Search Results (107)

With the rising performance demands in road engineering, traditional experiments often fail to reveal the microscopic mechanisms behind asphalt behavior. Molecular dynamics (MD) simulation has emerged as a valuable complement, enabling molecular-level insights into asphalt’s composition, structure, and aging mechanisms. This review summarizes the recent advances in applying MD to asphalt research. It first outlines molecular model construction approaches, including average models, three- and four-component systems, and modified models incorporating SBS, SBR, PU, PE, and asphalt–aggregate interfaces. It then analyzes how MD reveals the key performance aspects—such as high-temperature stability, low-temperature flexibility, self-healing behavior, aging processes, and interfacial adhesion—by capturing the molecular interactions. While MD offers significant advantages, challenges remain: idealized modeling, high computational demands, limited chemical reaction simulation, and difficulties in multi-scale coupling. This paper aims to provide theoretical insights and methodological support for future studies on asphalt performance and highlights MD simulation as a promising tool in pavement material science. Full article

The accurate assessment of the structural condition of airfield pavements is of paramount importance to airport authorities as it determines the planning of maintenance activities. On this basis, Non-Destructive Testing (NDT) techniques provide a powerful tool to assess the mechanical properties of the individual layers of the pavement. However, information from laboratory testing of cores taken from the pavement is expected to provide a more accurate assessment of material properties. Against this background, the present research aims to investigate the accuracy of the mechanical properties of in-situ layers derived from NDT data and the associated back-calculation procedures for airfield pavements, where higher pavement thicknesses are usually required due to the high aircraft loads, while few similar studies have been conducted compared to road pavements. For this reason, the assessment of the structural condition of a flexible runway pavement is presented. The analysis shows that there is a strong correlation between the moduli estimated in the laboratory and the moduli estimated by back-calculation. Furthermore, the back-calculated moduli appear to lead to a conservative approach in assessing the structural condition of the pavement. This conservatism promotes a more proactive pavement management by airport authorities. Full article

Semi-flexible pavement (SFP) materials have garnered extensive application and research attention owing to their exceptional deformation resistance. The crack resistance of SFP materials constitutes a critical aspect of their road performance. This study conducts a comprehensive analysis of the crack resistance of SFP materials through material characterization and structural mechanical response evaluation. To assess the cracking behavior of SFP materials across the entire temperature spectrum, three experimental methodologies were employed: low-temperature flexural tensile testing, indirect tensile testing, and semi-circular bending tensile testing. Experimental findings reveal that SFP materials exhibit superior crack resistance compared to SMA-13 under ambient and elevated temperature conditions, while demonstrating inferior performance relative to SMA-13 in low-temperature environments. Through a comparative analysis of structural mechanical responses between SMA-13 and SFP pavements, it was determined that the implementation of a single-layer SFP material can reduce pavement tensile strain by 30–50%. This investigation provides comprehensive insights into the crack resistance characteristics of SFP materials and offers valuable guidance for material selection in pavement structural design. Full article

Pavement structures are one of the most critical civil infrastructures for the socio-economic development of communities. However, pavement construction demands an elevated financial budget and generates large amounts of environmental impacts. Accordingly, the new trends in daily engineering practices have integrated sustainability criteria verification into traditional pavement design procedures. Thus, this research explores the sustainability implications of asphalt pavement incorporating a Cement-Treated Base (CTB) and Recycled Concrete Aggregate (RCA) within the local context of a Global South country. The environmental and economic performances of four different types of asphalt structures were assessed, each differing in how the CTB is employed. These structures include conventional flexible pavement, semi-rigid pavement, inverted base pavement, and simple composite pavement. Furthermore, each structure is evaluated under four varying contents of coarse RCA (i.e., 0%, 15%, 30%, and 45%) in their asphalt mixtures. This approach results in a comprehensive analysis spanning 16 unique scenarios, providing valuable insights into the interplay between RCA content and CTB inclusion for sustainable infrastructure development. It is important to highlight that the Life-Cycle Assessment and Life-Cycle Cost Analysis methodologies were implemented to perform the environmental and economic inspections, respectively. Overall, this investigation demonstrates that although pavement structures comply with mechanistic design standards, they can yield significantly different cost effectiveness and environmental burdens from each other. Therefore, executing a sustainability-related appraisal is essential for accomplishing definitive infrastructure designs. Consequently, this research effort is expected to be used by stakeholders (e.g., civil engineers, designers, and governmental agencies) to support data-driven decision making in the road infrastructure industry. Full article

Flexible pavements are susceptible to distress when subjected to long-term vehicle loads and environmental factors, thereby reqsuiring appropriate maintenance. To overcome the hectic field data collection and traffic congestion problems, this paper presents an intelligent prediction system framework utilizing Extreme Gradient Boosting (XGboost) to predict two relevant functional indices: rutting deformation and cracks damage. The model framework considers multiple essential factors, such as traffic load, material characteristics, and climate data conditions, to predict rutting behavior and employs image data to classify cracks behavior. The Extreme Gradient Boosting (XGboost) algorithm exhibited good performance, achieving an R² value of 0.9 for rutting behavior and an accuracy of 0.91, precision of 0.92, recall of 0.9, and F1-score of 0.91 for cracks. Moreover, a comparative assessment of the framework model with prominent AI methodologies reveals that the XGboost model outperforms support vector machine (SVM), decision tree (DT), random forest (RF), and K-Nearest Neighbor (KNN) methods in terms of quality of the result. For rutting behavior, a SHAP (Shapley Additive Explanations) analysis was performed on the XGboost model to interpret results and analyze the importance of individual features. The analysis revealed that parameters related to load and environmental conditions significantly influence the model’s predictions. Finally, the proposed model provides more precise estimates of pavement performance, which can assist in optimizing budget allocations for road authorities and providing dependable guidance for pavement maintenance. Full article

The increasing demand for sustainable road construction materials necessitates innovative solutions to overcome the challenges of Recycled Asphalt Pavement (RAP), including aged binder brittleness, reduced flexibility, and durability concerns. Waste Plastic Aggregates (WPA) offer a promising alternative; however, their thermal aging behavior and interactions with RAP remain insufficiently understood. This study evaluates the performance of RAP-based asphalt mixtures, incorporating three types of WPA—Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), and Polypropylene (PP)—under three thermal aging conditions: mild (60 °C for 7 days), moderate (80 °C for 14 days), and severe (100 °C for 30 days). The mixtures were designed with 30% RAP content, 10% and 20% WPA by aggregate weight, and SBS-modified binder rejuvenated with 2% and 4% sewage sludge bio-oil by binder weight. It is considered that thermal aging may impact the performance of WPA in RAP mixtures; therefore, this study evaluates the durability and mechanical properties of RAP mixtures incorporating LDPE, HDPE, and PP under varying thermal aging conditions to address these challenges. The results showed that incorporating WPA and bio-oil significantly enhanced the mechanical performance, durability, and sustainability of asphalt mixtures. Marshall Stability increased by 12–23%, with values ranging from 12.6 to 13.2 kN for WPA-enhanced mixtures compared to 12.7 kN for the control. ITS improved by 15–20% in dry conditions (1.34–1.44 MPa) and 12–18% in wet conditions (1.15–1.19 MPa), with TSR values reaching up to 82.64%. Fatigue life was extended by 28–43%, with load cycles increasing from 295,600 for the control to 352,310 for PP mixtures. High-temperature performance showed a 12–18% improvement in softening point (57.3 °C to 61.2 °C) and a 23% increase in rutting resistance, with rut depths decreasing from 7.1 mm for the control to 5.45 mm for PP mixtures after 20,000 passes. These results demonstrate that combining RAP, WPA, and bio-oil produces sustainable asphalt mixtures with superior performance under aging and environmental stressors, offering robust solutions for high-demand applications in modern infrastructure. Full article

The materials traditionally used in the construction of flexible and rigid pavements in modern road infrastructure present challenges in achieving sustainable development goals. Advances in technology have introduced the use of different pavement material mixes, leading to the introduction of earth-based alternatives. These materials are environmentally friendly, cost-effective, recyclable, and offer excellent insulation properties. Stabilization of earth-based materials improves their mechanical properties, reducing road construction costs and increasing durability. The present study investigates the mechanical and durability properties of earth-based materials stabilized with various additives, including cement, lime, polymer, and biopolymer, over 28 and 56 days. Fresh properties are assessed using unit volume weight, flow table, air content, and fall cone tests, while hardened properties are assessed using flexural strength, compressive strength, and water absorption. Microstructural analysis is carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The cement-stabilized samples show improved strength and durability, with the 5% cement group showing a 67% increase in compressive strength over the control group and the 10% cement group showing over 200% higher compressive strength. These results suggest that stabilized earth-based materials could provide a cost-effective and sustainable alternative to conventional pavements for low-traffic roads. Full article

Road infrastructure sustainability and pavement performance may be increased by using waste materials like polyethylene terephthalate (PET) and polyethylene waste (PE waste) in polymer-modified asphalt mixtures. As seen by a more pronounced rise in the softening point, which exceeds 110 °C with 8% PE waste, PET was found to improve the tensile strength, resistance to cracking, and thermal stability of asphalt mixes. PE waste also increases ductility up to 4% PE waste, beyond which the combination becomes more brittle, and dramatically decreases penetration, strengthening the asphalt’s resistance to deformation. Additionally, bitumen treated with PE waste is more workable than asphalt without PET, even though bitumen treated with PE waste had a viscosity of up to 4500 Pa. Complex shear modules decreased as the PE waste and PET content increased. PET, on the other hand, increases the binder’s overall stiffness, elasticity, and tensile strength. Nevertheless, when PET content rises, ductility steadily decreases. Previous studies concentrated on the effects of each component separately, and this paper fills this knowledge gap by investigating the combined effects of PET and PE waste. The results indicate that the highest compressive strength (7.5 MPa) was obtained with 6% PE + 2% PET, while the highest tensile strength (1.40 MPa) was achieved with a balanced mix of 4% PE waste + 4% PET. Additionally, the viscosity of asphalt is increased by PET and PE waste, enhancing its performance at high temperatures. These findings demonstrate how combining PET and PE waste improves the mechanical and thermal characteristics of asphalt, providing a balance between stiffness and flexibility, a crucial feature for durable road materials under a variety of circumstances. Full article

Road agency initiatives to reduce traffic-related greenhouse gas emissions are limited by the inability of current experimental methods to assess pavement impacts on vehicle energy consumption. This study addresses this by examining the rolling resistance of a semi-trailer suspension under highway conditions using a precise measurement system with embedded transducers. Data were collected over 174 km of highway, covering various pavement types under mild summer conditions. The analysis revealed notable differences in rolling resistance due to pavement characteristics, with more pronounced variations observed within pavement types than between them. For instance, geographically consecutive jointed rigid pavements showed a 34% variation in rolling resistance, likely correlated with harmonic excitations generated by slab presence, while flexible pavements exhibited up to a 21% variation under similar tire operating conditions. Composite pavements generally performed the worst, possibly due to interactions between bituminous materials and older cement-based foundations. The study also highlighted the critical role of tire operating conditions, showing a decrease of 0.09 kg/tonne in rolling resistance for every 1 °C increase in temperature. This research shows that precisely measuring the rolling resistance (±0.1 kg/tonne) in situ for heavy vehicles is feasible and underscores the need for additional data in diverse weather scenarios to better align laboratory results with on-road realities. Full article

The escalating impacts of climate change have led to significant challenges in maintaining road infrastructure, particularly in tropical climates. Abnormal weather patterns, including increased precipitation and temperature fluctuations, contribute to the accelerated deterioration of asphalt pavements, resulting in cracks, plastic deformation, and potholes. This study aims to evaluate the durability of a novel pellet-type stripping prevention material incorporating slaked lime and epoxy resin for pothole restoration in tropical climates. The modified asphalt mixtures were subjected to a series of laboratory tests, including the Tensile Strength Ratio (TSR) test, Indirect Tension Strength (ITS) test, Hamburg Wheel Tracking (HWT) test, Cantabro test, and Dynamic Modulus test, to assess their moisture resistance, rutting resistance, abrasion resistance, and viscoelastic properties. Quantitative results demonstrated significant improvements in the modified mixture’s performance. The TSR test showed a 6.67% improvement in moisture resistance after 10 drying–wetting cycles compared to the control mixture. The HWT test indicated a 10.16% reduction in rut depth under standard conditions and a 27.27% improvement under double load conditions. The Cantabro test revealed a 44.29% reduction in mass loss, highlighting enhanced abrasion resistance. Additionally, the Dynamic Modulus test results showed better stress absorption and reduced likelihood of cracking, with the modified mixture demonstrating superior flexibility and stiffness under varying temperatures and loading frequencies. These findings suggest that the incorporation of slaked lime and epoxy resin significantly enhances the durability and performance of asphalt mixtures for pothole repair, making them a viable solution for sustainable road maintenance in tropical climates. Full article

Cracked and deteriorated asphalt are common problems on our roads, leading to safety concerns and requiring significant resources for rehabilitation and reconstruction. This study investigates bio-fog seals, a promising eco-friendly solution utilizing bio-based rejuvenators. These treatments penetrate aged asphalt, restoring its flexibility and resistance to cracking. We assessed the effectiveness of two bio-fog seal formulations—one containing sub-epoxidized soybean oil (SESO) and the other combining SESO with a biopolymer (BioMag). Applied to real pavement sections, the research evaluated how these bio-seals impacted key performance factors, such as stiffness, permeability, and drying time, and safety factors, including skid resistance and pavement marking visibility. The results indicate the bio-seals did not compromise skid resistance and the reflectivity of the markings, eliminating the need for repainting stripes. Additionally, they successfully reduced pavement stiffness, making the asphalt more flexible and crack-resistant. Remarkably, with rapid setting times, under 30 min, these treatments minimize traffic disruption and do not require a blotter material. Overall, this research demonstrates the potential of bio-fog seals as a sustainable solution for extending pavement lifespan and lowering long-term maintenance costs. Full article

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential “GWP”) for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures. Full article

Ultra-thin overlays (UTOL) are a standard highway pre-maintenance method used to improve the road surface performance of asphalt pavements and to repair minor rutting and cracking. However, the thin thickness makes it very sensitive to external changes, which increases its wear and shortens its life. So, this paper aims to prepare a durable and skid-resistance asphalt ultra-thin overlay using epoxy asphalt (EA) and steel slag. First, the physical properties of EA were characterized by penetration, softening point, flexibility, and kinematic viscosity tests. The dynamic shear rheometer (DSR) test characterizes EA’s rheological properties. Differential Scanning Calorimetry (DSC), kinematic viscosity, and Fourier transform infrared spectroscopy (FTIR) characterized the EA’s curing process. Finally, the pavement performance of an epoxy ultra-thin overlay (EUTOL) prepared with EA and steel slag was tested. The results show that the epoxy resin particles increase with the increase in epoxy resin dosage, and at 40%, its epoxy particles are uniformly distributed with the most significant area share. With the addition of epoxy resin, the needle penetration of EA decreases and then increases, the flexibility decreases at a slower rate, and the softening point rises significantly. Moreover, the growth of the elastic component in EA significantly improved the high-temperature viscoelastic properties. Considering its physical and rheological properties, the optimal doping amount of 40% was selected. By analyzing the curing behavior of EA (optimum dosage), the combination temperature of EA is 150 °C, which meets the needs of mixing and paving asphalt mixtures. After 12 h of maintenance at 120 °C, its reaction is sufficient. The skid-resistance durability, high-temperature, low-temperature, water stability, and fatigue resistance of UTOL can be effectively improved using steel slag coarse aggregate. Full article

Nano-organic montmorillonite (OMMT) not only inhibits the harmful asphalt fume generation during the production and construction processes of asphalt mixtures but also effectively improves the performance of asphalt pavements. In order to prepare asphalt materials with smoke suppression effects and good road performance, this study selects nano-OMMT and SBS-modified asphalt for composite modification of asphalt mixtures and systematically investigates its road performance. Through the temperature sweep test, the frequency sweep test, the multiple stress creep recovery (MSCR) test, the bending beam rheometer (BBR) test, and the atomic force microscope (AFM) test, the high-temperature rheological properties, low-temperature rheological properties, high-temperature properties and aging resistance of the modified asphalt are studied. The research findings indicate that OMMT can effectively reduce the sensitivity of modified asphalt to load stress and improve its high-temperature rheological properties. SBS-modified asphalt shows increased creep stiffness and a decreased creep rate after OMMT modification, resulting in reduced flexibility and decreased low-temperature crack resistance. After short-term and long-term aging, the complex modulus aging index of OMMT/SBS composite-modified asphalt is lower than that of SBS-modified asphalt, and the phase angle aging index is higher than that of SBS-modified asphalt, demonstrating that OMMT enhances the aging resistance of SBS-modified asphalt. OMMT inhibits oxidation reactions in the asphalt matrix, reducing the formation of C=O and S=O bonds, thereby slowing down the aging process of modified asphalt and improving its aging resistance. Full article

Cracks in asphalt mixtures compromise the structural integrity of roads, increase maintenance costs, and shorten pavement lifespan. These cracks allow for water infiltration, accelerating pavement deterioration and jeopardizing vehicle safety. This research aims to evaluate the impact of synthetic fibers, specifically glass fiber (GF) and polypropylene fiber (PPF), on the crack resistance of Hot-Mix Asphalt (HMA). An optimal asphalt binder content of 5% was used in all sample designs. Using the dry mixing technique, GFs and PPFs were incorporated into the HMA at dosages of 0.50%, 1.00%, and 1.50% by weight of the aggregate. The effects of these fibers on the mechanical fracture properties of the HMA were assessed using Semi-Circular Bending (SCB), Indirect Tensile Asphalt Cracking Tests (IDEAL-CTs), and Three-Point Bending (3-PB) tests. This study focused on fracture parameters such as fracture work, peak load, fracture energy, and crack indices, including the Flexibility Index (FI) and Crack Resistance Index (CRI). The results from the SCB and IDEAL-CT tests showed that increasing GF content from 0.5% to 1.5% significantly enhances the flexibility and crack resistance of HMA, with FI, CRI, and CT Index values increasing by 247.5%, 55%, and 101.35%, respectively. Conversely, increasing PPF content increases the mixture’s stiffness and reduces its crack resistance. The PP-1 mixture exhibited higher FI and CT Index values, with increases of 31.1% and 10%, respectively, compared to the PP-0.5 mixture, based on SCB and IDEAL-CT test results. The SCB, IDEAL-CT, and 3-PB test results concluded that fibers significantly influence the fracture properties of bituminous mixtures, with a 1% reinforcement dosage of both PPFs and GFs being optimal for enhancing performance across various applications. Full article