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Intelligent compaction (IC) technology based on the continuous compaction control (CCC) technology enables real-time monitoring, evaluation, and feedback of compaction quality. However, the lack of a viscoelastoplastic constitutive model of hot asphalt mixture under triaxial stress states, as well as the difficulty in simulating the time-varying characteristics of material properties, hinders the research and application of IC in asphalt concrete (AC) layers. Therefore, this paper proposes a viscoelastoplastic constitutive model for AC20 asphalt mixture and establishes a vibrating compaction numerical model for time-varying characteristics in material properties using finite-element modeling (FEM) analysis software Abaqus. Additionally, the stress state of the pavement was analyzed, and adjustment methods for vibrating compaction technology are proposed to further improve the compaction quality of the AC lower surface layer. Subsequently, the intelligent compaction measurement values (ICMVs) were calculated according to the acceleration and displacement response of the roller, and the reasons for the change in ICMVs were determined. Field test results verified that the established numerical model can realistically simulate the mechanical behavior of asphalt pavement under actual vibrating compaction conditions, thus providing a theoretical basis for the application of IC feedback control technology in AC lower surface layer. [ABSTRACT FROM AUTHOR]

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential "GWP") for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures. [ABSTRACT FROM AUTHOR]

When exposed to sun radiation and heat, asphalt binders age, resulting in reduced flexibility, cracking, and pavement failure. Given the increasing demands of traffic, environmental concerns, and resource scarcity, highway agencies and researchers are actively seeking solutions that meet performance requirements and demonstrate awareness of using non-renewable resources. Epoxy asphalt (EA) promotes sustainability concepts due to its production at significantly lower mixing and compaction temperatures, enhanced durability, improved serviceability, reduced maintenance needs, and successful recycling and reuse in hot asphalt mixtures. Crumb rubber, a widely recognized recycled waste tire material, is considered a viable option for promoting sustainability and enhancing asphalt binder properties. This study aims to enhance the durability and long-term performance of asphalt binders by utilizing sustainable materials. Six types of asphalt binders were employed: PG 67-22 base asphalt binder; styrene–butadiene–styrene (SBS)-modified PG 76-22 and PG 88-22H (3.5% and 7.0% dosage rates, respectively); a hybrid PG 76-22CS-modified asphalt binder prepared with SBS and crumb rubber modifiers; and 25EAB and 50EAB epoxy-modified asphalt binders prepared at 25 and 50% dosage rates, respectively. Results indicate that the sustainable asphalt binders PG 76-22CS, 25EAB, and 50EAB demonstrated comparable or superior performance compared to SBS-modified asphalt binders, as measured by rutting and fatigue factors. Additionally, epoxy asphalt binders had better anti-aging and cracking resistance, as shown by the outcomes of Fourier-transform infrared spectroscopy and linear amplitude sweep tests, respectively. This study contributes valuable insights into the potential of sustainable materials to enhance the overall performance and resilience of asphalt binders. [ABSTRACT FROM AUTHOR]

This paper is aimed to validate the trend between thermal-related parameters and field-measured thermal cracking. Field thermal cracking is collected from four projects with twelve pavement sections. The material properties include creep compliance m-value and tensile strength of mixture, and asphalt low-temperature performance grade (PG). A lower value of m-value and tensile strength leads to a higher thermal cracking, while the low-temperature PG has the contrary trend. One or even several material properties cannot fully characterize field thermal cracking for all projects. Then the change of material properties, pavement structures, and climatic conditions are considered in three-dimensional finite element models (FEM). The aging effect of material properties attributes to the increase of thermal stress. The placement of chip seal could greatly reduce the aging rate, and the thicker pavement result in less thermal stress. Both material property and thickness are important design factors for thermal cracking resistance. [ABSTRACT FROM AUTHOR]

There is growing interest in sustainable road pavement technologies to protect the environment and provide economic benefits. Post-consumer recycled (PCR) plastics are considered for construction to address the threat of plastic waste materials (PWM) and to improve sustainability. Asphalt pavement construction is highly considered for PWM recycling due to its large daily production. The purpose of this study is to investigate the performance of asphalt mixture containing PWM, specifically high-density polyethylene (HDPE), and compare its performance with two conventional mixtures. Three asphalt mixtures were considered: (1) mixture with asphalt binder PG 76-22 (SBS-modified); (2) mixture with asphalt binder PG 70-22 (SBS-modified); and (3) mixture with binder PG 67-22 and 3% HDPE (the plastic mixture). The rheological properties of the modified asphalt binders and the performance of the modified asphalt mixtures were evaluated. The long-term field performance of the pavements was modeled using AASHTOWare software (v.1.1.6) for the three mixtures considered. The results showed that all the mixtures were able to comply with the cracking threshold specified by the Louisiana Department of Transportation and Development (LaDOTD) for high-traffic volume roads. In addition, the plastic asphalt mixture showed similar performance to the one containing PG 70-22 (SBS-modified) asphalt binder. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the efficiency of an innovative light-induced self-healing polymers in enhancing the durability of asphalt mixtures and improving its self-healing properties. Mixtures were prepared using two different binders, with and without recycled materials, and self-healing polymer. Results showed that the addition of recycled asphalt material to mixtures prepared with an unmodified binder negatively affected the healing recovery at room temperature. Furthermore, Self-healing properties of the mixtures were improved by increasing the healing temperature. The addition of 5% self-healing polymer to the control mixture, followed by UV light exposure resulted in an increase in self-healing properties of the mixtures prepared with PG 67-22 binder. Semi-Circular Bending (SCB) test results showed that the incorporation of self-healing polymer and 48 h of UV light exposure improved the cracking resistance. Loaded-Wheel Test (LWT) results showed that the self-healing polymer caused an increase in the rut depth of the samples prepared with an unmodified binder. However, the final rut depth was less than the acceptable rutting performance. Thermal-Stress Restrained Specimen Test (TSRST) test results showed that self-healing polymer improved the low temperature cracking performance of the mixtures.

Self-healing products such as hollow-fibers filled with an asphalt rejuvenator present an emerging technology that would enhance an asphalt mixture’s resistance to cracking damage. The objective of this study was to evaluate the rejuvenating efficiency of sodium-alginate fibers containing a rejuvenator product using asphalt binder blends containing extracted binder from recycled materials. The effects of adding extracted binder from recycled materials and sodium-alginate fibers on asphalt binder blends were evaluated by conducting a series of chemical and binder tests. HP-GPC and FTIR test results showed that the addition of fibers in blends containing recycled materials resulted in an increase in the HMW/LMW ratios. Some of the added polymeric fibers are thought to have increased the HMW fraction, thus leading to increase in the HMW/LMW ratio. The increase of the HMW fraction suggests that some of the fibers, which are polymers, caused the increase in the HMW/LMW ratios. MSCR test results showed that a binder blend with extracted binder from recycled materials and sodium-alginate fibers would have less rutting susceptibility than a conventional virgin binder would.

This study evaluates field asphalt aging based on material property changes in pavement with time, and investigates if such changes could have an impact on field rutting performance. Four projects from three different climate zones were monitored as part of the NCHRP 9–49A project at two stages: during pavement construction and two to three years after opening it to traffic. Construction information were collected, and field cores were drilled at both stages to evaluate the material properties of recovered asphalt binder and asphalt mixture. Field rut depth was also measured. In addition, pavement structure, climate and base/subgrade modulus information were also obtained. Results indicate that the asphalt mixture stiffening is caused in major part by asphalt aging. However, the effect of asphalt aging on pavement mixture property may not follow a proportional liner trend. The parameters that are most sensitive to field ageing are MSCR R3.2 and dynamic modulus. It is also found that the variables which showed a good ranking trend with the field rut depth are climate condition (relative humidity, high temperature hour, solar radiation), material properties (Hamburg rut depth, rutting resistance index, high temperature performance grade, MSCR, and dynamic modulus, base and subgrade moduli), as well as air voids. [ABSTRACT FROM AUTHOR]

The main objective of this study was to establish the relationship between asphalt binder deformation properties at intermediate and low temperatures, its molecular compositions, and mix performance. To achieve this objective, nine straight binders obtained from two asphalt suppliers were tested using the ductility and the direct tensile tests. To assess the results of these tests, selected asphalt binders were evaluated using high pressure gel permeation chromatography (HP-GPC), differential scanning calorimetry (DSC), and dynamic mechanical analysis. Measurements showed that an inverse correlation exists between binder ductility at intermediate temperatures and failure strain at low temperatures. In other words, a binder that provides high ductility at intermediate temperatures would be characterized by poor elongation properties at low temperatures. This trend was related to the binder molecular compositions as characterized by HP-GPC. An increase in the binder content of low molecular weight results in an increase in its ductility at intermediate temperatures. However, an increase in paraffinic maltene content results in the binder tending to crystallize at higher temperatures as it approaches the glassy region. This was confirmed through DSC measurements, which showed that an increase in crystalline fractions may have a negative impact on the binder stiffness at low temperatures. In general, physical properties of the binder can be strongly linked to its molecular constituents. In addition, there was a positive correlation between the binder ductility and the measured tensile strength of the mixture as well as its strain at failure. Using a binder with a high ductility resulted in a mixture with greater indirect tensile strength and a stronger ability to resist cracking at intermediate temperatures. DOI: 10.1061/(ASCE)MT.1943-5533.0000138 CE Database subject headings: Asphalts; Binders, material; Ductility; Temperature effects; Deformation. Author keywords: Asphalt binder; Ductility; Direct tensile test; Molecular composition.

Field and laboratory testing programs were conducted to develop an efficient methodology for estimating resilient modulus ([M.sub.r]) values of subgrade soils for use in the design of pavement structures. The field testing program consisted of obtaining Shelby tube samples of subgrade soils from different pavement projects throughout Louisiana. The laboratory program included conducting repeated load triaxial M,. tests as well as physical property tests on the collected samples. The validity of the correlation equations developed by the long-term pavement performance (LTPP) to predict the Mr was examined. In general, the LTPP model underestimated the values of M,. coefficients obtained in this study. A comprehensive regression analysis was conducted to develop models that predict the M,. coefficients of different subgrade soils in Louisiana using different physical properties. A good agreement was observed between the measured and predicted Mr coefficient values. Furthermore, the developed models had a better prediction of measured Mr coefficient values than the LTTP models. Finally. a catalog of resilient modulus of subgrade soils at different moisture content levels was developed. DOI: 10.1061/(ASCE)MT.1943-5533.0000073 CE Database subject headings: Resilient modulus; Subgrades; Pavements; Design. Author keywords: Resilient modulus; Subgrade soils; Pavement design; MEPDG; Regression models.

To facilitate the use of recycled materials in pavement construction, a mechanistic-based approach is required to better characterize pavement base materials. This paper demonstrates the application of the shakedown theory to characterize the behavior of traditional and recycled base materials based on laboratory repeated load triaxial (RLT) tests and full-scaled accelerated loading tests. A new approach that is based on dissipated energy is proposed to explain different shakedown responses of tested materials under repeated loading. The dissipated energy approach illustrated that there are two responses during RLT tests, namely, stable and unstable responses, which are dependent on the loading levels and type of tested material. It was also observed that the transition from the stable to unstable response represents gradual microstructural adjustments of tested materials to accommodate the applied loading. This gradual transition explains the difficulties in identifying some material responses within the shakedown theory based only on the permanent strain rate criteria. Based on the results of this study, a mechanistic-based design procedure to incorporate various recycled materials into pavement bases is recommended. DOI: 10.1061/(ASCE)0733-947X(2010)136:3(214) CE Database subject headings: Energy dissipation: Deformation; Pavements; Base courses; Recycling; Triaxial tests; Resilient modulus. Author keywords: Dissipated energy; Permanent deformation: Pavement base courses: Recycled materials: Repeated load triaxial tests; Resilient modulus; Shakedown theory.