Asphalt Concrete Research Articles

Physical, rheological and micro characteristics of ARA/Nano-TiO2 composite modified asphalt before and after short-term aging

This paper aims to investigate the composite application of nanomaterials and natural asphalt in order to enhance the road performance of asphalt pavement. The objective is to develop high-performance modified asphalt that improves the durability, reliability, and load resistance of asphalt roads while reducing resource waste and environmental pollution. The composite modified asphalt was prepared by adding different blends of Albanian natural rock asphalt (ARA) and 1% of nano titanium dioxide (Nano-TiO2), and the basic properties and rheological properties of the asphalt before and after aging were tested by using basic performance tests and temperature scanning tests. Subsequently, the microscopic morphological characteristics of the asphalt were observed by scanning electron microscope and atomic force microscope, and the number of bee structures, the area share of bee structures, root mean square roughness Rq, and arithmetic mean roughness Ra were used as microscopic quantitative indexes. The results indicate that the complex modulus and rutting coefficient of ARA/Nano-TiO2 composite-modified asphalt increase with an increase in ARA dosage when the dosage of Nano-TiO2 is 1%. The asphalt modified with Nano-TiO2 composite blended with 15% ARA exhibits higher residual needle penetration, composite modulus ratio, rutting coefficient ratio and lower softening point increment compared to 70# asphalt. The bitumen modified with titanium dioxide nanocomposite blended with 15% ARA exhibits higher Rq and Ra and a more stable phase structure before and after aging. 15% of ARA/Nano-TiO2 composite-modified asphalt has higher Rq and Ra before and after aging, and its phase structure is more stable. The results show that ARA/Nano-TiO2 composite-modified asphalt has better high-temperature deformation resistance and aging resistance than 70# and that 15% ARA is recommended as the optimum amount of composite-modified asphalt.

Optimizing waste management and enhancing asphalt performance: A sustainable approach using discarded baby diapers and face masks

This research introduces an innovative approach to address the management of waste Baby Diapers (BD) and Face Masks (FM) in order to mitigate environmental risks associated with the indiscriminate disposal of BD and FM waste. The study focuses on leveraging the utilization of BD and FM in road pavement hot mix asphalt (HMA) to enhance bitumen and aggregate performance, respectively. The approach involves the direct incorporation of 4% shredded BD during the bitumen melting process, while varying percentages of shredded FM (0%, 0.5%, 1%, and 1.5% relative to aggregate weight) are utilized as aggregate coating through a melting process. The inclusion of BD enhances the modified bitumen’s (MB) resistance to permanent deformations under high temperatures compared to conventional bitumen. Simultaneously, the treatment of FM significantly improves the physical and mechanical attributes of the aggregates. The combination of 4% BD and 1.5% FM results in improved densification, fostering robust bonding between aggregates and asphalt paste. This enhancement leads to a 39% increase in stability, a 18% increase in indirect tensile strength, and a 27% reduction in permanent deformations. Notably, there is a remarkable 53% increase in resistance to rut depth and a 33% increase in resilient modulus. Ultimately, the implementation of 4% BD as a bitumen enhancer and 1.5% FM as an aggregate modifier demonstrates the potential to achieve waste reductions of 36% and 61%, respectively. This approach extends beyond pavement enhancement, contributing to the broader societal mitigation of adverse effects associated with BD and FM waste.

Univariate and Multivariate Exploration of Resilient Modulus for Warm Mix Asphalt Mixtures

Univariate and Multivariate Exploration of Resilient Modulus for Warm Mix Asphalt Mixtures

Mechanistic Performance and Distress Model of Bottom Ash Modified Porous Asphalt Concretes with Various Thailand Aggregates

Mechanistic Performance and Distress Model of Bottom Ash Modified Porous Asphalt Concretes with Various Thailand Aggregates

Prediction of the Skid Resistance of Recycled Hot Mix Asphalt Mixture

Typically, the skid resistance of pavement surfaces is used to indicate road safety levels. The initial value and long-term behavior of skid resistance can be reportedly determined by modulating asphalt mixture properties during their mix design process. In this study, a skid-resistance prediction equation for recycled asphalt concrete was formulated based on ANOVA test results. An accelerated polishing device was used to replicate the abrasion encountered by road surfaces owing to vehicle–tire interactions for characterizing the skid resistance of recycled asphalt concrete. Notably, key parameters, including initial and terminal values and reduction rate of skid resistance induced by vehicle-related abrasion, were determined. These findings suggest that the initial values and reduction rate of skid resistance can be estimated from the mixed binder properties and initial MTD value. However, the final/terminal skid resistance predicted using aggregate gradations has a limited degree of confidence. To further improve the accuracy of the prediction equation, additional data collection and validation tests are required. In addition, field tests using recycled asphalt concrete are necessary to refine the accuracy and precision of the prediction equations for practical road construction scenarios. This study represents a significant step toward the development of safe and effective road infrastructure.

Recycling of copper tailing as filler material in asphalt paving mastic: A sustainable solution for mining waste recovery

Copper tailings are a category of solid waste discharged after the beneficiation process in mining plants. The significant concern raising stringent environmental issues give impetus to explore the multi-channel utilization of copper tailings in a sustainable manner. Concerning the fact that no study has systematically compared properties of copper tailings filled (CTP) asphalt mastic with conventional limestone filler mastic (LP) at different filler-to-asphalt ratios, multiscale and multi-dimensional comparisons between the characteristics of CTP-asphalt and LP-asphalt mastics were made in this study to thoroughly explore the feasibility and potential of recycling CTP as alternative filler in asphalt materials. Four ratios from 0.3 to 1.2 were used to manufacture asphalt mastics. The in-service pavement performance of asphalt mastics including resistances to rutting, low-temperature cracking and moisture damage was explored. Finally, the environmental and economic perspectives regarding the recycling of copper tailings are analyzed. Results indicate that CTP possesses a rougher surface, a larger specific surface area, and a more uniform pore size distribution than LP, particularly across the mesopores range. These characteristics could promote the adsorption of asphalt on its particle surface, potentially leading to enhanced filler-particle interaction. Regarding pavement performance, CTP-asphalt mastic outperforms LP-asphalt mastic in terms of high-temperature performance. Meanwhile, its low-temperature performance and moisture stability are only limitedly declined with the acceptable performance. Further, heavy metals leaching tests suggest that the risk for the substantial utilization of CTP in paving asphalt is absent. The related outcomes have verified the promising potential of CTP as an alternative candidate to substitute the conventional filler in paving asphalt from comprehensive consideration of in-service performance, and environmental and economic benefits.

Warm-Mix Asphalt Containing Reclaimed Asphalt Pavement: A Case Study in Switzerland

Among the technologies proposed for achieving carbon neutralization in asphalt road pavements, warm-mix asphalt (WMA) has garnered increasing attention in recent years. While WMA holds the potential for various environmental and technical benefits, a comprehensive understanding of its implementation, technology selection, and additives is essential for successful application. This study presents a case where a bio-based chemical additive was employed to produce WMA containing 50% reclaimed asphalt pavement (RAP) for a surface course in Bern, Switzerland. To minimize additional variables during testing and analysis, no other additive or rejuvenator was introduced into the mixtures. The testing plan encompassed laboratory tests on samples collected during material placement and recompacted at varying temperatures in the laboratory, as well as cores extracted from the job site. As anticipated, the presence of the chemical WMA additive did not alter the rheological properties of the reference bitumen. Although in the mixture-scale tests, the WMA mixture exhibited comparable properties to the control hot-mix asphalt (HMA), it is not expected that the small dosage of the chemical additive functions the same grade after reheating and compaction. Nevertheless, the cores extracted from the job site proved the efficiency of the applied WMA technology. In addition, consistent with existing literature, the cracking tolerance (CT) index values of 62 for HMA and 114 and 104.9 for WMA mixtures indicated that the latter is less susceptible to cracking. Consequently, this characteristic could contribute to the enhanced durability of asphalt pavements.

Analysis of the compactibility of bituminous mixtures for reflective crack relief interlayers (RCRI)

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

ASPHALT MIXTURES AND ASPHALT CONCRETE USING OIL RESIDUES AND BITUMEN MODIFIED WITH MALEIC ANHYDRIDE AND POLYETHYLENE GLYCOLS

A number of problems arise during the production and use of petroleum road bitumen. One of them is unsatisfactory performance characteristics, mainly heat resistance, plasticity, elasticity, and adhesion between the binder and the surface of the mineral material. With the increase in traffic intensity, the growth of heavy traffic volumes, the weight of cars, along with the impact of weather and climatic factors on the structure, this leads to the destruction of the road surface. One of the most promising areas in improving the quality of binders to obtain pavements with improved performance characteristics is their modification with polymeric materials. However, the use of modifiers is limited due to their high cost. Therefore, it is important to find inexpensive substances that would improve the performance characteristics of bitumen. This work is devoted to a completely new binder for asphalt mixtures, including crushed stone mastic mixtures. As a binder, we used raw materials for the production of bitumen - tar, modified with maleic anhydride and polyethylene glycol. The design of crushed stone and mastic asphalt mixtures using the obtained binders was carried out, and samples of crushed stone and mastic asphalt concrete were formed from them and tested. It was found that when binders were obtained from tar by modifying it with maleic anhydride and polyethylene glycol, crushed stone mastic mixtures with lower strength values were obtained compared to binders obtained by modifying oxidized bitumen. Comparison of crushed stone and mastic mixtures obtained using SBS modified bitumen and the studied binders showed that the use of the studied binders (oxidized bitumen modified with maleic anhydride and maleinized oxidized bitumen modified with polyethylene glycol) is characterized by lower water saturation and strength compared to the use of oxidized bitumen modified with SBS.

Effectiveness of Cashew Nut Shell Liquid as a Green Additive for Warm-Mix Asphalt

Effectiveness of Cashew Nut Shell Liquid as a Green Additive for Warm-Mix Asphalt

Research on noise reduction and data mining techniques for pavement dynamic response signals

Purpose This study aims to ensure reliable analysis of dynamic responses in asphalt pavement structures. It investigates noise reduction and data mining techniques for pavement dynamic response signals. Design/methodology/approach The paper conducts time-frequency analysis on signals of pavement dynamic response initially. It also uses two common noise reduction methods, namely, low-pass filtering and wavelet decomposition reconstruction, to evaluate their effectiveness in reducing noise in these signals. Furthermore, as these signals are generated in response to vehicle loading, they contain a substantial amount of data and are prone to environmental interference, potentially resulting in outliers. Hence, it becomes crucial to extract dynamic strain response features (e.g. peaks and peak intervals) in real-time and efficiently. Findings The study introduces an improved density-based spatial clustering of applications with Noise (DBSCAN) algorithm for identifying outliers in denoised data. The results demonstrate that low-pass filtering is highly effective in reducing noise in pavement dynamic response signals within specified frequency ranges. The improved DBSCAN algorithm effectively identifies outliers in these signals through testing. Furthermore, the peak detection process, using the enhanced findpeaks function, consistently achieves excellent performance in identifying peak values, even when complex multi-axle heavy-duty truck strain signals are present. Originality/value The authors identified a suitable frequency domain range for low-pass filtering in asphalt road dynamic response signals, revealing minimal amplitude loss and effective strain information reflection between road layers. Furthermore, the authors introduced the DBSCAN-based anomaly data detection method and enhancements to the Matlab findpeaks function, enabling the detection of anomalies in road sensor data and automated peak identification.

Automating the determination of low-temperature fracture resistance curves of normal and rubberized asphalt concrete in single-edge notched beam tests using convolutional neural networks

As materials undergo large-scale yielding or exhibit large sizes of fracture process zone in the crack tip region, multi-parameter fracture concepts should be employed to describe the complex crack-tip stress-strain fields. Fracture resistance curves (R-curves) are an established tool in characterizing the entire fracture process of such materials. However, for complex materials such as bituminous mixtures, the development of these curves is subject to experimental and computational intricacies. In this research, a framework is developed to automate the construction of R-curves for normal and rubberized asphalt concrete (AC) mixtures. AC mixtures are produced using PG58–22 and PG58–28 binders. Limestone and siliceous aggregates are used, and three binder contents are considered for the mixtures. Single-edge notched beam (SE(B)) fracture testing is conducted on AC beams with two different notch patterns. A convolutional neural network (CNN) model is developed and trained over 1260 test images with varying temperatures, notch geometries, and setups. The CNN model was used to detect the growing crack on the beam surface and each crack-detected image was sent to an image processing framework to measure the crack length. Crack extension increments were calculated and synchronized with test time and magnitude of load, load-line displacement, and cumulative fracture energy, and the R-curve could be constructed. A training accuracy of 0.91 was obtained for the model and a loss of below 0.10 as a result of a hyperparameter tuning indicating reliable classifications by the CNN architecture. The R-curves showed desirable agreement for control mixtures at temperatures of 0 °C and −15 °C. As the mixtures are rubberized, the R-curves showed favorable agreement in the crack blunting phase, transition zone, as well as the unstable propagation phase at −20 °C. Cohesive energy magnitudes were compared for the two methods with a Pearson coefficient of 0.81 while fracture rate and fracture energy magnitudes showed favorably close magnitudes with coefficients of 0.89 and 0.98 respectively.

Ensemble Learning Approach for Developing Performance Models of Flexible Pavement

This research utilizes the Long-Term Pavement Performance database, focusing on devel-oping a predictive model for flexible pavement performance in the Southern United States. Analyzing 367 pavement sections, this study investigates crucial factors influencing asphaltic concrete (AC) pavement deterioration, such as structural and material components, air voids, compaction density, temperature at laydown, traffic load, precipitation, and freeze–thaw cycles. The objective of this study is to develop a predictive machine learning model for AC pavement wheel path cracking (WpCrAr) and the age at which cracking initiates (WpCrAr) as performance indicators. This study thoroughly investigated three ensemble machine learning models, including random forest, extremely randomized trees (ETR), and extreme gradient boosting (XGBoost). It was observed that XGBoost, optimized using Bayesian methods, emerged as the most effective among the evaluated models, demonstrating good predictive accuracy, with an R2 of 0.79 for WpCrAr and 0.92 for AgeCrack and mean absolute errors of 1.07 and 0.74, respectively. The most important features influencing crack initiation and progression were identified, including equivalent single axle load (ESAL), pavement age, number of layers, precipitation, and freeze–thaw cycles. This paper also showed the impact of pavement material combinations for base and subgrade layers on the delay of crack initiation.

Laboratory and Field Performance Evaluation of Cracking of Airfield Warm Mix Asphalt with Reclaimed Asphalt Pavement at the National Airport Pavement and Materials Research Center

The U.S. Federal Aviation Administration is exploring initiatives to decrease transportation greenhouse gas emissions by developing carbon reduction strategies, including using low-embodied carbon materials, such as reclaimed asphalt pavement (RAP), in airport pavement construction. However, verifying RAP’s viability for airfield pavements with laboratory and field performance measures is essential. This study compared the cracking susceptibility of a P-401 hot mix asphalt and warm mix asphalt (WMA)+RAP airfield mixes using laboratory performance tests and conducted a preliminary evaluation of pavement responses from accelerated pavement testing (APT) fatigue tests. The observations and outcomes presented in this paper found that adding 20% of recycled materials with WMA additives had a decreasing impact in mix performance but did not overly affect the asphalt mix properties, as cracking properties from the different test procedures were found with comparable outcomes. Additional observations from strain gauges and temperature probes in the National Airport Pavement and Materials Research Center test cycle 2 APT fatigue test sections showed that the maximum tensile strains in the WMA surface lane 5 south section were consistently higher than those in the WMA+RAP lane 6 south section, which may be because of the higher load level that it was exposed. Additionally, the hardened or aged RAP binder in the entire lane 6 south section may have increased its stiffness, resulting in lower strain levels than in the lane 5 south section. Notably, both sections showed an increase in tensile strains with an increase in asphalt concrete temperature, which confirmed the temperature dependency behavior of asphalt concrete.

Laboratory and Environmental Assessment of Asphalt Mixture Modified with a Compound of Reclaimed Asphalt Pavement and Waste Polyethylene

The use of reclaimed asphalt pavement (RAP) in manufacturing asphalt concrete has become indispensable all over the world. This is due to the limited number of areas that are required to stockpile scraped pavement, as well as a lack of natural aggregate, which is necessary in manufacturing asphalt concrete. Thus, this research aims to evaluate the mechanical characteristics and environmental impact of using RAP and waste polyethylene in hot mix asphalt (HMA). RAP was added to hot mix asphalt in proportions of 25%, 50%, 75%, and 100% instead of the same amount of coarse aggregate. Then, the optimum RAP hot mix asphalt was modified by adding polyethylene in proportions of 1%, 2%, 3%, and 4% into the hot mix asphalt. The Marshall mix design was used to define the optimum asphalt content. As a final point in this experimental work, tests on the loss of stability, indirect tensile strength, and wheel loading tracking were performed to assess the performance of asphalt mixes modified with RAP and polyethylene in different conditions. A life cycle assessment (LCA) was applied using the ReCipe 2016 Endpoint method to evaluate the environmental impacts of these mixtures using the SimaPro software, V9.1. The laboratory tests showed that the mixture containing 50% RAP instead of the same amount of coarse aggregate and 2% polyethylene recorded better Marshall characteristics than the control mixture and the mixture with RAP alone. Finally, the modified hot mix asphalt with added RAP and polyethylene not only achieved superior performance in rutting, water damage resistance, and the stiffness modulus of bituminous mixtures, but it has been verified that there is no serious risk to the environment.

Preparation of Conductive Asphalt Concrete Based on the Action Mechanism of Conductive Phase Materials

Carbon fiber powder (CFP) was first applied to conductive asphalt concrete as a conductive phase material, but its action mechanism has not been clarified. In this paper, atomic force microscopy (AFM) and molecular dynamics (MDs) simulation are used to study the carbon fiber powder mechanism of action, guide the preparation of conductive asphalt concrete, and study the electrothermal properties of conductive asphalt concrete. The results show that carbon fiber powder weakens the adhesion property of asphalt mastic, and this weakening further strengthens in the water–temperature coupling, so water stability and conductivity are used as evaluation indicators to determine that the optimal content of carbon fiber powder is 2.0% and that the optimal content of carbon fibers (CFs) is 0.4%. Carbon fiber–carbon fiber powder conductive asphalt concrete with a resistivity of 0.98 Ω·m was finally prepared. In the temperature rise test of the Marshall specimen and rutting slab, its warming effect is obvious, and the heat transformation rate is more than 75%, so it has a very good ability to melt snow and ice.

Three-Dimensional Meso-Structure-Based Model for Evaluating the Complex Permittivity of Asphalt Concrete.

Microwave heating is an emerging alternative pretreatment method for road maintenance in cold seasons. The thermal behavior of asphalt pavement under microwave heating is mainly determined by the complex permittivity of the asphalt mixture. In this study, an innovative approach for calculating the complex permittivity of an asphalt mixture based on a three-dimensional meso-scale heterogeneous structure was proposed. A series of experiments was conducted to verify the accuracy of this approach. The effect of porosity, void size, moisture content and aggregate gradation on the complex permittivity for an asphalt mixture were computationally analyzed based on the validated approach. Moreover, the applicability of commonly used classical dielectric models was analyzed. The classical Lichtenecker-Rother (LR) dielectric model was modified on the basis of simulation data for various conditions. The results showed that the real part of the complex permittivity decreased with the increase in porosity. Some sudden change in the imaginary part of the complex permittivity was observed within the frequency range from 2.6 GHz to 3.9 GHz. A larger air void size would lead to a larger frequency at which sudden change occurs. The real part and imaginary part of the complex permittivity tend to be smaller when more coarse aggregates are replaced with fine aggregates. Both the real part and the imaginary part of the complex permittivity increase with higher moisture content due to the stronger dielectric property of water. Each 1% increase in moisture content would lead to about a 3~4% increase in the real part of the complex permittivity. The determination coefficients R2 for the real part and the imaginary part of the complex permittivity fitted by the modified Brown model were the maximum values, which were 0.922 and 0.980, respectively. The method presented in this study is useful for transportation agencies to optimize microwave heating during winter maintenance.

On the effect of nano calcium carbonate on the flexibility and tensile-shear cracking resistance of greener WMA asphalt concretes containing RAP contents

Asphalt mixtures are widely used materials for paving roads, however, they need a significant amount of virgin materials, and their preparation process is environmentally unfriendly. In this regard, using less harmful production processes and using recycled materials can be beneficial. In the current study, the cracking resistance parameters (fracture toughness and fracture energy) of warm mix asphalt (WMA) mixtures, prepared with high contents of reclaimed asphalt pavement (RAP) were investigated, while different contents of nano calcium carbonate (NC) were used as a modifier. The cracking resistance studies were done for the full range of mode I/II fracture conditions. From the results, it is seen, that the addition of RAP increases both fracture toughness and fracture energy, regardless of the mode mixity and NC contents (respectively by an average, of 30 % and 20 %). The NC also made the mixture more resistant to cracking, so the enhancement of fracture energy by up to 30 % and the enhancement of fracture toughness by up to 20 % is observed. The NC optimum content was calculated in the range of 2–4 % (in weight of binder), varied based on the considered variables. As a result of increasing the material’s brittleness by adding RAP and NC, the flexibility index showed a decrease. In separate evaluations, the effect of variables on strength parameters was studied statistically, showing that the fracture toughness in mode II, is about 1.2–1.5 times higher than fracture toughness in mode I. Also, theoretical frameworks were used to predict the trend of fracture data, showing the consistency of experimental results and theoretical predictions.

Development of a laboratory medium-term oven aging (MTOA) protocol with field validation for asphalt mixes containing RAP

In this study, laboratory loose mix oven aging was compared to field aging to begin calibration for a medium-term oven aging (MTOA) protocol. Five different oven aging temperatures were implemented at different durations to evaluate the change in chemical and rheological aging parameters for four plant-produced asphalt concrete (AC) mixes. The sulfoxide (SUL) index failed to show a consistent trend with aging for extracted binders obtained from both loose mixes and field slabs. The carbonyl area (CA) index was found to show a linear trend with the binders’ rheological parameters. The results of the field calibration indicate that loose mix oven aging of 20 h at 100 °C can simulate field aging at 0.5–0.6 in. (12 mm to 15 mm) depth after six years of pavement life in the climate region and for the material tested. Based on these results for a hot climate, loose mix aging of 20 h at 100 °C was proposed as the MTOA protocol for AC mixes for future studies.

The Effect of Recycled High-Density Polyethylene (HDPE) as an Additional Binder in Porous Asphalt Pavement

Porous asphalt has excellent permeability and larger air voids. Due to the low stability strength of asphalt binder with aggregates, Malaysia uses porous asphalt roads for lightweight vehicle road transportation. Numerous studies indicate utilizing Recycled High-Density Polyethylene in porous asphalt road surface. As a result, it was utilised as an additional binder material to enhance the asphalt binder. The main purpose of this study is to investigate the stability of modified porous asphalt samples and evaluate the optimum percentage of HDPE plastic waste from 3%, 6% and 9%. The aggregates, asphalt properties, Marshall Parameters and waster absorption test are in comply with JKR Standard and PWD 2008. At 3% of plastic addition has improved the stability of porous asphalt specimens. Adding plastic waste as a binder helps strengthen asphalt binding.