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Bitumen is a major construction material that can emit harmful fumes when heated. These fumes pose health risks to workers and communities near construction projects or asphalt mixing plants. The chemical complexity of bitumen fumes and the increasing use of additives add to the difficulty of analytically quantifying the harmful chemicals emitted using a single technique. Research on bitumen emissions consists of numerous sample preparation and analytical methods. There are a range of considerations to be made when deciding on an appropriate sample preparation method and instrumental configuration to optimise the analysis of specific organic contaminants in emissions. Researchers investigating emissions from bituminous materials may need to consider a range of analytical techniques to quantify harmful chemicals and assess the efficacy of new additives. This review summarises the primary methodologies for sample preparation and analytical techniques used in bitumen research and discusses future challenges and solutions.

Accurate characterisation and appropriate binder selection are essential to increase the load-induced cracking resistance of asphalt mixtures at an intermediate temperature. Hence, the primary goal of this study was to correlate the cracking resistance exerted by the binder with the cracking performance of asphalt mixtures. The laboratory-based experimental plan covered various types of laboratory tests specified by various agencies and road authorities to study the correlation of a neat bitumen and five polymer-modified binders with their corresponding asphalt mixtures. The fatigue life of the binders was assessed through a Linear Amplitude Sweep (LAS) test and statistically correlated with various load-induced cracking parameters from the indirect tensile test, semi-circular bending (SCB) test, and four points bending beam test (FPBB) of asphalt mixtures at 25 °C. Binders and mixes were further grouped depending on their polymeric family (i.e., modified with a particular type of polymer) to validate their statistical correlation. The indicator that mostly correlated the binder properties with the asphalt mixture properties is the secant modulus from the SCB test. Fatigue parameters obtained through LAS better explain the asphalt fatigue performance obtained through FPBB; specifically, asphalt tests at high strain levels (e.g., 400 micro strain) better correlate to the LAS fatigue parameter (Nf).

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.

In this study, the mechanical and rheological properties of hybrid polymer-modified bitumen (PMB) have been investigated. For this purpose, nine different polymers-including crumb rubber, elastomers and plastomers at varying content-were studied to evaluate their mechanical performance as single polymers, first, and as a combination of two or more polymers as a hybrid polymer blend. Subsequently, the hybrid polymer blends were added in a relatively small percentage into the base bitumen to study its influence on the rheological performance of hybrid PMB. The mechanical properties identified from the analysis of the stress-strain curve of the single polymers were the Young's Modulus, tensile stress, and elongation at break. The chemical structure of the polymer hybrid blends was analysed using FTIR, followed by frequency sweep tests conducted using the dynamic shear rheometer (DSR) to determine the bitumen rheological properties. Results showed that hybrid PMB enhances the viscoelastic behaviour of bitumen at both low and high temperature compared to other PMBs only including single polymers., Competing Interests: The authors declare no conflict of interest.

Waste management has become an issue of increasing concern worldwide. These products are filling landfills and reducing the amount of livable space. Leachate produced from landfills contaminates the surrounding environment. The conventional incineration process releases toxic airborne fumes into the atmosphere. Researchers are working continuously to explore sustainable ways to manage and recycle waste materials. Recycling and reuse are the most efficient methods in waste management. The pavement industry is one promising sector, as different sorts of waste are being recycled into asphalt concrete and bitumen. This paper provides an overview of some promising waste products like high-density polyethylene, marble quarry waste, building demolition waste, ground tire rubber, cooking oil, palm oil fuel ash, coconut, sisal, cellulose and polyester fiber, starch, plastic bottles, waste glass, waste brick, waste ceramic, waste fly ash, and cigarette butts, and their use in asphalt concrete and bitumen. Many experts have investigated these waste materials and tried to find ways to use this waste for asphalt concrete and bitumen. In this paper, the outcomes from some significant research have been analyzed, and the scope for further investigation is discussed., Competing Interests: The authors declare no conflict of interest.

Littering waste is among the top environmental issues in the world, and the management of the waste has turned into a challenge in almost every city. It has been reported that 75% of smokers dispose of their cigarette butts (CBs) on the ground, even in public places. Researchers have discovered that CBs make up more than one-third of the total littered waste on the planet. Cigarette butts predominantly consist of a cellulose acetate fiber (plastic)-based filter wrapped in paper. Waste CBs contain burnt tobacco and tar, along with many other toxic chemicals. They take years to biodegrade depending on the environmental conditions, and toxic chemicals leach out and contaminate the environment. As part of an ongoing project, this paper presents a novel and sustainable technique to recycle cigarette butts in bitumen for the construction of flexible pavements. In this research, CBs have been pre-processed and mixed with bitumen classes C320, C170, and PMB A10E as a fiber modifier. Comprehensive laboratory investigations, including a penetration test, softening point test, and viscosity test, have been performed along with a binder drain off test to evaluate the performance of the modified samples. During this investigation, samples were prepared with 0.3% cellulose fiber, 0.2%, 0.3% 0.4%, and 0.5% CBs. The results of the CB-modified samples were compared with the sample with cellulose fiber and fresh bitumen (0% fiber). The results show that the physical and rheological properties of bitumen incorporating CBs improve significantly, and CBs could be used instead of virgin cellulose fiber as a fiber modifier.