Durability Of Asphalt Research Articles

Effect of air voids on the fracture resistance of HMA in the indirect tensile cracking (IDEAL-CT) test

ABSTRACT Air voids (density) is a key volumetric property of asphalt mixes and play an unignorable role in anti-cracking. While lower voids were expected to result in more durable asphalt mixtures, contradictory trends were found in lab testing. In this study, several plant-produced mixtures were compacted to three levels of air voids (7%, 9%, and 11%) and tested to evaluate the sensitivity to the crack resistance. The results indicate that the higher the air voids, the better the cracking resistance as measured by the CTindex. To understand the cause, a stepwise regression analysis was conducted to model the IDEAL-CT parameters with volumetric and gradation parameters. The air void, percent passing the 0.6 mm (P0.6) and binder content (Pb) are found to have significant effects on CTindex and post-peak slope. The analysis of the CT change rate shows that the Pb, dust to binder ratio (D/B), and P0.6 can be used to predict the effect of the voids with a correlation factor (R2) of 0.96. For further understanding, the asphalt film thickness was calculated and found that compared with using film thickness as the single fitting parameter, combining the film thickness with D/B in modelling can dramatically increase the R2 of correlation from 0.67 to 0.92.

Feasibility of Sustainable Asphalt Concrete Materials Utilizing Waste Plastic Aggregate, Epoxy Resin, and Magnesium-Based Additive.

This research addresses the urgent need for sustainable and durable asphalt mixtures by quantitatively investigating the effects of incorporating waste plastic aggregate (WPA) and magnesium-based additives. This study explores WPA content levels of 3%, 5%, and 7% wt of aggregate in combination with a fixed 3% wt epoxy resin content to the asphalt binder, supplemented with the 1.5% wt magnesium-based additive. The novelty of this research lies in its comprehensive analysis of various performance parameters, including deformation strength, indirect tensile strength (ITS), rut depth, and dynamic stability, to assess the impact of WPA, epoxy resin, and the magnesium-based additive on asphalt mixture properties. The results demonstrate significant improvements in key performance aspects with increasing WPA content. The WPA mixtures exhibit enhanced deformation strength, with values of 4.01, 3.7, and 3.32 MPa for 3, 5, and 7% wt WPA content, respectively, compared to the control mixture. Furthermore, the inclusion of WPA and epoxy resin, along with the magnesium-based additive, contributes to improved adhesion, cohesion, and resistance to stripping damage. Notably, the 7% wt WPA mixture showcases exceptional performance, characterized by a final rut depth of 2.66 mm and a dynamic stability of 7519 passes per millimeter, highlighting its superior rutting resistance and load-bearing capacity. This study also reveals the influence of WPA content on ITS and stiffness properties, with the 5% wt WPA mixture achieving an optimal balance between strength and stiffness. Overall, this research highlights the potential of incorporating WPA, epoxy resin, and magnesium-based additives in asphalt mixtures to enhance their performance and durability. By utilizing plastic waste materials and optimizing their combination with epoxy reinforcement, along with the innovative use of magnesium-based additive, the findings contribute to the development of sustainable infrastructure materials and pave the way for further advancements in the field.

Mitigating Stripping in Asphalt Mixtures: Pretreatment of Aggregate by Thermoplastic Polyethylene Powder Coating

Thermoplastic polyethylene (PE) powder coating is proposed as a new technique to pretreat the aggregate of asphalt mixtures and improve the corresponding moisture resistance. In this paper, ethanol solution is investigated as a fluidized bed to disperse the PE powder. The surface tension of the solution, indicating the wettability of the liquid phase, decreases with increasing ethanol concentration and temperature. The PE powder could be stably dispersed into the solution when 15% ethanol solution heated to 40 to 50°C is used to reduce the surface tension of liquid to less than 40 mN/m. The suspension carrying the PE particles could be uniformly sprayed onto a hot aggregate surface (180–190°C) where the liquid phase evaporates fast while the PE powder melts and stays. The powder coating technique could prevent the aggregate from lumping and achieve a high-quality and efficient coating for aggregate. The PE monolayer model considering a hexagonal close packing of PE on aggregate surface is tentatively proposed to determine the theoretical amount of PE required to perfectly coat the aggregate. The predicted PE content was reasonably lower than that determined by the experimental results considering the ideal monolayer coating was hard to achieve. However, the modeling results could be used to determine the lower bound of the required PE content. The optimum PE content significantly increased with increasing particle size of PE and specific surface area of aggregate. The use of high-density polyethylene (HDPE) powder with a smaller particle size was more effective in the coating process. In addition, excessive PE could not further enhance the moisture resistance of asphalt mixtures efficiently. This study can contribute to both the recycling of waste plastic and the construction of durable asphalt pavements.

Effect of Aggregate Gradation on Asphalt Concrete Properties

Economic expansion is a positive side effect of national highway construction initiatives. So, the plan is to construct these projects rapidly. This calls for premium asphalt. As a result of aggregate gradation variation, numerous asphalt mixes have been rejected and rebuilt on-site in recent decades, resulting in the waste of valuable resources and valuable time. Consequently, the goal of this study was to examine the durability of asphalt mixes where the aggregate gradation ranged from +4% above to 2% below the standard range. The aggregate gradation is inconsistent throughout HMA manufacture. The aggregate is graded at 2, 4, and 6 percent over and below the allowed range. Case in point: the gradation of the control mix design. Marshall There was a quantitative evaluation of mixed properties throughout the design phase. HMA mix performance was evaluated via high temperature and water cycles by vehicle pressure observation and Indirect Tensile Strength (ITS) testing. In hot climates, asphalt with gradations above +4% and 2% of both the higher and lower standard values showed the greatest resilience to water damage and the least rutting. In warm regions, asphalt mixture design will be constrained by the higher aggregate gradation limits.

Evaluation of the Effect of Thermo-Oxidative Aging and UV Radiation on Asphalt Stiffness.

The complex factors during the asphalt production process and subsequent traffic loading, climatic and weather conditions lead to a decrease in durability of asphalt thereby reducing pavement surface service life. The research focused on the effect of thermo-oxidative aging (short and long term), ultraviolet radiation and water on stiffness and indirect tensile strength of asphalt mixtures with 50/70 and PMB45/80-75 bitumen. The stiffness modulus at different temperatures (10, 20 and 30 °C) using the indirect tension method and indirect tensile strength have been evaluated in relation to the degree of aging. The experimental analysis showed a significant increase in the stiffness of polymer-modified asphalt with increasing aging intensity. Exposure to ultraviolet radiation adds to an increase of 35 to 40% in stiffness for unaged PMB asphalt and 12 to 17% for short-term aged mixtures. Accelerated water conditioning reduced the indirect tensile strength of asphalt by an average of 7 to 8%, significant in long-term aged samples using the loose mixture method (9 to 17%). The indirect tensile strengths for dry and wet conditioning showed greater changes due to the degree of aging. An understanding of the changes in asphalt properties during design allows for predicting asphalt surface behaviour after a period of use.

Uncertainty analysis of life cycle assessment of asphalt surfacings

The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data, deterministic solution, and asphalt durability. This framework was applied to six asphalt mixtures; the results show that there is significant uncertainty in the processes that contribute to the environmental impacts. They also showed that considering asphalt durability and its uncertainty is critical and can significantly change the results and interpretation of LCA.

Integrating Quality Assurance in Balance Mix Designs for Durable Asphalt Mixtures: State-of-the-Art Literature Review

Delivering durable asphalt concrete within a reasonable cost is one of the great ambitions of pavement material engineers. This state-of-the-art review article documents the efforts spent in the past two decades to ensure the durability and performance of asphalt mixtures in mix design and production. A perspective with the attempt to integrate laboratory mix design, plant production quality assurance, and field place acceptance is applied in the review. The development of the performance specification and performance mix design is summarized. The paper categorizes performance specification into index-based performance specification and predictive performance specification that include performance-related specification and performance-based specification. The approaches to developing index-based performance mix design/balanced mix design and predictive performance mix design are also compared in the review. The challenges and solutions in incorporating performance tests in asphalt productions are documented and discussed. The challenges include selecting performance testing methods, determining index threshold limits, estimating and incorporating testing variability and uncertainty, determining sampling position and testing frequency, and so forth. The paper also provides suggested areas of future research and implementation activities.

Cleaner Asphalt Production by Suppressing Emissions Using Phenolic Compounds

Asphalt-paved surfaces have been reported as an important and long-lasting potential source of emissions of a complex mixture of volatile organic compounds into the atmosphere. Accelerated aging of asphalt under high temperatures and sunlight exposure is closely related to the mass loss due to asphalt-related emissions. This paper studies the capability of biomodifiers to retain oxygenated compounds in bitumen and thereby extend bitumen’s durability. It is hypothesized that phenolic compounds of biomodifiers enhance intermolecular interactions with oxygenated compounds that would otherwise be released to the atmosphere as bitumen ages. Computational modeling based on density functional theory (DFT) confirms the capability of phenolic compounds in bio-oil from wood pellets (WPs) as a modifier for bitumen to interact with bitumen’s volatile oxygenated compounds through strong hydrogen bonding. DFT-based energy results show that the efficacy of a phenolic molecule to trap bitumen’s oxygenated compounds is influenced by its molecular structure and substituents attached to the phenolic moiety; electron donor groups such as −CH3 and −OCH3 can enhance the scavenging activity of phenolic compounds. Molecular modeling also shows that the interacting complexes formed between bitumen’s oxygenated compounds and WP’s phenolic components are more thermodynamically favored than complexes formed by these volatiles and non-phenolic molecules in waste vegetable oil (WVO). Laboratory experiments confirm the delay in UV aging of biomodified rubberized bitumen containing wood-pellet bio-oil (WP-BMR) by showing lower values for aging indexes based on rheological properties (the crossover modulus and frequency, the complex modulus, activation energy, and a rutting indicator) compared to the rubberized bitumen containing a low-phenol WVO biomodifier (WVO-BMR). Therefore, the extent of aging varies between two biomodified bitumen samples depending on the biomodifier’s source and chemical composition. This study’s outcomes show how to improve the durability of asphalt by tuning bitumen’s aging resistance using phenol-rich biomodifiers made from lignin-based biomass. This can be a key to open a doorway to resource conservation and sustainability in the construction industry while maintaining or enhancing air quality.

Effect of nanomaterials on the durability of hot mix asphalt

Traffic volume and loads have increased significantly in recent years, coupled with the high summer temperature and the low temperature in winter, premature failure in asphalt concrete pavement becomes the main challenge for pavement construction companies and engineers. The use of modifiers in asphalt concrete mixes become of considerable interest in the improvement of pavement performance and service life. With the advent and evolvement in nanotechnology, many researchers focused on how these materials could serve in rising the serviceability of pavement in terms of reducing rutting, fatigue cracking as well as moisture induced damage. In this study, nanomaterials, including nano silica (NS), nano carbonate calcium (NCC), nano clay (NC), and nano platelet hydroxyapatite (NP), were used to examine the prospect of enhancing the durability and resilience of asphalt mixtures. Specifically, this study aimed to evaluate the effect of adding nanomaterials as a modifier to the bitumen on the Marshall properties, resilient modulus as well as the durability of the asphalt concrete mixture, which was assessed for moisture susceptibility using indirect tensile strength (ITS) and permanent deformation using the uniaxial repeated load test. The investigated nanomaterial dosages were as follows; NS (1, 3 and 5%), NCC (2, 4 and 6%), NC (3, 5 and 7%), and NP (2, 4 and 6%), by weight of asphalt cement. The results were compared with the control mix (CM), i.e., an unmodified mix. The results revealed that nanomaterials significantly improved the properties of asphalt concrete. Also, this work provides a basis for producing more durable mixtures with higher resistance to distress.

Effect of Hydration Products on the Interfacial Bonding Properties between Asphalt Binder and Steel Slag Coarse Aggregate

Steel slag needs aging treatment before being used for the coarse aggregate of asphalt mixtures because it has volumetric instability due to the hydration of calcium oxide. This paper investigates the effect of hydration products on the bonding properties between asphalt binder and steel slag coarse aggregates subjected to natural aging treatment. A scanning electron microscope, a fluorescence microscope, and X-ray diffraction testing were used to study the surface morphology, microstructure, and mineral phase of the hydration product layer generated on the aggregate surface of steel slag. A modified water boiling test was conducted to evaluate the water stripping resistance of asphalt film with different boiling times. Pull-off testing on real steel slag aggregates was performed to investigate the effect of the hydration product layer and surface treatment on the bonding strength and interface failure mode. Test results indicated that the hydration products exhibited a loose and porous structure and formed an interlayer to prevent the asphalt film from directly adhering to the aggregate surface of steel slag. The hydration product layer could improve the initial stripping resistance but impair the long-term stripping resistance with increased boiling time. The interlayer of hydration products tended to be the weakest link between asphalt film and steel slag aggregate when subjected to pull-off strength damage. The bonding strength showed a negative linear relation with the stripping rate of asphalt film. After steel slag surface treatment with water-based capillary inorganic waterproofer, the pull-off failure of hydration product layer was avoided and thus improved the bonding strength between asphalt film and steel slag aggregate. The bonding strength and failure mode between asphalt-slag adhesion could be well examined by using pull-off tests. Better insights into asphalt–slag adhesion are useful to design durable asphalt mixtures containing steel slag aggregate.

Rheological Properties and Microstructural Analysis of Asphalt Binder Doped with Anti-Stripping Agent after Aging

In order to comprehensively explore the long-term durability of asphalt mixed with an anti-stripping agent, laboratory tests were carried out on base asphalt, SBS modified asphalt and base asphalt mixed with an anti-stripping agent after long-term aging. The rheological properties, chemical composition and microscopic morphology of the three asphalts before and after aging were compared and analyzed from macroscopic and microscopic angles. The results show that the modulus of asphalt is more affected by temperature than aging, and the anti-aging ability of the asphalt with the anti-stripping agent is better than that of base asphalt and slightly worse than that of SBS modified asphalt. The change in the absorption peak intensity before and after the aging of asphalt with the anti-stripping agent is the same as those of the base asphalt and SBS modified asphalt at 2920 cm−1 and 2850 cm−1, while the opposite pattern is observed in other four places. The honeycomb structures of the base asphalt and SBS modified asphalt became longer and the number of peaks increased slightly after aging. However, the asphalt surface with the anti-stripping agent had no obvious honeycomb structures before aging, and there were obvious honeycomb structures after aging, the number of which was between those of the base asphalt and SBS modified asphalt after aging; moreover, the lengths of honeycomb structures were still significantly smaller than those of the base asphalt after aging. This study investigated the performance changes of the anti-stripping-agent asphalt before and after long-term aging at multiple scales and compared the asphalt mixed with the anti-stripping agent with base asphalt and SBS modified asphalt to fully evaluate its long-term durability.

Comparing the Effect of Thermal-Oxidation and Photo-Oxidation of Asphalt Mixtures on the Rheological and Chemical Properties of Extracted Bituminous Binder.

The reliable and representative ageing of asphalt samples in the laboratory is critically important to research on asphalt durability, waste material recycling and rejuvenation treatments. However, standard laboratory ageing protocols omit ultraviolet radiation and moisture, and are also based on a universally applied oven temperature and ageing duration. The aim of this research was to demonstrate the importance of ultraviolet radiation in laboratory asphalt aging, motivated by the need for more realistic ageing protocols. Asphalt cores were thermally aged in a standard laboratory oven for 98 days, while other cores were aged for the same period in a weathering chamber that combined thermal–oxidative (heat) and photo-oxidative (ultraviolet irradiation) aging. The bitumen was then extracted from the top, middle and bottom of each asphalt core, and tested for rheological, chemical, and compositional properties. The results were used to compare the effects of the aging protocols, and the effects of depth below the pavement surface. It was concluded that accelerated laboratory asphalt ageing must include photo-oxidation, in combination with thermal oxidation. It was also concluded that both chemical and rheological properties were effective indicators of extracted asphalt binder aging, although the rheological testing was preferred.

Effect of freeze–thaw cycles on the void topologies and mechanical properties of asphalt

Frost and thawing damage asphalt in cold climates. Water that enters the pores of asphalt at low temperatures may accelerate its degradation. Water can expand into pores, altering the void content and shape, thus affecting the asphalt's internal structure and fracture properties.We can develop more durable asphalt types if we understand how void topology changes with freeze–thaw cycles.The purpose of this study is to establish a correlation between the mechanical properties of asphalts and the topological properties of voids. To determine their internal structure, various asphalt types representing dense asphalt and asphalt with voids were made and X-rayed before and after each freeze–thaw cycle. We also obtained the mechanical properties of asphalt and correlated them with the void properties. It was found that dense asphalt has the lowest degradation rate in wet conditions characterised by non-connected gaps, which was approximately constant with freeze–thaw cycles; however, dense asphalt was least durable under dry conditions compared with asphalts with more voids. Due to its high water retention rate, asphalt with a 10% void content degraded at an accelerated rate during the initial cycles. As a result of bigger voids, asphalt with a higher pore content plateaued in later cycles due to reduced water retention. This study demonstrates that the internal void topology affects the mechanical properties of asphalt during freeze–thaw cycles.These results can be used to understand changes in asphalt mechanical losses resulting from freeze-thaw cycles and to validate numerical models to perform parametric studies of the asphalt's freeze–thaw degradation.

Advanced Self-Healing Asphalt Reinforced by Graphene Structures: An Atomistic Insight

Graphene can improve the self-healing properties of asphalt with high durability. However, the self-healing behaviors of graphene-modified asphalt nanocomposite and the role of incorporated graphene are still unclear at this stage. In this study, the self-healing properties of pure asphalt and graphene-modified asphalt are investigated through molecular dynamics simulations. Asphalt bulks with two crack widths and locations for graphene are introduced, and the molecular interactions among asphalt components and the graphene sheet are analyzed. The results show that the location of graphene significantly affects the self-healing behaviors of asphalt. Graphene near the crack surface can greatly accelerate the self-healing process by interacting with the aromatic molecules through π-π stacking, while graphene at the top area of the crack tip has a minor impact on the process. The self-healing process of asphalt goes through the reorientation of asphaltene, polar aromatic, and naphthene aromatic molecules, and the bridging of saturate molecules between crack surfaces. This in-depth understanding of the self-healing mechanism contributes to the knowledge of the enhancement for self-healing properties, which will help to develop durable asphalt pavements.

Effect of morphology characteristics on the polishing resistance of coarse aggregates on asphalt pavement

Skid resistance performance of asphalt pavement is an important factor affecting the traffic safety. The long-term skid resistance performance of asphalt pavement depends on abrasion and polish resistance of aggregates. However, the mechanical properties and surface morphological characteristics of aggregates not only affect the road bearing capacity, but also impact the long-term abrasion and polish resistance of asphalt pavement. In this study, the mechanical properties of limestone, basalt, granite and 88 # calcined bauxite were investigated. The macro morphology characteristic parameters (MACP) of coarse aggregates were obtained by Image Pro Plus (IPP) software analysis with strong applicability, and the distribution models and characteristics were further analyzed. In order to present quantitatively the dynamic change process of the macro and micro morphology characteristics of coarse aggregates with the polished stone value (PSV) during the polishing process, a long-term polishing test was carried out on the coarse aggregates. The MACP and micro morphology characteristic parameters (MICP) of coarse aggregates were obtained by the IPP analysis and three-dimensional laser microscope. The grey relation entropy analysis method was used to analyze the correlation degree between morphological characteristic parameters and PSV. The results show that the contents of corundum and mullite in 88 # calcined bauxite are 85.2% and 14.8% severally. Corundum and mullite have the highest Mohs hardness, 9 and 6 respectively. The IPP analysis is suitable for quickly obtaining the MACP of coarse aggregates, and the MACP distribution of four kinds of coarse aggregates satisfies well normal distribution. In addition, in the process of PSV attenuation, the grey entropy correlation coefficients between PSV and fractal dimension, Rq are the highest, 0.9037 and 0.8882 respectively. The fractal dimension of MACP and Rq of MICP are selected as the main various indexes. Meanwhile, the average correlation coefficients of fractal dimension, Rq and PSV are 0.9589 and 0.9809 separately. Therefore, the fractal dimension and Rq are proposed to evaluate the long-term polishing resistance performance of coarse aggregates, and to provide useful references for the long-term skid resistance modeling of durable asphalt pavement.

Spray water cooling of newly laid asphalt pavement for rapid opening to traffic

Freshly paved asphalt must be sufficiently warm before it can be trafficked to prevent premature failure. In countries with high air ambient temperature, the newly laid asphalt temperatures reduce slowly; thus, it requires lengthy periods to reach the opening-to-traffic asphalt temperature. Some contractors practice spraying water onto the freshly paved asphalt to accelerate the cooling time, so the new sections can be quickly opened to traffic. However, no particular research has been performed regarding this practice. This study aims to investigate the effectiveness of spray water cooling and examine the potential detrimental effects on the asphalt material properties. For this purpose, laboratory temperature measurements and heat transfer analyses of natural cooling and water spray cooling were performed. In addition, Cantabro and indirect tensile strength (IDT) testing were carried outto investigate the possible drawbacks of water. The results indicate the water spray application onto newly laid asphalt pavement does not necessarily adversely affect the asphalt durability (resistance to cohesion loss) and or the moisture damage of asphalt pavement. However, it is likely to be of limited value in accelerating the cooling of overlays, except when they are relatively thin.

Moisture characteristics of warm mix asphalt containing reclaimed asphalt pavement (RAP) or steel slag

Issues like limitation of natural resources of aggregates, global warming, need for eco-friendly, cost-effective, and high performance and durable asphalt mixture, have made the Reclaimed Asphalt Pavements Warm Mix Asphalt (RAP-WMA) and Steel Slag Warm Mix Asphalt (SS-WMA) interesting substitutions for conventional Hot Mix Asphalt mixtures. Furthermore, presence of moisture initiates and accelerates the deterioration of both of these mixtures. In this way, the response of the RAP-WMA to the moisture damage was compared with the SS-WMA using experimental tests including Indirect Tensile fatigue failure, Resilient Modulus, Indirect Tensile Strength, Semi-circular Bending, and Dynamic Creep tests. The obtained results show that although the RAP-WMA and SS-WMA mixtures contain hydrophilic and moisture sensitive aggregates and aged binder, they had an appropriate performance against the effect of moisture. Also, the SS-WMA mixtures showed better performance against moisture than the RAP-WMA mixtures, and therefore, they can be recommended as a substitution for RAP-WMA in regions where moisture damage is prevailing.

The study of the feasibility of using recycled steel slag aggregate in hot mix asphalt

Significant growth in the road network around the world has increased the need for pavement materials. The growing demand for producing original asphalt pavements from non-renewable natural resources can deplete natural resources, cause environmental issues, and consume significant amounts of energy. The idea of using waste materials such as steel slag or reusing recycled aggregated of old pavements was evaluated to increase the sustainability of pavements. Rutting resistance, marshall stability, moisture susceptibility, resilient modulus, and fatigue life of slag and conventional asphalt mixtures containing different percentages (0, 25, 50, and 75 wt%) of (Recycled Asphalt Pavement) RAP or slag aggregates were compared to evaluate the mechanical performance of recycled asphalt with slag aggregate, The recycled asphalt mixtures were rejuvenated by 3 or 6 wt% of automobile waste oil. The results showed that slag asphalt had a better performance in all areas. Additionally, replacing the original aggregate with RAP or recycled slag improved marshall stability, tensile strength, and rutting resistance of the asphalt or slag asphalt mixture. Using higher percentages of the recycled aggregate resulted in further improvements. The fatigue life of the recycled samples increased under loading with low strain level when higher percentages of the recycled aggregate were replaced, but it reversed at higher strains. Finally, the results indicated that using recycled steel slag for producing hot mix asphalt could produce a more durable asphalt in comparison to using RAP.

Evaluation of the rejuvenation of asphalt by means of oil-saturated porous aggregates

Road degradation is an increasing problem for assets managers. Roads deteriorate mainly due to the combination of different factors, such as temperature, climate and traffic loads. This causes the asphalt to age and, consequently, the bituminous mixtures become more fragile and microcracks begin to appear. To eliminate these degradation effects, the most widely used performed actions are based on the renovation of the pavement to achieve an asphalt surface under acceptable conditions of use. In order to reduce the application of corrective measures when the asphalt pavement is already facing significant defects, it is important to perform regular preventive maintenance that minimise the renovation works of the pavement and improves the asphalt durability. This paper shows a method for the continuous rejuvenation of asphalt, by analysing the evolution of asphalt mixture stiffness and the resistance to cracking on asphalt mixtures with rejuvenator added after having been submitted to a laboratory ageing protocol (short and long-term ageing). The rejuvenator was added to the mixtures following either of these two procedures: first, directly added to the mixture and the second, saturated in porous aggregates, what the authors call encapsulated. Results from this study demonstrate the effectiveness of the second method (encapsulated rejuvenator) as an original solution to achieve long-term performance mixtures with reduced cracking.

Validation of Performance-Based Specifications for Surface Asphalt Mixtures in Virginia

The Virginia Department of Transportation (VDOT), like many owner agencies, is interested in ways to facilitate the increased durability of asphalt mixes in an effort to make its roadway network more sustainable, longer lasting, and more economical. The balanced mix design (BMD) method proposes to address this through the incorporation of performance criteria into mix design and acceptance. VDOT has committed to the implementation of the BMD method in an effort to improve asphalt mix performance. The purpose of this study was to continue advancing efforts toward implementation of BMD through the evaluation of 13 asphalt mixes using performance-indicating laboratory tests, validation of the initial performance tests selected for BMD use, and validation of the initial test threshold criteria. Based on the results, the asphalt pavement analyzer (APA) rut test, indirect tensile cracking test (IDT-CT), and Cantabro test were found suitable for continued use in BMD. The current threshold criteria for all three tests were found reasonable based on additional mix testing. The study recommends that APA rut test and IDT-CT results should be compared and correlated to fundamental rutting and cracking tests, respectively, as well as to performance predictions obtained from mechanistic-empirical pavement design simulations, and to field performance for full assurance that test threshold values are appropriate. It was further recommended to evaluate the Cantabro, IDT-CT, and APA rut tests to determine acceptable variability and establish precision statements.