetic Resonance (1H-NMR) analysis was conducted in solution, using CCl4 as solvent, on three different neat bitumens and on their asphaltene and maltene fractions. The combined application of TLC and 1H-NMR spectroscopy enables the advanced characterization of bitumens supplied from different sources or obtained from different processes. This further allows addressing the use of specific modifications according to the bitumen final applications.

A good adhesion between bitumen, the common binder used in the construction of pavements, and mineral aggregates is a key property for optimal performance of the road paving material (asphalt). Moreover, as bituminous material is viscoelastic in nature, an improvement of its mechanical response does represent an equally important factor in the design of roads. To date, a variety of chemical compounds has been tested as bitumen modifiers and evaluated in their capacity to improve the adhesion of binder to the aggregates and promote an increase of the bitumen softening point, especially in warm ambient conditions. This contribution explores, for the first time, the potentialities of a class of lipophilic food grade additives, i.e., non-toxic and eco-friendly biocompatible compounds, acting both as adhesion promoters and as rheological modifiers. Their effects on the high temperature mechanical performance of a tested bitumen have been investigated through time cure rheological measurements and the sol-transition temperature determined in a wide range of temperatures. Measurements of the contact angle between the aggregate surface and modified bitumens preventively blended with increasing amounts of food grade additives were also carried out. We believe that those results could provide an alternative opportunity to use additives from natural resources in the design of sustainable and much more performant asphalts.

This synthesis explores the state-of-the-knowledge and state-of-the-practice regarding the latest updates on polymer-modified bitumens (PmBs). The information in this study was gathered from a thorough review of the latest papers in the literatures related to modified bituminous materials, technologies, and advances. For this purpose, the paper is presented in two principle sections. In the first part, the bitumen itself is investigated in terms of chemical structure and microstructural systems. In the second part, the paper focuses on bitumen modification from different aspects for assessing the effectiveness of the introduced additives and polymers for enhancing the engineering properties of bitumen in both paving and industrial applications. In conclusion, the knowledge obtained in this study has revealed the importance of the chemical composition of base bitumen for its modification. It can be declared that while some polymers/additives can improve one or some aspects of neat bitumen properties, they can lead to compatibility problems in storage and production. In this respect, several studies showed the effectiveness of waxes for improving the compatibility of polymers with bitumen in addition to some benefits regarding warm mix asphalt (WMA) production.

The rheological effects of polyphosphoric acid (PPA) on bituminous binders with similar mechanical and chemical–physical properties, but with different chemical compositions, have been investigated. The effects of polyphosphoric acid were studied through traditional bituminous-binder-type characterization tests and via rheological investigations by dynamic and steady shear rheometry. It was observed that PPA, probably reducing the asphalten aggregate size, extends the range of viscoelastic behavior, moving the transition to a viscous liquid towards higher temperature and, therefore, improving the mechanical behavior for high temperature applications. These effects seem more evident at low PPA concentrations and suggest the potential existence of saturation effects.

In the present work a laboratory evaluation of the low-temperature rheological properties of neat and polyphosphoric acid (PPA) modified bitumens by using a Dynamic Mechanical Analyzer (DMA) is presented. Fundamental rheological properties were evaluated in controlled kinematic conditions and the results obtained were compared with traditional procedures such as the Fraass breaking point. The results show that the effect of polyphosphoric acid addition at low temperature is strongly dependent on bitumen composition (i.e. wax and asphaltene content), nevertheless it seems that PPA is able to decrease the glass transition temperature (Tg) and to increase the stiffness, improving the low temperature performance of the modified materials.

Pavement materials play an important role in overall pavement sustainability including material acquisition processing, and transportation. The main objective of the present study is to evaluate the effectiveness of new additives, to reduce bitumen’s fume emission expelled into the atmosphere, during the processing of asphalt concrete. The new additives act by trapping bitumen’s volatile substances avoiding their release at high temperatures. In this paper, we have been tested the performance of 2 types of mesoporous silica-based additives (AntiSmog 1 and AntiSmog 2). The idea of using these additives to reduce the emission of fumes in bitumen has been submitted as a patent. To quantify and characterize the emitted fumes, thermogravimetry (TGA) and gas chromatography-mass spectrometry (GC-MS) technique have been used. Dynamic Shear Rheology (DSR) has been used to check the rheological properties and the possible sedimentation issues that could occur after the addition of the additives