Search Results (448)

This study investigates the blast-protective performance of RC slab strengthened on the blast face with various concrete protective layers under contact-detonation loading. The research focuses on analyzing shock wave propagation characteristics, peak pressures at measurement points, energy absorption capacities of the protective layers, the development of damage, and the governing failure mechanisms of the RC slab. The protective layers used for structural reinforcement include Steel Fiber-Reinforced Cellular Concrete (SFR-CC), Asphalt Concrete (AC), Rubberized Concrete (RBC), and Foamed Concrete (FC). Among these, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer (T-1) is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Based on the damage coefficient calculated from the remaining sectional moment of inertia of the protected RC slabs, the destruction grades of the structures at different concrete protective schemes were classified. Among these, the SFR-CC layer exhibits the most effective attenuation of shock wave peak pressure. Additionally, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Damage grades were assigned according to a coefficient derived from the residual sectional moment of inertia of the protected RC slabs. The SFR-CC configuration (T-1) gives the lowest damage index, 0.178, approximately 64.5% below that of the NC scheme, and is classified as slight damage. In contrast to the severe damage sustained by the protected RC slabs strengthened with the NC concrete scheme, those strengthened with the AC, RBC, and FC protective layer schemes exhibit only a moderate damage grade. Empirical formulas predicting the damage index of protected structures under the combined effects of varying blast charges and concrete layer thicknesses were further developed for rapid damage assessment. Full article

This study aims to systematically evaluate the balancing mechanism between road performance, carbon emissions, and economic cost when selecting asphalt materials for severe cold regions, filling the gap in multi-criteria decision-making for composite chemical modifications. To address alternating temperatures, heavy traffic, and modified asphalt transport difficulties, this study presents a novel evaluation framework focusing on the performance–environmental–cost nexus of a desulfurized rubber powder composite SBS-modified asphalt mixture, which provides a clear technological breakthrough for high-ratio scrap tire recycling in seasonal frost zones. Two reference mixtures serve as comparisons: a conventional rubber powder composite SBS (styrene–butadiene–styrene triblock)-modified asphalt mixture (CR-SBS) and an SBS-modified asphalt mixture (SBS). A comparative experiment was conducted between the two materials and the SBS-modified asphalt mixture (ACR-SBS) compounded with desulfurized rubber powder. High-temperature stability was tested by the rutting test, low-temperature crack resistance by the beam bending test, and water stability by the immersion Marshall and freeze–thaw splitting tests. Life cycle carbon emissions and economic costs were quantified from raw material acquisition to construction. The results show that desulfurized rubber powder composite with ACR-SBS delivers the most superior overall road performance. However, it also generates the highest life cycle carbon footprint. Its total carbon emission reaches 162,800 kgCO₂eq, which is 13.7% (19,600 kgCO₂eq) higher than SBS (143,200 kgCO₂eq) and 7.7% (11,600 kgCO₂eq) higher than CR-SBS (151,200 kgCO₂eq). The total cost of ACR-SBS is 391,000 CNY, which is 1.5% (6000 CNY) higher than SBS (385,000 CNY) and 1.3% (5000 CNY) lower than CR-SBS (396,000 CNY). These findings provide a basis for the selection of high-performance, low-carbon, and economical composite-modified asphalt in severe cold regions. Full article

Fatigue cracking remains a critical challenge in asphalt pavement design, yet conventional prediction methods fail to capture the fundamental damage mechanisms governing failure evolution. This study proposes an innovative residual strain-based approach to predict the fatigue life of crumb rubber modified asphalt (CRMA) mixtures. Through semi-circular bending (SCB) tests under varying aging conditions and stress ratios, a modified Burgers model was employed to decompose residual strain into residual viscoelastic strain (RVES) and residual viscous-flow strain (RVFS) components. The key innovation lies in establishing the residual strain ratio (RSR) as a damage evaluation parameter, with its plateau value (PV) serving as the independent variable in a novel fatigue prediction equation. Results demonstrate that while RVES stabilizes after initial loading, RVFS accumulation drives fatigue damage progression. The RSR-defined damage factor exhibits a distinct three-stage evolution accurately characterized by the ExpAssoc model (R² > 0.97). The proposed PV-based fatigue equation achieves prediction errors below 15% when validated against field core samples, offering a mechanistically sound and practically viable alternative to conventional phenomenological approaches. Full article

Conventional crumb-rubber-modified asphalt (CRMA) often shows high viscosity, storage separation, and limited low-temperature relaxation, whereas existing engineered rubber or single-activation methods do not fully clarify the combined contribution of biomass–oil swelling and microwave treatment. This study develops a rapeseed heavy oil (RHO)–microwave composite activation route for CRMA. Microwave activation, RHO pre-swelling, and their composite treatment were compared by varying rubber size, microwave intensity, and oil-to-rubber ratio. Binder workability, storage stability, DSR/MSCR/BBR rheology, FTIR, SEM, fluorescence microscopy, TGA, and AC-13C mixture performance were evaluated. Microwave activation mainly reduced viscosity and improved rubber dispersion, whereas RHO pre-swelling improved ductility and storage stability. The optimal F84 binder (80-mesh rubber, RHO-to-rubber ratio 1:2, 1.2 kJ/g microwave) reduced 180 °C viscosity and top–bottom softening-point difference by 42.95% and 55.68%, respectively, and increased 10 °C ductility from 10.5 to 19.5 cm relative to inactivated CRMA. Although F84 weakened creep recovery compared with inactivated CRMA, it improved low-temperature relaxation and mixture failure strain (3527.8 µε). The composite route is therefore suitable for CRMA applications prioritizing workability, storage stability, low-temperature cracking resistance, and rubber valorization, while rutting-critical projects require mixture-level verification. Full article

The emergence of a novel crumb rubber (CR)/SBS-polymerized pellet has simplified the complex preparation process of composite-modified asphalt. However, the effectiveness of CR/SBS-polymerized pellets in improving asphalt performance has not been confirmed. This study mainly investigated the performance and reinforcement mechanism of polymerized pellet-modified asphalt. First, polymerized pellet-modified asphalt samples with different contents (10%, 20%, 30% and 40% of the asphalt mass) were prepared. Then, the physical properties, rheological behavior, thermal stability, and aging resistance of the pellet-modified asphalt samples were systematically evaluated, using both base asphalt and a commercially available styrene–butadiene–styrene triblock copolymer (SBS)-modified asphalt as control groups for comparison. Finally, the modification mechanism was explored through Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM). The findings demonstrated that the incorporation of polymerized pellets could effectively decrease the penetration, elevate the softening point, and enhance the viscosity of asphalt. In addition, the high- and low-temperature performance, as well as the aging resistance of the modified asphalt, were significantly improved. These enhancing effects became more pronounced with increasing modifier content. The performance of SBS-modified asphalt is between 20% pellets MA and 30% pellets MA. The pyrolysis temperature range of all asphalt samples is 220 °C~500 °C, and infrared spectroscopy indicated that CR/SBS pellet-modified asphalt is mainly a physical mixing process. This work provides a scientific basis for further engineering applications of CR/SBS pellets. Full article

The incorporation of crumb rubber derived from waste tires in asphalt pavements has gained increasing attention as a strategy to enhance performance while reducing environmental impacts, particularly in cold regions such as the Midwestern United States, where pavements are subjected to severe thermal stresses and freeze–thaw cycles. Despite the numerous performance benefits observed in previous laboratory-scale studies, field demonstrations can play a critical role in validating the use of recycled waste tires as asphalt additives. This study examines the performance benefits and environmental impacts of incorporating recycled tire rubber into asphalt mixtures via a dry modification process for cold-climate applications. Building on these findings, this paper is based on a full-scale field demonstration of a dry-process rubber-modified asphalt pavement constructed in Ann Arbor, Michigan. Performance testing was conducted at both the binder and mixture levels, and field cores were collected during the construction of field sections. To complement the performance evaluation, a life-cycle assessment (LCA) was conducted to quantify the environmental impacts of rubber-modified asphalt and conventional asphalt. The results indicate that successful rubber incorporation, combined with improved low-, intermediate-, and high-temperature performance, enhances long-term durability compared with control sections. Moreover, despite slightly higher initial environmental impacts associated with rubber incorporation, improved durability and reduced maintenance frequency can lead to lower life-cycle impacts over the long term. The findings highlight the potential of rubber-modified asphalt as a sustainable, resilient solution for cold-region pavements, offering practical insights for agencies seeking to balance performance and environmental impacts in future infrastructure design. Full article

Considering the production efficiency and performance limitations inherent in conventional wet process asphalt mixtures, this study investigates the synergistic potential of fast-melting styrene–butadiene–styrene (F-SBS) and crumb rubber (CR) in enhancing the performance of asphalt mixtures when applied through the dry process modification method. Firstly, high- and low-temperature rheological tests were conducted on modified asphalt containing different dosages of F-SBS (1–3%) and CR (1–10%) to determine the optimal dosage of the modifier for the asphalt mixture. Furthermore, a comprehensive comparative analysis was conducted to evaluate the performance of asphalt mixtures modified with conventional SBS/CR against the F-SBS/CR system across both wet and dry modification processes. Finally, microscopic tests were conducted on the modified asphalt and asphalt mixtures to further investigate the synergistic mechanisms and effects of F-SBS and CR. The results indicated that F-SBS (2.5%)/CR (8%)-modified asphalt exhibited superior rheological properties, enhanced compatibility, and improved storage stability. Additionally, the dry process F-SBS/CR asphalt mixture demonstrated a 12.9% improvement in high-temperature stability, a 19.1% improvement in split strength after freeze–thaw cycles, and a 14.4% improvement in fatigue resistance compared to wet process conventional SBS/CR asphalt mixtures. The microscopic test results indicate that F-SBS and CR modify the asphalt primarily through physical blending. Observations further confirm that the dry process enhances interfacial bonding among the modifiers, asphalt binder, and aggregates, promoting closer and more stable interactions and thus improving mixing efficiency and overall performance. This study confirms the advantages of applying F-SBS and CR in dry process asphalt mixtures, thereby providing guidance for establishing a connection between laboratory investigations and field construction practices in the future. Full article

End-of-life tyres present a significant waste management challenge, prompting increasing interest in the use of tyre-derived materials in engineering applications. This review critically evaluates the performance of tyre-derived materials across concrete, asphalt, geotechnical, and mining systems with emphasis on application-specific engineering trade-offs. The reviewed literature shows that tyre-derived materials commonly reduce compressive strength and stiffness, particularly in cementitious systems, due to their weak interfacial bonding and increased porosity. However, these reductions are often accompanied by improvements in ductility, energy absorption, crack resistance, damping behaviour, tolerance during deformation, and post-cracking integrity. The magnitude of these responses strongly depends on rubber size, content, material origin, and interaction with the host matrix. Mining backfill applications show emerging potential, with tyre-derived inclusions improving brittle to ductile transition behaviour and residual integrity in cemented rock fill systems, although current evidence remains largely laboratory-based. Overall, the review demonstrates that tyre-derived materials should be evaluated according to application-specific performance requirements rather than strength-based criteria alone, while environmental benefits should be assessed on individual cases separately. Full article

To achieve warm-mix production of crumb rubber-modified asphalt (CRA), an organic warm-mix agent, a surfactant-based warm-mix agent, and a composite warm-mix agent were employed to prepare warm-mix CRA. The effects of warm-mix agents on the physical properties of CRA were evaluated using the penetration test, softening point test, viscosity test, ductility test, and elastic recovery test. The effects of warm-mix agents on the high- and low-temperature rheological properties were investigated through dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) tests. Moreover, the viscosity–temperature characteristics and the VOC emissions of different warm-mix CRAs were explored. The results show that Sasobit, an organic warm-mix agent, increases the elastic fraction and stiffness of CRA, which enhances its high-temperature resistance to permanent deformation but compromises its low-temperature cracking resistance. UWM, a surfactant-based warm-mix agent, elevates the viscous fraction and flexibility of CRA, which improves its low-temperature cracking resistance but weakens its high-temperature rutting resistance. The composite warm-mix agent, consisting of 2 wt.% Sasobit and 5 wt.% UWM, can balance the stiffness and flexibility of CRA, endowing CRA with satisfactory pavement performance. All three warm-mix agents effectively reduce the viscosity, mixing temperature, and VOC emissions of CRA. The composite warm-mix agent reduces the VOC emissions of CRA by 53.0%, exhibiting the most pronounced reduction. Full article

To address the durability limitations of conventional crack sealants under coupled extreme temperatures and traffic loads in long-life pavements, a bio-oil composite-modified patching material was developed using 90# base asphalt as the matrix, synergistically modified with crumb rubber (CR) and epoxidized soybean oil (ESO). To resolve the contradictory requirements for high elasticity and thermal expansion/contraction coordination in sealants, ESO was introduced; its polar epoxy groups optimize phase compatibility and promote low-temperature stress relaxation without restricting thermal deformability. Rheological evaluations revealed that the optimal system (OPT) successfully extended the service temperature window from PG 76–−24 °C (baseline) to PG 82–−24 °C, significantly enhancing its adaptability to extreme climatic fluctuations. At −24 °C, OPT exhibited a reduced creep stiffness (S) of 164 MPa and an increased creep rate (m) of 0.312, with a cracking resistance ratio (k) as low as 525.6; the quantitative significance of these metrics lies in granting the sealant superior stress relaxation capacity, enabling it to accommodate dynamic crack widening without interfacial debonding or brittle fracture. Fatigue testing via time sweeps demonstrated that N_f50 reached 2890 cycles, highlighting robust long-term resistance against high-frequency shear strains induced by tire edges. Micro-mechanistic analyses (FTIR, TG/DTG, and DSC) confirmed that the modification is primarily driven by physical blending. The elevation of the thermal decomposition threshold (T5%) to 302.4 °C and the residue at 600 °C to 44.8% provide a critical safety margin for high-temperature construction heating, preventing thermal degradation. Furthermore, the glass transition temperature (T_g) decreased to approximately −35.2 °C. These findings establish a rigorous quantitative and mechanistic framework for designing sustainable, high-performance patching materials for resilient pavement maintenance. Full article

Increased and excessive axle loads (exceeding design specifications) at high temperatures stimulate premature distresses in flexible pavements. This study utilizes the novelty of engineered bituminous composite—crumb rubber-modified (CRM) stone mastic asphalt (SMA) for pavement longevity and sustainable performance. Dynamic modulus testing was employed at four temperatures and six frequency sweeps. The experimental design included the preparation of SMA 19 specimens with six different percentages of crumb rubber (CR) mixed in bitumen. CR addition to the mix translated into an improved stiffness of the mix, as a 64% increase in dynamic modulus (on average) was reported at 10% CR as compared to a neat mixture. Master curves were produced using |E*| test results, which revealed that 10% modified SMA was relatively stiffer and more rut-resistant than the other mixtures. Performance prediction models were developed for |E*| using artificial neural networks (ANNs) and non-linear regression, wherein the former proved to be more robust. Sensitivity analysis revealed that a temperature rise (21.1 to 37.8 °C) translated into a 65% drop in |E*| (on average) and a rise in frequency (0.1 to 25 Hz) divulged a 72% upsurge in |E*| (on average). This research demonstrates the promise of deploying CR SMA mixtures, particularly for high-traffic and heavy-load scenarios. Full article

Facing the challenges in field monitoring of the mechanical response of geogrids in asphalt pavements, this study integrated two types of Fiber Bragg Grating (FBG) sensors, unarmored and armored, into geogrids using the pillar-stitching technique on industrial warp-knitting production lines. The integrated FBG-geogrid systems were comprehensively evaluated in both wound and flattened configurations, enabling the selection of a sensor type suitable for industrial production. After precise strain calibration, a full-scale field damage test was performed during the construction of the Qu-Gang Expressway in Hebei Province, China. The results demonstrate that the helical steel armor layer significantly enhances the mechanical durability of the FBG sensor. Specifically, the armored sensor maintained stable optical transmission over its entire 60-m length, with an average performance retention rate of 98.86% in the flattened state. Moreover, a strong linear correlation was established between the wavelength shift of the armored FBG sensor and the tensile strain of the geogrids. In contrast, the unarmored FBG sensor underwent irreversible shear deformation during production and contained at least two breakpoints. Additionally, a protection scheme employing fiberglass-reinforced silicone rubber on the hot side and standard silicone rubber on the cold side effectively shielded the sensors from high-temperature and compaction loads during asphalt paving. Consequently, the proposed FBG-geogrid integration method and the corresponding field protection strategy provide technical support for the real-time monitoring of geogrid performance in asphalt pavements and have significant engineering value. Full article

Runway friction is a critical factor for aircraft operational safety, yet the role of adhesion in wet friction remains insufficiently understood, especially in areas where tyre rubber contaminates the surface. This study evaluated approximate adhesive contribution for representative common runway surfaces, using contact angle measurements and British pendulum tester friction tests. The results show that approximate adhesion influence varies strongly with surface type: negligible on cement concrete, 16% to 19% on rubber-contaminated asphalt, and up to 49% on roughened rubber. A linear correlation between friction and contact angle confirmed that wetting behaviour governs adhesion-driven friction. Friction tests at different temperatures also confirmed the adhesive nature of the temperature influence on friction. The analysis further indicates that material properties and greater effective surface area correlate with stronger adhesive contributions, explaining material-specific differences in friction performance. These findings may provide a conceptual basis for interpreting variability in continuous friction measurements and suggest the importance of considering adhesion effects in runway surface characterisation and maintenance systems. Full article

To reveal the long-term anti-aging mechanisms of rubber–plastic elastomer-modified asphalt in complex service environments and overcome the inherent defects of single polymer modifiers—namely their susceptibility to degradation or phase separation—this study prepared styrene-butadiene-styrene (SBS), low Mooney rubber (LMMR), and low-density polyethylene (LDPE)-modified asphalts. Simultaneously, an LMMR-LDPE rubber–plastic thermoplastic elastomer (TPE) was fabricated utilizing twin-screw extrusion technology and subsequently used to prepare a composite-modified asphalt. Three aging protocols were simulated: short-term thermo-oxidative aging (RTFOT), long-term pressure aging (PAV), and ultraviolet light aging (UV). A multi-scale quantitative characterization was conducted using a dynamic shear rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy to evaluate the rutting factor, carbonyl index, and surface microroughness of each system before and after aging. The experimental results indicate that the coupled effect of long-term stress and thermal oxidation causes the most severe damage to the colloidal structure of modified asphalt. Conventional SBS-modified asphalt, due to its abundance of unsaturated double bonds, exhibits a sharp increase in the carbonyl index and aging index of the rutting factor after aging, making it highly susceptible to oxidative chain scission. Although LDPE-modified asphalt possesses chemical inertness, it is prone to crystalline phase separation under aging conditions, resulting in a microroughness distortion rate of up to 86.36%. In contrast, the LMMR-LDPE composite system, leveraging the high chemical stability of the saturated aliphatic carbon chain and the flexibility-enhancing and crystallization-inhibiting effects of LMMR, effectively reduces active oxidation sites and improves interfacial compatibility. This composite system exhibits the lowest carbonyl increment and rheological attenuation under all aging conditions, while effectively inhibiting the free migration and agglomeration of macromolecular components. The LMMR-LDPE composite modification technology effectively overcomes the inherent drawbacks of single polymers, such as susceptibility to degradation or segregation, demonstrating excellent long-term macroscopic rheological stability and microscopic phase morphology anti-aging capability. The present findings provide laboratory-scale mechanistic support for the design of durable rubber–plastic-modified asphalt systems, while further pilot-scale, economic, and field validation is still required before practical engineering application can be fully assessed. Full article

In cold and arid regions, the durability of asphalt pavement materials is often inadequate, and the hot mixing process further accelerates pavement ageing and releases harmful gases. To address the high-viscosity of pavement materials in such regions, lower mixing temperatures, extend the construction duration, and enhance pavement durability, this study systematically investigates a warm-mix technology for rubber-composite-modified asphalt. First, the influence of processing conditions on the viscosity-reducing effect was examined, and the optimal warm-mix preparation process was determined. Second, the properties of warm-mix rubber-modified asphalt were optimised through high- and low-temperature rheological testing. Finally, the mechanism of warm-mix modification was elucidated using microscopic techniques such as scanning electron microscopy, fluorescence microscopy and infrared spectroscopy. The results show that the 40-mesh pelletised desulphurised rubber treated with activator at a 5:1 ratio of activator at 220 °C for 50 h exhibits the optimal viscosity reduction effect. As the proportion of cracked rubber increases, the viscosity-reducing effect first intensifies and then diminishes optimal results are achieved at a dosage of 5%; the optimal comprehensive performance is achieved at a 5% proportion, where the asphalt simultaneously exhibits excellent high-temperature stability and low-temperature crack resistance. The cracking process effectively disrupts the cross-linked network structure of rubber, significantly reducing viscosity while enhancing the compatibility and stability of the asphalt system. Notably, the proposed warm-mix process reduces the production temperature of rubber-modified asphalt by 40–60 °C and lowers its viscosity by approximately 30% compared to conventional asphalt. This improvement provides crucial support for low-temperature construction and viscosity control of rubber-modified asphalt in cold and arid regions. Full article