Polymer modified bitumen: Rheological properties and structural characterization

Use of modified chitosan as bitumen modifier and its impact on rheological properties in bitumen modification

Conventional bitumen is a viscoelastic material composed of asphaltene and maltene. It is prepared by air-blowing, but this approach makes the bitumen more brittle and susceptible to temperatures. To decrease the temperature susceptibility, synthetic polymers or additives are used to make polymer-modified bitumens. Polymer-modified bitumens have poor storage stability and phase separation and are costly. Chitosan has free amino and hydroxyl groups. Some studies showed that chitosan can be used as a bitumen emulsifier, increasing emulsion viscosity. This study describes the synthesis of O-carboxymethyl chitosan (OCMC) from chitosan, and the same was blended in base bitumen VG10 and VG30 to improve its constitutive properties. VG10 and VG30 grade bitumen were characterized for penetration, softening point, kinematic and absolute viscosity, and ductility. OCMC-modified bitumens were also characterized by their rheological and mechanical properties. OCMC was used in the concentration range of 0.5 to 4.5 wt%. The study revealed that using sulfur increases the ductility and penetration of modified bitumen with 1.5 wt% of OCMC and meets the specification of VG40-modified bitumen as per BIS specification IS:73:2013. The study showed that blending 1.5 wt% of OCMC in VG30 base bitumen enhances the complex modulus to 76,517 Pa (at 42 °C) with a minimum phase angle of 68.58° and meets the VG40 bitumen specification. Simultaneously, blending 1.5 wt% of OCMC in VG10 base bitumen enhances the complex modulus to 64,454 Pa with a minimum phase angle of 77.39° (at 42 °C) and meets the VG30 bitumen specification. Studies showed that using SBS in a small amount of 0.25 wt% along with modified chitosan improves the rutting resistance and shear modulus by more than 67 °C at 1.1 kPa.

Potential Additives in Natural Rubber-Modified Bitumen: A Review

Conventional bitumen pavement is no longer suitable for handling increasing loads and weather variations, which cause road deterioration, Thus, the modification of bitumen has been suggested to counter this issue. This study provides a detailed assessment of various additives for modifying natural rubber-modified bitumen used in road construction. This work will focus on the use of additives with cup lump natural rubber (CLNR), which has recently started to gain attention among researchers, especially in rubber-producing countries such as Malaysia, Thailand and Indonesia. Furthermore, this paper aims to briefly review how the addition of additives or modifiers helps elevate the performance of bitumen by highlighting the significant properties of modified bitumen after the addition of modifiers. Moreover, the amount and method of application of each additive are discussed further to obtain the optimum value for future implementation. On the basis of past studies, this paper will review the utilisation of several types of additives, including polyphosphoric acid, Evotherm, mangosteen powder, trimethyl-quinoline and sulphur, and the application of xylene and toluene to ensure the homogeneity of the rubberised bitumen. Numerous studies were conducted to verify the performance of various types and compositions of additives, particularly in terms of physical and rheological properties. In general, additives enhance the properties of conventional bitumen. Future research should investigate CLNR because studies on its utilisation are limited.

Research on Performance of SBS-PPA and SBR-PPA Compound Modified Asphalts

Although several studies indicated that the addition of Styrene-Butadiene-Styrene (SBS) and Styrene-Butadiene Rubber (SBR) bring a lot of benefits on properties of asphalt binders, high production costs and poor storage stability confine the manufacture of better modified asphalt. To reduce the production costs, polyphosphoric acid (PPA) was applied to prepare better compound modified asphalt binders. In this research, five PPA (0.5%, 0.75%, 1.0%, 1.25% and 1.5%) and two SBR/SBS (4% and 6%) concentrations were selected. Dynamic shear rheometer (DSR) and Bending Beam Rheometer (BBR) tests were performed to evaluate the rheological properties of the compound modified asphalt. Rolling Thin Film Oven (RTFO) test was performed to evaluate the aging properties of the compound modified asphalts. The results indicate that SBS/SBR modified asphalts with the addition of PPA show better high-temperature properties significantly, the ability of asphalt to resist rutting is improved, and the elastic recovery is increased. However, the low-temperature properties of the compound modified asphalts are degraded by increasing the creep stiffness (S) and decreasing the creep rate (m). At the same time, RTFO tests results show that PPA was less prone to oxidation to improve the anti-aging ability of modified asphalts. Overall, the combination of 4% SBS and 0.75–1.0% PPA, the combination of 4% SBR and 0.5–0.75% PPA is recommended based on a comprehensive analysis of the performance of compound modified asphalt, respectively, which can be equivalent to 6% SBS/SBR modified asphalt with high-temperature properties, low-temperature properties, temperature sensitivity and aging properties.

The Structure of Bitumen: Conceptual Models and Experimental Evidences

Bitumen, one of the by-products of petroleum industry processes, is the most common binder used in road pavements and in the construction industry in general. It is a complex organic mixture of a broad range of hydrocarbons classified into four chemical families, collectively known with the acronym SARA fractions, which include saturates, aromatics, resins and asphaltenes. Since the 1940s, researchers working on bitumen and the science behind its existence, nature and application have investigated the spatial organization and arrangement of several molecular species present in the binder. Therefore, several models have been proposed in the literature, and they are more or less corroborated by experimental studies, although most of them are model-dependent; for example, the structural investigations based on scattering techniques. One of the most popular models that has met with a wide consensus (both experimentally and of the modeling/computational type) is the one aiming at the colloidal description of bitumen's microstructure. Other types of models have appeared in the literature that propose alternative views to the colloidal scheme, equally valid and capable of providing results that comply with experimental and theoretical evidence. Spurred by the constant advancement of research in the field of bitumen science, this literature review is aimed at providing a thorough, continuous and adept state of knowledge on the modeling efforts herein elaborated, in order to more precisely describe the intricacy of the bituminous microstructure. In this body of work, experimental evidence, along with details of bitumen's microstructure (depicting the colloidal state of bitumen), is particularly emphasized. We will also try to shed light on the evolution of the experimental and theoretical results that have focused on the aspect of the association and aggregation properties of asphaltenes in various models and real systems.

Sustainable Polymers from Recycled Waste Plastics and Their Virgin Counterparts as Bitumen Modifiers: A Comprehensive Review

The failure of bituminous pavements takes place due to heavy traffic loads and weather-related conditions, such as moisture, temperature, and UV radiation. To overcome or minimize such failures, a great effort has been put in recent years to enhance the material properties of bitumen, ultimately improving field performance and increasing the pavement service life. Polymer modification is considered one of the most suitable and by far the most popular approach. Elastomers, chemically functionalised thermoplastics and plastomers * (* Note: notwithstanding the fact that in Polymer Science the word 'plastomer' indicates a polymer with the simultaneous behaviour of an elastomer and plastics (thermoplastics), this paper uses the term 'plastomer' to indicate a thermoplastic polymer as it is more commonly found in Civil and Pavement Engineering.) are the most commonly used polymers for bitumen modification. Plastomers provide several advantages and are commonly acknowledged to improve high-temperature stiffness, although some of them are more prone to phase separation and consequent storage instability. Nowadays, due to the recent push for recycling, many road authorities are looking at the use of recycled plastics in roads. Hence, some of the available plastomers-in pellet, flakes, or powder form-are coming from materials recycling facilities rather than chemical companies. This review article describes the details of using plastomers as bitumen modifiers-with a specific focus on recycled plastics-and how these can potentially be used to enhance bitumen performance and the road durability. Chemical modifiers for improving the compatibility between plastomers and bitumen are also addressed in this review. Plastomers, either individual or in combination of two or three polymers, are found to offer great stiffness at high temperature. Different polymers including HDPE, LDPE, LLDPE, MDPE, PP, PS, PET, EMA, and EVA have been successfully employed for bitumen modification. However, each of them has its own merit and demerit as thoroughly discussed in the paper. The recent push in using recycled materials in roads has brought new light to the use of virgin and recycled plastomers for bitumen modification as a low-cost and somehow environmental beneficial solution for roads and pavements.

Study on Styrene-Butadiene-Styrene Modified Asphalt Binders Relaxation at Low Temperature

The paper presents the results of laboratory investigation on asphalt binders relaxation at low temperature, carried out in a ductilometer using the tensile test with continuous force measurement. Polymer modified asphalt binder samples consisting of a 50/70 penetration grade bitumen mixed with a concentrate of styrene-butadiene-styrene (SBS) modified bitumen—a 160/220 penetration grade bitumen modified with a SBS copolymer in the amount of 9%—were tested. Therefore, polymer modified binders containing 3%, 4.5%, 6% and 7.5% SBS, respectively, were obtained and investigated. Tensile tests were performed at −16 °C on samples before aging and subjected to short-term aging (RTFOT). Test results in the form of relaxation curves have been mathematically described using a modified generalized Maxwell model. Based on the acquired results, it was shown that the increase of the SBS copolymer content in asphalt binder precipitates the relaxation process, while aging slows down this phenomenon. It has also been proven that with increased content of SBS elastomer in asphalt binder, the effect of short-term aging on binder’s stress relaxation ability at low temperatures is reduced.

NMR Diffusiometry Spectroscopy, a Novel Technique for Monitoring the Micro-Modifications in Bitumen Ageing

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’ findings, FT-NMR-SDC observations confirm that the asphaltene content increases during ageing processes.

A Study of Rubber-REOB Extender to Produce Sustainable Modified Bitumens

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–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–REOB ratios were considered and investigated by means of low and high frequency nuclear magnetic resonance (NMR) spectrometers and scanning electron microscope (SEM).

A Review on Bitumen Rejuvenation: Mechanisms, Materials, Methods and Perspectives

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.

Effects of Cement–Mineral Filler on Asphalt Mixture Performance under Different Aging Procedures

Cement-containing mineral powder can effectively improve the moisture stability of an asphalt mixture; therefore, this study systematically summarizes the research status of cement–mineral fillers on the performance of an asphalt mixture and determines the limitations of related studies. In this study, long-term performance tests of styrene-butadiene-styrene- (SBS)-modified asphalt mixtures are designed and evaluated with different blending ratios of the cement–mineral powder under three aging conditions. Moreover, the effect of the cement–mineral composite filler on long-term performance of the asphalt mixture using different blending ratios is determined. Cement improves the high-temperature performance and water stability of asphalt mixtures, but only for certain aging conditions. Considering the regulations for the road performance of asphalt mixtures for three aging conditions, as well as long-term performance considerations, the results indicated that the mass ratio of Portland cement to mineral powder must not exceed 2:2. Low-temperature bending and splitting tensile tests confirmed that an excessive amount of cement filler will embrittle the modified asphalt mixture during long-term aging, thereby deteriorating the tensile properties. The mechanism by which the filler influences the performance of the asphalt mixture should be further studied from the perspective of microscopic and molecular dynamics.

Use of plastic scrap in asphalt mixtures added by dry method as a partial substitute for bitumen

In recent decades, the generation of plastic waste has increased substantially worldwide, with the result that more of such waste is introduced into the environment. Currently, most polymers (polyethylene terephthalate, polyethylene, polyvinyl chloride, and others) are recycled. However, some are rejected for recycling in the primary separation processes due to their physical condition, contamination, or size. These materials are called plastic scrap. In this research, the use of plastic scrap added by dry method was evaluated as a replacement for bitumen in asphalt mixtures. Two sizes of plastic scrap, coarse and fine, were considered. An AC16S semi-dense mixture was designed for this purpose, with a 10% reduction in binder, and 10% and 20% of plastic scrap binder was added in coarse and fine sizes. The results obtained in the Marshall stability and flow test showed reduced moisture damage, greater indirect tensile strength, higher air void content, and a 2% decrease in the conserved tensile strength ratio while the same usage field as the conventional mixture was maintained. Meanwhile, significant decreases in plastic deformations, as compared to traditional values, were obtained from resilient modulus and rutting tests.

Bitumen and Bitumen Modification: A Review on Latest Advances

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 Effect of Direct-to-Plant Styrene-Butadiene-Styrene Block Copolymer Components on Bitumen Modification

Five types of material, styrene-butadiene-styrene block copolymer (SBS), ethyl-vinyl-acetate (EVA), naphthenic oil, maleic anhydride grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) and butylated hydroxytoluene (BHT) were used as the raw ingredients for manufacturing direct-to-plant SBS in this paper. Thirteen kinds of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS were prepared as well as the processes diagrammatic sketch of dispersion and swelling of direct-to-plant SBS modifier in bitumen were discussed. Microscopic images of direct-to-plant SBS modified bitumen with different components were obtained using fluorescence microscopy. The micro-images were analysed and quantified with MATLAB software. The influence of key components on the micro-morphology of direct-to-plant SBS-modified bitumen is discussed, followed with the tests on melting points and the melting indexes of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS. The performances test of bitumen and bituminous mixture modified by these direct-to-plant SBS were also conducted. Results show that, with the ratio improvement of EVA/SBS or naphthenic oil/SBS, the number of the pixel dot number of area (SBS) in microscopic images increased. Enlargement of the pixel dot number of centre line elongate and the structure fineness was observed, indicating that the dispersion and swelling effect of the SBS modifier in bitumen had been improved. Meanwhile, the macro index, such as the melting point and melting index of direct-to-plant SBS, was also improved corresponding to the increase of EVA/SBS ratio or naphthenic oil/SBS ratio. With the addition of EVA or naphthene oil content, penetration and ductility of direct-to-plant SBS modified bitumen received gradual enhancement, but the softening point and viscosity were found out to be decreased. The high-temperature and low-temperature performances of direct-to-plant SBS modified bituminous mixture can be effectively improved by adding EVA or naphthenic oil. By meeting the required performances of direct-to-plant SBS, modified bitumen and bituminous mixture, the component of direct-to-plant SBS is recommended as, SBS:EVA:naphthenic oil:EVA-g-MAH:BHT is 1:0.1⁻0.5:0.05⁻0.2:0.03:0.05. For the compatibleness of SBS with different bitumen are different, necessary tests verification is recommended to be carried out prior to usage.

Thermal and Rheological Formulation and Evaluation of Synthetic Bitumen from Reprocessed Polypropylene and Oil

Bitumen from the catalytic cracking of petroleum is widely used in the construction industry as a binder for mineral aggregates paving asphalt cement (PAC). However, this material has serious limitations for use at different temperatures. Modifications with polymers have been widely studied to improve the properties of this material and increase its useful life. As a result of the increased environmental risk, the volume of solid waste (MSW) can be used as an alternative to the best use of this material. One of these is the formulation of synthetic bitumen (binders) from mixtures of lubricant oil/polymer that can show better when compared to traditional and modified bitumen. In this work, a mixture of lubricating oil and recycled polypropylene (PP) was made for the formulation of synthetic bitumens. The rheological analyses carried out on the material indicate that at low temperatures the formulated material shows high loading modulus values, indicating high mechanical strength, and the material also presented high resistance to permanent deformation; the viscosity profile indicates that the material is highly pseudoplastic presenting high viscosity at zero shear rate and low visibility at high shear rates, highlighting the samples containing 10 and 20% of polymer material in the formation as the best for use as one of the components of the pavement cement.

Effects of Natural Antioxidant Agents on the Bitumen Aging Process: An EPR and Rheological Investigation

Bitumen aging is the major factor contributing 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 out 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.

NMR-Spectroscopy Determination of Fragmentary Composition of Bitumen and its Components

This paper represents and discusses the results of quantitative determination for fragmentary composition of road bitumen of grade BND 100/130 and its components (asphaltenes, resins and oils) by NMR spectroscopy method. Group chemical composition of the bitumen has been determined by adsorption chromatography method. It has been identified that the bitumen and its components consist only of aromatic and aliphatic protons, which account for 2.4‒10.2% and 9.8‒97.6% respectively. Availability of olefinic elements in them has not been identified. The most part (79‒81%) of nuclei of carbon atoms relates to quaternary carbon atoms of saturated compounds. Primary carbon atoms at methylene group (CH2) are contained in the least quantity: bitumen ‒ 1.32%; asphaltenes – 0.6%; resins – 3.24% and oils – 2.11%. Primary carbon atoms, linked with CH-group or aromatic nucleus, occupy an intermediate position and are contained in the quantity of 17‒20%.

Polymer Modified Bitumen: Review

The main reasons and ways of bitumen modification by polymers were examined. Positive and negative aspects of the usage of different polymer modifiers (elastomers, thermoplastic elastomers, reactive polymers, thermoplastics) were analysed. The authors’ achievements concerning modification of bitumen by various polymers, namely indene-coumarone, petroleum, phenol-formaldehyde and epoxy resins, were described.