Performance Of Asphalt Mixtures Research Articles

A Fundamental Study on an SAP Mixed Asphalt Mixture for Reducing the Urban Heat Island Effect

As the average temperature in summer rises and heat waves occur more frequently, the urban heat island (UHI) phenomenon is becoming a social problem. Asphalt road pavement stores heat during the day, raising the surface temperature, and releases the stored heat at night, thereby aggravating the UHI phenomenon. Government authorities often spray water to lower the temperature of road pavement for the safety and convenience of citizens. However, the effect is immediate and does not last long. Therefore, in order to reduce the urban heat island phenomenon by spraying water, the recovery time of the surface temperature must be delayed. In this study, Super Absorbent Polymer (SAP), a highly absorbent polymer that absorbs 100 to 500 times its weight in water, was applied to asphalt road pavement. SAP is commonly used in diapers, feminine hygiene products, soil moisturizers, and concrete, and its scope is gradually expanding. The purpose of this study is to reduce the urban heat island phenomenon by mixing the SAP into asphalt and to increase the latent heat flux by evaporating the water absorbed by the SAP, thereby delaying the recovery time of the surface temperature of the road pavement. In this study, the performance of asphalt mixtures mixed with the SAP and the thermal characteristics according to the mixing amount were analyzed. In this study, the physical properties and temperature reduction performance of the asphalt mixture according to the SAP type and content were studied. The results of indoor and outdoor experiments on asphalt mixtures using the SAP showed that they satisfied the mechanical performance criteria as asphalt pavement materials and that the temperature recovery delay effect was improved.

Stability/instability analysis of advanced nanocomposite-reinforced bridge asphalt mixtures at low temperatures: Verification of the results via AI-driven approach

This study investigates the stability/instability analysis of advanced nanocomposite-reinforced bridge asphalt mixtures under low-temperature conditions, incorporating a fractional viscoelastic plate model for more accurate simulation of time-dependent material behavior. The nanoclay reinforcement is introduced into the asphalt matrix to enhance its mechanical properties, particularly improving the stiffness and thermal stability, which are critical for the long-term performance of bridge structures. The fractional viscoelastic plate formulation captures the complex viscoelastic behavior of the reinforced asphalt at low temperatures, where traditional models may fall short in accounting for the intricate time-dependent response of the material. The stability/instability analysis is conducted to assess the behavior of the nanocomposite asphalt mixtures under varying temperature conditions. The analysis identifies critical conditions leading to structural instability, ensuring the durability of bridge decks exposed to severe thermal environments. The results are validated using an AI-driven approach, leveraging machine learning algorithms to model the response of the nanocomposite asphalt mixtures more effectively. The AI model is trained using experimental data and computational simulations, with hyperparameters, such as learning rates, neural network architectures, and optimization techniques carefully selected to optimize prediction accuracy. The findings offer valuable insights into the performance of nanoclay-reinforced asphalt mixtures for bridge applications, with the AI-driven verification enhancing the reliability and applicability of the proposed models in practical engineering scenarios.

Study on road performance of asphalt mixture based on surface modification of coal gangue

In order to solve the problem of coal gangue environmental pollution and the shortage of aggregate resources in road engineering, this paper studies the feasibility of using waste coal gangue as coarse aggregate of asphalt mixture. Through the physical and mechanical properties test, the difference between coal gangue and natural aggregate was compared and analyzed. The surface modification and strengthening treatment of coal gangue aggregate was carried out by using methyl sodium silicate solution, and the best modification scheme was determined. The influence of different content and surface modification on the road performance of coal gangue asphalt mixture was studied by laboratory test. With the help of scanning electron microscope test, the change characteristics of the microstructure of coal gangue asphalt mixture before and after surface modification were explored. The results show that although the indexes of coal gangue are inferior to those of natural aggregate, it can be used to prepare asphalt mixture within the scope of specification requirements. The modification effect of sodium methyl silicate solution with modification time of 6h is the best, which can significantly improve the water absorption, density and crushing value of coal gangue. When the content of coal gangue is controlled within 30%, the performance of asphalt mixture meets the requirements of the specification, and the amount of coal gangue in asphalt mixture can be increased after surface modification. After surface modification, the surface pores and cracks of coal gangue asphalt mixture are reduced, and the surface micro-damage under high temperature immersion and freeze-thaw cycle conditions is improved.

Exploring mechanical properties and cracking behavior of AC-13 and OGFC-16 aggregate-segregated asphalt mixtures

Aggregate segregation compromises the homogeneity of asphalt pavement, which diminishes the road performance of the asphalt mixture. The segregation behavior and damage mechanism of asphalt mixture are complex. To investigate the mechanical properties and cracking behavior of asphalt mixtures with varying degrees of aggregate segregation, the dense-graded asphalt mixture with the nominal maximum size of 13.2mm (AC-13) and Open Graded Friction Course with the nominal maximum size of 16.0mm (OGFC-16) with varying degrees of segregation were designed. Indirect tensile test and the digital image correlation (DIC) technology was employed to analyze the strain distribution and strain evolution at the crack initiation point within the asphalt mixtures. The parameters were also proposed to evaluate the resistance to cracking for the segregated asphalt mixtures at a mesoscopic scale. The results show that increased segregation of coarse aggregates in AC-13 mixtures leads to decreased indirect tensile strength, lower maximum tensile strain along the horizontal direction (E11), and reduced failure displacement. Conversely, segregation of fine aggregates in OGFC-16 mixtures results in increased tensile strength, maximum strain, and failure displacement. Higher amount of coarse aggregates in the asphalt mixture contributes to a more intricate strain distribution and a greater number of strain peaks. Dense-graded mixtures show larger strain concentration zones prior to cracking, while smaller stress concentration zones are observed in open-graded mixtures. The horizontal strain-time curve displays distinct stages of stable growth, rapid growth, and rapid decline. Aggregate segregation results in more intricate crack patterns with larger inclination angles, influenced by the random distribution and shapes of coarse aggregates. Novel indexes such as strain uniformity (P1,2) and strain density during crack development (DW) effectively evaluate mesoscopic cracking resistance of asphalt mixtures. The results offer valuable insights into cracking behavior and improve evaluation methods for the mechanical performance of aggregate-segregated asphalt mixtures.

Towards a durable and sustainable warm mix asphalt: techno-economic and environmental evaluation considering balanced mix design approach

In response to the worldwide inclination towards sustainability and circular economy targets, there is a need to employ innovative and eco-friendly paving technologies. This research aims to investigate the mechanical performance (rutting and cracking resistance) and durability characteristics (resistance against moisture susceptibility) of long-term aged warm mix asphalt (WMA) mixtures containing reclaimed asphalt pavement (RAP), a WMA additive, an anti-stripping agent, and three chemically different recycling agents (RA) (an aromatic extract (A), a triglyceride/fatty acid (TF), and a tall oil (T)) through conducting the semi-circular bending (SCB) fracture, dynamic creep (DC), and indirect tensile strength (ITS) tests. Then, two-dimensional (2-D) and three-dimensional (3-D) performance interaction diagrams (PID) were used to identify asphalt mixtures with satisfactory performance in terms of moisture susceptibility, rutting failure, and fatigue cracking. Furthermore, an integrated environmental-economic comparison of the mixtures was conducted using a sustainability rating system developed by the authors. This system aims to identify cost-effective asphalt mix designs with lower CO2 equivalent emissions. The results of mechanical properties and Tukey’s honest significant difference (HSD) analysis indicated that the performance of RAP-blended mixtures is superior or equal to the performance of the mixtures without RAP when modified with RAs, WMA additive, and anti-stripping agent. Furthermore, the long-term aging performance of WMA mixtures containing RAP was significantly influenced by the RA' type. Results of economic and environmental analyses also indicated that virgin asphalt binder contributed the most to both cost burden and Greenhouse Gas (GHG) emissions, accounting for an average of 60% of the total cost and 45% of the total GHG emissions during the material and mixture production phase. Therefore, RAP recycling which decreases the need for virgin asphalt binder in addition to being replaced by a part of the required virgin aggregates is considered as one of the extremely environmentally friendly and cost-effective strategies. The environmental impacts of asphalt mixtures are significantly influenced by the choice of RAs, particularly when using a high RAP content. This study suggests that the utilization of tall oil and aromatic extract, as demonstrated, could be a better choice from an environmental perspective.

Evaluation of the Mechanical Performance of Asphalt Mixtures Containing Waste Tire Rubber and Graphene

Evaluation of the Mechanical Performance of Asphalt Mixtures Containing Waste Tire Rubber and Graphene

Effects of Environment-friendly Polymer Composite Modifiers on the Modulus and Pavement Performance of Asphalt Mixtures

Background: In the current context of low-carbon environment, it is particularly important to use waste plastics to prepare modifiers that increase the modulus of the bituminous mixture. Objectives: The study aimed to find out the influence of environment-friendly polymer composite modifier (E-FPCM) on modulus and pavement performance of bituminous mixture. Methods: The influence of the optimum component E-FPCM on the dynamic modulus (DM) has been explored. The E-FPCM content’s effect on the rheological properties of bitumen has been analyzed. Also, the influence of E-FPCM on pavement performance has been analyzed. Results: The degree of influence on SR of bituminous mixture has been in the order of recycled low-density polyethene (R-LDPE) > aromatic oil > lignin fiber. The optimum composition of E-FPCM has been found to be 10% aromatic oil, 4.8% C9, 62% R-LDPE, 7.0% lignin fiber, 0.2% antioxidant 1076, 2% silane coupling agent, and 14% mineral powder. By using E-FPCM with the optimum components, the SBS bituminous mixture or 90# bituminous mixture has been found to meet the standard of a high-modulus bituminous mixture (HMBM). E-FPCM has been found to reduce the phase angle (δ) of bitumen and increase the complex shear modulus (G∗) and rutting factor [G∗/sin(δ)], which may help improve the rutting resistance (RR). Conclusion: E-FPCM is beneficial for improving the RR of the bituminous mixture, and reasonable content of E-FPCM has a great role in improving the water stability (WS) and low-temperature crack resistance (LTCR) of the bituminous mixture.

Experimental study of asphalt mixtures with recycled resources: Influence of electric arc furnace slag aggregate roughness and bitumen film thickness on fatigue performance

Electric arc furnace slag (EAFS) is a viable alternative in asphalt mixtures due to its favourable mechanical properties. This study examines the impact of EAFS content and bitumen film thickness (TF) on the fatigue performance of asphalt mixtures. Mixtures with varying levels of EAFS replacement were designed, and their mechanical properties were evaluated through indirect tensile strength and stiffness tests, followed by fatigue tests using the four-point bending method and EBADE (Strain Sweep Test). The results indicated that mixtures with EAFS exhibited increased stiffness, but fatigue performance decreased at high strain levels. At low strain levels, EAFS mixtures performed similarly or better than the control. HMA_GL had the highest TF (13.97 μm), followed by HMA_GS (13.60 μm), HMA_SL (12.66 μm), and HMA_SS (11.77 μm), showing that as the EAFS content increases, the TF decreases. This finding was verified through Digital Image Analysis. This decrease in TF is due to the high porosity and roughness of the EAFS, which in turn reduces the effective bitumen (Pbe) in the mixture. HMA_SL*, with a TF equal to the control, demonstrated a 22 % improvement in fatigue performance compared to HMA_SL. In the EBADE tests, HMA_GL achieved 44.69 MJ/m3 of dissipated energy, HMA_GS 31.55 MJ/m3, HMA_SL 34.45 MJ/m3, and HMA_SS 35.54 MJ/m3. The improved HMA_SL* recorded 42.15 MJ/m3, nearly matching the control. EBADE results confirmed that higher EAFS content increased initial stiffness, but the complex modulus (|E*|) decreased more rapidly as deformation increased. These results are consistent with the stiffness tests. These findings suggest that EAFS can successfully replace natural aggregates in asphalt mixtures, with a moderate increase in bitumen content recommended to improve fatigue performance.

Investigation of fracture performance of asphalt mixtures considering size effect law and equivalent crack propagation law

The integration of the Size Effect Law (SEL) and the equivalent Linear Elastic Fracture Mechanics (LEFM) in characterizing the fracture behavior of asphalt mixtures has received limited attention. This study presents a preliminary exploration into the application of equivalent LEFM on the fracture characteristics of two asphalt mixtures, AC10 and AC16, accounting for variations in specimen size. Semi-circular Bending (SCB) tests were conducted on specimens with four different diameters (D = 76 mm, 100 mm, 125 mm, and 150 mm) and three notch-to-radius ratios (α = 0.2, 0.4, and 0.6) at a temperature of −10 °C. The equivalent crack propagation (ECP) length, crack growth resistance, and the size of the Fracture Process Zone (FPZ) were determined and subjected to analysis. The findings revealed a size effect on the ECP length, crack growth resistance, and FPZ size, with an increase in specimen size leading to a corresponding increase in these parameters. Conversely, an increase in α resulted in a decrease in all three types of data. A power law relationship was established between the ECP length and crack growth resistance. It was observed that AC16 demonstrated superior fracture resistance compared to AC10, particularly in terms of crack growth resistance. The initial notch length, ECP length, and FPZ size were found to be of the same order of magnitude, suggesting that the equivalent LEFM can produce more accurate fracture results under low temperatures than the traditional LEFM.

Upcycling Coal Gasification Slag to Enhance the Self-Healing Performance of Asphalt Mixtures

Upcycling Coal Gasification Slag to Enhance the Self-Healing Performance of Asphalt Mixtures

Evaluating the dynamic response and phase angle behavior of SBS-modified asphalt mixtures for enhanced pavement performance

Bitumen exhibits viscoelastic properties, showcasing both viscous and elastic behaviors, which are characterized by the phase angle and dynamic modulus. Issues like early fatigue fractures, rutting, and permanent deformations in bituminous asphalt pavements arise due to moisture susceptibility, high-temperature deformation, low-temperature cracking, and overloading. These distresses result in potholes, alligator cracks, and specific deformations that lead to early pavement failure, increasing rehabilitation and maintenance costs. To address these issues, this study examines the dynamic modulus and phase angle behavior of Styrene Butadiene Styrene (SBS) modified and unmodified asphalt mixtures. SBS was incorporated in various proportions, ranging from 2 to 7% by the weight of bitumen. The asphalt mixture performance tester (AMPT) was utilized to measure the dynamic modulus at temperatures of 4.4, 21.1, 37.8, and 54.4 °C, and frequencies of 0.1, 0.5, 1, 5, 10, and 25 Hz. The study found significant correlations between dynamic modulus, temperature, loading frequency, and SBS content. Additionally, Multi Expression Programming (MEPX) and regression modeling were employed to estimate the dynamic modulus of SBS-modified HMA. Results indicated that increasing SBS content up to 7% decreased penetration and ductility values by up to 46% and 56%, respectively, while raising the softening point by 63% due to increased stiffness. The blend with 6% SBS by weight of bitumen exhibited superior performance compared to other mixtures. Phase angle initially increased with rising temperature, peaking at 37.8 °C at lower frequencies, and continued to increase at higher frequencies. Isothermal and isochronal plots showed that the 0% SBS mix had a higher phase angle due to increased bitumen content. Overall, the HMA mix with 6% SBS provided the best outcomes.

Effect of different filler substitution ratios on the service performance of asphalt mixtures: Using coal-based synthetic natural gas slag as substitute filler

To investigate the effect of using coal-based synthetic natural gas slag (CNS) as a solid waste-based substitute filler on the service performance of asphalt mixtures, and validate its potential value as a substitute filler in asphalt pavements, thus the CNS powder (CNP) was selected as a solid waste-based substitute filler in this study, and then the variation trends of service performance of asphalt mixtures under different substitution ratios were evaluated by several mechanical tests. Subsequently, the grey relation analysis (GRA) model was conducted to explore the correlation between the different performance indicators and substitution ratios. The results indicate that the incorporation of CNP improved the high temperature performance of the mixture by 25.67–76.93 %, and increased its moisture stability by 15.44–26.99 %. Although the low temperature performance decreased by 0.54–6.19 %, it still met the required standards. Additionally, the incorporation of CNP enhanced the fatigue performance of the mixture by 3.39–7.64 %, while reducing its sensitivity to temperature and strain, and the dynamic modulus master curve constructed by using the Sigmoidal function accurately described the changes in the dynamic viscoelasticity of the mixture. A comparison study revealed that in different mixtures, the high temperature performance indicator consistently exhibited the highest correlation with filler substitution ratio, and this variation pattern was not influenced by filler type and substitution ratio.

Optimization Design of Cotton-Straw-Fiber-Modified Asphalt Mixture Performance Based on Response Surface Methodology

This research explored the application of cotton straw fiber in asphalt mixtures, aiming to optimize the asphalt mixtures’ performance. Firstly, 17 experiments were designed using Response Surface Methodology (RSM). Subsequently, the Box–Behnken Design (BBD) was used to examine how the asphalt content, fiber length, and cotton straw fiber content interacted to affect the modified asphalt mixes’ pavement performance. Based on the experimental findings, performance prediction models were created to direct optimization. The optimized design was then validated through pavement performance tests and bending fatigue tests. The findings revealed that cotton straw fiber content, length, and asphalt content significantly influence the performance of modified asphalt mixtures. The inclusion of cotton straw fibers enhanced various properties of the mixtures. When the fiber content was set at 0.3%, fiber length at 6 mm, and asphalt content at 5.3%, the response indicators, including Marshall stability, dynamic stability, flexural strength, and freeze–thaw strength ratio, were measured at 12.246 kN, 2452.396 times/mm, 12.30 MPa, and 92.76%, respectively. These results indicate that the cotton-straw-fiber-modified asphalt mixture achieved optimal performance while meeting regulatory requirements. Additionally, fatigue tests showed that the cotton-straw-fiber-modified asphalt mixture exhibited superior fatigue resistance compared with the SBS-modified asphalt mixture. The maximum error between the RSM predictions and the experimental measurements was within 10%, demonstrating the accuracy of the predictive models in estimating the impact of different factors on asphalt mixture performance. The application of RSM in designing and optimizing cotton-straw-fiber-modified asphalt mixtures proved to be highly effective, offering valuable insights for utilizing cotton straw fibers in road construction.

Performance evaluation of welded galvanized steel wire mesh reinforced asphalt pavements

Welded galvanized steel wire mesh is fabricated from longitudinal and transverse steel wires welded at specific intervals, followed by hot-dip galvanizing. To address the issue of asphalt pavement cracking, this study incorporates the welded galvanized wire mesh between the base and surface layers, thereby reducing the stress-strain levels of the pavement structure and mitigating the stress concentration at cracks. This results in a novel reinforced asphalt pavement structure. To validate the road performance of asphalt mixtures reinforced with welded galvanized steel wire mesh, this paper presents an indoor experimental study comparing various reinforcing materials: unreinforced, glass fiber geogrid, a polyester fiberglass geotextile, and 1.0 mm welded galvanized steel wire mesh. The results demonstrate that welded galvanized steel wire mesh significantly constrains asphalt mixture deformation under wheel loads, enhancing shear strength by 58.9 % compared to unreinforced asphalt mixtures, and exhibiting robust high-temperature deformation resistance. Moreover, the flexural tensile strength of asphalt mixtures reinforced with welded galvanized steel wire mesh increased by 36.3 %, and the maximum bending and tensile strains rose by 79.9 %, showcasing exceptional low-temperature crack resistance and crack propagation properties. Additionally, the fatigue life of the asphalt mixtures was markedly improved. Comprehensive analysis indicates that welded galvanized steel wire mesh is cost-effective, enhances the integrity and continuity of asphalt pavements, and extends their service life. Over the pavement's life-cycle, this method reduces overall investment, providing a robust basis for extensive application of welded galvanized steel wire mesh in asphalt highways.

Study on the properties and self-healing ability of asphalt and asphalt mixture containing methanol-modified melamine-formaldehyde microcapsules

Methanol-modified melamine-formaldehyde (MMF) microcapsules have been demonstrated as feasible for asphalt applications. However, the full range of their effects on asphalt and asphalt mixture performance remains unclear. To systematically address this, this paper synthesized MMF microcapsules via in situ polymerization and evaluated their impact on the temperature sensitivity, self-healing capacity, and fatigue resistance of both asphalt and asphalt mixtures. Additionally, three potential environmental factors (damage degree, healing time and healing temperature) influencing the self-healing ability of asphalt mixtures containing MMF microcapsules were assessed. The findings show that incorporating microcapsules enhanced the self-healing rates of asphalt and asphalt mixtures by 73.6 % and 119.2 %, respectively. While there was a moderate reduction in the low-temperature performance, the microcapsules contributed positively to anti-aging properties, fatigue resistance, and particularly high-temperature performance, evidenced by a 30.6 % increase in dynamic stability compared to matrix asphalt. Among the environmental factors considered, damage severity had the most significant effect on self-healing, leading to a notable reduction in healing rates.

Experimental investigation and statistical analysis of performance of ceramic fiber-reinforced warm asphalt mixtures containing reclaimed asphalt pavement

Asphalt recycling can help conserve natural resources while reducing associated costs. However, the production of hot mix asphalt (HMA) with reclaimed asphalt pavement (RAP) generates a high heat rate, leading to the stiffening of the asphalt binder and the release of toxic gases. Warm Mix Asphalt (WMA) is a cost-effective technique that softens and delays the aging of the asphalt binder while producing asphalt mixtures at lower temperatures, resulting in decreased energy usage and harmful pollutants. However, increasing the RAP content in WMA mixtures could have a detrimental impact on several asphalt mixture properties, such as fatigue and moisture resistance. Consequently, increasing the RAP content in WMA mixes could require devising a strategy to offset the drawbacks of RAP material. Fibers are recognized as one of the additives that are incorporated directly into the mixes and improve the fatigue and moisture resistance of asphalt mixtures. Therefore, this study is conducted to evaluate the impact of ceramic fibers (CFs) on the performance of WMA-RAP mixtures. The response surface methodology (RSM) was employed to find out how the CFs changed the responses of WMA-recycled asphalt mixes at low and intermediate temperatures. These responses included Marshal stability, rutting resistance, moisture susceptibility, and fatigue life resistance. RSM was used to find the best amounts of factors like CFs, WMA additive (Sasobit), and RAP using central composite design (CCD). The results of the analysis of variance (ANOVA) showed a significant interaction between the CFs, RAP, and Sasobit. The CFs significantly improved every studied attribute, particularly the fatigue life at 5 °C and 20 °C. The excellent value of the adjusted coefficient of determination (adjusted R2) of all responses indicates a excellent correlation between the model and experimental results. The outcomes of the validation test demonstrate that every response has a percentage error of less than 5 %, exhibiting strong agreement and the accuracy of the model.

Comprehensive Study on Dynamic Modulus and Road Performance of High-Performance Asphalt Mixture

Asphalt pavement durability significantly impacts the service life of roads, and hence, understanding the performance of high-performance asphalt mixtures is crucial. This study investigates the performance of four high-performance asphalt mixtures: heavy-load AC-20, high-viscosity AC-20, heavy-load SMA-13, and heavy-load SMA-10. Linear Amplitude Sweep (LAS) tests revealed that heavy-load asphalt mixtures exhibit superior fatigue resistances, with the fatigue life of heavy-load SMA-13 exceeding 1.5 times that of high-viscosity AC-20 under similar stress levels. Bending Beam Rheometer (BBR) tests at −6 °C, −12 °C, and −18 °C demonstrated that both heavy-load and high-viscosity asphalts had comparable low-temperature crack resistance, with heavy-load SMA-13 showing a stiffness modulus of 627 MPa at −18 °C. Marshall tests indicated that heavy-load AC-20 had the highest stability (14.3 kN) among the tested mixtures, while heavy-load SMA-13 exhibited the highest density (2.603 g/cm3). Dynamic modulus tests spanning a frequency range of 10−4 Hz to 105 Hz at various temperatures showed that heavy-load SMA-13 had a higher dynamic modulus than heavy-load SMA-10, particularly at lower frequencies (higher temperatures). Rutting tests at 60 °C indicated that heavy-load SMA-13 had the lowest rut depth (18.5 mm), outperforming other mixtures by up to 25%. The heavy-load SMA-13 asphalt mixture demonstrated the best overall performance, especially in terms of high-temperature stability, fatigue resistance, and rutting resistance. This study provides essential material performance parameters for the development of durable high-performance asphalt pavement structures.

Effects of clogging and cleaning on sound absorption performance of rubberized porous asphalt mixture

ABSTRACT The rubberized porous asphalt mixture (RPAM) has both the sound absorption capacity of air voids and the damping performance of rubber particles, which is a high-potential noise reduction pavement. However, the air voids are inevitably subjected to clogging, resulting in insufficient sound absorption performance. Moreover, it is not clear whether a large amount of rubber particles exacerbates the attenuation of sound absorption performance. Therefore, the purpose of the paper was to explore the attenuation law of sound absorption performance of RPAM under the action of multiple clogging cycles, and then optimise the preparation parameters to improve noise reduction durability. Constant head permeability test was carried out to simulate the clogging process, and manual and high-pressure washing were used to clean the clogged samples. The results showed that the attenuation process of sound absorption coefficient conformed to exponential function. The interconnected air voids were mainly clogged in the fast attenuation phase, and the open voids were clogged in the slow attenuation phase. It was more efficient to clean samples completely clogged than to clean samples clogged for three cycles. More importantly, rubber particles accelerated the attenuation of sound absorption performance during the clogging process. However, the noise reduction durability of RPAM optimised by orthogonal test was significantly improved, even better than that of porous asphalt mixture without rubber particles.

Field Performance of Asphalt Mixture Modified with Reactive Isocyanate Based Modifier

The reactive isocyanate-based modifier chemically reacts with asphalt components, overcoming the issues of increased viscosity and phase separation encountered with conventional modified binders. It can be used to modify binders to meet the highest performance grades currently specified by state highway agencies. This project aimed to demonstrate the constructability of an asphalt mixture modified with the reactive isocyanate-based modifier in the field and compare its performance with that of a control mixture. The project involved milling an approximately 5.0-cm (2-in) thick surface layer of two 30.5-m (100-foot) sections with similar foundation support. One section was resurfaced with a reactive isocyanate-modified mixture and the other with a conventional SBS-modified mix. The mixtures have shown no significant difference in field performance and laboratory performance test results. This study has provided insights into the field applicability of reactive isocyanate-based modifiers in asphalt mixtures, facilitating the ongoing efforts to develop durable road surfaces.

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

The severe agglomeration of Reclaimed Asphalt Pavement (RAP) particles not only leads to high gradation variability during recycling, but also impedes the miscibility between new-old binders. This phenomenon imposes significant limitations on maximizing the utilization of RAP with high content and value. This paper first realized the effective separation of asphalt milling material by the self-developed RAP refined processing equipment to obtain coarse RAP with low binder content and fine RAP with high binder content. The fine RAP with high binder content underwent a deep rejuvenation process, and the recovery efficiency of the asphalt mortar was evaluated by CT scanning test, microscope observation test, and dynamic shear rheology test. Moreover, to investigate the strength formation characteristics of recycled asphalt mixtures with high RAP content, specific tests including wheel tracking test, three-point bending test, Hamburg Wheel Tracking test, dynamic modulus test, and two-point bending fatigue test, were conducted. By using the refined processing equipment, the asphalt film on the RAP can be precisely removed, thereby addressing the issue of aged binder agglomeration. In the coarse RAP with low binder content, the binder content was reduced to 1.48 %, allowing it to be used as a direct substitute for new aggregate, whereas the binder content of fine RAP exceeded 10 %. It was found that the direct incorporation of unrefined RAP enhanced the high-temperature stability and dynamic modulus of recycled asphalt mixture, but impacted their low-temperature cracking resistance, moisture stability, and fatigue performance. After refined processing and differentiated recycling design, the agglomeration of aged binder was reduced and the miscibility of new-old binders was improved, effectively enhancing the comprehensive performance of the recycled asphalt mixture. It should be noted that the mixing homogeneity and miscibility decrease as the RAP content exceeds 75 %, resulting in the reduction of moisture stability, cracking resistance, and fatigue performance of recycled asphalt mixture.