Transport Research International Documentation (TRID)

Experimental assessment of hot mixtures of asphalt concrete (HMAC) properties after the use of polyester fibers

Wed, 12 Aug 2026 15:14:49 GMT

Cracks are one of the principal distress mechanisms in asphalt pavements that substantially reducing their long term durability and service life. The use of substandard materials in production of Hot Mixtures of Asphalt Concrete (HMAC) affects the performance of asphalt pavement. Polyester fibers have been incorporated into HMAC to improve its resistance to cracking. Polyester fibers act as a three dimensional reinforcing network connects the components of HMAC together thus helping to reduce the occurrence of thermal and fatigue cracks under various climatic conditions and repeated loading. In this research, three different ratios of polyester fibers were selected (0.4, 0.5 and 0.6%). A total of forty eight (48) specimens were created and subsequently examined to evaluate optimum asphalt content (OAC) for the control mixture and three asphalt mixtures containing polyester fibers. Following the determination of OAC, twenty four (24) specimens were produced and tested to assess the behavior of polyester fibers and its impact on the characteristics of HMAC using the Marshall and indirect tensile strength tests. The laboratory results revealed that the addition of polyester fibers to HMAC improves the cracking resistance of the mixture by increasing its flexibility and ability to withstand repeated stresses and strains. The results further indicate that the mixtures incorporating polyester fibers exhibited higher values of ITS relative to the control mixture. Polyester fibers also showed potential sustainability benefits through improved pavement durability. The research results confirmed good agreement with the findings established in previous European studies on the polyester fibers asphalt mixtures. Finally, statistical analysis of data confirmed that the observed differences were significant and reliable.

Field Evaluation of High-Performance Cold Mix (HPCM) Products

Wed, 12 Aug 2026 09:58:15 GMT

This research project evaluated the field performance of nine High-Performance Cold Mix (HPCM) products from various producers to determine suitability for inclusion on ARDOT’s Qualified Products List (QPL). The test section was constructed in September 2024 on Hwy 338 (Sweet Home Cutoff/Dixon Road) in south Little Rock. Nine unique HPCM products, both bagged and plant-produced, were installed in simulated potholes and monitored over 12 months. Monthly inspections assessed durability, compaction retention, rutting, and adhesion performance. All nine products demonstrated satisfactory performance with minimal degradation through one full freeze-thaw cycle and a summer season. Based on the results, all tested products were approved for inclusion on the Department’s QPL for HPCM. The research also established evaluation criteria for future product submissions, enabling ARDOT to adopt HPCM materials into maintenance and construction projects without requiring individual project-based approvals.

Generation and characterization of wear particles from ferrochrome containing asphalt

Fri, 07 Aug 2026 08:36:54 GMT

Ferrochrome slag is a byproduct of high carbon ferrochrome alloy production and has promising material properties for use as aggregate in asphalt wearing courses. However, concerns remain regarding chromium-containing particle emissions during asphalt pavement wear. This study investigates the wear behaviour, particle size distribution, and elemental composition of wear particles generated from asphalt mixtures containing ferrochrome slag. Eight SMA11 and SMA16 asphalt mixtures with different combinations of slag and granite (as aggregate and filler) were prepared and tested using Tröger and Prall abrasion methods. Airborne particles were measured with Aerodynamic Particle Sizer (APS) and Scanning Mobility Particle Sizer (SMPS), and elemental composition was analysed with X-ray fluorescence (XRF). Prall and Tröger results show that ferrochrome slag provides wear resistance comparable to the reference material (with granite from Skärlunda as aggregate and filler), despite mixtures not being optimized for slag-specific density or porosity. All mixtures generated particles across a broad size spectrum. Tröger abrasion resulted in coarser particles due to loss of the finest particles during dry collection, while Prall testing yielded finer fractions because particles were collected in water. Airborne PM10 concentrations were similar for all mixtures, and ultrafine particles (<100 nm) were emitted regardless of aggregate type. Elemental analysis of filters (total suspended fraction), collected wear particles from the Tröger apparatus (coarse fraction), and the fine fraction (PM2.5. revealed the presence of chromium in slag-containing materials. Chromium was also detected at low levels in the granite samples, likely due to abrasion of the steel needles in the Tröger apparatus. While chromium was clearly present in the generated wear particles, its oxidation state was not determined. Overall, the results indicate that ferrochrome slag can be used in asphalt wearing courses without increasing airborne particle emissions compared with conventional asphalt pavement. Further investigations on chromium speciation, leaching of fine fractions, and field-scale validation are recommended to ensure environmental and health safety. However, the results are based on laboratory experiments conducted under controlled conditions and although the methods are designed to simulate real studded tire wear, emissions and particle characteristics may differ under actual road conditions.

Preparation and toughening mechanism of high-toughness cold-mixed epoxy asphalt

Tue, 28 Jul 2026 08:40:34 GMT

This study presents a formulation and preparation process for high-toughness cold-mixed epoxy asphalt (HTCEA). The optimal formulation was determined as: 140 parts epoxy resin, 80 parts curing agent, 40 parts epoxy diluent, 10 parts toughening agent, and 20 parts compatibilizer, through analyzing the influence of these components on HTCEA performance. Following this, the preparation process for Component A (composed of epoxy resin, diluent, toughening agent, and compatibilizer) and Component B (composed of base asphalt, asphalt diluent, and curing agent) was optimized. The established parameters involved stirring Component A at 60 °C and 500 r/min for 30 min, followed by mixing Components A and B at 500 r/min for 3 min. The optimized formula and process resulted in an HTCEA with a tensile strength of 2.45 MPa, an elongation at break of 166.28%, and a pot life of 50 min. Compared with conventional CEA, the tensile strength increased by 93% (from 1.27 MPa to 2.45 MPa) and the elongation at break improved by 35% (from 123.60% to 166.28%). It exhibits excellent mechanical properties and processability. The mechanical behavior and toughening mechanism were further investigated at the microscopic scale using molecular dynamics simulation. The simulation results indicate that the optimized HTCEA possesses a bulk modulus of 2.71 GPa, a shear modulus of 0.83 GPa, and a Young's modulus of 2.97 GPa, confirming excellent micro-mechanical properties. The enhancement is primarily attributed to the incorporation of flexible chain segments from the polyurethane toughening agent, which modifies the epoxy cross-linked network. At the same time, it significantly enhances the intermolecular interactions and entanglements, promoting the formation of a more uniform and dense three-dimensional network. Consequently, it effectively improves the material's toughness, crack resistance, and overall structural stability. This research focused on the formulation design, process optimization, and microscopic mechanism analysis of cold-mixed epoxy asphalt. It provided effective solutions and theoretical basis for developing cold-mixed epoxy asphalt with high toughness and ease of operation.

Components optimization and curing characteristics of cold-mixed polyurethane-modified asphalt based on response surface methodology

Tue, 28 Jul 2026 08:40:34 GMT

The cold-mixed polyurethane-modified asphalt (CPUA) can be utilized at ambient temperatures, along with excellent mechanical properties, which make it a preferred choice for high-performance pavements and rapid repair projects. The composition of CPUA was optimized using a Box-Behnken design within response surface methodology, followed by analyzing the microstructure morphology and curing behavior of the binder. All factors were found to be significant (p < 0.005), with biodiesel exerting the strongest influence on viscosity, tensile strength, and elongation at break, followed by polyurethane (PU) and the latent curing agent. The optimized formulation (20% biodiesel, 100% PU, 3.5% latent curing agent) yielded a close agreement between prediction and experiment. During the curing process, concurrent with the reaction of isocyanate groups with water to form urea bonds, the asphalt phase size was reduced, the uniformity of the two-phase structure and the crosslinked density were increased. The CPUA mixture was rapidly cured at −10 °C, achieving a Marshall stability higher than 30 kN and thus demonstrating considerable low-temperature strength development capability. The findings offer important theoretical insights and practical guidance for the design and application of CPUA materials.

Performance Evaluation of High-RAP Asphalt Mixtures with Compound Bio-Based Rejuvenators

Tue, 28 Jul 2026 08:40:34 GMT

The use of reclaimed asphalt pavement (RAP) in road construction offers significant environmental and economic advantages. However, asphalt mixtures with high RAP content can lead to reduced performance compared with conventional asphalt pavement. This study investigated the potential of compound bio-based rejuvenators, derived from waste cooking oil (WCO), to improve the road performance of recycled hot-mix asphalt (RHMA) with high RAP content. The effects of different rejuvenators at three dosages (4.8%, 6.0%, and 7.2% for 30% RAP and 8%, 10%, and 12% for 50% RAP, by mass of recycled binder) on the high-temperature performance, moisture susceptibility, and medium- and low-temperature cracking resistance of RHMA containing 30% and 50% RAP were evaluated. The degree of blending (DoB), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA) were used to represent changes in volumetric characteristics. A comprehensive evaluation of the rejuvenator’s effectiveness was conducted using principal component analysis (PCA). The results indicated that bio-based rejuvenators effectively activate aged asphalt, and optimal dosages vary based on RAP content. The addition of compound bio-based rejuvenators with SBS-repairing capabilities partially mitigates the reduction of high-temperature performance of RHMA caused by adding WCO, and also restores moisture resistance compromised by RAP. Increasing rejuvenator content improves midtemperature flexibility and overall low-temperature cracking resistance, though it may reduce low-temperature fracture toughness. PCA results indicated that at a 50% RAP content, the comprehensive rejuvenation effect of compounded bio-based rejuvenators is superior to that of conventional bio-based rejuvenators in RHMA with high RAP content. However, at a 30% RAP content, the compounded rejuvenator did not exhibit a comprehensive advantage compared with traditional bio-based rejuvenators. Compound bio-based rejuvenators demonstrate significant potential in improving the road performance of RHMA with high RAP content, promoting sustainable pavement construction practices.

Application of Crumb Rubber Pyro Oil (CRPO)-Modified Bitumen in Flexible Pavements

Mon, 27 Jul 2026 11:16:39 GMT

As the automotive industry experiences faster growth, it has become imperative to address the escalating solid waste, particularly non-biodegradable tire and rubber. This paper explores the potential of crumb rubber pyro oil (CRPO) as a modifier for base bitumen VG30 in flexible pavements. Examining different concentrations of CRPO, the research assesses their impact on the physical characteristics of modified bitumen, including viscosity, penetration, softening point, and ductility. Mechanical strength is further examined through the Marshall stability test. Beyond the study of physical attributes, the study delves into CRPO’s role in reducing permeability in the surface layer and its resultant influence on binding strength. This inquiry addresses challenges in bituminous mixes, often assumed impermeable. Pavement distresses, such as stripping and pothole formation, have been correlated with water presence in the bituminous layer. The study evaluates bituminous mixtures using falling head permeability testing techniques. The study intends to strategically decrease water intrusion into bituminous mixes by examining how CRPO modification affects permeability in the surface layer. This decrease in permeability can become an important component of the overall goal of reducing pavement distresses and guaranteeing the longevity of flexible pavements in the face of changing difficulties in the automobile sector.

Comprehensive Study of Asphalt Mixtures with Reclaimed Asphalt Pavement (RAP) and Expanded Polystyrene (EPS)

Mon, 27 Jul 2026 11:16:39 GMT

Reclaimed asphalt pavement (RAP) is being recognized as a valuable waste material, offering a solution to address the challenges of pavement recycling and enhance environmental sustainability in transportation infrastructure. The purpose of this research is to assess the performance of hot mix asphalt obtained from disintegrated existing asphalt pavement. This paper deals with the evaluation of the mechanical properties of bitumen mixtures incorporating RAP and expanded polystyrene (EPS) as sustainable alternatives. Marshall testing was conducted to evaluate the flow values and stability of the mixtures on twelve bitumen samples with varying RAP percentages (30%, 50%, and 70%) and individual bitumen percentages (3.5%, 4%, 4.5%, and 5%). Results show that a 70% RAP mixture with 4% bitumen exhibits superior stability, achieving a Marshall stability of 14.76 kN. Additionally, the inclusion of EPS in different proportions (3%, 4%, and 5%) improved mechanical properties and optimum stability of 15092.06 KN-specific EPS percentages at 5%. This study emphasizes the advantages of incorporating RAP and EPS into bituminous mixtures, thereby fostering sustainable pavement construction by recycling waste materials and reducing costs.

Unmodified Bitumen in SMA: A Sustainable and Cost-Effective Approach

Mon, 27 Jul 2026 11:16:39 GMT

Stone Matrix Asphalt (SMA) is a Hot Mix Asphalt (HMA) mixture consisting of a discontinuous aggregate gradation characterised by a high coarse aggregate content (between 70 and 80%), a high percentage of binder (typically between 6 and 7%) and a filler content as high as about 10%. SMA has an aggregate skeleton which imparts high strength and rutting resistance to the mixture. The high binder content though provides the mixture with durability, it also drains through the void spaces in the aggregate skeleton during production, transportation and placement of the mixture in the field. Hence, to reduce the drainage of bitumen and bitumen mortar, the SMA guidelines suggest using a modified bitumen or pelletised cellulose fibres in the mixture when a conventional bitumen such as Viscosity Graded (VG 30) is used. However, the production of cellulose fibres is not only expensive but also requires trees to be cut since cellulose is obtained from plant sources leading to deforestation. Due to the high cost of Polymer Modified Bitumen (PMB), the SMA mixtures prepared with the modified bitumen are also expensive. Hence, the present study focuses on the laboratory evaluation of SMA mixes using a conventional Viscosity Graded bitumen (VG 40) without the use of pelletised cellulose fibres. The results indicated that the susceptibility of mixtures to drainage of binder and/or binder mortar was within the permissible limit of 0.3% by weight of the mixture. The mechanical and moisture susceptibility tests conducted on compacted specimens indicated that the performance is comparable to that of the mixtures prepared using PMB. Further, it was noted that only the grades of bitumen softer than VG 40 required cellulose fibres to reduce drain-down. The study also revealed a reduction in cost due to not using cellulose fibres with VG 40 bitumen or modified bitumen, which makes it more environmentally friendly and sustainable.

Innovative Utilization of Waste Zanthoxylum Seed: Enhancing Rheological and Thermal Stability of Rejuvenated Asphalt Binder

Tue, 21 Jul 2026 15:15:18 GMT

The limited stability and antiaging performance of traditional asphalt rejuvenators hinder the effective use of reclaimed asphalt pavement in hot mix asphalt. This study investigates Zanthoxylum seed oil (ZSO), derived from agricultural waste, as a rejuvenator and antioxidant for long-term aged asphalt. Using Pen60/80 asphalt as the control, asphalt binders at different service life stages are simulated using a rolling thin-film oven and pressure aging vessel. The physical, rheological, and molecular structure properties of virgin, aged, rejuvenated, and rejuvenated aged binders are evaluated using the Dynamic Shear Rheometer, Bending Beam Rheometer, and Fourier-Transform Infrared Spectroscopy (FTIR). The results show ZSO significantly enhances the viscoelastic properties of aged asphalt through a softening effect rather than substantial molecular structure repair. The phase angle increase stabilizes between 0.2% and 0.7% when the ZSO content exceeds 8%, but further increases in concentration accelerate strain accumulation and reduce permanent deformation resistance. The optimal ZSO dosage for long-term aged Pen60/80 asphalt is 8%–9% (by mass of aged asphalt), which improves fatigue and low-temperature properties while maintaining rutting resistance comparable with virgin asphalt. Asphalt rejuvenated with ZSO, characterized by a lower activation energy, shows reduced thermal oxidative sensitivity and improved thermal cracking stability during aging, with a low-temperature performance decay rate at 68% of virgin asphalt. In addition, the FTIR analysis indicates that the aging pattern of carbonyl in the binder matches rheological property degradation. In conclusion, ZSO demonstrates remarkable effectiveness in enhancing the performance and antiaging capacity of aged asphalt, highlighting its potential for asphalt rejuvenation.

Influence of Fillers in Performance of Cold Mix Asphalt Using Reclaimed Asphalt Pavement Material

Tue, 21 Jul 2026 09:49:16 GMT

The present research investigated the influence of different fillers on the performance of cold mixtures using 50% and 100% Reclaimed Asphalt Pavement (RAP) materials in place of virgin aggregates stabilized with bitumen emulsion for the sub-base layer. Bitumen emulsion is a two-phase system in which water, bitumen, and one additive are added to enhance its formation and stabilization. Soft water (having a calcium amount of less than 75 ppm) is used to make an emulsion of bitumen. In the research, three different fillers, cement, fly ash, and Stabil road, were used at various dosages (1, 2, and 3% of dry aggregate weight) with cold recycled mixes to enhance the performance of mixes. Fillers are used to achieve higher strength and resistance to water damage. The results show that the 50% RAP define mixes have more stability and resilient modulus than CM and 100% RAP mixes with the same curing temperature, which depends on aggregate gradation and filler characteristics.

Enhanced Understanding of Hot Mix Asphalt (HMA)

Fri, 17 Jul 2026 13:08:30 GMT

Michigan Department of Transportation (MDOT) interest is to have the Michigan State University (MSU) Center provide specialized technical expertise and examinations related to further development of its pavement design program, specifically as it relates to Pavement Mechanistic-Empirical Design (PMED).

Multi-scale evaluation of adhesion property between warm-mix rejuvenated styrene-butadiene-styrene (SBS) modified asphalt and aggregates: Integrating experiments and molecular dynamics simulations

Wed, 15 Jul 2026 09:23:58 GMT

This study aims to comprehensively evaluate the adhesion properties between warm-mix recycled styrene-butadiene-styrene (SBS) modified asphalt and aggregates. The different types of asphalt materials included virgin (VA), aged (AA), rejuvenated-aged (RA), warm-mix-aged (WA), and warm-mix-rejuvenated-aged (WRA) asphalt binders were used. A multi-scale adhesion characterization approach was employed, namely integrating surface free energy (SFE) theory, binder bond strength (BBS) tests, and molecular dynamics (MD) simulations. Results indicate that long-term aging significantly improves cohesion and adhesion work, attributed to increased polar components. While rejuvenators or warm-mix agents individually reduce these properties, their combined use in WRA leads to the most pronounced decline in both thermodynamic adhesion and macroscopic bond strength. MD simulations further reveal that adhesion is governed mainly by van der Waals energy and is strongest on CaO, followed by MgO and SiO₂. A strong correlation (R²=0.84) was established between SFE-derived adhesion work and BBS-measured strength.

Optimization of Hot-Mix Asphalt Rolling Pattern Using Ground-Penetrating Radar and Markov Decision Processes

Mon, 13 Jul 2026 08:47:46 GMT

Ground-penetrating radar (GPR) has been used for nondestructive evaluation of hot-mix asphalt (HMA) pavements including density prediction. HMA density is an acceptance quality characteristic (AQC) used across the U.S. AQCs are the basis for quality control and acceptance, and are used by agencies to determine contractors’ pay. Recently, roller-mounted GPR was introduced to monitor HMA density in real-time, enabling roller operators to make more informed decisions to avoid under- and over-compaction of HMA layers. In this study, a Markov decision process (MDP) is formulated to represent the rolling pattern optimization problem. This formulation accounts for GPR prediction error, density spatial variability, and uncertainty in density progression. The introduced MDP provides contractors and roller operators with a tool to minimize operational costs while achieving target density, thereby enhancing pavement service life and reducing maintenance activities. Data collected from several field projects were used in the MDP formulation. The benefits of using the developed MDP for compaction decisions were demonstrated using project data from Illinois, U.S. The analysis was conducted for an actual project scenario under Illinois’ quality control for performance (QCP) program and was extended to a hypothetical pay for performance (PFP) scenario to evaluate the generalizability of the approach under different risk levels. Compared with an experienced roller operator, MDP decisions reduced the construction time by 40.3% and 18.1% and increased the revenue by 9.7% and 50.2% for the QCP and PFP scenarios, respectively. Additional benefits in energy savings, reduced construction-related delays, and improved worker safety are expected.

Understanding the interfacial adhesion mechanism between bitumen emulsion and RAP: A combined experimental and molecular simulation study

Thu, 09 Jul 2026 13:29:26 GMT

Understanding the interfacial adhesion between bitumen emulsion and reclaimed asphalt pavement (RAP) is crucial for improving the performance of cold recycled mixtures. This study combines experimental testing and molecular dynamics (MD) simulations to elucidate the adhesion mechanism between bitumen emulsion and RAP surfaces. Contact angle measurements showed that bitumen emulsion wets limestone more effectively than aged RAP binder, leading to a higher work of adhesion. Binder bond strength increased steadily during curing, reaching about 40% higher values on limestone after 14 days. Rheological and cohesion tests indicated faster modulus and cohesion development in emulsion–limestone systems, while RAP mixtures exhibited delayed stiffening and weaker bonding. MD simulations revealed that the emulsifier adsorbs more strongly on aggregate with an adsorption energy of about –43 mJ/m⁻², nearly 20 mJ/m⁻² higher than on aged bitumen. Emulsifier molecules adsorb more strongly and form denser micellar structures on the hydrophilic aggregate surface, whereas adsorption on the aged bitumen surface is governed by π–π stacking and hydrogen-bonding interactions, resulting in a less compact interfacial layer. These findings provide molecular-level insight into why the hydrophobic and low-energy surface of RAP hinders emulsifier adsorption and delays the demulsification and strength gain in cold recycled asphalt mixtures.