Full depth reclamation (FDR) with cementitious binders is progressively being implemented in India for rehabilitating the distressed low-volume roads (LVRs). Unlike conventional cement-treated base (CTB) mixes, FDR mixes are highly heterogeneous, comprising reclaimed bituminous materials, aggregates from granular layers, subgrade soil, and varying binders. Extensive laboratory testing evaluated the fatigue performance of CTB and FDR mixes stabilised with Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC). The FDR mixes exhibited lower flexural strength (<1 MPa) and modulus (1700–2700 MPa) than the CTB mixes, along with greater variability in fatugue behaviour. Initial tensile strains ranged from 115 to 568 µε. A laboratory fatigue constant of 600.9 was established; after applying a lab-to-field shift factor of 1.55. This exceeded the upper limiting value of the in-service fatigue constant having flexural modulus less than 5000 MPa. Therefore, a conservative in-service fatigue constant of 439 was calculated, based on AUSTROADS (2017). Incorporating reliability considerations for LVR design, this study proposes a fatigue equation and pavement design catalogues for varying traffic levels, subgrade conditions, and crack relief options. Future refinement of shift factors is recommended as more field data become available.

To elucidate the modification and pre-swelling mechanisms of instant bituminous modifiers and their contribution to bituminous materials' performance, this study investigates an instant ultra-high-performance bitumen modifier (SHVE-M). Fluorescence microscopy (FM), gel permeation chromatography (GPC), physical property tests, viscoelastic properties tests, dynamic shear rheometer (DSR), and mixture pavement performance tests were employed to systematically characterise the instant modified bitumen (SHVE-MB) and its mixture (SHVE-MBM). The results indicate that SHVE-M forms a stable "bitumen phase-polymer spherical phase" structure. ImageJ-win64 analysis revealed that SHVE-M exhibits a modifier area fraction of 46.68% and an average area fraction of 0.22‱, while SHVE-MB achieves a modifier area fraction of 17.54% and an average area fraction of 0.18‱. This morphology is supported by a large molecular size (LMS) content of 43% in SHVE-M. In terms of physical properties, the SHVE-MB (prepared via 10 min shearing) exhibited a penetration of 46.2 dmm, a softening point of 91.7 °C, and a ductility of 34.3 cm. These values are highly comparable to the conventional wet-process HVE-MB (prepared via 4 h maturation), with negligible differences of 0.5 dmm, 1.7 °C, and 1.4 cm, respectively. Quantitatively for viscoelasticity, SHVE-MB achieved a dynamic viscosity of 425,283.4 Pa·s at 60 °C and an elastic recovery rate of 92.1%, paralleling the 414,623.7 Pa·s and 93.6% of HVE-MB. Regarding mixture performance, the high-temperature dynamic stability (DS) of SHVE-MBM reached 7974 times/mm, approaching the 8256 times/mm of HVE-MBM. The water stability was excellent with a splitting tensile strength ratio (TSR) of 97.4% (vs. 98.0% for HVE-MBM). Furthermore, the low-temperature fracture toughness (KIC) reached 39.8 N/mm1.5, significantly outperforming SBS-MBM (27.9 N/mm1.5) and remaining close to HVE-MBM (43.9 N/mm1.5). These findings indicate that SHVE-MB effectively bridges the performance gap between instant and traditional high-viscosity modified bitumen, and the pre-swelling mechanism of SHVE-M is well characterized in this study.

HighlightsWhat are the main findings?Resonant Acoustic Spectroscopy (RAS) was successfully applied to bitumen for the first time and can determine the complex modulus of bitumen in a temperature range from −30 °C to 20 °C.At low temperatures, RAS-derived complex modulus values show good agreement with Dynamic Shear Rheometer (DSR) measurements, especially at −20 °C and −30 °C.What are the implications of the main findings?RAS provides a fast, cost-effective, and non-destructive method for assessing stiffness and ageing effects in bitumen, offering potential for quality control and routine material evaluation.Due to the determination and use of natural resonant frequencies, RAS alone cannot generate a full master curve of bitumen and is not suitable for characterizing bitumen behaviour at high temperatures or low loading frequencies.The complex modulus is one of the intrinsic properties of bituminous materials, and, hence, is of importance for their rheological characterization. It was shown by various authors that the complex modulus of asphalt mixtures can be calculated from dynamic modulus measurements using the Resonant Acoustic Spectroscopy (RAS). This paper extends the RAS technique to bitumen. For the purpose of validation, rheological data for the same bitumen are also derived from standard Dynamic Shear Rheometer (DSR) tests, and the master curves resulting from both methods are compared. The laboratory programme comprised a temperature range from −30 °C to 20 °C, and four different bitumens in unaged and aged condition, resulting in 36 different test variants. RAS successfully characterizes the complex modulus of bitumen and reflects temperature and ageing effects, with good agreement to DSR results at low temperatures. At higher temperatures, viscosity and damping introduce deviations, indicating that RAS is effective for modulus evaluation but not sufficient for complete master curve development.

This study examines the influence of virgin polyethylene (vPE), recycled polyethylene (rPE), and Aerosil (A) on the performance of bitumen binders modified with partially devulcanized rubber (DVR). The experimental program included morphology analysis, determination of devulcanization degree, dynamic viscosity measurements, shear stress-shear rate analysis, load-displacement (F-Δl) testing, storage-stability evaluation, ring and ball softening point (R&B), penetration (P), and elastic recovery (ER) testing. The results show that DVR-rPE-modified bitumen binders exhibit 20-35% higher viscosity and up to 25% greater elongation at the break compared to DVR-vPE-modified bitumen systems, indicating more effective interaction with the bitumen matrix. The incorporation of Aerosil increased viscosity ca. 1.5-2 times for DVR-rPE and DVR-vPE-modified systems, respectively. Meanwhile, top and bottom differences in R&B decreased by a factor of 1.6-5 for DVR-rPE and DVR-vPE-containing composites, respectively, demonstrating significant enhancement in structural stability during storage. Mechanical testing further revealed that DVR-rPE + A binders absorbed 10-20% more deformation energy and consistently maintained ER values above 70-80%, corresponding to a higher elastic recovery grade at 25 °C. Overall, the DVR-rPE + A system provided the most balanced improvements in rheological, mechanical, and thermal properties, confirming its potential for use in high-performance, thermally stable, and environmentally sustainable bituminous materials for pavement applications.

The increasing volume of recycled plastic waste has become a significant environmental challenge. Recent studies have highlighted the potential for using recycled plastic in various applications, including construction materials. One such application is in bituminous mixes for road construction, where recycled plastic waste is incorporated to improve the performance of bituminous materials used in footpaths and low-volume roads. This review examines the feasibility of incorporating recycled plastic into bituminous mixes, evaluating its effects on the mechanical properties of the mix, its environmental benefits, and practical guidelines for the preparation of such mixes. Various types of recycled plastic waste, including polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), have been explored for use in road construction, with significant improvements in properties such as strength, durability, and resistance to cracking. However, concerns regarding the environmental impact of plastic use and the long-term sustainability of these mixes remain unresolved. The research outlines the mechanisms through which recycled plastic waste enhances the properties of bituminous mixtures and discusses the challenges associated with its integration into the current road construction practices. Practical mix guidelines are provided, based on a thorough analysis of different recycled plastic waste types, their effect on the mix composition, and optimal usage rates. The review concludes by emphasizing the need for further research on the long-term environmental impact of plastic-modified bituminous mixtures and the potential for wider adoption in low-volume road construction.

This study investigated the effects of Reclaimed Asphalt Pavement (RAP) on the fracture parameters and damage evolution pattern using an extrinsic nonlinear viscoelastic cohesive zone (NVCZ) model integrated with the Gaussian damage evolution function. The primary objectives were to evaluate the sensitivity of the model’s parameters to variations in the RAP content as well as to assess the effect of each parameter on the complex non-linear fracture process of bituminous materials. Two similar laboratory-produced asphalt mixtures with different RAP percentages (25 and 65 %) were assessed through dynamic modulus test to capture linear viscoelastic properties and the semi-circular bending test to obtain fracture test parameters by means of experimental-numerical calibration. A numerical parametric analysis was also performed to verify the influence of each NVCZ-Gaussian model parameter on the fracture response of RAP-produced asphalt mixtures. The calibration results revealed that two NVCZ model parameters, cohesive zone length (δ) and initiation stress ( σ i f ), could be identified without calibration, while Gaussian damage parameters (λ associated with mean value and RMS associated with standard deviation value in the damage-rate vs. displacement graph) varied systematically with RAP content. The variation in these parameters demonstrated a rational and consistent sensitivity to changes in RAP content, in line with the parametric trends observed in the study. To validate the outcomes, a third mixture with 45 % RAP (M45) was used. Its NVCZ parameters were predicted using an interpolation technique, eliminating the need for additional SCB testing or numerical calibration. The numerical predictions closely matched the experimental results, capturing both the initial and post-peak cracking behavior. Key cracking-related parameters (peak load, fracture energy, and flexibility index) further confirmed the strong agreement between numerical and experimental results. These findings demonstrate the potential of the NVCZ-Gaussian model as a promising mechanistic tool for predicting fracture behavior across mixtures with varying RAP contents and supporting more efficient performance-based mix design. • The viscoelastic CZ model with a Gaussian damage function, effectively predicted fracture behavior for varying RAP content levels. • Key model parameters of the Gaussian damage function demonstrated sensitivity to varying RAP content. • Mechanistic modeling with experimental data can be used to support more efficient RAP-recyclled mixture design. • Numerical modeling can provide additional insights into the damage evolution of RAP-recycled asphalt mixtures.

The possibilities of using petrochemical wastes as additives to bituminous materials were discussed

This review examines scientific and engineering strategies for adapting bituminous and asphalt concrete materials to the highly diverse climates of Central Asia. The region’s sharp gradients—from arid lowlands to cold mountainous zones—expose pavements to thermal fatigue, photo-oxidative aging, freeze–thaw cycles, and wind abrasion. Existing climatic classifications and principles for designing thermally and radiatively resilient pavements are summarized. Special emphasis is placed on linking binder morphology, rheology, and climate-induced transformations in composite bituminous systems. Advanced characterization methods—including dynamic shear rheometry (DSR), multiple stress creep recovery (MSCR), bending beam rheometry (BBR), and linear amplitude sweep (LAS), supported by FTIR, SEM, and AFM—enable quantitative correlations between phase composition, oxidative chemistry, and mechanical performance. The influence of polymeric, nanostructured, and biopolymeric modifiers on stability and durability is critically assessed. The review promotes region-specific material design and the use of integrated accelerated aging protocols (RTFOT, PAV, UV, freeze–thaw) that replicate local climatic stresses. A climatic rheological profile is proposed as a unified framework combining climate mapping with microstructural and rheological data to guide the development of sustainable and durable pavements for Central Asia. Key rheological indicators—complex modulus (G*), non-recoverable creep compliance (Jnr), and the BBR m-value—are incorporated into this profile.

This paper presents a novel, low-cost, and portable microwave sensing system for non-destructive classification of bituminous pavement materials using a log-periodic feedline-based ring resonator integrated with a software-defined radio (SDR) platform. Traditional mechanical tests, such as Marshall stability and fatigue testing, are often time-consuming, destructive, and lack sensitivity to microstructural variations. In contrast, the proposed system measures attenuation and group delay with high spatial resolution at 400 MHz and 600 MHz. These parameters are extracted from the frequency-domain response using the Fast Fourier Transform (FFT). The system successfully distinguishes between bituminous concrete (BC) and open graded friction course (OGFC) samples, achieving a classification accuracy of 97.42%. Its low cost and high portability make it a promising tool for real-time, field-level pavement diagnostics.

Cup lump rubber and natural rubber latex biopolymers as promising modifiers for asphalt binders and mixtures: A review

To conserve natural resources and reduce waste generation, the effective valorization of industrial waste and byproducts in engineering applications is becoming increasingly important. Among these materials, aluminum production residues (APRs) offer a promising and sustainable solution for road pavement applications. Unlike previous reviews, this paper uniquely examines recent research on the use of various APRs in bituminous materials across multiple scales, with particular attention to their roles as additives and fillers. The APRs examined included red mud (RM), aluminum dross (AD), and spent pot lining (SPL) residues, as well as secondary aluminum waste (SAW). These materials have been employed as additives in asphalt binders (microscale), as fillers in asphalt mastics (mesoscale), and as additives or fillers in asphalt mixtures (macroscale). Overall, this review indicates that adopting appropriate treatment approaches for APRs as asphalt modifiers can enhance their dispersion, thermal stability, rheological behavior, and leaching performance. In particular, the use of RM has been shown to improve thermal stability, tensile strength, intermediate-temperature cracking resistance, and rutting resistance, largely due to the increased stiffness it imparts to asphalt mastic and mixture phases. However, there is no clear consensus among researchers regarding other properties, as performance outcomes depend strongly on multiple factors, particularly the physicochemical characteristics of the RM, filler–binder ratios, testing methods, and reference filler types. Other APRs—such as AD, SPL, and SAW—have also shown beneficial effects on the performance of asphalt mixtures. There is still limited research on the influence of APRs physicochemical variability on asphalt–filler interactions and the performance of bituminous materials. For the safe and large-scale adoption of APRs, it is essential to establish standardized characterization procedures, testing methods, and application guidelines while considering diverse climatic conditions. Comprehensive assessments of cost and environmental impacts should also be incorporated to support informed decision-making by engineers and industrial stakeholders.

Emulsification capacity of by-products bituminous binding materials with presence of inorganic solids

Model dimensional scale effects on molecular dynamics simulations of bituminous materials

Background: The use of bitumen-polymer composites is a relevant and promising approach to improving the performance characteristics of bituminous materials in road construction. Studying the structure and interaction mechanisms of components in such composites enables the optimization of formulations and enhancement of the final product’s quality. Aim: The aim of this research is to investigate the structure and the nature of interactions between the components of bitumen-polymer composites based on bitumen, polypropylene, and heavy petroleum residues using infrared (IR) spectroscopy. Materials and methods: The IR spectroscopy method was used to analyze structural changes in the composites. The spectra of the initial components (bitumen, polypropylene, heavy petroleum residues) and the modified bitumen were studied. A comparative analysis of the position and intensity of characteristic absorption bands corresponding to the main functional groups was carried out. Results: It was found that the introduction of polypropylene causes changes in the bitumen absorption spectra, particularly in the region of the stretching vibrations of carbon-hydrogen and carbon-oxygen bonds. This indicates structural transformations and redistribution of molecular interactions within the system. The additional incorporation of heavy petroleum residues amplifies these effects, resulting in changes in the physical properties of the composite, – notably, increasing the softening temperature and decreasing penetration. It was shown that the degree of interaction between components depends on polymer concentration and modification conditions. Conclusion: The obtained results reveal the mechanisms of structure formation and component interaction in bitumen-polymer composites, providing a scientific foundation for optimizing modified bitumen formulations. The work contributes to the development of research methodologies and expands the application of bituminous materials in construction and road industries.

Abstract Volatile organic compound (VOC) emissions from bituminous materials pose environmental and health risks during application. In this study, molecular dynamics and quantum chemical simulations were integrated to construct a four‐component average molecular structure model of asphalt. VOC release models of SARA fractions were developed. The release pathways of VOCs from the SARA model under pyrolysis were simulated and predicted. The effects of heating temperature and SARA components on VOC emissions were further examined by pyrolysis–GC/MS (Py–GC/MS), and simulation results were validated with controlled pyrolysis experiments. Simulations indicated that the carbon skeletons in saturates and aromatics are mainly C─C bonds, whereas resins and asphaltenes contain aromatic ring structures with uniformly distributed electron density. Asphaltenes, with more aromatic rings and the lowest frontier orbital energy levels, were the most stable, while saturates, with the highest frontier orbital energy levels, volatilized most readily. Pyrolysis experiments showed that alkanes were the predominant VOCs in asphalt, largely originating from saturates, which exhibited the highest unit VOC release. Asphaltenes emitted the least VOCs, mainly polycyclic aromatic hydrocarbons (PAHs), while aromatics and resins were also major PAH sources. The pyrolysis results agreed well with model predictions, elucidating the release mechanisms of asphalt VOCs.

Lignin, a prominent by-product of the wood and paper industry, presents a promising alternative to bitumen or a modifier to enhance the performance of bituminous mixtures. As a natural biopolymer, lignin offers the dual benefits of improving the properties of bituminous materials while promoting environmental sustainability. This study investigates the use of two types of lignin (lignin A and lignin B) as additives to enhance the characteristics of bitumen and the performance of bituminous mixtures. Various weight percentages of lignin were incorporated into control bitumen (VG30) at levels of 5%, 10%, and 20%. The effects of lignin on bitumen properties were assessed through penetration tests, softening point evaluations, ductility measurements, and elastic recovery analysis. Following this, bituminous mixtures were formulated, and their performance was evaluated using tests such as Marshall stability, flow value, resilient modulus, crack tolerance index, indirect tensile strength (ITS), and Cantabro abrasion tests. The experimental results indicate that adding lignin to bitumen significantly improves both the physical and mechanical properties of the material. Specifically, incorporating up to 10% lignin in both modified bitumen types resulted in increased Marshall stability and reduced flow values, suggesting enhanced resistance to permanent deformation. Moreover, the ITS of the bitumen improved with a 10% lignin modification. Notably, lignin B at 10% content exhibited the highest resilient modulus, indicating improved cohesion and structural integrity, which contributed to increased stiffness. Furthermore, the lignin-modified bitumen demonstrated superior adhesion to aggregates compared to the control bitumen. As the lignin content increased, the fracture energy consistently increased, reflecting an enhanced resistance to crack initiation and propagation. This finding suggests that lignin inclusion contributes to the toughness of the asphalt mixture, enhancing its resilience against cracking. In addition, a significant reduction in mass loss was observed, particularly at higher lignin contents, highlighting the material’s decreased susceptibility to abrasion and wear. Overall, these results underscore the substantial impact of lignin on improving the durability and performance of bituminous mixtures.

ABSTRACT Self-sensing conductive bitumen pavement materials hold critical importance for smart transportation systems. While current research predominantly focuses on conductive asphalt concrete, the insulating nature of aggregates necessitates dependence on bitumen binders for pavement conductivity. This study addresses the fundamental challenge of constructing conductive networks within bituminous materials. A polyurethane (PU) prepolymer was synthesised via reaction between diphenylmethane diisocyanate (MDI) and polypropylene glycol (PPG), subsequently employed for bitumen modification. To enhance conductivity, carbon nanotubes (CNT) were introduced through dual pathways: direct incorporation into the bitumen matrix and integration during PU-prepolymer synthesis. Comprehensive evaluations including dynamic shear rheological (DSR) analysis, dynamic mechanical analysis (DMA), thermal conductivity, and electrical conductivity measurements were conducted. Remarkably, minimal CNT addition (2 wt.% relative to PU-prepolymer, equivalent to 0.4 wt.% in final composites) induced a four-order-of-magnitude conductivity enhancement. Mechanistic investigations via Fourier transform infrared spectroscopy (FTIR), optical microscopy, and scanning electron microscopy (SEM) revealed that CNT participation in PU-prepolymer synthesis facilitates percolated network formation. This structure concurrently improves electrical pathways and interfacial reinforcement within the bitumen matrix.

ABSTRACT The characterization of cold recycled bituminous materials (CRMs) at a very young age, shortly after compaction, is inherently challenging due to the nature of the material. The granular aspect of CRM at this stage and its high-water content render the use of conventional mechanical techniques impractical. Following previous work, the use of a nondestructive technique based on the frequency analysis of mechanical elastic shear waves, piezoelectric ring actuator technique (P-RAT), has enabled assessment of the behavior of cold in-place recycled material treated with bitumen emulsion from 10 min after compaction to 30 days of curing. Emphasis on shear wave velocity (Vs) measurements during the early age confirmed the rapid stiffening of the mix along with the departure of water present in the mix. A 6 °C drop of the surface temperature is observed along with this rapid increase of Vs and water loss. The initial and final Vs values range from 287 to 330 m s−1 and from 461 to 578 m s−1, respectively. To assess the capabilities of P-RAT, specimens with different void contents were tested, mainly 12, 15, and 17 %. It was observed that in each tested specimens, a similar behavior was exhibited during the first few hours of curing. Based on these observations, hypotheses are put forth regarding the phenomena governing the increase in stiffness during this period. Finally, the influence of the compaction of the specimens on the Vs values is consistent and comparable with the information available in the literature for such CRM.

Increased traffic volumes and the relatively poor performance of traditional asphalt concrete mixtures have created a demand to improve bituminous material quality and, in turn, the performance of hot mix asphalt concrete mixes. As a result, innovative materials and techniques are necessary for road construction, upkeep, and renovation to guarantee better-performing pavements. In this study, bitumen is modified with inexpensive nanoparticles to create an asphalt concrete mix that is more affordable, simpler to manufacture, more climate change-friendly, and provides a sustainable solution. This work includes two different kinds of nanomaterials: Graphitic Carbon Nitride (G-C3N4) and Mesoporous Silica Nanoparticles (MSNs). While MSNs have been used to asphalt concrete mixes in the past, this work introduces G-C3N4 as a novel kind of bitumen nanomaterial additive. The mechanical properties of modified bitumen, asphalt concrete mixes, and nanomaterials under various circumstances were evaluated in a laboratory setting. Various percentages of nanoparticles were added to the bitumen, and the results were compared to the control samples. Nanomaterials were tested in laboratories using x-ray diffraction and transmission electron microscopy. Dynamic Shear Remoter (DSR), Rotational Viscometer (RV), Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy were among the methods used to test bituminous materials. The modified bitumen’s properties were significantly improved as compared to the control samples, according to test results. A significant improvement in performance grade was shown by the DSR data, increasing resistance to permanent deformation. Both Marshall stability and maintained strength of indirect tensile strength were improved by the asphalt concrete mix including modified bitumen.

The circular economy (i.e., reuse and recycling of waste materials) is gaining attention for the goal of achieving net-zero waste. In this regard, the use of waterproofing membrane waste in bituminous materials can be a valid option, as every year, a lot of bituminous membrane wastes are generated both as production scraps or end-of-life wastes. Given this background, the recycling feasibility of end-of-life bituminous membrane waste (MW) in asphalt mixtures was assessed in this research study. To this aim, MW shreds (≤20 mm) were added to dense-graded bituminous mixtures using the dry-mixing method. The shreds were dosed at 0.5% by the mix weight (mix coded as SH-) or at 2% by mix weight (mix coded as SH+). A corresponding reference mix without MW was also tested for comparison purposes. The mixtures' workability, strength and stiffness as well as permanent deformation, moisture and fatigue resistance were evaluated. Overall, the laboratory experimental findings showed that MW-modified bituminous mixtures with a higher dosage of membrane waste (SH+) have relatively higher moisture resistance, fatigue resistance, stiffness and high-temperature performance with respect to the corresponding reference mix. Moreover, both the reference and MW-modified mixtures showed similar workability regardless of the MW content.