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Interface bonding between different asphalt pavement layers is crucial in maintaining the integrity of the pavement structure. To improve the interface bonding, bitumen emulsion is commonly used as the tack coat material. However, the bonding performance of conventional bitumen emulsion is limited. This study investigated the possibility of using waterborne epoxy resin modified bitumen emulsion as a novel tack coat material. The resistance to moisture damage of waterborne epoxy resin modified bitumen emulsion was evaluated using the boiling water test, followed by the characterization of the interface adhesion between waterborne epoxy resin modified bitumen emulsion and aggregate using the binder bond strength test. To further determine the interface bonding between different asphalt layers bonded by waterborne epoxy resin modified bitumen emulsion, a two-layer asphalt mixture structure was fabricated, and the shear strength was measured. The results indicated that the incorporation of waterborne epoxy resin can increase the interface bonding between the two asphalt mixture layers. [ABSTRACT FROM AUTHOR]

Different types of additives are used in asphalt modification to enhance several properties within the asphalt pavement. In various cases, modification is needed by using multiple additives, which is called composite modification. In this study, glass fibre and nano clay were used to modify the asphalt pavement. The amount of these two additives, together with the optimum bitumen content, was determined by the response surface methodology (RSM). Central composite method (CCD) was used for determining the optimum amount of independent variables (nano clay, glass fibre, bitumen content), by evaluating the dependent variables. Marshall mixture design criteria and minimum bitumen content, were the optimal conditions. As a result, the mixture containing 0.2% glass fibre, 3.693% nano clay and 4.096% bitumen content, was predicted to give the most desirable characteristics. Additionally, verification tests were conducted to evaluate the adequacy of the predicted model. The results were within the 95% confidence intervals for all response variables, which demonstrates the validity of the model obtained in the study. Consequently, CCD can be used to obtain design optimisation of asphalt modification with less mixture production for experimental stages. This is a substantial advantage, which supports human safety and environment- friendly practices. [ABSTRACT FROM AUTHOR]

Different types of additives are used in asphalt modification to enhance several properties within the asphalt pavement. In various cases, modification is needed by using multiple additives, which is called composite modification. In this study, glass fibre and nano clay were used to modify the asphalt pavement. The amount of these two additives, together with the optimum bitumen content, was determined by the response surface methodology (RSM). Central composite method (CCD) was used for determining the optimum amount of independent variables (nano clay, glass fibre, bitumen content), by evaluating the dependent variables. Marshall mixture design criteria and minimum bitumen content, were the optimal conditions. As a result, the mixture containing 0.2% glass fibre, 3.693% nano clay and 4.096% bitumen content, was predicted to give the most desirable characteristics. Additionally, verification tests were conducted to evaluate the adequacy of the predicted model. The results were within the 95% confidence intervals for all response variables, which demonstrates the validity of the model obtained in the study. Consequently, CCD can be used to obtain design optimisation of asphalt modification with less mixture production for experimental stages. This is a substantial advantage, which supports human safety and environment- friendly practices. [ABSTRACT FROM AUTHOR]

Quantifying recycled asphalt binder availability in recycled asphalt pavement (RAP) mix design is very essential, as the widely adopted 100% RAP binder availability assumption in RAP mix design never holds correct. Depending on the mix production condition, recycled binder stiffness, and virgin binder properties, the degree of binder availability in the mix is always partial. The present study proposes a simple procedure to estimate the degree of recycled binder availability in RAP mix design. In the proposed methodology, the designer needs to compare optimum binder content of bituminous mixes prepared using white rock aggregate gradation and virgin aggregates, along with mixes designed by blending black rock gradation and virgin aggregates blended in proportion to achieve the target white rock gradation. The binder content in the RAP fraction used in the blending exercise was determined using ignition oven method. RAP mix designs were performed for RAP material collected from two different sources, and design was performed for three mixing durations in a laboratory pug mill—60, 120, and 180s. The mixes were prepared with 50% RAP incorporation level. RAP material was conditioned at 110°C for 2 h, whereas virgin aggregates were superheated to 175°C. Using the methodology proposed, RAP binder availability was found to vary between 92.5% and 96.6% for softer RAP material, 75.9% to 91.5% for mixes incorporating stiffer RAP. With increasing mixing time, even though the total active binder content did not change significantly, a mixture performance test quantified the implication of increased RAP binder availability in mixes. A higher degree of binder activation resulted in mixes being rut resistant, while the same mixes exhibited relatively higher cracking susceptibility. Recycling of bituminous mixes has been considered as one of the sustainable practices in the highway construction industry. In a recycled bituminous mix, the milled material contributes good quality aggregates, and aged bituminous binder. The amount of aged bituminous binder that can be mobilized in the recycling process largely depends on mix production condition, milled, and virgin material property. The paper presents a simple methodology to quantify the degree of bituminous binder which becomes available in recycled mix design. The methodology can be used by mix designers to account for appropriate adjustment in virgin binder grade selection. The knowledge of degree of binder availability would also enable, if one targets to synthesize recycled mixes of a definite binder content. The paper also investigated the implication of different degree of binder availability on mix performance, arising due to different mixing time (production condition) and milled material property. [ABSTRACT FROM AUTHOR]

Asphalt pavements inevitably deteriorate over time, requiring frequent maintenance work to ensure the proper serviceability of the road network. Small interventions, such as resurfacing for pavement preservation, are preferable to reconstruction at the end of roads' in-service lives as they limit environmental- and economic-related impacts. Thin asphalt overlay (TAO) mixture represents a suitable maintenance solution to restore the functional properties of road surfaces. Due to the increasing awareness of the depletion of non-renewable resources and the importance of promoting the circular economy, this study evaluated the possibility of using fully recycled TAO mixes by investigating their volumetric and mechanical properties. Two eco-friendly TAO mixes were designed using recycled aggregates from reclaimed asphalt pavements, a municipal solid waste incinerator, and steel slags in order to meet EN 13108-2 requirements. The TAO mixes differed in regard to the type of bituminous binder (neat/SBS-modified bitumens) and fibres (natural/synthetic) employed. The preliminary results demonstrated that the presence of recycled aggregates did not negatively affect the workability and the mechanical performances of the two sustainable mixtures in terms of stiffness, tensile resistance, rutting and moisture susceptibility. Of these, the TAO mix with neat bitumen and synthetic fibres showed enhanced mechanical performance highlighting the structural effects of the used fibres. [ABSTRACT FROM AUTHOR]

This research effort is geared towards revealing the latent potential of discarded shoe polish that might be repurposed as an asphalt fluxing agent for the construction of durable and sustainable road surfaces. To drive this creative invention, the effect of various proportions of waste shoe polish (e.g., 5, 10 and 15 wt. % WSP) on the performance of base AP-5 bitumen was inspected in great detail. A meticulous investigation of the chemical, physical, and rheological properties of the resultant combinations was carried out using a variety of state-of-the-art laboratory techniques, specifically: thin-layer chromatography-flame ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), needle penetration, ring-and-ball softening point, Brookfield viscometer, ductility, flash/fire points, dynamic shear rheometer (DSR), multiple stress-creep recovery (MSCR), and bending beam rheometer (BBR) tests. The Iatroscan data disclosed that the continuous feeding of binder with WSP had a minor impact on SARA fractional distribution, regardless of aging. According to the FT-IR scan, the stepwise addition of WSP to the binder did not result in any significant chemical alterations in the blends. The combined outcomes of the DSR/BBR/empirical test methods forecasted that the partly bio-sourced additive would greatly improve the mixing–compaction temperatures, workability, and coating–adhesion properties of bituminous mixtures while imparting them with outstanding anti-aging/cracking attributes. In short, the utilization of waste shoe polish as a fluxing agent for hot asphalt mix production and application is not only safe, feasible, and affordable, but it has the potential to abate the pollution caused by the shoe-care market while simultaneously enhancing the overall performance of the pavement and extending its service lifespan. [ABSTRACT FROM AUTHOR]

(i) Recycled and renewable materials in asphalt pavements may be employed for the modification of asphalt binders and/or for the full or partial replacement of natural aggregates and mineral filler in asphalt mixtures [[1]]. A sustainable approach in asphalt pavement engineering should focus on materials, design methods, and technologies that can contribute to minimizing environmental impacts through a reduction in energy consumption and natural resources, while ensuring that all performance standards and requirements are met. By comparing the performance of various binders based on Zero Shear Viscosity (ZSV), grey relational analysis showed the highest correlation with an anti-rutting indicator for a high-viscosity-modified asphalt binder, thus indicating its pronounced anti-rutting potential. [Extracted from the article]

Waste foundry sand (WFS) are industrial by-products from the foundry process which represent challenges for environmental departments with respect to the proper disposal in landfills due to their high production. The road infrastructure such as asphalt paving is a major consumer of mineral aggregates originating from the mining activity of exhaustible natural resources. Thus, the WFS reuse for the construction of roads is an alternative to discarding of waste and a reduction in the use of mineral aggregates. In this article hot mix bituminous (HMB) mixtures were produced containing WFS (by weight) substitution contents in relation to manufactured sand of 25%, 50%, 75% and 100% from two origins: industrial landfill and the steel industry; after mechanical and gyratory compaction, these cylindrical specimens were subjected to mechanical tests of splitting tensile strength and resilient modulus obtaining very similar performances as that of the control mixture (which did not contain WFS). These mechanical results as well as the microstructural characterisation of this HMB containing residue led to the conclusion that the reuse of WFS in the asphalt pavement is technically viable, creating an alternative to by-product disposal and reduction of the financial-environmental costs of highways. [ABSTRACT FROM AUTHOR]

Purpose: In order to unravel the evolution of microstructure characteristics and the change of mechanical properties of bituminous mixture in the freezing and thawing environment in cold region, this study starts from macroscopic experiments and analyzes the changes in mechanical properties of asphalt mixtures before and after freezing and thawing in detail. On this basis, the displacement of key particles in the structure of asphalt mixture under the action of external forces (before and after freezing and thawing) is simulated through the combination macroscopic and microscopic methods. Design/methodology/approach: The climate in China exhibits high complexity and diversity, divided into five zones based on the temperature difference from south to north. Considering that the significant effect of geography and natural climate on the design, construction and maintenance of asphalt pavement, the criterion for the road construction at different areas should be highly different. Findings: The results show that the mechanical properties of asphalt mixture greatly decrease due to the influence of freeze-thaw, and the displacement of key particles in the structure of asphalt mixture (several representative particle sizes were selected through experiments) is obviously observed because of the action of external force. By analyzing the variation of several key particle sizes after freezing-thawing cycle, the gradation standard of asphalt mixture aggregate suitable for cold area was obtained. The research results have certain theoretical and practical value for the design and application of asphalt mixture in cold area. Originality/value: The results show that the mechanical properties of asphalt mixture greatly decrease due to the influence of freeze-thaw, and the displacement of key particles in the structure of asphalt mixture (several representative particle sizes were selected through experiments) is obviously observed because of the action of external force. By analyzing the variation of several key particle sizes after freezing-thawing cycle, the gradation standard of asphalt mixture aggregate suitable for cold area was obtained. The research results have certain theoretical and practical value for the design and application of asphalt mixture in cold area. [ABSTRACT FROM AUTHOR]

Recently, the reduction of the environmental burdens related to highway infrastructures has been in the spotlight. Within this context, the use of recycled materials in bituminous mixtures for road pavement construction and maintenance has the potential to mitigate the excessive use of non-renewable resources. Nevertheless, the material consumption is only one of the aspects that affects the sustainability of an infrastructure. Other relevant aspects related to environmental issues should be considered. The objective of this work is to evaluate the potential environmental impacts of asphalt mixtures containing crumb rubber (CR) (vulcanised or devulcanised) and reclaimed asphalt pavement (RAP) assuming different Degree of binder Activation (DoA) of the aged binder by means of a life cycle assessment (LCA). The results show that the small amount of CR used for bituminous mixtures application does not justify all the additional consumption of resources and emissions associated with its treatment. These results are explained by the higher environmental impacts stemming from the treatment of the rubber and the higher amount of bitumen employed in the mixture. In turn, for mixtures containing RAP the analysis revealed an improvement in the score of all the environmental indicators considered. [ABSTRACT FROM AUTHOR]

• Two additives, namely carbon black and hydrocarbon obtained from Covid-19 hospital waste, were used. • Cohesion and adhesion of asphalt mixture improved based on RV and moisture susceptibility tests. • Moisture susceptibility of HMA mixture modified with carbon black and hydrocarbon improved. • Additives increased the fracture toughness and fracture energy of the HMA mixture under 1 and 3 FTD cycles (at −15 °C). • The flexibility of HMA mixture containing additives was improved based on three indices FI, CRI, and TI. Moisture susceptibility and cracking are considered as two major causes of distress in asphalt pavement, which are developed and expanded under environmental factors such as Freeze-Thaw Cycles (FTC) and traffic loading. These causes of distress may be controlled by improving two factors of bituminous phase cohesion and adhesion between aggregates and bitumen. This article was aimed to study the rheological properties of bitumen, such as rotational viscosity, as well as the mechanical properties of asphalt mixture, such as moisture susceptibility, fracture resistance, and fracture brittleness, by using two additives, carbon black and hydrocarbon, which were obtained from the pyrolysis recycling of hospital waste caused by Covid-19. In this regard, a total of 8 mixtures were made, including a mix without any additive, three mixes of 1.25, 2, and 2.75 % hydrocarbon, three mixes of 6, 12, and 18 % carbon black, and a mix of 2.75 % hydrocarbon + 18 % carbon black. In order to determine the effect of FTC on the asphalt samples and to adapt the laboratory conditions to the road conditions, 1 and 3 cycles of Freeze-Thaw Damage (FTD) were applied, respectively, indicating 4 and 12 years of pavement distress. The results showed that the addition of different percentages of carbon black and hydrocarbons (separately and together) through improving bituminous phase cohesion and adhesion between aggregates and bitumen increased the samples resistance to the moisture susceptibility. It was also found that fracture energy (G F) and fracture toughness (K IC) of all mixes improved compared to the base sample. At last, the results of brittleness indicators revealed that all mixes containing 6, 12, and 18 % carbon black and 1.25, 2, and 2.75 % hydrocarbon had a more flexible behavior than the base mix under 1 cycle of FTD; while the mixes containing 18 % carbon black and 2.75 % hydrocarbon were just flexible under 3 cycles of FTD. Accordingly, it can be concluded that a mix containing 2.75 % hydrocarbon + 18 % carbon black had the best results in terms of viscosity, moisture susceptibility, and fracture resistance (under 1 and 3 FTD cycles). [ABSTRACT FROM AUTHOR]

• The bonding between layers when one is thin is analysed for different emulsions. • The bonding between layers evaluation is also important through cyclic loads. • A cyclic shear test to analyse the asphalt ultra-thin layers bonding is developed. • Energy laws show the greater fatigue behaviour of highly modified emulsion. Bonding between layers is a critical aspect in the durability and performance of asphalt pavements. The life of the pavement can be significantly reduced due to poor bonding between bituminous mix layers. For this reason, the analysis of the link between these layers is fundamental. Thus, the aim of this work is to analyse the bonding between layers, provided by different types of emulsions, when one of the layers is thin. The bond between these layers was studied by means of a monotonic shear adhesion test, with an analysis of the effect of the dosage, the temperature and ageing, and by means of a new cyclic shear test especially developed in this work. The results obtained show the great influence of temperature on the shear stress for any of the emulsions used, which increases as the temperature decreases, and how the differences between the three emulsions are reduced after ageing. As regards fatigue strength, the choice of the emulsion that will withstand a greater number of cycles will depend on the stresses that occur at the interface. [ABSTRACT FROM AUTHOR]

Moisture damage is a critical problem of asphalt pavements. Some factors affecting the moisture sensitivity of asphalt mixtures include bitumen properties, air void content, and the type of anti-stripping additive. This study investigated the use of nano-silica for improving the properties of different bitumens and to increase the moisture resistance of asphalt mixtures at different traffic loading conditions. Two types of bitumen (60-70 and 85-100 pen grade) were modified with various percentages of nano-silica (0, 0.2, 0.4, 0.7, and 0.9% by the weight of the bitumen), and physical and rheological tests were conducted to determine the optimum nano-content. Then, the optimal content was used to prepare asphalt mixtures at three different air void contents (4, 5, and 6%) to simulate the heavy, medium, and low traffic loading conditions. Indirect tensile strength (ITS) and compressive strength tests were performed on the specimens in dry and wet conditions, and the effect of air void content and the type of bitumen on the moisture sensitivity and compressive strength of unmodified and nano-silica-modified asphalt concrete was investigated. The results showed that nano-silica improved the moisture sensitivity of asphalt mixtures with 60-70 and 85-100 pen grade bitumens at all air void contents and the effect of nano-silica was higher on the moisture sensitivity of asphalt mixtures with 60-70 than 85-100 pen grade bitumen. [ABSTRACT FROM AUTHOR]

In the rehabilitation of flexible pavements with asphalt layers, it is necessary to apply a bituminous tack coat with a pre-established dosage, which usually does not take into account the degree of texture generated if a milling operation is previously performed since this increases the surface at the interface. On the other hand, when milling, grooves are obtained that could lead to the runoff of bitumen emulsion with excessive deposition in their valleys due to dosages greater than those needed. This work analyses the above mentioned and achieves a compromise solution, with its corresponding method of application, based on the mechanical behaviour obtained with different degrees of texture and validated for typical materials used in Argentina. [ABSTRACT FROM AUTHOR]

A research was conducted to assess the effectiveness of different kinds of Modified Fibres (MF) on the thermal cracking performance of a Stone Mastic Asphalt (SMA) compared to the conventional SMA mixtures modified with SBS Polymer modified Bitumen (PmB). In addition, the capability of rubberised fibres to alleviate the thermal cracking sensitivity was investigated. Besides the main scope, a series of the same SMAs were also produced containing 25% of Reclaimed Asphalt Pavement (RAP) to investigate the effects of RAP on the low-temperature performance of the mixtures, which were modified either with MF or PmB. The experimental plan included both binder and mixture characterisation by means of Bending Beam Rheometer (BBR) test and Thermal Stress Restrained Specimen Test (TSRST). Binder-scale test results showed that the stiffness of all bituminous compounds is increased by the addition of fibres and rubber improves the elasticity of both neat and PmB compounds. In the mixture scale, TSRST results showed no significant difference between the mixtures. However it is noteworthy that, in addition, better low-temperature performance was recorded for virgin mixtures compared to to RAP containing ones. The overall results may confirm the feasibility of modified fibres in the modification of mixtures at low temperatures. [ABSTRACT FROM AUTHOR]

Reflection cracking is a critical issue in asphalt overlay pavement. Temperature variation and traffic loading are the main fracture modes acting on the material. In this paper, a multi-modal overlay tester is proposed for the evaluation of the reflection cracking resistance of an asphalt mixture, an approach that simulates three loading modes on asphalt specimens. A fine dense-grade hot mix asphalt is used as the test specimen and subjected to different loading conditions such as single Mode I, II, and III loading simulations and combined I+II and I+II+III loading simulations. Results show coefficients of variation (CVs) of 2.5%, 10.3%, and 7.4% for the Mode I, II, and III loading simulations, respectively. Furthermore, the β coefficient, with a CV of 7%, is used to represent the crack resistance of the asphalt mixture. Finally, the crack propagation occurs rapidly when subjected to tension and lateral displacement prior to repeated traffic loading simulations. [ABSTRACT FROM AUTHOR]

Asphalt Pavement Alliance (APA) created the Perpetual Pavement Award program in 2001. This program requires that the roadway has at least 35 years of service at the time of award and had experienced no structural failures. In addition, the program limits candidate roadways to those that have not received more than 100 mm of new asphalt nor have been resurfaced at a frequency exceeding 13 years. Minnesota Department of Transportation (MnDOT) currently owns the record for the most award winners and has received an award every year from 2002 through 2017. This study reviews all the award-winning roadways in Minnesota to determine common material, design factors and considerations which may have contributed to the roadways extended life, often exceeding 50 years, despite the harsh Minnesota climate. For these projects, all the available information and any pertinent supporting information were reviewed. Findings from this review showed that a combination of many different factors including large-scale subgrade correction, utilizing non-frost susceptible base and subbase materials, bituminous treatment of the granular layers, utilization of prime coat, and staged construction may have contributed to the outstanding performance of these award-winning roadways. In addition, a more in-depth analysis was performed on the four project locations within the Minnesota Metro District. To further investigate and characterize these sites, coring and hand auger borings were performed in cracked and un-cracked areas along with Dynamic Cone Penetrometer (DCP) test which the results indicated that the in-situ materials were strong in all the projects. The cores were then used to measure thicknesses, densities, asphalt contents, extracted gradations, and also to perform resilient modulus testing at low and intermediate temperatures. Resilient Modulus testing showed that the asphalt mixtures from different projects perform differently at intermediate temperatures, but this difference is much less pronounced at low temperatures. This could be one reason for the similar long-life behavior of these pavements, as they have been subjected to the low temperature condition in a substantial portion of their service life in the state of Minnesota. [ABSTRACT FROM AUTHOR]

The article examines the microstructure influence mechanism to mechanical behavior of open graded friction course (OFGC) asphalt mixture. It details the use of digital image processing technology to process the fault images of the specimen and obtain the microstructure parameters of the OGFC asphalt mixture with different gradation. The microstructure influence on mechanical behavior of OGFC asphalt mixture is also explored using the Grey correlation theory.

Using of Reclaimed Asphalt Pavement (RAP) has been become indispensable in most of the world nations as for its many benefits as significant cost savings and provide environmental benefits. Many factors such as virgin materials, binder content, availability of RAP, viscosity of binder and extent of deterioration had important role in effecting on Optimum percentage of RAP. In this study, effect of using RAP on the asphalt mixture properties and the its optimum ratio was determined to achieve the objective of the study. The glass fiber (GS) was used as additives to improve the asphalt mixture. It has been observed from the previous researches that the optimum percentage of reclaimed asphalt use is not determiner and is disagreed from project to project. So, different percentages of RAP was (25%, 50%, 75%, 100%) by weight of aggregate were added as well as using the additive GS at optimum bitumen content. The study is revealed that untreated 100% RAP materials are not good as a bituminous mix. and was showed that mix prepared with 25% RAP gave nearly the same physical and strength parameters as virgin bituminous mix. From results of study, the use of RAP until (%50) as a maximum percentage in unmodified asphalt mixture course sustained good results. To achieve better performance, the percentage of 25% RAP was used with percentage of 0.26% GS. This mix achieved the specification requirements and ensured the degree of better performance for paving. The economical evaluation of using percentage of 25% RAP with percentage of 0.26% GS was also studied. The results indicated that, about 21% of the cost was saved. [ABSTRACT FROM AUTHOR]

Growing economy and increasing pollution evoke the need for more environmentally friendly road construction techniques and the saving of natural resources. In this context, cold recycling plays an important role since, on the one hand, it allows to reduce CO2 emissions drastically and, on the other hand, it offers a variety of opportunities for high percentages of recycling. Inspired by experience in Sweden, the international project "Optimal Recycling of Reclaimed Asphalts for low-traffic Pavement" (ORRAP) for low-volume roads in the Upper Rhine region aims to develop and establish a new strategy for 100% reclaimed asphalt pavement (RAP) at ambient temperature (20°C) without adding virgin bituminous binders or rejuvenators. The still ongoing research project involves laboratory experiments as well as in situ test sections. The link between small-scale laboratory experiments and in situ testing is provided by medium-scale traffic simulation in the laboratory. This paper describes results from medium-scale compaction in the laboratory using different methods as well as traffic simulation with a medium-scale mobile traffic load simulator. The results show that compaction in the laboratory at ambient temperature (20°) is very difficult to achieve. Nevertheless, it was found that compaction at a temperature of 60°C appears possible and provides promising results regarding stability and rutting enabling the in situ construction. The in situ pavement construction at ambient temperature on a low-volume road in Switzerland resulted in a visibly well-compacted and stable base course which was covered by a hot mix asphalt surface course the day after. The test section will be monitored closely over the next 12 months. [ABSTRACT FROM AUTHOR]

• Enhanced viscosity and improved adhesion to aggregate particles could be regarded as other advantages of Nano polymer modified bitumen. • Rutting performance was highly influenced by binder modification in HMA mixtures. • In comparison with conventional asphalt mixtures, modified samples possessed higher rates of final strain upon stress enhancement at any temperature. Nanoparticles have exhibited a promising potential in enhancing the bituminous materials' performance. As a cost-effective material, hot mix asphalt (HMA) has been employed in pavement structure for a long time. Their viscoelasticity however results in various modes of failure under different temperature profiles and loading stress. Rutting of asphalt pavements is considered as the most prominent distress factor under almost all climate conditions. Moreover, steel slag has been employed for improvement of asphalt mixture properties as it exhibits excellent physical features. In this content the aim of the present research is to analyze improving effects of nano clay and styrene-butadiene-styrene (SBS) on the rutting resistance of modified steel slag asphalt mixture (SSAM). Various tests were employed to investigate the asphalt binder properties and the rheological characteristics of modified bitumen among which penetration grade, softening point, ductility and dynamic shear rheometer (DSR) can be mentioned. Marshal Test was applied to examine the optimum bitumen content in conventional and modified asphalt mixture. The rutting resistance against was then evaluated through two tests: repeated load axial (RLA) test and wheel track test. The results indicated respective improvement of toughness and viscosity by an average of 25% and 101% upon addition of nano-polymer which enhanced the bitumen rheological characteristics while reducing the penetration grade. The asphalt rutting resistance and rutting depth exhibited some improvements as well. [ABSTRACT FROM AUTHOR]

• The aging sensitivity of the mixtures is highly affected by the rejuvenator type. • The aging severity is higher in rejuvenated recycled mixtures than the virgin HMA. • Rapiol and Cyclogen performed acceptable in terms of cracking and aging. • Waste cooking oil had the poorest performance in terms of aging resistance. Shortage of natural resources and the high price of bitumen have encouraged the pavement engineers to use high contents of reclaimed asphalt pavement (RAP) material in new asphalt mixtures. Nevertheless, there are a number of problems associated with increasing the RAP content in asphalt mixtures due to the stiff aged bitumen existing in RAP materials such as poor fatigue and cracking performance and low workability. To compensate for this disadvantage, different kinds of rejuvenators are introduced to restore the properties of the aged bitumen. However, the rejuvenated bitumen of RAP material may have low resistance against re-aging and get aged quickly. In this research, oil-based and organic rejuvenators were used in asphalt mixtures containing 50% RAP, and the aging performance of the mixtures was studied by conducting resilient modulus, dynamic creep, indirect tensile fatigue and intermediate-temperature fracture tests on short and long term aged mixtures. The results indicated that the aging resistance of the recycled mixtures was highly affected by the rejuvenator type, and the mixtures containing organic rejuvenator were more susceptible to aging than those containing oil-based rejuvenators. [ABSTRACT FROM AUTHOR]

• Incorporation of self-designed rejuvenator can improve the colloidal stability of aged bitumen. • Self-designed rejuvenator improved the low-temperature cracking resistance of recycled asphalt mixtures. • The addition of rejuvenators increased the fatigue life of recycled asphalt mixtures. Recycling and reuse of reclaimed asphalt pavement (RAP) in recycled asphalt mixtures is now gaining great interests for sustainability-driven and cost-effective development of asphalt pavements. However, the properties of recycled asphalt mixtures prepared with RAP would be determined by using a suitable rejuvenator to restore original properties of aged (oxidized) bitumen in the RAP. This study investigated the properties of rejuvenated bitumen recovered from RAP as well as the properties of recycled asphalt mixtures prepared with a developed rejuvenator. The properties of the rejuvenated bitumen were evaluated by the SARA (saturates, aromatics, resins and asphaltenes) method, softening point and penetration tests, and the properties of recycled asphalt mixtures prepared with different contents of RAP were determined by wheel tracking, three-point bending (3 PB) and four-point bending (4 PB) tests. Analysis on the conventional properties of the rejuvenated binder showed that the developed rejuvenator can restore the colloidal structure and rheological properties of the aged binder. The incorporation of rejuvenator in recycled asphalt mixtures can decrease the dynamic stability of recycled mixtures, and the maximum bending strain of recycled asphalt mixtures can be increased due to the rheological recovery of the aged binder in the RAP. The fatigue behavior of recycled asphalt mixtures incorporated with the developed rejuvenator was improved as well. Compared to the selected commercial rejuvenator, using the developed rejuvenator can improve more pavement performance of recycled asphalt mixtures. [ABSTRACT FROM AUTHOR]

• Homogeneity of reclaimed asphalt are assessing by variation of five indicators 81. • Composition of recycled asphalt mixture determining by the optimization methods 82. • Algorithms permit designing optimal mixture including technological restriction 81. • Numerical example shows that the simulation permit designing best mixture 76. • Designed optimal composition use on recycling mixture in asphalt mixing plant 78. Recycled hot-mix asphalt (RHMA) mixture is produced from reclaimed asphalt pavement (RAP) by adding an appropriate amount of new mineral materials improving the gradation of RHMA, a lower viscosity bituminous binder and a rejuvenator. The manufactured RHMA mixture must meet the same technical requirements as those for the hot-mix asphalt (HMA) mixture made of new materials only. It is also aimed at reducing its cost to the minimum in order to comply with technical requirements for the RHMA mixture in the asphalt mixing plant (AMP). These goals are ensured in the process of determining the composition of the RHMA mixture applying numerical and experimental methods for selecting an optimal content of old and new materials in the mixture. The article presents a method for determining the composition of the RHMA mixture, which allows calculating the maximum allowable percentage of RAP depending on its homogeneity. Setting the established maximum RAP amount as a constant size, the required content of new mineral materials is estimated thus taking into account bitumen capacities. The price of a single ton of the materials making the RHMA mixture and information on technical requirements for the composition of the RHMA mixture assist in applying certain technological restrictions, which makes it possible to calculate an optimal content of the components. The research findings obtained from the representative sample demonstrated that ready-for-use RAP was not homogeneous, and its five properties used for calculating its maximum allowable amount had different variations. The paper presents the algorithms that are actualized using mathematical programming methods upon the application of which the following objectives were solved: the assessment of technological requirements helped to obtain the RHMA mixtures of the cheapest or densest mineral part, and the mixture having the lowest content of bitumen was received. The article discusses mathematical analogues that can be used for determining whether the RHMA of the right gradation can be produced from the available mineral materials and allows analysing the mixtures that do not meet the established requirements thus identifying the causes of inappropriateness. The introduced algorithms can be applied at the initial stage of designing the RHMA mixture thus reducing the duration and cost of the design process. In order to determine whether the calculated content of old and new materials is appropriate, the standard specimens produced and examined in the laboratory need to be confirmed. [ABSTRACT FROM AUTHOR]

Bituminous binders have significant effect on the overall performance of the asphalt mixtures, although binders are not the main component of the asphalt mixture (4-6% by weight). This paper presents an overview of research efforts undertaken to evaluate the sensitivity of asphalt mixture performance to the change of the binder suppliers in the State of Arizona. The binders used in the asphalt mixture have identical Performance Grade (PG). However, the binders were from different suppliers. The laboratory testing program included the dynamic modulus and the repeated load/flow number tests. Asphalt mixtures were collected from four sections on a project constructed in northern Arizona. This project was unique in that all four asphalt concrete mixtures had the same aggregate structure and source but used PG 76-16 binders obtained from four different suppliers. Based on the test results, the tests were sensitive to variations in the properties of the same PG binders obtained from different suppliers. This was also confirmed through statisti cal analysis and comparison with the binder test data. In order to assess the sensitivity of the four asphalt binders on the pavement performance, the binder and mixture data were input into the Mechanistic-Empirical Pavement Design Guide (MEPDG) and design simulations were run to compare rutting and fatigue cracking associated with each of the four PG76-16 binders included in this study. Significant statistical differences in both distress mechanisms were also observed for the different mixtures with changing only the binder supplier. [ABSTRACT FROM AUTHOR]

Among the fabrication processes available for obtaining asphalt rubber, terminal blend is the most commonly used in Brazil. On the other hand, the use of field-blended rubber asphalt has been around in the United States for decades, especially in the state of Arizona. The lack of information regarding this technique in Brazil, however, inhibits a more common use in pavement construction/rehabilitation. This case history study was conducted in order to characterise the field performance of the first pavement rehabilitation job in Brazil using a field-blended rubber asphalt mixture and attempt to predict its future performance. A 500-m test section using a field-blended rubber asphalt mixture with a gap-graded aggregate as a surface course was monitored periodically through pavement deflection tests, roughness, rutting and surface conditions. Pavement monitoring revealed good functional and structural conditions after 4 years of service life. Accelerated pavement testing (f-sAPT), conducted in a representative test section using a full scale, mobile traffic simulator, exhibited promising performance. No cracking was observed in the test section and the average maximum rut depth was below limits after simulating 7 years of service life. Results from the f-sAPT simulation were then used to calibrate the performance cracking and rutting models in the Highway Development and Management Model (HDM-4). [ABSTRACT FROM AUTHOR]

The European building sector is facing a pressing issue of natural resources. Importing road building materials for the asphalt surfacing increases the cost of the asphalt mixture. The asphalt surfacing mixtures shall consist of a mixture of graded aggregates accounting for 80-90% of the total volume of the asphalt mixture, or 90-96% of the total weight of the asphalt mixture and binder: road bitumen or polymer modified bitumen. In the Republic of Lithuania, asphalt mixes are designed in accordance to the Design Regulations for Road Pavement Standardized Pavement Structures KP SDK 19 and accordance to the normative documents and their requirements for graded aggregates and binders. Road builders import graded aggregates to asphalt mixes from other countries, and this increases the cost of asphalt mixes. According to the scientific researches in the Lithuanian quarry Petrašiūnai II, using unique production technology is produced class I dolomite crushed stone, which mechanical, physical properties and designed asphalt mixtures can replace imported graded aggregates. The economic question remains as to the economic effect of the most commonly used asphalt mixtures in Lithuania AC 11 VS (asphalt mixture of asphalt pavement wearing course) and SMA 11 S (crushed and mastic asphalt) made from indigenous minerals compared to imported minerals. The aim of the paper is to perform the calculation and evaluation of the economic effect of asphalt mixtures AC 11 VS, SMA 11 S with different minerals and micro-aggregate. The paper identifies and analyses the properties of asphalt test mixtures, and identifies the locations of mineral suppliers in Lithuania. According to the economic impact assessment scheme, the economic effect of asphalt mixtures AC 11 VS, SMA 11 S with different minerals and micro-aggregate was calculated. According to the calculations made, the economic effect of producing asphalt mixtures AC 11 VS, SMA 11 S with class I dolomite chips is 13-14%. [ABSTRACT FROM AUTHOR]

This study explores effect of binder grade variation on the performance parameters of stiffness, fatigue, and permanent deformation using different asphaltic concrete paving mixtures. Two penetration grade binders (40/50 and 80/100), four gradations (two wearing and two base courses) and single limestone aggregate source were used. Superpave Gyratory Compactor (SGC) was employed to fabricate specimens for Dynamic Modulus ∣E*∣ test, Repeated Load Deformation Test (Flow Number Test, FN) and Static Creep Test (Flow Time test, FT) using Asphalt Mixture Performance Tester (AMPT). The ∣E*∣ test was carried out for a range of temperatures (4.4-54.4 °C) and a frequency sweep (25-0.1 Hz), while FN and FT tests were performed at a single effective temperature of 54.4 °C and 300 kPa stress level. The ∣E*∣ test results were subjected to the non-linear optimization technique to develop the stress-dependent master curves which reveal that the grade of bitumen significantly influences the stiffness of mixtures. The combination of the ∣E*∣ and the phase angle pronounced into fatigue parameter which describes the fatigue behavior of a mix, and results indicate that the softer grade translates into higher fatigue resistance and vice versa. We observe that the 40/50 binder, on average, is 1.8 times more rut-resistant than the 80/100 binder. Further, this study also develops a non-linear regression model to express ∣E*∣ as a function of testing temperature, loading frequency, and mixture volumetric parameter. [ABSTRACT FROM AUTHOR]

The Federal Highway Administration’s Every Day Counts (EDC) initiative focuses on saving time, resources and money. EDC has brought infrastructure preservation to the forefront of many conversations. Chip seals are a cost-effective pavement preservation strategy, and continued studies verifying their performance benefits continue to be in high demand as agencies struggle to fund preservation programs. This study documents the effectiveness of chip seals when good materials, good construction and good agency oversight work together. Chips seals extend the service life of pavements an average of 5–6 years. This study gathers two years of field performance data (June 2014–June 2016) from chip seal projects constructed in Oregon. The data includes laboratory and field-testing to assess chip seal materials used in construction and tracks the performance of the chip seal pavements, both emulsified asphalts and hot-applied asphalts. Findings show that chip seals constructed with good quality materials enhance the surface texture properties and reduce the appearance of distresses over the two-year monitoring period for most sections. [ABSTRACT FROM AUTHOR]

This paper analyzes pavement performance of five Ontario Ministry of Transportation contracts paved in 2011 in relation to the properties of asphaltic materials used during construction. Pavement cracking data collected in 2016 was compared with characteristics of asphalt cement supplied for paving and recovered from pavement cores at year five. A major finding was that the Extended Bending Beam Rheometer test; part of enhanced testing currently carried out on asphalt cement in Ontario, was more reliable at predicting pavement performance than the standard Superpave™ Bending Beam Rheometer test for both asphalt supplied to the contract and recovered from in-service pavements. [ABSTRACT FROM AUTHOR]

• Lignin as partial replacement of bitumen for producing bio-asphalt materials. • Raw material and production process of lignin significantly affect the performances of bio-materials. • Laboratory multi-scale approach and real-scale applications of bio-materials are discussed. • Life-cycle assessment and economic analysis are addressed. • Lignin-based asphalt materials represents a promising technical and environmentally friendly solution. Nowadays, one of the most interests of modern society is to replace increasingly larger quantities of petroleum-derived products, which is a non-renewable source progressively depleting, so promoting both environmental and economic benefits. In this context, the practice to employ renewable sources to replace part of the bituminous materials is an effective approach in pavement engineering. Among different biomasses which are recognized as possible sources mixable with bitumen, lignin can represent a valid material. Lignin is a natural resource commonly deriving from the by-product of the production of pulp and paper industry. It is the second most common biopolymer on Earth and represents a potentially attractive alternative as partial substitute of bitumen. However, in order to understand the environmental and technical feasibility of the application of lignin in bituminous pavement applications, a multi-scale approach must be adopted. For this purpose, the paper aims at providing an overview of the use of lignin as renewable source in bituminous binders and mixtures, by investigating chemical, rheological and mechanical properties of lignin modified asphalt materials. Moreover, based on the available literature, field application experiences and Life Cycle Assessment (LCA) analysis are also discussed. [ABSTRACT FROM AUTHOR]

• Asphalt mixture segregation detection using image texture features. • Otsu algorithm combined with Canny edge detection to obtain aggregate distribution image. • The two-dimensional entropy is used to calculate aggregate distribution uniformity. • A new indicator "U" is proposed to indicate the degree of asphalt mixture segregation. Surface segregation in asphalt mixture caused by the homogeneity of aggregates seriously influences the service life and road performance of asphalt pavements. However, existing segregation detection procedures are cumbersome and the detecting results are heavily influenced by the moisture content of the surface asphalt mixture. Therefore, this paper innovatively proposes two-dimensional (2D) entropy of the chunking image in calculating uniformity complexity (U) to evaluate surface segregation of bituminous mixtures with digital image processing (DIP). Before image chunking, Otsu algorithm and Canny edge detection are properly combined to obtain a more accurate aggregate distribution image. Furthermore, the feasibility of this detecting method is verified through a simulation experiment, a grading comparison experiment, and a noise interference experiment. These experimental results demonstrated that this study presents an efficient approach for the segregation detection of asphalt mixture with high accuracy. [ABSTRACT FROM AUTHOR]

In order to address pertinent issues in relation to the use of Warm Mix Asphalt (WMA) in pavement construction, it is imperative to understand the effects that such additives have on rheological and failure properties in service. In this study, two commercial WMA additives, a proprietary siloxane-based compound and an oxidized polyethylene wax, were added to a soft Roofing Asphalt Flux (RAF), a soft Recycled Engine Oil Bottom (REOB) tainted binder, and a somewhat harder binder containing 20% oxidized asphalt derived from Recycled Asphalt Pavement (RAP). Binders were aged according to standard Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) protocols. Selected compositions were subjected to a period of extended PAV aging for 40 h. Standard and advanced rheological and failure tests were used to predict the performance of these binders in service. Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests according to Superpave™ protocols were done to determine performance grades. Extended BBR (EBBR) and Double-Edge-Notched Tension (DENT) tests were done to provide further insights into durability and strain tolerance, properties of utmost importance to assure long term pavement performance. The findings of this study show that the addition of the oxidized polyethylene wax WMA additive to REOB and/or RAP tainted systems can provide binders that are unstable and likely prone to premature and excessive low temperature failure in service. In contrast, the siloxane-based WMA additive appears to be a better choice to avoid premature low temperature and fatigue cracking distress. [ABSTRACT FROM AUTHOR]

In some countries of the world, for economic and environmental reasons, recycled asphalt pavement (RAP) materials comes from old bituminous road pavements are increasingly investigated. In Algeria particularly, a huge quantity of this type of waste is produced every year but rarely quantified and rarely reused. This paper evaluate the effects of various RAP sizes as substitute of coarse and fine natural aggregate (NA) on the mechanical properties and durability of roller compacted concrete (RCC). The RAP and NA materials are characterized and compared. The mechanical properties and durability of RCC with RAP materials are analyzed and compared to the RCC with 100% of NA. The experimental results showed that it is possible to manufacture RCC with a maximum of 50% of RAP materials. In addition to that, it may be more environmentally efficient to valorise this type of waste in concrete, because this helps to remove in general some parts of wastes and protects the environment. [ABSTRACT FROM AUTHOR]

The on-site construction process undertaken by asphalt teams has a critical impact on pavement quality. Process improvement and learning require explicit information about the process. However, current on-site operational activities and key parameters are, in general, not systematically monitored and mapped. The lack of process information makes it difficult for contractors and asphalt teams to distinguish between good and poor practices and to improve. Although technologies to make the on-site process explicit are becoming widely available, their adoption has been slow. To overcome this knowledge gap regarding explicit information about the on-site construction process, this paper proposes a framework and utilizes technologies for the systematic monitoring and mapping of on-site activities and key parameters. Various technologies and sensors, such as a global positioning system (GPS), a laser linescanner, and infrared cameras, make it possible to track the on-site movements of machinery and asphalt temperatures during construction. This framework was applied and refined during 29 asphalting projects in the Netherlands, creating an extensive set of on-site process data. Considerable variability was found in the delivered asphalt temperatures, the asphalt cooling, the compaction process and density progression, and the movements of machinery. This variability offers opportunities where action could be taken to improve process quality by reducing process variability. The framework and explicit data can help asphalt teams to verbalize their tacit knowledge and make their own processes and choices transparent and further promotes learning processes. This paper contributes to a deeper understanding of the on-site construction process and highlights how to encourage technology adoption in construction. [ABSTRACT FROM AUTHOR]

The paper presents and discusses the calibration and validation of a three-dimensional constitutive visco-elasto-plastic model developed for the analysis of the mechanical response of asphalt concretes. The methodology, an inverse problem technique, uses a one-dimensional analytic formulation of the constitutive model and a non-linear constrained optimization based on the Conjugate Gradient algorithm. On the basis of the creep recovery data obtained from an experimental investigation in support of the model calibration, it has been verified that the values of the constitutive parameters can be reliably identified. A subsequent comparison between the experimental creep and numerical curves of the 3-D model demonstrated reasonable shifts, confirming the reliability of the identification procedure for the parameters. [ABSTRACT FROM AUTHOR]

One of the most important factors influencing the durability of asphalt mixtures is moisture-induced damage resulting from the presence and the transport of moisture in pavements. Moisture-induced damage is an extremely complicated phenomenon that is not completely understood but believed to be governed by the interaction of moisture with asphalt mix components (mastic and aggregates). The objective of this study was, therefore, to characterize the sorption and diffusion characteristics of asphalt mastic using gravimetric vapor sorption techniques. Moisture transport, in the hygroscopic region, in asphalt mastics was studied using both static and dynamic gravimetric vapor sorption techniques to determine equilibrium moisture uptake and diffusion coefficients as a function of aggregate and filler types. For the 25-mm diameter thin asphalt mastic films and the testing conditions (23°C and 85% relative humidity) considered, the kinetics of moisture uptake obtained were characteristic of Fickian diffusion with a concentration-dependent diffusion coefficient. Equilibrium moisture uptake and diffusion coefficient estimated from the static measurements were comparable and of the same order of magnitude as those from dynamic sorption techniques. Both measurement techniques ranked the mixes similarly, which suggest either method could be used to characterize moisture transport in asphalt mastics. Equilibrium moisture uptake was relatively higher in mixtures containing granite aggregates compared with limestone aggregate. In contrast, the diffusion coefficient of limestone aggregate mastics was higher than granite. Thus, an inversely proportional relationship exists between moisture uptake and diffusivity of the asphalt mastics studied. The results suggest moisture transport is a function of aggregate type and that both equilibrium moisture uptake and diffusion coefficient are useful in studying moisture susceptibility in asphalt mixtures. The effect of mineral filler type on diffusion coefficient was minimal in the mastics containing granite aggregate but relatively high in mastic samples containing limestone aggregates. Diffusion coefficient was found to increase with sample thickness, which was unexpected because diffusion coefficient (in an isotropic material) is considered an intrinsic property that is independent of sample size. The results suggested anisotropic diffusivity can occur in asphalt mastics and could be attributed to factors, including mineralogy, microstructure, air voids, and the tendency of the aggregates to settle at the bottom of asphalt mastic with time. In addition to characterizing moisture transport in asphalt mastics, the results presented in this paper will be useful as inputs for numerical simulation of moisture damage in asphalt mixtures. [ABSTRACT FROM AUTHOR]

The research presented by Gaudenzi et al. [[30]] involved rheological measurements aimed at evaluating the fatigue behaviour and comparing the self-healing capability of two plain bitumen and a bio-binder obtained by partially replacing one of the plain bitumen with a renewable bio-oil. The mineral composition, the physical and mechanical properties, the morphology and the texture of the aggregates, as well as the affinity between aggregate and bitumen were investigated. The results showed that both temperatures improved the properties of the base bitumen, although the bitumen modified at 190 °C contained more non-degraded rubber. Moreover, the complex modulus values confirmed that cold recycled asphalt mixtures provide an intermediate behaviour between asphalt concrete mixtures and cement-treated mixtures. [Extracted from the article]

As an important maintenance measure, de-icing agents are commonly used to ensure safe surface conditions of highways and airport runways during winter. There are however issues related to their use, such as deteriorating effects on road materials, causing particle loss and a decreased low-temperature stiffness of asphalt pavements. To avoid this, it is therefore important to be able to evaluate the effect of the deicer on the asphalt mixture with reliable results. The European standard method for this, EN12697-41, is however associated with several issues such as a high variability of the results and a lack of consistency with the field. Using both experimental testing and numerical simulations, this paper aims to explain the cause of these and to identify the main dominant parameters which can potentially be modified for an improvement. The experimental testing evaluated both the diffusive properties of de-icing fluid and water in mastic and the standard method itself, and the numerical simulations evaluated the effect of different parameters related to the set-up test. From the evaluations, it was concluded that both the set-up of the test and the geometry of the test sample contribute to the high variability of the test method and its lack of consistency with the field. Recommendations are therefore made regarding the potential for improvement and further evaluation of the method. • Evaluates standard method for resistance of bituminous materials to de-icing fluids. • The test set-up causes variability of results and inconsistency with field behavior. • Modifying the geometry could improve the results. [ABSTRACT FROM AUTHOR]

Building more sustainable pavements for the future requires knowledge of alternative and innovative materials for utilization in future road construction and maintenance activities. Being mindful of this need, the present study investigates a Reacted and Activated Rubber (RAR) compound modifier with the aim of defining an optimal RAR percentage in Asphalt Concrete (AC) mixes. It is acknowledged that when this type of modifier is incorporated within an AC mix as an alternative for the bituminous binder material, the associated economic, environmental and social benefits are significant. Simply put, the use of RAR modifiers provides the potential to utilize a waste product (rubber tires) as a more sustainable alternative to bitumen within AC mixtures. However, it seems that the information about the overall performance of AC mixes modified with RAR is currently limited. On these grounds, the present study focuses on the surface course layer and evaluates (a) achieved physical characteristics (compaction degree/voids), (b) mechanical characterization results (stiffness moduli) and (c) friction-based properties of tested mixtures incorporating varying RAR levels and different test temperatures. From the evaluation, it is concluded that for the case of the surface course mixture under investigation, the optimal percentage by weight of bitumen for inclusion of the RAR modifier is 10%. [ABSTRACT FROM AUTHOR]

Clogging of pore space is the leading cause of failure of permeable pavements. A study conducted at Villanova University on two permeable pavements, porous asphalt and pervious concrete, endeavored to answer the question of what materials were depositing in the pore spaces. In 2007, an existing parking lot at Villanova University was retrofitted with a 30 by 9 m section of permeable pavement. Half of the section (15 by 9 m) consisted of pervious concrete, whereas the other half was porous asphalt. The porous pavement area had a drainage area of , which was 100% traditional dense-graded (impermeable) asphalt. A stone infiltration bed underlaid the permeable pavements. Intensive vacuuming was performed using an industrial strength vacuum cleaner to extract the material contained in the pore spaces of the pavement surface layer. The material collected was analyzed to determine the grain size distribution, percentage of organic matter, and concentration of metals (copper, lead, and zinc). Most of the material removed during vacuuming was pieces of the pavements that had raveled. This analysis revealed that very little fines or organics were found in the pore spaces of the pavements, which is attributable to the measures taken on-site to reduce the influx of foreign materials into the pavement surfaces. Metals had sorbed onto the materials removed from the pore spaces; over 20.1 g of copper, 1.8 g of lead, and 18.7 g of zinc were retained because of trapping of sediments in the pores of the permeable pavements. These results indicate that permeable pavement infiltration systems not only reduce the volume of runoff by providing a means of infiltration, but that they improve water quality by removing pollutants at several steps along the water's path. Pollutants can sorb to the sediments in the pore spaces, the rocks in the infiltration bed, and the natural soils beneath the infiltration bed. [ABSTRACT FROM AUTHOR]

Most asphalt mixture rheology studies were limited to condition tests and condition-evaluation indices, which cannot describe the changes in mechanical properties along with changing external conditions. The full-temperature–full-frequency master curves of rheological functions for asphalt mixtures were obtained by dynamic shearing test and time-temperature-shift formulation. The Christensen-Anderson-Marasteanu rheological model and morphology theory were combined to obtain the morphological characteristics of the rheological master curves. These morphological parameters can better describe the pavement performances of asphalt mixtures. [ABSTRACT FROM AUTHOR]

This research work investigates approaches for computing the average asphalt film thickness in asphalt mixtures and examines whether the in-place asphalt film thickness has a rational relationship with the performance of hot-mix asphalt mixtures. Two methods for calculating the aggregate surface areas, the surface area factor and index methods, are discussed in this research and the analytical results show that both the fine aggregate particles and aggregate shapes significantly affect the calculation and should be taken into consideration to obtain greater accuracy for the surface area. A computation method is proposed and significantly improves the current conventional method for the asphalt film thickness calculation by incorporating shape factors and flat surface factors for all sieve sizes. Field performance data from MnROAD and rutting data from laboratory fabricated mixtures, including both coarse and fine gradations, were analyzed to investigate the asphalt film thickness and corresponding performance of asphalt mixtures. Both the field data and laboratory experimental results show that the asphalt film thickness is a significant factor affecting the rutting performance for asphalt mixtures. However, more research work is needed to investigate the relationship between the asphalt film thickness and the other performance parameters of asphalt mixtures, such as fatigue cracking, before a film thickness specification can be proposed. [ABSTRACT FROM AUTHOR]

Various models have been developed over the past several decades to predict the dynamic modulus |E*| of hot-mix asphalt (HMA) based on regression analysis of laboratory measurements. The models most widely used in the asphalt community today are the Witczak 1999 and 2006 predictive models. Although the overall predictive accuracies for these existing models as reported by their developers are quite high, the models generally tend to overemphasize the influence of temperature and understate the influence of other mixture characteristics. Model accuracy also tends to fall off at the low and high temperature extremes. Recently, researchers at Iowa State Univ. have developed a novel approach for predicting HMA |E*| using an artificial neural network (ANN) methodology. This paper discusses the accuracy and robustness of the various predictive models (Witczak 1999 and 2006 and ANN-based models) for estimating the HMA |E*| inputs needed for the new mechanistic-empirical pavement design guide. The ANN-based |E*| models using the same input variables exhibit significantly better overall prediction accuracy, better local accuracy at high and low temperature extremes, less prediction bias, and better balance between temperature and mixture influences than do their regression-based counterparts. As a consequence, the ANN models as a group are better able to rank mixtures in the same order as measured |E*| for fixed (e.g., project-specific) environmental and design traffic conditions. The ANN models as a group also produced the best agreement between predicted rutting and alligator cracking computed using predicted versus measured |E*| values for a typical pavement scenario. [ABSTRACT FROM AUTHOR]

As part of the validation effort to evaluate the consistency of a new cold in-place recycling using foamed asphalt (CIR–foam) mix design process for the Iowa Department of Transportation, the dynamic modulus and repeated load tests were conducted to evaluate the performance characteristics of CIR–foam mixtures over a wide range of loading and temperature conditions. The main objective of this research is to study the impacts of the foamed asphalt contents and reclaimed asphalt pavement (RAP) material characteristics on dynamic modulus and flow number. Dynamic modulus and repeated load tests were conducted on CIR–foam mixtures with RAP materials collected from seven different CIR project sites located throughout Iowa. Dynamic modulus values of the RAP materials varied depending on the sources and foamed asphalt contents. Coarse RAP materials with a small amount of residual asphalt content exhibited a higher modulus value at 4.4°C but exhibited a lower dynamic modulus value at 37.8°C than fine RAP materials with a large amount of residual asphalt content. Flow numbers were varied significantly depending on their RAP sources and foamed asphalt contents. Fine RAP materials with a hard residual asphalt binder exhibited a higher flow number than coarse RAP materials with a soft residual binder. The relative rankings of RAP materials in terms of the flow number did not change when the foamed asphalt was increased from 1.0 to 3.0%, which supports the repeated load test being consistent in evaluating a rutting potential of RAP materials. [ABSTRACT FROM AUTHOR]

A conventional grouted macadam is manufactured by producing a highly porous asphalt skeleton (25-35% voids), and filling the voids with a selected highly flowable cementitious grout. Grouted macadam combines some of the best qualities of concrete and asphalt pavements, namely the flexibility and absence of joints which characterise asphalt and the high static bearing capacity and wear resistance of concrete. Moreover grouted macadam layers are impermeable and efficiently distribute the stresses in the underlying base layer. The speed of construction of grouted macadam surfacings and the short duration required prior to opening to traffic is a major advantage over conventional concrete. Current fields of applications include: airport pavements, industrial floors, harbours, bus terminals, distribution centres, and other heavily stressed areas. The aim of this investigation was to assess the fatigue behaviour of a range of grouted macadam mixtures. Indirect tensile fatigue tests and two point bending tests were conducted on laboratory manufactured specimens and on samples extracted from a trafficked pavement test facility. The experimental work provided interesting data on the influence of mixture composition on fatigue life and highlighted differences between strain and stress-controlled fatigue tests on performance of grouted macadam mixtures compared with conventional asphalts. [ABSTRACT FROM AUTHOR]

The lifetime cost and environmental footprint of asphalt pavements hugely depend on their durability. It is widely accepted that water action plays a crucial role in the deterioration of hot mix asphalt concretes. Researchers seek solutions for promoting adhesion between bituminous binders and aggregate to avoid debonding (stripping) due to the presence of water and mechanical loading. In this research study, five different adhesion promoters were studied at multiple scales. The impacts on bituminous binders, their interactions with water and aggregates, and macroscopic properties of a selected type of asphalt concrete were assessed using both custom and standardized experimental test methods. The study revealed that the performance of additives cannot be assessed based on the results of a single test. A correlation was found between bituminous binder adhesion to aggregates, fracture-mechanical properties of asphalt concretes, and their susceptibility to deterioration in mechanical properties. The results indicate that silane-based adhesion promoter holds the biggest promise for increasing the resistance to stripping in asphalt concrete pavements. • Bitumen–aggregate bonding is crucial for performance and durability of asphalt concrete. • Five different adhesion promoters were studied at multiple scales. • Performance of additives cannot be assessed based on results of a single test method. • Silane-based additive holds the biggest promise for increasing the resistance to stripping. [ABSTRACT FROM AUTHOR]

This study investigated the influence of several construction practices on the bond strength at the interface between pavement layers. These practices included the surface treatment, curing time, residual application rate, and equipment tracking. Three tests were performed for estimating the bond strength between an existing hot mix asphalt (HMA) and a newly constructed HMA overlay, namely the Florida Dept. of Transportation shear tester, the University of Texas at El Paso pull off test, and the torque bond test. Testing involved a CSS-1 type emulsion as the tack coat. The results from the three tests were statistically analyzed. Generally, milling provided a significantly better bond at the interface between the existing surface and the new overlay. Curing time had a minimal effect on the bond strength. The results indicated that the absence of tack coat did not significantly affect the bond strength at the interface for the milled sections, whereas it severely decreased the strength for the nonmilled sections. The results also showed that increasing the residual rate of tack coat did not generally affect the bond strength at the interface. [ABSTRACT FROM AUTHOR]