Search Results (261)

Conventional asphalt is prone to cracking in cold climates due to its poor flexibility and limited ability to regulate temperature. This study investigates the use of low-temperature microencapsulated phase-change materials (MPCMs) to improve both the thermal storage and low-temperature performance of asphalt. MPCMs were incorporated into asphalt through physical blending at various concentrations. The physical, thermal, and rheological properties of the asphalt were then systematically evaluated. Tests included penetration, softening point, ductility, thermogravimetric analysis (TGA), and dynamic shear rheometer (DSR). The addition of MPCMs increased penetration and ductility. It slightly reduced the softening point and viscosity. These changes suggest improved flexibility and workability at low temperatures. Rheological tests showed reductions in rutting and fatigue factors. This indicates better resistance to thermal and mechanical stresses. Bending Beam Rheometer (BBR) results further confirmed that MPCMs lowered creep stiffness and increased the m-value. These findings demonstrate improved crack resistance under cold conditions. Thermal cycling tests also showed that MPCMs delayed the cooling process and reduced temperature fluctuations. This highlights their potential to enhance both energy efficiency and the durability of asphalt pavements in cold regions. Full article

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article

To elucidate the modification mechanism of waterborne polyurethane (WPU) on emulsified asphalt, anionic and cationic WPUs are utilized as modifiers. As well, their effects on physical properties, microstructure, and compatibility are characterized using basic performance tests, Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The results show that WPU-modified emulsified asphalt exhibited a higher softening point, reduced penetration, and decreased ductility, suggesting enhanced high-temperature stability but diminished low-temperature flexibility. Among all samples, the combination of cationic WPU with cationic emulsified asphalt shows the highest softening point (54.1 °C), whereas cationic emulsified asphalt alone exhibits the lowest one (52.9 °C). Anionic emulsified asphalt demonstrates the highest penetration (79 mm), while non-ionic WPU combined with cationic emulsified asphalt shows the lowest one (59.3 mm). The ductility decreases from 90.3 cm to 28.7 cm. The storage stability varies with WPU ion type. Cationic WPU-modified samples showed the poorest storage stability (0.7% residue), while anionic-modified samples exhibit the best one (0.4% residue). FTIR analysis confirms the presence of characteristic WPU absorption peaks, indicating that physical blending occurs, and chemical interaction is limited. AFM observations reveal that anionic WPUs provide superior compatibility, forming fine, uniformly distributed particles with the lowest surface roughness (5.655 nm). In contrast, cationic WPUs form chain-like structures that cure effectively but exhibit poor dispersion. This study provides a basis for the development of high-performance WPU-modified emulsified asphalt. Full article

To broaden clean asphalt modification methods, this study employs a composite polymer of maleic anhydride-grafted styrene-butadiene-styrene (MA-g-SBS) and styrene-butadiene-styrene (SBS) as a modifier. The composite is formulated into polymer latex and used to modify emulsified asphalt. Routine performance tests were conducted on MA-g-SBS/SBS composite latex-modified emulsified asphalt (MSMEA) with varying ratios to determine the optimal composition. The ideal ratio was found to be MA-g-SBS:SBS = 1:4. Subsequently, conventional property tests, rheological analyses, microphase structure observations, and bending beam creep tests were conducted on MSMEA with the optimal ratio to assess the impact of the composite latex on asphalt performance. Findings indicated that increasing the latex content significantly enhanced the softening point and ductility while reducing penetration. These macroscopic improvements were notably superior to those achieved with single SBS latex modification. Fluorescence microscopy revealed that at low dosages, the MA-g-SBS/SBS composite dispersed uniformly as point-like structures within the asphalt. At higher dosages (above 5%), a distinct network structure emerged. The addition of the composite latex raised the complex shear modulus and rutting factor while reducing the phase angle, with pronounced fluctuations observed between 4% and 5% dosages. This suggests a substantial enhancement in the high-temperature performance of the emulsified asphalt, attributed to the formation of the network structure. FT-IR results confirmed that a chemical reaction occurred during the modification process. Additionally, the bending beam creep test demonstrated that the composite latex reduced asphalt brittleness and improved its low-temperature performance. Full article

USP (usual temperature pitch)-modified asphalt optimizes its rheological properties through reactions between the modifier and the asphalt. This significantly enhances the high- and low-temperature adaptability and environmental friendliness of asphalt. It has now become an important research direction in the field of highway engineering. This article systematically investigates the impact of different dosages of USP warm mix modifier on asphalt binders through rheological and microstructural analysis. Base asphalt and SBS-modified asphalt were blended with USP at varying ratios. Conventional tests (penetration, softening point, ductility) were combined with dynamic shear rheometry (DSR, AASHTO T315) and bending beam rheometry (BBR, AASHTO T313) to characterize temperature/frequency-dependent viscoelasticity. High-temperature performance was quantified via multiple stress creep recovery (MSCR, ASTM D7405), while fluorescence microscopy and FTIR spectroscopy elucidated modification mechanisms. Key findings reveal that (1) optimal USP thresholds exist at 4.0% for base asphalt and 4.5% for SBS modified asphalt, beyond which the rutting resistance factor (G*/sin δ) decreases by 20–31% due to plasticization effects; (2) USP significantly improves low-temperature flexibility, reducing creep stiffness at −12 °C by 38% (USP-modified) and 35% (USP/SBS composite) versus controls; (3) infrared spectroscopy displays that no new characteristic peaks appeared in the functional group region of 4000–1300 cm⁻¹ for the two types of modified asphalt after the incorporation of USP, indicating that no chemical changes occurred in the asphalt; and (4) fluorescence imaging confirmed that the incorporation of USP led to disintegration of the spatial network structure of the control asphalt, explaining the reason for the deterioration of high-temperature performance. Full article

This study investigates the performance improvement of asphalt binders through the incorporation of two polymers, polyvinyl chloride (PVC) and styrene–butadiene–styrene (SBS), with asphalt grade (60–70), to address the growing demand for durable and climate-resilient pavement materials, particularly in areas exposed to high temperatures like Iraq. The main objective is to improve the mechanical characteristics, thermal stability, and workability of typical asphalt mixtures to extend pavement lifespan and lessen maintenance costs. A thorough set of rheological, physical, morphological, and workability tests was performed on asphalt binders modified with varying content of PVC (3%, 5%, 7%, and 9%) and SBS (3%, 4%, and 5%). The significance of this research lies in optimizing binder formulations to enhance resistance to deformation and failure modes such as rutting and thermal cracking, which are common in extreme climates. The results indicate that PVC enhances performance grade (PG), softening point, and viscosity, although higher contents (7% and 9%) exceeded penetration grade specifications. SBS-modified binders demonstrated marked improvements in softening point, viscosity, and rutting resistance, with PG values increasing from PG64-x (unmodified) to PG82-x at 5% SBS. Fluorescence microscopy confirmed optimal polymer dispersion at 5% concentration for both SBS and PVC, ensuring compatibility with the base asphalt. Workability testing revealed that SBS-modified mixtures exhibited higher torque requirements, indicating reduced workability compared to both PVC-modified and unmodified binders. These findings offer valuable insights for the design of high-performance asphalt mixtures suitable for hot-climate applications and contribute to the development of more durable and cost-effective road infrastructure. Full article

The goal of this study is to evaluate how the inclusion of synthetic wax, added in 0.5% increments from 1.5% to 3.5%, affects the characteristics of PMB 45/80-65 (polymer-modified bitumen) during both short-term (RTFOT) and long-term (PAV) aging processes. Tests were carried out to assess the fundamental properties of the binder, leading to the determination of the penetration index (PI) and the plasticity range (PR). The binder’s properties were examined at below-freezing operating temperatures, with creep stiffness measured using a bent beam rheometer (BBR) at −10 °C, −16° C, −22 °C, and −28 °C. The rheological properties of the asphaltenes were evaluated based on both linear and nonlinear viscoelasticity. The experimental study explored temperature effects on the rheological properties of composite materials using a DSR dynamic shear rheometer at 40 °C, 60 °C, and 80 °C over a frequency range of 0.005 to 10 Hz. The main parameters of interest were composite viscosity (η*) and zero shear viscosity (η₀). Viscoelastic parameters, including the dynamic modulus (G*) and phase shift angle (δ), were determined, and Black’s curves were used to illustrate the relationship between these parameters, where G*/sinδ was determined. The MSCR test was employed to investigate the impact of bitumen on the asphalt mixture’s resistance to permanent deformation and to assess the degree and efficacy of asphalt modification. The test measured two parameters, irreversible creep compliance (J_nr) and recovery (R), under stress levels of 0.1 kPa (LVE) and 3.2 kPa (N-LVE). The Christensen–Anderson–Marasteanu model was used to describe the bitumen behavior during binder aging, as reflected in the rheological study results. Ultimately, this study revealed that synthetic wax influences the rheological properties of PMB 45/80-65 polymer bitumen. Specifically, it mitigated the stiffness reduction in modified bitumen caused by polymer degradation during aging at an amount less than 2.5% of synthetic wax. Full article

The absence of standardized evaluation criteria for cold patch asphalt mixtures (CPAMs) leads to arbitrary material selection in pavement pothole repair, resulting in premature failure and recurrent damage. This study develops a comprehensive evaluation framework combining macro-performance tests with X-ray computed tomography (CT)-based meso-structural analysis. The macroscopic evaluation system incorporates six key parameters: aggregate gradation, binder–aggregate ratio, penetration strength, molding strength, residual rate, and stability retention. The CT-based meso-structural assessment quantifies void characteristics (longitudinal distribution, radial distribution, fractal dimension) and aggregate skeleton features (contact points, coordination number) through 3D reconstruction. Experimental results demonstrate that optimizing asphalt content (4.5–4.7%) with adjusted critical aggregate fractions (4.75 mm:35.0–45.0%; 2.36 mm:30.0–40.0%; 13.2 mm:1.0–1.2%; 9.5 mm:10.0–15.0%) significantly enhances repair durability. The established multiscale evaluation methodology provides a theoretical foundation for developing standardized CPAM quality specifications, particularly in emergency maintenance scenarios. Full article

Iraq’s extreme summer temperatures pose critical challenges to pavement durability, as conventional asphalt mixtures often fail under prolonged thermal stress. This paper provides a comparative evaluation of the high-temperature performance of unmodified (40/50 penetration grade) and polymer-modified (PG 76-10) asphalt mixtures for the asphalt course layer. Marshall stability, flow, and stiffness were measured at elevated temperatures of 60 °C, 65 °C, 70 °C, and 75 °C after short-term (30 min) and extended (24 h) conditioning. Results show that while both mixtures experienced performance degradation as the temperature increased, the polymer-modified mixture consistently exhibited superior thermal resistance, retaining approximately 9% higher stability and 28% higher stiffness, and displaying 18% lower flow deformation at 75 °C compared to the unmodified mixture. Stability degradation rate (SDR), stiffness degradation rate (SiDR), and flow increase rate (FIR) analyses further confirmed the enhanced resilience of PG 76-10, showing nearly 39% lower FIR under thermal stress. Importantly, PG 76-10 maintained performance within specification thresholds under all tested conditions, unlike the conventional 40/50 mixture. These findings emphasize the necessity of adapting mix design standards to regional climatic realities and support the broader adoption of polymer-modified asphalt binders to enhance pavement service life in hot-climate regions like Iraq. Full article

Rubber powder asphalt has been widely studied due to its favorable temperature sensitivity and fatigue resistance. However, because rubber powder does not easily swell in asphalt, it leads to poor storage stability and high viscosity, limiting its large-scale application. In this study, modified asphalt was prepared using desulfurized rubber powder (DRP) and styrene-butadiene-styrene (SBS) modifiers, aiming to identify the optimal formulation for enhanced performance. It was hypothesized that the combined use of DRP and SBS would produce synergistic effects, improving the overall mechanical and rheological properties of the asphalt. To test this, the effects of this composite modification were evaluated using Marshall tests (penetration, softening point, ductility, elastic recovery, and Brookfield viscosity) and Superpave tests (shear modulus, high-performance grade, rutting factor, fatigue factor, and creep and recovery). Additionally, moisture susceptibility, high-temperature stability, low-temperature cracking resistance, and fatigue resistance at the mixture level were assessed. Performance was evaluated according to the Chinese standard JT/T 798-2019 for rubberized asphalt using reclaimed tire rubber. Results show that DRP-modified asphalt demonstrates excellent temperature sensitivity, rutting resistance, deformation resistance, and fatigue performance. However, an excessive amount of DRP increases Brookfield viscosity, which negatively affects the workability of the asphalt binder. The addition of SBS further improves the softening point, ductility, and deformation recovery of the binder. Considering cost-effectiveness and overall performance, the optimal formulation was determined to be 25% DRP and 1% SBS. At this dosage, all performance indicators met the required standards. The rotational viscosity at 180 °C was approximately 35% lower than that of conventional rubber powder–modified asphalt, while the high-temperature rutting factor and fatigue resistance at medium-to-low temperatures outperformed those of SBS-modified asphalt. The mixture test results reveal that the gradation has an impact on the performance of the obtained mixture, but overall, the DRP-SBS composite-modified asphalt mixture has significant advantages in terms of performance and cost-effectiveness. Full article

Salts can have detrimental effects on asphalt pavements, leading to permanent damage that compromises their durability and sustainability. This study investigates the damage mechanisms of asphalt pavements under coupled salt–thermal–mechanical effects using multi-scale modeling. Pull-off and semicircular bending (SCB) tests were conducted to determine material parameters and validate numerical models. Experimental data demonstrated that after 48 h of salt treatment at −10 °C, specimens exhibited reductions in cohesive strength ranging from 23.5% to 26% and adhesive strength decreasing by 25% to 44% compared to untreated controls. More severe degradation was observed at 0 °C, with cohesive strength diminishing by up to 63.8% and adhesive strength declining by up to 71.6%. A multi-scale finite element (FE) pavement model incorporating cohesive zone modeling (CZM) was developed to simulate damage behavior within asphalt concrete. Salt diffusion analysis revealed limited penetration depth within short exposure periods, and results showed that salt penetration reached only about 10 mm into the pavement layers after 48 h. Results indicated significant reductions in adhesive and cohesive strengths due to salt exposure, with damage susceptibility increasing under combined thermal fluctuations and mechanical loading. Additionally, the effects of moving load magnitude and speed on pavement damage were examined, showing higher damage accumulation at lower speeds and heavier loads. This research provides insights into pavement deterioration mechanisms, contributing to improved durability and maintenance strategies for asphalt pavements in salt environments. Full article

Zinc oxide (ZnO) exhibits promising thermochemical properties when used as an asphalt binder modifier. Its micrometric size further enhances its potential as a substitute for natural fillers (NFs) in hot-mix asphalt (HMA). This study evaluates the effect of partially and fully replacing NFs with ZnO on the mechanical performance of HMA, addressing a research gap since the influence of ZnO as a filler in asphalt mixtures has not been previously investigated. NFs were replaced by ZnO at weight-based proportions of ZnO/NF = 25, 50, 75, and 100%. Initially, the morphology of NF and ZnO particles was analyzed using Scanning Electron Microscopy (SEM). Asphalt mastics were then produced with the same ZnO/NF proportions and subjected to conventional characterization tests, including penetration, softening point, and viscosity. In the next phase, HMA samples were designed using the Marshall method, incorporating ZnO at 0, 25, 50, and 100% replacement levels (designated as Control, HMA-25, HMA-50, and HMA-100, respectively). The mechanical performance of these mixtures was assessed through indirect tensile strength (ITS) and Cantabro tests. Based on the initial results, further evaluations were conducted on the Control, HMA-50, and HMA-100 mixtures to determine their resilient modulus, fatigue behavior under stress-controlled conditions, and resistance to permanent deformation (static creep test). The findings indicate that ZnO can replace NF in HMA without compromising Marshall stability or Cantabro strength. Additionally, ZnO-modified HMAs exhibit increases in stiffness under cyclic loading, and improvements in resistance to permanent deformation, fatigue performance, and moisture damage. These enhancements occur despite a 0.5% reduction in binder content compared to the Control HMA and a slight increase in porosity. Full article

In order to explore the influence of steel slag on the road performance of asphalt mastic and its mixtures, steel slag powder (SSP) and steel slag aggregate (SSA) were used to replace limestone mineral powder filler (MF) and natural limestone aggregate (LA) respectively to prepare asphalt mastic and mixture. A series of standardized tests including penetration, softening point, ductility, viscosity, pull-off strength, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) were carried out to evaluate the performance of asphalt mastics with SSP. Meanwhile, high- and low-temperature performance, moisture stability, volumetric stability, and fatigue resistance were evaluated by wheel tracking, uniaxial penetration strength, Hamburg, three-point bending, freeze–thaw splitting, immersed Marshall stability, water immersion expansion, and two-point bending trapezoidal beam fatigue tests. The results show that compared to the asphalt mastic with MF, enhanced high-temperature deformation resistance and reduced low-temperature cracking resistance of asphalt mastic with SSP were observed, as well as superior aging resistance. The improvements in high-temperature stability, moisture resistance, and fatigue performance were confirmed for asphalt mixtures with SSP/SSA. Additionally, compromised volumetric stability and low-temperature crack resistance were found when SSP/SSA was used in mixtures. Although asphalt mixtures with SSA exhibited 257.79%–424.60% higher expansion rate after 21-day immersion than those with LA, the 3-day immersion expansion rates complied with specification limits (<1.5% per JTG F40-2004). Critical volume expansion control measures should be adopted for full-component applications of steel slag powder/aggregates due to the hydration potential of free lime (f-CaO) and magnesium oxide (MgO) in steel slag under moisture exposure. Full article

Rubber-modified asphalt (RMA) faces several challenges, including poor workability, difficult construction, and high energy consumption. The incorporation of renewable light oils offers a promising solution to address issues such as high viscosity and elevated carbon emissions in asphalt modified with a high dosage of rubber powder. The investigation of light oil and rubber powder composite-modified asphalt under low-temperature (160 °C) and short-term (30 min) shear processes is essential for understanding its rheological behavior and modification mechanism. This study explores composite-modified asphalt prepared with four types of light oils (fatty acids, aromatic oil, tall oil, and paraffin oil) at dosages of 10% and 15%, combined with 20% rubber powder. Conventional penetration and viscosity tests were carried out to assess the overall physical properties of the composite-modified asphalts, while rheological tests were conducted to examine their performance at high temperatures. Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were employed to explore the interaction mechanisms that occurred between the light oils, rubber powder, and asphalt. The results suggest that the addition of various light oils leads to a reduction in the viscosity of rubber-modified asphalt, with the extent of reduction varying across different oils. Notably, 10% tall oil demonstrates the most significant reduction in viscosity while also facilitating the dissolution of rubber powder. The high-temperature PG-grade rubberized asphalt improved with the incorporation of light oils, with 5% tall oil yielding the highest PG grade of PG 82-34. FTIR analysis confirmed that light oils and rubber were physically blended in the asphalt, with the light components of the oils being absorbed by the asphalt. FM observations revealed that light oils promote the swelling of rubber particles, with the rubber particles fully swelling in tall oil. Considering the reduction in viscosity, the performance at both high and low temperatures, elasticity, and the extent of rubber particle swelling, tall oil is identified as the most effective material for preparing light oil–rubber composite-modified asphalt using the low-temperature, short-term shear process. Full article

In the context of the rapid advancement of reconstruction and expansion projects, there has been a significant increase in the demand for the inspection and evaluation of existing asphalt pavements. In order to enhance the efficiency and effectiveness of joint detection using 3D ground-penetrating radar and falling weight deflectometers, this study investigates non-destructive testing methods for existing asphalt pavements based on geostatistical correlation principles. The relationship between crack rate and deflection is analyzed using group average values. The characteristic sections division method based on the crack rate guideline was realized. Research on the prediction method for deflection using Kriging interpolation has been conducted. Research has revealed that there is a positive correlation between the crack rate and the deflection index. The principle of the singularity index can be employed to divide characteristic sections. The falling weight deflectometer is capable of conducting targeted testing in accordance with characteristic sections. Furthermore, the superior performance of Kriging interpolation in predicting deflection compared with linear interpolation has been demonstrated. According to the Kriging interpolation principle, the detection interval of slow lane deflection should not be more than 100 m. Kriging interpolation on one way lane of matrix data has the best effect, and it can predict deflection using a limited amount of slow lane and hard shoulder data. This facilitates analysis of the changing trend of the deflection index in cases where detection conditions are constrained. This method is of great significance for grasping the true performance status of the existing asphalt pavement structure. Full article