Search Results (70)

Recycled polymer-modified binders have emerged as a sustainable solution for improving the performance and durability of pavement materials. This review examines the rutting and aging properties of pavements modified with recycled polymers, highlighting their potential for sustainable infrastructure development. The incorporation of recycled polymers into bitumen enhances resistance to rutting and aging by improving the binder’s mechanical stability and oxidative durability. Key laboratory techniques, including the rolling thin-film oven test (RTFOT) and the pressure aging vessel (PAV), are evaluated for their effectiveness in assessing the thermal and oxidative aging behavior of modified binders. The review demonstrates that recycled polymers improve binder elasticity, delay oxidative degradation, and mitigate deformation under repeated loading, thus extending pavement lifespan and reducing maintenance costs. However, challenges such as optimizing polymer dosage, ensuring homogeneity, and predicting long-term performance require further investigation. This paper underscores the environmental and economic benefits of utilizing recycled polymers in pavement construction and advocates for improved testing protocols and advanced characterization techniques to enhance the reliability and sustainability of polymer-modified pavements. Full article

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures has increased due to its economic and environmental benefits. However, RAP integration can negatively impact the durability and performance of asphalt binders, particularly at low temperatures. This study evaluates the effects of RAP modification on the $\Delta T_C$ parameter, a key indicator of binder brittleness and resistance to non-load-related cracking, focusing on PG XX-34 and PG XX-28 grades commonly used in Kansas. Laboratory testing was conducted on virgin and RAP binders subjected to Rolling Thin-Film Oven (RTFO) and Pressure Aging Vessel (PAV) aging. Blended binders were prepared with RAP replacement levels of 15%, 25%, and 40%. The critical temperatures $T_{C,m}$, $T_{C,S}$, and $\Delta T_C$ values were calculated using data from Bending Beam Rheometer (BBR) testing. The results showed that increasing RAP content generally led to more negative $\Delta T_C$ values, indicating reduced relaxation capacity and higher susceptibility to thermal cracking. RAP source variability also affected performance, with some sources causing more severe deterioration than others. These findings highlight the limitations of conventional linear blending assumptions and underscore the need for improved RAP characterization in binder selection. The study recommends limiting RAP replacement to 25% unless the RAP source demonstrates favorable properties, incorporating $\Delta T_C$ thresholds (−2.5 °C and −5.0 °C) into binder specifications, and further investigating RAP–virgin binder interactions to enhance long-term pavement performance. The findings support the potential adoption of $\Delta T_C$ as a specification criterion for binder evaluation, helping agencies like the Kansas Department of Transportation (KDOT) balance binder durability and RAP use. Full article

The viscoelastic behavior of asphalt mixtures is a crucial consideration in the analysis of pavement mechanical responses and structural design. This study aims to elucidate the molecular structure and component evolution trends of polyphosphoric acid (PPA)/styrene butadiene styrene block copolymer (SBS)/styrene butadiene rubber copolymer (SBR) composite modified asphalt (CMA) under rolling thin film oven test (RTFOT) and pressure aging (PAV) conditions, as well as to analyze the viscoelastic evolution of CMA mixtures. First, accelerated aging was conducted in the laboratory through RTFOT, along with PAV tests for 20 h and 40 h. Next, the microscopic characteristics of the binder at different aging stages were explored using Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) tests. Additionally, fundamental rheological properties and temperature sweep tests were performed to reveal the viscoelastic evolution characteristics of CMA. Ultimately, the viscoelastic properties of CMA mixtures under dynamic loading at different aging stages were clarified. The results indicate that the incorporation of SBS and SBR increased the levels of carbonyl and sulfoxide factors while decreasing the level of long-chain factors, which slowed down the rate of change of large molecule content and reduced the rate of change of LMS by more than 6%, with the rate of change of overall molecular weight distribution narrowing to below 50%. The simultaneous incorporation of SBS and SBR into CMA mixtures enhanced the dynamic modulus in the 25 Hz and −10 °C range by 24.3% (AC-13), 15.4% (AC-16), and reduced the $\phi$ by 55.8% (AC-13), 40% (AC-16). This research provides a reference for the application of CMA mixtures in the repair of pavement pothole damage. Full article

This paper examines the improvement in the performance characteristics and the rheological properties of modified bitumen through the addition of the thermoplastic polymer polyvinyl acetate (PVA). PVA is a synthetic polymer derived from the polymerization of the vinyl acetate. The effect of PVA on bitumen and bituminous mixtures was investigated through the conventional (penetration, softening point, force-ductility, elastic recovery, Marshall and Nicholson stripping tests) and Superpave (rotational viscosity (RV), rolling thin film oven (RTFOT), pressure aging vessel (PAV), dynamic shear rheometer (DSR) and beam bending rheometer (BBR)) tests. PVA was added to bitumen at rates of 2%, 4%, 6% and 8% by mass. Based on the bitumen test results, a PVA rate of 6% was selected for the mixture tests. The modification process was carried out at relatively low temperature (150 °C) and mixing time (20 min) based on various trials, considering the short-term aging of the bitumen. With PVA modification, the penetration value of the bitumen decreased while the softening point increased. As a result, the calculated penetration index (PI) increased and the thermal sensitivity of the bitumen decreased. Significant improvements were detected in elastic recovery and force-ductility tests. Additionally, PVA improved the resistance of asphalt to settling and cracking. Similar results were observed in the DSR and BBR tests. Furthermore, the stripping resistance increased and the stability value improved significantly in the mixture tests. Full article

The inadequate resistance of traditional asphalt binders to aging, temperature fluctuations, and fatigue cracking underlines the necessity for innovative modifications to boost pavement durability. This study aims to state the inadequate exploration of the direct application of composite nanomaterials in asphalt binders by assessing their direct effects on physiochemical and durability properties without the inclusion of additional additives. The composite nanomaterials, combined with different amounts of Nano-Silica, Nano-Alumina, and Nano-Copper oxide, were incorporated into the binder at 2%, 4%, and 6% by weight. A series of conventional and rheological tests were conducted, including penetration, temperature susceptibility, Dynamic Shear Rheometer (DSR), Rolling Thin Film Oven Test (RTFOT), and Bending Beam Rheometer (BBR). The results demonstrated that the addition of 2% nanomaterials improved penetration by 34% and 41% for unaged and aged samples, respectively, while a 4% addition reduced temperature susceptibility by 64% for aged binders in a mix containing equal amounts of combined nanomaterials. DSR analysis indicated enhanced stiffness and viscoelastic properties, with increased complex shear modulus (G*) and reduced phase angle (δ). Aging resistance was enhanced as established by RTFOT, and acceptable low-temperature performance was attained per BBR results. These results found composite nanomaterials as a capable key for advancing asphalt binder performance. Full article

Asphalt pavements make up a majority of the essential transportation systems in the US. Asphalt mixtures age and degrade over time, reducing the pavement performance. Pavement performance critically depends on the aging of asphalt binder. The aging of asphalt binder during construction is traditionally modeled by rolling thin film oven (RTFO) testing, while aging during service life is modeled by pressure aging vessel (PAV) testing. Comparing these models to the aging of binders in actual pavements is limited because, to be used for current testing, binders must be separated from the pavement’s aggregate by solvent extraction. Solvent extraction will, at least in part, compromise the structural integrity of asphalt binder samples. Spin-lattice NMR relaxometry has been shown to nondestructively evaluate asphalt properties in situ through the analysis of hydrogen environments. The molecular mobility of hydrogen environments and with it the stiffness of asphalt binder samples can be determined by characteristic T₁ relaxation times, indicating the complexity of asphalt-binder aging. In this study, two laboratory-generated asphalt mixtures, a failed field sample, and several laboratory-aged binder samples are compared by NMR relaxometry. NMR relaxometry was found to be able to differentiate between asphalt samples based on their binder percentage. According to the relaxometry findings, the RTFO binder aging compared favorably to the 6% laboratory-mixed sample. The PAV aging, however, did not compare well to the relaxometry results found for the field-aged sample. The amount of aggregate was found to have an influence on the relaxation times of the binder in the mixed samples and an inverse proportionality of the binder content to the primary NMR relaxation time was detected. It is concluded that molecular water present in the pores of the aggregate material gives rise to such a relationship. The findings of this study lay the foundation for nondestructive asphalt performance evaluation by NMR relaxometry. Full article

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%. Full article

Nanomaterials enhance the performance of both asphalt binders and asphalt mixtures. They also improve asphalt durability, which reduces resource consumption and environmental impact in the long term associated with the production and transportation of asphalt materials. Thus, this paper studies the effectiveness of Nano Calcium Carbonate (Nano CaCO₃) and Nano Hydrated Lime (NHL) as modifiers and examines their impact on ranges from 0% to 10% through comprehensive laboratory tests. Softening point, penetration, storage stability, viscosity, and mass loss due to short-term aging using the Rolling Thin Film Oven Test (RTFO) were performed on asphalt binders. Results indicated a significant improvement in binder stiffness, particularly at 4% Nano CaCO₃ and 6% NHL content by weight. Dynamic Shear Rheometer (DSR) tests further revealed substantial improvements in rutting resistance, with NHL exhibiting superior high-temperature stability and a notable increase in the rutting factor. Marshall stability tests on asphalt concrete (AC) mixtures showed a 22.3% increase in stability with 6% NHL by weight, surpassing the 20.2% improvement observed with Nano CaCO₃ and indicating enhanced load-bearing capacity. The resilient modulus of the mixtures consistently increased with the addition of NHL, suggesting improved durability in rutting. Moisture susceptibility tests revealed that NHL significantly enhances moisture resistance, exceeding the 80% TSR benchmark at just 2% content by weight and reaching an impressive 94.6% at 10% content by weight. In contrast, Nano CaCO₃ demonstrated a more gradual improvement, achieving an 88.2% TSR at 10% content. Furthermore, permanent deformation analysis indicated a 68.64% improvement in rutting resistance with 10% NHL content by weight, exceeding Nano CaCO₃’s improvement rate. Optimal fatigue resistance was achieved at 4% for Nano CaCO₃ and 6% for NHL by weight, with respective CT index improvements of 30% and 35.4%, showing NHL’s consistent benefits across various nanomaterial contents. Overall, the study suggests that both Nano CaCO₃ and NHL positively impact asphalt performance, with NHL offering more pronounced benefits across a range of properties. These findings provide valuable insights for pavement engineers and underscore NHL’s potential as an effective additive in asphalt mixture design. Real-world applications and validations are essential for a comprehensive understanding of these nanomaterials in practical pavement engineering scenarios. Full article

This research addresses the significant challenge posed by early water damage in highway asphalt pavement, a critical concern affecting pavement service performance. To counteract this issue, the utilization of anti-stripping agents in asphalt is explored as a highly effective technical intervention. In this investigation, a carefully selected amine-free additive was employed to modify the asphalt binder. A comprehensive array of physical and rheological tests, covering aspects such as storage stability, penetration, softening point, ductility, elastic recovery, rolling thin-film oven, retained penetration, the ductility of residue, and rotational viscometer assessments, were conducted to examine the multifaceted impact of the anti-stripping agent on the asphalt binder. Additionally, we assessed the asphalt mixture’s sensitivity to moisture through Marshall stability tests after conditioning for 40 min and 24 h, followed by an enhanced immersion test and moisture susceptibility measurement. The results reveal a nuanced interplay of chemical and physical mechanisms influencing the behavior of the asphalt binder. Notably, the incorporation of an anti-stripping agent at a concentration of 0.25–0.5% (by weight of asphalt binder) led to a substantial improvement in the tensile strength ratio (TSR) to 94.9%, a noteworthy enhancement compared to the 80.6% observed with virgin asphalt mixture. Furthermore, the retained stability index (RSI) exhibited a remarkable increase to 98.1%, surpassing the 87.6% recorded for virgin asphalt. This study not only provides crucial insights into the intricate dynamics of asphalt binder performance but also emphasizes the pivotal role of anti-stripping agents in augmenting the structural integrity and resilience of asphalt pavement. Full article

The present study investigates the effects of the simultaneous use of two additives, an organosilane warm mix asphalt (WMA) agent and a grade-bumping polyolefin compound, on the conventional and high-temperature performance properties of a paving grade 50/70 bitumen and a polymer-modified 45/80-55 bitumen. The WMA agent and polyolefin additive were introduced to the binders at rates of up to 0.3% and 2%, respectively. The base asphalt binders and their blends with the additives were tested before and after aging in a rolling thin film oven test at a temperature of 143 °C. The effects of the investigated additives were found to be dependent on the type of base binder and its aging state. It was generally observed that the WMA additive decreased the performance of the asphalt binders and limited the effects of the other additive, which increased the high-temperature stiffness and non-recoverable compliance of the blends. This interaction amounted to as much as an approx. 20% decrease in high-temperature stiffness and non-recoverable compliance of the binders. The additives caused a small increase in the elasticity of the binders and improved their creep performance when measured in multiple stress creep recovery tests. Full article

The use of polymer-modified binders in asphalt concrete makes it possible to increase the efficiency and durability of highways. However, at present, there is an important and unresolved problem in this area, making it impossible to fully exploit the potential of modified binders. This is a tendency of aging processes that leads to the premature destruction of the pavement. In many literary sources, it is reported that reasons are related to the peculiarity of the chemical composition and occur at the submicron level. Therefore, the influence of single-walled carbon nanotubes has been studied for a better understanding of aging processes. The aging processes of the RTFOT (rolling thin film oven test) and PAV (pressure aging vessel) modified with SBS (styrene–butadiene–styrene) polymer, single-walled carbon nanotubes, and waste industrial oil were simulated in a laboratory furnace. Microstructural features were studied using the method of infrared spectral analysis. The dependences of viscoelastic properties on the component composition of binders were investigated. The optimal content of single-walled carbon nanotubes (0.001%), SBS (styrene–butadiene–styrene) polymer (3.5%), and waste industrial oil (4%) in the binder composition was established, which synergistically improved the performance of the modified binder from PG (52-22) (performance grade) to PG (64-34). It was established that single-walled carbon nanotubes provide improvement in the durability parameter ∆T_c binder by 150%, improved relaxation properties at low temperatures, and resistance to fatigue damage. Full article

Rheological test standards require asphalt samples, both original and under ageing conditions. The most common laboratory equipment in specifications for short-term and long-term ageing simulation tests are the rolling thin film oven (RTFO) and the pressure ageing vessel (PAV). However, the cost of acquiring PAV and the duration of long-term ageing tests can be a limiting factor. This work aimed to establish the equivalent time of the long-term ageing test in the RTFO that corresponds to the PAV. For this, the Brazilian asphalt PEN 50/70, specified by penetration, was aged at different times (85, 170, 255, and 340 min) in the RTFO at the standard temperature (163 °C). For each time, using a dynamic shear rheometer (DSR), tests such as Multiple Stress Creep Recovery (MSCR) and Linear Amplitude Sweep (LAS) were performed, and the rheological properties (complex modulus (G*) and phase angle (δ)) were measured. The same tests were conducted on the samples aged in the long term and in the PAV. The test parameters obtained from applying different times while using the RTFO were compared with the PAV results, and the equivalent time was settled through linear regression, resulting in 300 min. In order to confirm the equivalent time, samples aged in the RTFO for 300 min were assessed using the same rheological tests, and the parameters were compared to those obtained after PAV ageing. At the equivalent time, the difference between RTFO and the PAV for the rutting parameter (G*/sinδ, 58 °C) was 6%, while for the fatigue parameter (G*.sinδ, 19 °C), the difference was 1.0%. The MSCR non-recoverable creep compliance parameter differences, considering stress levels of 0.1 kPa and 3.2 kPa, were 9.7% and 11.7%, respectively. For the fatigue life obtained in the LAS test at strain levels of 1.25% and 2.5%, the difference between RTFO and PAV, at the equivalent time, was 7.6% and 7.8%, respectively. For the Brazilian unmodified asphalt PEN 50/70 and parameters evaluated in this work, 300 min is the equivalent time that simulates long-term ageing in the RTFO. Full article

The rapid growth of the world population and the rapid diversification of consumption habits due to technological advancements have increased waste production. An investigation of the effects of biomass products, such as waste vegetable oil and waste agricultural ash, on bitumen’s physical and chemical properties was conducted in this study. By recycling biomass products, this study aimed to improve the performance and stability of bituminous hot mixtures, optimize the number of additives, and create more economical designs. Using the Taguchi method, 0%, 2%, 4% by weight of waste vegetable oil and 0%, 3%, and 6% by weight of waste agricultural ash were added to 70/100 penetration pure bitumen with an orthogonal array of L9. For 10, 20, and 30 min, modified bitumen samples were prepared at 170 °C, 180 °C, and 190 °C with a constant mixing speed of 3000 RPM. The samples were tested for penetration, softening point, flash point, rolling thin film oven (RTFOT), FTIR, and Marshall Design stability and flow. Based on the obtained performance statistics, 95% confidence levels were assigned to the predictions. The stability and softening point values decreased as the oil content increased, while flash and penetration values increased. With increasing ash content, stability, flash, and softening point values increased, and penetration values decreased. Compared to oil and ash additives, mixing temperature and time had relatively little effect on the modification process. Overall, the optimum parameter levels were 4% for oil, 0% for ash, 170 °C for temperature, and 10 min for time. Full article

The copolymer ethylene–octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene–butadiene–styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE (i.e., POE-g-GMA) may solve this problem, for the epoxy groups in GMA can react with the active groups in asphalt. Asphalt modified with linear and crosslinked POE-g-GMA were prepared, and the hot storage stability, physical properties and thermal oxidation aging properties were discussed in detail. The results show that linear and low-degree crosslinked POE-g-GMA-modified asphalts are storage-stable at high temperatures via measurements of the difference in softening points and small-angle X-ray scattering (SAXS) characterizations from macro and micro perspectives. The difference in softening points (ΔSP) between the upper and lower ends is no more than 3.5 °C for modified asphalts after 48 h of being in an oven at 163 °C. More importantly, the crosslinking modification of POE-g-GMA can further increase the softening point and reduce the penetration as well as rheological properties via conventional physical property, dynamic shear rheometer (DSR) and multiple-stress creep recovery (MSCR) tests. Furthermore, asphalt modified with crosslinked POE-g-GMA reveals better aging resistance via measurements of the performance retention rate and electron paramagnetic resonance (EPR) characterizations after a rolling thin film oven test (RTFOT). This work may provide further guidelines for the application of polymers in asphalt. Full article

This study assessed the fundamental physical properties and chemical composition of three specific waste engine oil residue (WEORs) asphalt regenerants. Through dynamic shear rheometer and rolling thin-film oven tests, the performance of aged asphalt was evaluated using three key indicators. Thin-layer chromatography investigations probed the WEOR-induced changes in the aging asphalt components, leading to the creation of two novel asphalt regenerants, WEOR-H and WEOR-G. WEOR-G was developed from WEOR-1, liquid rubber, ultraviolet absorber, light shielding agent, and antioxidant, while WEOR-H was formulated from WEOR-2, aromatic oil, and liquid rubber. The study employed differential scanning calorimetry and conventional laboratory tests to analyze the road performance attributes of Ingevity J type regenerant (J), WEOR-G, and WEOR-H. The results indicated that WEORs increase the saturate and aromatic content in asphalt and partially replenish the missing lightweight components of aged asphalt, moderately improving the three key indicators, though the regenerative effect is restricted. Achieving a full restoration of component proportions within aged asphalt to their initial levels proved unattainable, and direct application of any of the three WEORs as asphalt regenerants is impractical. WEOR-H and WEOR-G demonstrated potential in enhancing aged asphalt binder road performance, outpacing three other WEORs. At a 14% dosage, WEOR-G and WEOR-H could increase the 10 °C ductility to 23.5 and 21.4 cm, respectively, effectively counterbalancing the insufficient ability of WEOR-1 and WEOR-2 to restore the low-temperature performance of aged asphalt. Among the regenerants, WEOR-G, possessing superior regenerative effects, the lowest glass transition temperature, and optimal low-temperature deformation resistance, emerged as the most efficacious. This inquiry furnishes vital data support for future applications of WEOR-G asphalt regenerant. Full article