Originally built in 1907, the Traffic Bridge was Saskatoon’s first bridge to carry vehicular traffic. The Traffic Bridge was designed as a 5-span Parker through truss and came into being when residents of the Village of Nutana agreed to merge with the Town of Saskatoon and the Village of Riversdale to form the City of Saskatoon. The heritage value of the Traffic Bridge lies in its status as a landmark in the community, its form, massing, and location, the engineering technology used (steel truss architecture), and the original concrete piers and abutments.
Throughout its 103-year history, the bridge has been used for horse and carriage, street car, and modern vehicle use. The bridge also has historical notoriety as Saskatoon’s only marine disaster when the sternwheeler S.S. City of Medicine Hat collided broadside into the southern-most pier of the bridge and sank on June 10, 1908.
The bridge was closed in August 2010 due to public safety concerns due to advanced deterioration of critical structural members. In 2010, the City commissioned a needs assessment and planning study of the Traffic Bridge, which investigated multiple alternatives and potential replacement, included extensive public consultation, regulatory review and debate, as well as City Council presentations.
Many elements of the existing bridge were to be incorporated into the new bridge. Engineering studies were completed on the existing elements to determine strengths and compatibility with the new structure.
A P3 model was used for the design and construction of the replacement bridge. Many challenges presented themselves during the design and construction of the structure and these challenges provided unique resolutions. The bridge is currently under construction, and upon completion, the contractor will be responsible for the maintenance of the bridge for the next 30 years.
The Bonaventure Project is a series of strategic undertakings aimed at providing user-friendly, functional and safe mobility options to all users. The Bonaventure Project Vision includes three main objectives: Create a prestigious, functional and user-friendly gateway into the downtown core; Facilitate the re-weaving of the urban fabric through the removal of an elevated highway structure in the urban environment; Support private sector driven urban development through the implementation of key strategic initiatives in the downtown core.
North American cities need excellent bicycle infrastructure between regional destinations to allow residents to cycle long distances. Planners must make long distance bicycle travel feasible if they are serious about treating cycling as a form of mass transportation (Transport for London, 2014).
Bicycle highways are high quality bicycle routes that connect major destinations and are designed for safe and comfortable long-distance travel. They facilitate comfortable and safe long distance travel. Preliminary research has shown that they are effective in increasing ridership and attracting users from other modes such as cars or transit.
The purpose of this review is to offer guidance on how practitioners can plan, design, and implement bicycle highways as part of a bikeway network. The study draws upon literature and design guidance and seven case studies that are emerging in Europe and Asia. Through this review we propose a definition for bicycle highways, differentiate them from other bikeway facilities, present research on their effects, and characterize their planning, design, and implementation. We conclude this papers with seven policy takeaways for North American practitioners.
This paper summarizes the performance of a steel truss railway bridge near Saskatoon, SK, which remained in service during pile driving activities for pier rehabilitation and new pier construction.
289 H section piles were driven to embedment depths of 9 m for rehabilitation of existing concrete piers, and 12 m for new piers, for the western portion of the bridge, over an approximate one-month timeline. Piles for existing piers were driven within one metre of the existing pile caps, which were supported on timber piles. Monitoring instrumentation included surveying of prisms mounted to the bridge deck and piers and installation of tilt loggers, and a vibration monitoring system, to monitor the lateral deflection and accelerations, respectively, of the structure during pile driving. The collected data provides an understanding of the response of the bridge structure from pile driving into the hard foundation till, along with expansion and contraction effects due to extreme temperature variations. Survey and tilt logger data were found to correlate well together, and with changes in ambient temperature.
Wave Equation Analysis of Pile Driving (WEAP) was conducted to estimate pile termination criteria and driving hammer performance. Pile Dynamic Analyzer (PDA) testing was conducted on 10% of the piles; 9 and 12 m long piles driven into Sutherland Till exhibited average vertical capacities in the range of 1,940 kN and 2,700 kN, respectively.
In the summer of 2015, Standard General Inc. – Calgary (SGIC), a subsidiary of Colas Canada Inc., introduced a new paving material called Betoflex® with the goal of resolving a recurring permanent deformation issue of two taxiways leading to Runway 17/35 at the Calgary Airport. The 2015 mixture was developed using the French Level 2 methodology to ensure that rutting resistance performance was achieved while maintaining good mixture workability to facilitate placement and compaction.
In the spring/summer of 2016, Level 4 testing was performed on various Betoflex® mixtures that could potentially be used in the Calgary area. Level 4 testing was also performed on typical mixtures used in Calgary to benchmark Betoflex® with local mixtures. The Level 4 mix-design provides information for pavement design (stiffness modulus and fatigue resistance) using the French ALIZÉ-LCPC software.
This paper provides an overall perspective of the engineering of asphalt mixtures to achieve “in-service” performance not only for durability (moisture resistance and rutting), but also for pavement design performance (stiffness modulus and fatigue resistance). It also discusses how the ALIZÉ-LCPC pavement design software uses Level 4 mix-design information to optimize pavement thicknesses and/or pavement performance reliability with respect to fatigue and large radius rutting.
Asphalt binder rejuvenator use in Hot Mix Asphalt (HMA) has been gaining momentum not only to delay aging of the asphalt binder, but also to permit higher levels of binder replacement from recycled materials. In this study, an HMA mixture was designed with approximately 35 percent binder replacement from Reclaimed Asphalt Pavement (RAP). Per specifications, a binder grade adjustment from PG 64-22 to PG 58-28 was required. The control mixture contained a neat PG 58-28 binder. Three experimental binders contained asphalt binder that were a blend of PG 64-22 plus rejuvenator materials to produce a PG 58—28 binder. HMA mixtures containing all four asphalt were tested for cracking and rutting resistance.
The laboratory study indicated that the control and experimental mixes had no difference I rutting resistance. Under short-term aging, all three experimental mixtures with rejuvenators had improved cracking resistance as measured by the Illinois Flexibility Index Test (IFIT). Under long-term aging conditions, no significant difference was observed among the control and the three experimental mixtures according to the Disc-Shaped Compact Tension (DCT) test. However, IFIT testing of long-term aged specimens showed improved cracking resistance for two of the three experimental mixtures compared to the control.
The focus in recent years has been to make asphalt mixes more affordable, and this has led to the increased use of recycled materials and binder modifications. Consequently, one often-heard complaint is that the recent mixes are more susceptible to cracking. There is an urgent need for a practical cracking test for routine use in the process of mix design, quality control, and quality assurance testing. This paper develops an indirect tensile asphalt cracking test (IDEAL-CT). The IDEAL-CT is typically run at room temperature with 150-mm diameter and 62-mm high cylindrical specimens with a loading rate of 50 mm/min. The IDEAL-CT is a simple (no instrumentation, cutting, gluing, drilling, or notching of specimens), practical (minimum training needed for routine operation), and efficient test (test completion less than one minute). The test can be performed with regular indirect tensile strength test equipment. As described in this paper, the IDEAL-CT is sensitive to key asphalt mix components and volumetric properties including reclaimed asphalt pavement and recycled asphalt shingles content, asphalt binder type, binder content, aging conditions, and air voids. The proposed test also has a much lower coefficient of variation than traditional repeated load cracking tests. Furthermore, the IDEAL-CT results were compared with field cracking data collected from the Federal Highway Administration’s accelerated load facility, Texas SH15 and SH62, and MnROAD. The IDEAL-CT characterization correlated well with field performance in terms of fatigue, reflective, and thermal cracking. Last but not the least, the ruggedness test performed in this study indicated that the IDEAL-CT, after combining both statistical and practical views, could be considered as rugged with all four variables: specimen thickness, loading rate, test temperature, and air voids.
Several highway agencies have either implemented or considered implementing performance tests to predict the cracking potential of asphalt concrete (AC) mixes in the laboratory setting. One such test, the overlay tester (OT), simulates the opening and closing of cracks induced by daily temperature variations and tensile strain generated by traffic loads. The variability of the OT results is expressed as a major concern in reliably characterizing cracking potential of AC mixes. A more fundamental analysis process and more mechanistic performance indicators were implemented that consider the two stages of the cracking mechanism (i.e., crack initiation and crack propagation). The repeatability of the proposed performance indices, critical fracture energy and crack progression rate, seems to be better than the current criterion based on the number of cycles to dissipate 93% of the initial maximum peak load. The proposed cracking methodology and associated preliminary failure limits seem to characterize and satisfactorily discriminate the cracking resistance of AC mixes. Given its promise in this study, the proposed OT test method is recommended as a routine test during the mix design process of AC mixes to predict and screen their cracking susceptibility.
The existing design method for RAP mixtures assumes virgin and RAP binders fully blend. However, full blending may not occur and the impact of partial blending on mixture cracking performance is still unclear. A previous study revealed that RAP gradation, which is not currently considered from the standpoint of binder blending, controls the distribution of RAP binder within a mixture and consequently affects cracking performance. The objective of this study was to develop a methodology that overcomes the uncertainty of blending and effectively predicts fracture properties of RAP mixtures. This methodology is based on the evaluation of the interstitial component (IC) of a mixture (i.e., the fine portion that governs cracking performance) by means of a direct tension test named ICDT test. Two RAP sources and four RAP contents were considered. ICDT specimens were produced by blending the fine portion of RAP and virgin aggregate with virgin binder in the same way and corresponding proportions as in RAP mixtures. Binder and mixture fracture properties from the previous study were used for comparison. Mixture and IC exhibited almost similar reduction in fracture energy density (FED) with increasing RAP content, whereas fully blended binder exhibited a less pronounced reduction. This indicated that IC better simulated the actual blending that occurred in mixtures. Mixtures with coarsely graded RAP (less RAP content in the IC) exhibited better fracture properties; thus, the key to satisfactory cracking performance appears to be minimizing the amount of RAP in IC. Consequently, the stiffening effect of RAP on the fine portion that controls cracking performance should be directly evaluated, instead of placing focus on the fully blended binder or the whole mixture. The ICDT test was proven to be a valuable tool to predict fracture properties of RAP mixtures.
The objective of this study was to evaluate the effects of incorporating recycled materials, i.e., reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), and the use of warm-mix technologies on fatigue performance of asphalt mixtures and pavement structures using the viscoelastic continuum damage (VECD) approach. For this purpose, ten mixtures from the full-scale test lanes constructed at the Federal Highway Administration (FHWA) Accelerated Loading Facility (ALF) were acquired and characterized in the laboratory. The dynamic modulus test and direct tension cyclic fatigue test were employed to assess the linear viscoelastic property and fatigue characteristics, respectively. Within the VECD framework, two parameters, namely material fatigue sensitivity (MFS) and structure fatigue sensitivity (SFS) were developed to represent the fatigue resistance of asphalt mixtures and their performance in pavement structures, respectively. Both parameters can be easily obtained via the strain-based fatigue simulation using the experimental data without extra requirements on the specimen failure location and the number of cycles to failure in the cyclic fatigue test. The validity of MFS was verified by the critical strain energy release rate obtained from semi-circular bend (SCB) testing at intermediate temperature. Based on the obtained dynamic modulus and MFS data, an increase in the content of recycled materials was able to enhance the stiffness of hot-mix asphalt (HMA) mixtures while compromising the fatigue resistance. Implementation of warm-mix technologies benefited materials’ fatigue performance but the improvement was not substantial. Use of soft binder yielded pronounced fatigue benefits for HMA mixtures with high RAP content. The proposed SFS parameter resulted in the same performance ranking of the ALF lanes as the measured fatigue lives. Moreover, quantitatively a power-law function was found to adequately correlate SFS with the field measurements.
Warm mix asphalt (WMA) technology and reclaimed asphalt pavement (RAP) materials have been increasingly used in asphalt paving mixtures due to environmental and cost benefits. Combining WMA and RAP offers more economic and environmental benefits compared to using either alone. To evaluate the combined effect of WMA and RAP, two WMA mixtures with 20% and 30% RAP were produced using water-injection plant foaming, and they were compared with two comparable HMA mixtures with 20% and 30% RAP. The four mixtures were paved on I-70 near Eagle, Colorado, in May 2013. Laboratory performance properties of plant-produced mixes and field performance of the four test sections after 13, 25, 38 months were evaluated. The research results showed that the effect of water foaming WMA and RAP was not significant on the laboratory performance properties, construction quality and field performance. Thus, water-injection plant foaming WMA could be used to produce WMA mixtures with 20% and 30% RAP at a lower production temperature. These sections will continue to be monitored to evaluate their long-term performance and compare with the laboratory test results.
Illinois has many years of experience using various reclaimed materials in highway construction, and in recent years, recycled asphalt shingles (RAS) have been adopted for use in hot-mix asphalt (HMA), along with much higher amounts of reclaimed asphalt pavement (RAP). These reclaimed asphalt materials usually contain aged asphalt binders, which may increase the mix brittleness and hence, pose a challenge for maintaining a flexible pavement and ensuring good performance. To counter these hard asphalt binders, softer asphalts are incorporated into the HMA. The goal is for the final mix to provide acceptable mix properties for the life of the pavement.
To determine the impact of recycled materials on pavement performance, this study monitored nine field projects in terms of the testing, construction, and performance of surface mixes that have a variety of asphalt binder replacement (ABR) levels from RAP and RAS which used different virgin asphalt binder grades. Simple performance tests (Hamburg wheel tracking test and the Illinois flexibility index test (I-FIT)) were used to evaluate the mix designs. Flexibility index (FI) from the I-FIT showed good correlation with field crack development, especially after first year performance of the mix. Early-age field performance showed that placing the HMA overlay directly over existing bare concrete pavement or milling off all the HMA and placing the new overlay on concrete pavement results in higher extents of cracking in early age than the sections that left an HMA layer in place. Regardless of which mix type is designed and what material sources are used, the performance of the mix should be evaluated to ensure it has sufficient flexibility to resist cracking before the mix is used in road construction. This allows owners and contractors to use low-cost reclaimed and recycled materials to the extent possible without negatively impacting pavement performance.
In the present study, rutting performance, cracking resistance, and durability of five plant-produced asphalt mixes containing 12% reclaimed asphalt pavement (RAP) and 3% recycled asphalt shingles (RAS) and produced with different warm mix asphalt (WMA) technologies were evaluated through characterization of extracted asphalt binder and performance tests conducted on asphalt mix specimens. For all of the extracted and recovered asphalt binders, continuous grades and the difference between critical low temperatures, Tcr parameter, were determined from the performance grading and a Glover-Rowe (G-R) damage zone was evaluated at 45°C and 10 rad/s. It was revealed that application of a rejuvenating agent (RA) significantly reduced the high PG grade of the overall asphalt binder. The binder test results also indicated that the chemical-additive-based WMA technology had an advantage over the foaming-based technology in terms of asphalt binder durability. Furthermore, application of RA improved the asphalt binder durability. Comparison of G-R parameters of the recovered asphalt binders showed that using RA and lowering the virgin binder high PG true grade improves the overall binder ductility and damage resistance.
Asphalt mix performance tests included dynamic modulus, flow number, and semi-circular bend. The dynamic modulus test data indicated that application of RA and lowering the virgin binder high PG grade lowered the mix stiffness at low frequencies. Comparison of the methods to compensate the effects of highly aged RAP and RAS binders indicated that the mix prepared with RA and one level high PG grade drop performed better than the mix prepared by dropping the PG grade by two levels in terms of cracking resistance and rutting performance. The findings give credence to utilization of rejuvenating agents and softer virgin binders in balanced RAP/RAS mix design approaches.
Although the use of high reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) contents in asphalt mixtures is desirable for environmental and economic reasons, these mixtures are prone to cracking, raveling, and other durability-related pavement distresses mainly due to the heavily aged recycled binders. Highway agencies and the asphalt paving industry have been exploring the use of recycling agents (RA) in order to produce these mixtures with desirable performance. This study focused on characterizing the long-term rejuvenating effectiveness of RA on asphalt blends and mixtures with high RAP and RAS contents. Materials from two field projects were used to prepare a number of asphalt blends and mixtures with various combinations of base binder, recycled material, and RA. These blends and mixtures were subject to various aging protocols prior to being characterized for their oxidation kinetics, rheological properties, and cracking resistance. The test results indicated that the RA evaluated in this study were effective in partially restoring the properties of recycled materials, but their rejuvenating effectiveness diminished with aging. Nevertheless, the recycled blends and mixtures with RA achieved equivalent or even better rheological properties and cracking resistance than those with an allowable amount of recycled materials per agency specifications but without RA. In addition, adding RA had no significant effect on the oxidation kinetics of the recycled blends, but increased their susceptibility to physical hardening in response to oxidation. Finally, the correlation between laboratory aging protocols for asphalt blends and mixtures were determined; the laboratory long-term oven aging protocols of five days at 85°C on compacted specimens and one day at 135°C on loose mix yielded binders with equivalent rheological properties to those subjected to rolling thin film oven (RTFO) plus approximately ten and 40 hours of pressure aging vessel (PAV), respectively.
The use of porous friction course (PFC) provides numerous safety benefits and improves the noise quality of surrounding areas. Many agencies once used PFC for these reasons, but have since stopped using PFC due to performance issues. PFC pavements have reportedly been prone to raveling and cracking which leads to reduced service life. In addition, PFC is also typically more expensive than a dense-graded mix due to its use of high quality aggregates, modified asphalt binder and higher asphalt binder contents. Research is needed to extend the service life of PFC pavements in order to encourage agencies to start, or continue, use of PFC for its safety benefits. The objective of this research is to address the raveling and cracking distresses commonly seen by adjusting the asphalt and dust content of PFC mixes to improve durability. This was accomplished by using an array of performance tests to evaluate the effect of additional fine aggregate passing the 0.075 mm (P-0.075) sieve on two PFC mixtures: one that had good field performance (up to 18 years) and one that had poor field performance (less than eight years). It was found that the Cantabro test was a good indicator of mix performance and a maximum loss of 20% is recommended. The study revealed the importance of increased percent passing the 0.075 mm sieve to provide more durable PFC mix designs. An increased P-0.075 content had a positive effect on almost all of the results; thus, it is recommended that the current P-0.075 gradation band be expanded.
The characterization of asphalt binder at low temperature is of fundamental importance for selecting and designing asphalt materials with good and durable performance in regions experiencing severely cold climates. The current specification addresses this issue based on the Performance Grading (PG) system, developed during the Strategic Highway Research Program, and on low temperature creep tests performed on asphalt binder with the Bending Beam Rheometer (BBR). Recently, an alternative experimental method was proposed to relate the complex modulus, obtained with the Dynamic Shear Rheometer (DSR) at low temperature, to the BBR creep stiffness. However, while DSR tests are performed in air, the BBR relies on an ethanol bath for conditioning the binder specimens, making the relation between complex modulus and creep stiffness dependent on the specific cooling medium. In this paper, the effect of cooling medium on the low PG and on the rheological properties obtained from DSR and BBR tests is experimentally investigated and modeled. First, DSR and BBR tests, in ethanol and air, are performed on a set of different asphalt binders. Then, a relationship between the complex modulus in the time domain and the creep stiffness obtained both in ethanol and air is derived and the low PG for both cooling media is estimated. Finally, 2 Springs 2 Parabolic Elements 1 Dashpot (2S2P1D) and the Huet models are used to compare the effects of ethanol and air on the rheological properties of the asphalt binders. It is found that air results in higher creep stiffness and smaller m-values compared to ethanol. The two rheological models indicate that complex modulus and creep stiffness present the same kernel model parameters only in the case of air. This suggests that the low performance grade, obtained from BBR tests in ethanol, is strongly affected by the cooling medium, as well as the recently proposed procedure based on DSR tests. Based on the finding of the present research, the use of air for BBR creep tests is recommended.
Cracking is one of the most prevalent types of distresses in asphalt pavements. There are different cracking index parameters that are determined from tests conducted on binders and mixtures to assess cracking potential. The objective of this study is to compare binder and mixture parameters and evaluate the similarities and differences between the rankings and values obtained. This study includes binder- and mixture testing on 14 plant produced mixtures including three different binder grades, three binder sources, three aggregate gradations, and mixtures containing a range of RAP and/or RAS contents. Testing included PG grading and 4-mm DSR testing on the extracted and recovered binders that were long-term aged. Mixture testing included complex modulus, SVECD fatigue, and DCT testing on short-term aged mixtures. Parameters evaluated included high and low PG temperatures, Tcr, Glover-Rowe parameter (binder- and mix-based), R value, dynamic modulus, phase angle, number of cycles to failure from SVECD and LVECD analysis, and fracture energy. The results show that generally the binder parameters correlate well with each other but the mixture parameters do not. Good correlation was observed between binder and mixture stiffness-based parameters, but there was generally low correlation observed between binder and mixture cracking parameters for the mixtures evaluated in this study, possibly a result of differences in aging level. Recommended future work includes non-linear statistical analysis, incorporation of field performance, and testing on long-term aged mixtures
The AASHTO M 320 specification for thermal cracking—meant to limit damaging temperatures to only a 1 in 50 risk in any given winter—stipulates that asphalt cement chemically (irreversibly) aged in the rolling thin film oven (RTFO) and pressure aging vessel (PAV) be tested after minimal cold conditioning. Creep stiffness and creep rate (m-value) are determined with specimens rapidly cooled to 10°C above the pavement design temperature and then conditioned for only an hour prior to testing. As a result, materials are often tested in a non-equilibrium state and pavements end up under-designed for thermal cracking; adjacent sections can show from best-case to worst-case performance.
Several Ontario user agencies have recently implemented a specification to effectively limit cracking due to reversible aging: “Determination of Performance Grade of Physically Aged Asphalt Binder Using Extended Bending Beam Rheometer (EBBR) Method” (Ministry of Transportation of Ontario designation LS-308 and recently adopted by AASHTO under designation TP 122-16). This empirical protocol tests beams after 72 hours of cold conditioning to determine a low temperature grade as well as a grade loss from the 1 hr results specified in AASHTO M 320. Grade losses are sensitive to the presence of deleterious additives (waxes, air blown residues, recycled engine oil bottoms (REOB)). Further, by testing recovered material from paving mixtures, the protocol also provides a secure way to account for the presence of recycled pavement (RAP), and to monitor for overheating during production.
The extended BBR method has several limitations: (1) it requires a relatively large quantity of 150 grams of aged material; (2) it takes a relatively long 72 hours to complete; and (3) it quenches the binder from room temperature to two cold temperatures, namely 10°C and 20°C above the pavement design limit (Td+10 and Td+20), and therefore, because of its empirical nature, it is unclear if the results obtained are relevant for other thermal histories. Since these drawbacks have slowed implementation, current research is focused on the following improvements: (1) modeling the aging/hardening processes within the Ozawa theoretical framework; (2) reducing sample requirement to less than 12 grams; (3) shortening testing time to less than 24 hours; (4) conditioning at more temperatures between ambient and the pavement design limit; and (5) automating the procedure.
Modeling efforts are based on an analysis of non-isothermal phase transformation kinetics. This paper presents results obtained from differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) three-point bending tests on a number of Ontario asphalt cements under varying cooling rates. The application of the Ozawa theory provides an improved understanding of how thermal history and variable aging tendencies can explain vast performance differences between pavement sections of identical AASHTO M 320 grades. It is suggested that by adding an upper limit on the Ozawa exponent to the low temperature asphalt cement specification, in order to reduce the rate of reversible aging, user agencies will be able to better control this type of cracking.
Aging of asphalt binders has a significant impact on the rheological properties of asphalt binders and thus affects the performance of asphalt pavements. The rate of binder aging is accelerated at high temperatures. This study presented a case study on the effect of aging of the asphalt binder properties in the State of Qatar where asphalt mixtures experience harsh environmental conditions of elevated temperatures. The researchers collected field cores from five-year old trial pavement sections in Qatar, recovered the binder and tested to evaluate the change in the rheological properties of the binders. Test results indicated that there is a significant effect of aging on the rheological properties of asphalt binder in Qatar. This effect was more prominent in the wearing course of pavements, diminishing with an increase in pavement depth. Binders along the wheel path experienced less aging compared to the shoulder. Aggregate type and mix design methods were also found to be affecting the extent of aging of asphalt binder in the field. Furthermore, the researchers found that the current practice of aging asphalt binders in the PAV to simulate aging in the field is not sufficient for Qatar’s conditions. It is recommended to extend the PAV aging period from the standard 20 hours for a hot climate like Qatar and it might go up to about 70 hours based on the results of this study.
The asphalt foaming process, as one of the major warm mix asphalt (WMA) technologies, can significantly increase the volume of asphalt binder with large surface area in the unit volume and thus generate a strong coating with high shear strength of the mix and improved workability. It allows lower production and construction temperatures and less greenhouse gas and other emissions. Foaming asphalt has generally been achieved by introducing water as a foaming agent into hot asphalt flow before mixing with aggregate at a certain temperature. The water will evaporate and expand the asphalt volume and reduce its viscosity. However, both the formation and decay of the foamed asphalt binder is a highly thermodynamic process, which makes the characterization of the foamed asphalt binder extremely difficult. A high fidelity model to simulate the foaming process will provide a powerful tool to conduct virtual experiments of WMA production and optimize the asphalt foaming process and WMA design. To this end, a numerical model using smooth particle hydrodynamics (SPH) is developed to simulate the asphalt foaming process. A self-developed nozzle-based foamer was used to generate foamed asphalt binder at different water contents. Three primary parameters, i.e., expansion ratio, half-life and foam index, that have been widely applied to evaluate the foaming characteristics of foamed asphalt, have been studied. It was found that the simulation results agree well with the experiments. Parametric studies were further conducted by using the numerical model to evaluate the effects of environmental controlling parameters on the foaming characteristics of the foamed asphalt binder.
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