Since the early l 990's, asphalt interlayers of about 25-mm thick have been used in the United States (U.S.) to greatly delay the onset of reflective cracking over Portland cement concrete and asphalt pavements. Koch Materials Company introduced technology to the U.S., which had been previously used in France. The asphalt interlayer mixture is comprised of fine aggregate with high dust and high asphalt content. This is not just a "recipe" mixture, but a performance-based specification that consists of a high-strain, 4-point flexural beam fatigue test to ensure extreme flexibility and a mixture stability test (Hveem Stability, Asphalt Pavement Analyzer, etc.) for adequate rut resistance. Interlayer test sections were placed strategically thought the U.S. in various climatic zones to further adjust the performance specification and testing temperatures. Today, the asphalt Reflective Crack Relief Interlayer (RCRI) is used in some form in Texas, Kentucky, Kansas, Wisconsin, Iowa, New Jersey, along with other states. With the need to control cracking, RCRI is a valid option for contractors to use local materials to build asphalt interlayers to control/delay cracking. Today, the interlayer can be designed with newer tests like the indirect tensile asphalt cracking test (IDEAL-CT) or flexural beam fatigue coupled with a rutting test such as the Hamburg Wheel Tracker, all with climate-adjusted test temperatures.
Despite the advantages of utilizing High-Float (HF) emulsions in asphalt surfacing applications, formulation and development of such emulsions is a challenging task. This is mainly due to current testing practices used by agencies in specifying the so called "consistency or flow behaviour" of HF residue. These testing practices are informally known as the penetration test, the viscosity test, and the float test. These test methods are empirical in nature and have limitations when properly characterizing non-Newtonian materials, such as HF residues. This technical paper is a sequel to a 2016 CTAA paper "High-float Emulsion Residue: Its Unique Rheology and Microstructure," where a detailed review of current HF residue testing used in Canada was reported. The current paper provides further insight on how current empirical methods of testing could be potentially replaced by one-single, more practical test procedure using the Dynamic Shear Rheometer (DSR). In addition to rheological studies, employment of various residue recovery techniques are also included to demonstrate significant effects of distillation techniques on behaviour of an HF residue. Based on the findings, the stress-ramp procedure can be used to set appropriate shear rates for specific HF residues, measure apparent viscosity, and indicate whether the residue is effectively viscoplastic.
La popularité croissante que connaît le cyclisme comme mode de transport au Canada a entraîné le développement, par de nombreuses juridictions, de nouvelles infrastructures cyclables qui répondent mieux aux besoins de sécurité et de mobilité des cyclistes. Toutefois, il existe une incompréhension globale de la performance de sécurité des différents types d’infrastructures cyclables dans le contexte canadien. La présente étude caractérise la performance de sécurité de diverses infrastructures cyclables dans le but d’aider les spécialistes canadiens à évaluer la performance de sécurité potentielle de nouvelles infrastructures cyclables.
Ce rapport, dont le but est de servir de document d’information, repose sur une analyse documentaire exhaustive, une enquête auprès des juridictions, une série d’études de cas locales et internationales et un sondage auprès des utilisateurs finaux. En outre, ce document comporte un organigramme de sélection des installations qui peut aider les spécialistes à mieux choisir des installations cyclables appropriées en mettant en évidence des points dont il faudra tenir compte dans le choix d’installations cyclables et d’aménagements aux carrefours.
L’une des principales conclusions de cette étude est qu’il existe de vastes lacunes en matière de données et de connaissances quant à la performance de sécurité des infrastructures cyclables au Canada. Ces lacunes portent sur les collisions et autres données de substitution sur la sécurité, les données portant sur les débits de vélos et de piétons (données sur l’exposition), les débits de circulation par type de véhicule, l’information sur la performance des installations cyclables en hiver et autres sujets. De plus, il existe d’importantes lacunes en matière de connaissances sur les seuils associés à une meilleure performance de sécurité quant à différents facteurs qui influent sur la sécurité des infrastructures cyclables au Canada (par ex., le débit de circulation, le débit de vélos, la proportion de camions et d’autobus et la fréquence des points d’accès). On note également un manque de connaissances à l’étranger.
The mixing process in the laboratory is directed by standards. Those standards make recommendations and present some limits. The influence of the laboratory technique to produce asphalt mixes affects the properties and performance of the mixes. Different mixers that produce different mixing energy that are used for different mixing time are considered acceptable, and those variations affect the materials. It could have major impact on aggregates and asphalt mix properties, on the bitumen oxidation, and on the compaction. This paper presents the effect of the mixing process in laboratory for Hot-Mix Asphalt (HMA) with high content of Reclaimed Asphalt Pavement (RAP). Three types of mixers have been used for this research project. For each mixer type, four mixing times were selected based on the mixer properties. The stiffness of bituminous mixture was also evaluated with dynamic tests (waves propagation) and indirect tensile modulus tests (ITSM). According to the results, voids during the SCG compaction have changed with the mixing time for all mixer types and all gyrations. A translation based on the mixing time between the different curves has been observed. For stiffness, results changed through the mixing time and an optimum was obtained for each mixer type.
Every year, the government spends a huge sum of money on repairing roads. The damage incurred on the roadways is attributed to several factors, one of which is the asphalt mixture used to pave the roadways. Sometimes, raw asphalt binder does not have adequate properties to make the roadways durable. Therefore, additives or modifiers are sometimes incorporated to improve the asphalt mixtures, which in turn enhances the performance of asphalt pavements. This study aims to examine the effect of incorporating biochar in asphalt mix. While previous studies have been conducted on the effect of biochar on the asphalt binder, not much has been done to study the effect of biochar on the asphalt mix. This study will help bridge the gap of a lack of substantial research on this aspect. From the tests completed, it was deduced that biochar could have the potential to improve the cracking resistance of the mixes; however, the susceptibility to permanent deformation would increase. From the investigation, the use of fast pyrolysis biochar is preferred. Further research is required to study the performance of asphalt mixes using biochar as an asphalt modifier instead of using it as a filler.
Illinois Flexibility Index Test (I-FIT) and Disc-Shaped Compact Tension (DC(T)) test have shown promise to characterize the intermediate and low temperature cracking resistance of asphalt mixtures, respectively. In this research five plant-produced mixtures were subjected to two laboratory long-term aging protocols and tested with DC(T) and I-FIT. The statistical analysis of the results showed that both aging methods have comparable Flexibility Index values DC(T) test results showed that asphalt mixtures containing hard PGAC were more sensitive to long-term aging. The I-FIT test was also conducted at three temperatures to investigate the sensitivity of I-FIT parameters to testing temperature variations. The statistical analysis of the results showed that asphalt mixtures containing hard PGAC were more sensitive to the drop of testing temperature. In addition, I-FIT test was conducted at various intermediate temperatures to investigate the effect of intermediate temperatures on I-FIT parameters. Finally, the DC(T) test was conducted at three testing temperatures to investigate the effect of temperature sensitivity on DC(T) results, which showed that a reduction in testing temperature caused the fracture energy values to decrease.
This paper presents an asphalt mixture solution that can be placed as a thin layer (less than 40 mm) over granular base to provide a hard-top driving surface. This paper further provides steps in understanding the response of the mix and steps required to translate such responses into developing a performance-based requirement for the asphalt mix. The performance-based design steps are explained in this paper to provide an insight into how low-temperature flexibility and long-term fatigue behaviour of a mix is assessed and related to repetitive stresses expected from low to medium level of traffic coupled with environmental conditions expected in Southern Ontario. Production and paving experience with this asphalt mix solution are also included in this paper, as well as more than two-year field performance of a trial section in Southern Ontario.
The bio-modifiers used were Sub-Epoxidized Soybean Oil (SESO), Epoxidized Methyl Soyate (EMS), and Poly(Acrylated Epoxidized High Oleic Soybean Oil), PAEHOSO. The EMS and SESO, being bio-renewable reactive recycling agents, were used for recycling Reclaimed Asphalt Pavement (RAP) and increasing the mixtures' resistance to low-temperature cracking. The PAEHOSO, being a bio-renewable polymer, was used for increasing the mixtures' resistance to rutting. The rheological tests proved that the EMS and SESO can improve the low-temperature properties and the PAEHOSO can improve the high temperature properties of asphalt binders. Disk-shaped Compact Tension (DCT) and Hamburg Wheel Tracking (HWT) were the mechanical performance tests used for evaluating the mixtures' resistance to low-temperature cracking and rutting, respectively. According to the results obtained from the DCT test the SESO and EMS, when used for modifying the asphalt binders and mixtures, can successfully increase the low temperature cracking resistance. Based on the HWT and DCT test results, the PAEHOSO has a significant influence on increasing the resistance to rutting and low temperature cracking that is all due to increasing the elasticity of asphalt mixtures.
Due to the continuous increase in truck traffic loading to accommodate population growth needs, and also due to the impact of climate change, York Region is experiencing premature pavement failure in many of its heavy truck traffic intersections mostly in the form of pavement deformation or rutting and in some cases shoving. This suggests that pavement materials historically used in the Region may not satisfy the expected life cycle. Six approach intersections were selected by the Region to investigate the in-service performance and identify any need for material improvement. Field work included rut depth measurement and geotechnical investigation such as extracting core specimens, boreholes, and transverse Ground Penetration Radar (GPR) survey. Laboratory testing to test the resistance to rutting and shoving for the three asphalt mixtures placed at the intersections included 1) the Hamburg Wheel Tracking Device (HWTD) to evaluate the rutting resistance of mixtures as well as moisture susceptibility of compacted specimens while submerged in water, (2 the repeated load permanent deformation test or Flow Number (FN) test for predicting the rutting behaviour of the specimens, (3 a newly developed Uniaxial Shear Tester (UST), and (4) IDEAL Rutting Test to measure the shear properties of the asphalt mixes.
The George Massey Tunnel is a major Fraser River Crossing on Highway 99 in Lower Mainland Vancouver. It is a 4- lane tunnel with an average daily traffic of about 100,000 vehicles. The tunnel was constructed in 1950's and is close to the end of its service life. The Province is considering replacing the existing tunnel with a new tunnel or a bridge in the near future. Therefore, the Ministry was looking at potential solutions to fix the water seepage issues for the 5-10- year term. The tunnel approaches have been exhibiting water seepage issues for the past several years. The river water seeps through the joints of the approach slabs, and the pavement surface stays wet at most times. Water seepage poses potential safety concerns during the winter season. Continuous water seepage results in poor pavement performance. Different options were considered as possible rehabilitation solutions. Considering potential of clogging of the voids in the OGFC surface layer, a solution involving the placement of a drainage layer on top of the approach slab followed by placement of two lifts of conventional HMA were constructed. This allowed for the seeping water to flow through the drainage layer without reaching the pavement surface.
Airport runways and taxiways are commonly comprised of a flexible type of pavement surfaced with asphalt mixture that need to endure extreme stresses induced by slow-moving aircrafts, combined with extreme climatic conditions. Additionally, asphalt surfaces could be exposed to fuel spills and/or de-icing chemicals which can further lead to accelerated deterioration of asphalt mixes. So, it is extremely important for airport owners to utilize asphalt mixtures that provides increased level of resistant to load-associated and environmental surface distresses, while providing high level of resistant to detrimental effects of fuel and hydraulic fluid spills. This paper provides information on steps employed in designing a high stability and fuel-resistant asphalt mixture for the busiest airport in Canada, the Toronto Pearson International Airport. Performance testing included: (a) 24-hour fuel immersion test, (b) rutting performance by using Asphalt Pavement Analyzer, Hamburg Wheel Tracking Test, and Flow, and ( c) compression-tension fatigue and dynamic modulus, and ( d) Tensile Strength test. Production and paving experience observed during the first-in-Canada field trial are also included in this paper. This paper further explains the applicability of methodology adopted to develop this mix to other airports in Canada.
High Modulus Asphalt Concretes (HMACs or EME in French) using very hard bitumen were developed in Europe in the 1980s. This type of mix, but adapted for the northern climate, was introduced in Canada in 2012. These high-performance mixes have distinct rheological characteristics, superior to conventional Hot Mix Asphalt (HMA), particularly in terms of structural contribution with an exceptional "modulus of rigidity- fatigue strength" couple. Their adaptation to the Canadian climate must also be ensured by sufficient resistance to low temperature cracking. Their mix designs are ensured by advanced laboratory analyses and based mainly on measurements of mechanical performance such as their modulus of rigidity, their resistance to fatigue, thermal cracking, rutting and their water sensitivity. This article focuses on the formulation approach, the structural contribution in comparison to conventional mixes, and presents several examples of applications (both in new constructions .and in rehabilitation) for various operating conditions. The results show that the combined use of high modulus asphalt pavement and a Mechanistic-Empirical Pavement Design (M-EPD) method allows the reduction of the pavement thickness and a reduction in CO2 emissions and in cost.
A major challenge in current asphalt material selection and specification is the lack of a clear process to determine compatibility between different binder types and additives. In this study, a comprehensive state of the art review on the available tools and techniques to assess the compatibility of complex binder blends was conducted. The promising tools and methods identified from the review were grouped into four categories based on their evaluation purpose and testing procedures: analytical methods; microscopy techniques; thermal property characterization; and performance-based tests. The binder colloidal indices and functional group indices measured from binder analytical tests, and the thermal parameters measured from binder thermal characterization methods have been extensively used in attempts to identify incompatible binder blends. Morphological mapping using microscopy techniques have been used to detect the issue of phase separation. Performance based parameters also show the ability to identify incompatible binders based on measured properties. Preliminary results from on-going research on various binder and mixture tests for compatibility assessment is discussed in the latter part of paper. Study materials consisting of three binders, three recycled asphalt sources are being utilized to evaluate the selected testing methods/parameters and to identify the materials with potential incompatibility issues.
The observation of significant aggregate fracturing during testing is a challenge in interpretation of low-temperature cracking resistance testing of recycled asphalt mixtures. This challenge is becoming more important due to increased interest of using high contents of Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) in the production of Hot Mix Asphalt (HMA). It is believed that such aggregate fracturing is an artifact of the test conditions in the laboratory and does not represent field conditions. ) In this study, a modified procedure of the Indirect Tensile Cracking Test (IDEAL) was developed to reduce or eliminate aggregate fracturing through adjusting testing temperatures and loading rates. The results show that mixture CTindex values measured with the modified IDEAL procedure can differentiate effectively based on RAP/RAS amounts, recycling agent types, and laboratory aging conditions. The CTindex values also correlate very well with blended binder Bending Beam Rheometer (BBR) results, indicating that the test procedure reduces the interference of aggregate fracturing and showing the effects of binders low-temperature properties on the high recycled asphalt mixtures. It is recommended that this issue of aggregate fracturing needs to be carefully considered in IDEAL and other types of low-temperature cracking tests being used today.
The base layer is an essential part of the pavement structure to distribute the traffic load towards the subgrade. Deformation, fatigue cracking, and moisture damage are typical distresses in the pavement due to excessive traffic load and environmental effects. Stabilization is one of the best methods to improve base layer performance to achieve sufficient bearing capacity and resist these problems. Asphaltenes extracted through deasphalting of oil sands bitumen are a by-product of the bitumen with no significant use in the road industry. In the previous research, it was shown asphaltenes could be used as an appropriate modifier to enhance the mechanical properties of asphalt emulsion stabilized mixes, including compressive strength, permanent deformation and tensile strength without causing a significant stiffness and cracking problem. This study aims to compare the addition of cement or asphaltenes on the mechanical properties of asphalt emulsion stabilized bases. It was found that the addition of asphaltenes had a greater impact on increasing the strength and cracking resistance of the mixes as compared to cement. Also, cement-modified samples were more prone to low temperature cracking as compared to the asphaltenes-modified mixtures. However, asphaltenes-modified samples were found to be more susceptible to moisture damage.
Increasing traffic loads and climate stressors are key drivers of the deterioration of asphalt concrete pavement. In response to these challenges, asphalt binder modification has gained prominence to improve both the mechanical and the rheological properties of the material. One notable application of asphalt binder modification is the use of nanomaterials, which are capable of altering the asphalt binder at the nanoscale, thereby improving rutting resistance, low-temperature cracking resistance, fatigue resistance, and healing. In this study, the use of nanoclays for binder modification is investigated in a laboratory setting, focusing on the self-healing behaviour of the binder. The healing potential of nanoclay-modified asphalt is assessed for two different organo-modified montmorillonites at 2 and 4 percent dosages. For this purpose, a two-piece healing test employing a Dynamic Shear Rheometer is used to measure the intrinsic healing behaviour of these binders compared to an unmodified binder. Meanwhile, the effectiveness of the high shear mixing is analyzed using a Scanning Electron Microscope. It is observed that the complex shear modulus is recovered sooner after cracking when nanoclay is added to the mixture. Overall, this research yields promising results regarding the use of organo-modified montmorillonites as a nanomodifier to reduce asphalt deterioration.
Premature failure of asphalt longitudinal construction joints continues to be a concern of roadway authorities throughout North America. In Canada, improving joint performance often ranks as a priority amongst roadway agencies. The key factor affecting joint performance is generally insufficient compaction (high air voids). If left unattended (i.e., with little or no maintenance), the joint issues will greatly impact the overall performance of the pavement. Infrared heaters that pre-heat the joint prior to paving the second lane have been successfully used for over twenty years and are becoming more common as a very effective method to improve joint density and performance. Independent studies have shown that using joint heaters provides lower in-place air voids and permeability, and ultimately improves the bond resulting in longer durability. The City of Hamilton has specified the use of infrared joint heaters since 2007 where maintaining a hot joint is not viable. In Alaska, Ground Penetrating Radar (GPR) is being evaluated in conjunction with joint heaters to verify joint density. This paper will provide an in-depth review of the construction issues associated with longitudinal joint construction. The review will include current use of infrared joint heaters, and the associated specifications along with observed performance improvements.
Canada has over 1.13 million kilometres of roads (two-lane equivalent), making it the seventh-largest road network in the world. Roads in Canada are managed primarily by four different jurisdictions:· federal authorities, provincial authorities, territorial authorities, and regional authorities. Federal authorities manage the federal highways and roads in national parks. Provincial and territorial authorities are responsible for managing provincial and territorial roads, respectively. Trans Canada highways are also managed exclusively by the provincial and territorial authorities, while regional authorities are responsible for managing local roads and streets in their respective region. Approximately 80 percent of public roads in Canada are governed by the regional authorities, which refer to cities, towns, and municipalities, making them the most important contributors to the Canadian road management system. To understand the pavement management practices at the regional level, a country-wide road management survey was conducted. The survey covered all the essential components of a pavement management system, such as road type, inventory information, road condition assessment system, treatment program, maintenance priority program, pavement performance prediction model, etc. Forty-one cities, towns, and municipalities from nine different provinces participated in this survey and yielded a tremendous amount of data to explain contemporary roadway management practices in Canada at the regional level.
This guide is intended for use by agencies in evaluating soil and material stabilization products being promoted by suppliers. It also identifies soil stabilization products and processes used across Canada and internationally, with a look at their optimal applications and performance when data is available.
This guide considers soil stabilization to include both soil and material modification and stabilization activities. Modification of soil considers soil improvement during or shortly after mixing to improve engineering properties such as plasticity and moisture sensitivity, to help facilitate or expedite construction operations. Stabilization of soil, on the other hand, considers a chemical and/or mechanical treatment of a mass of soil to improve its shear strength and durability for inclusion in a pavement structure.
This guide focuses on the stabilization of pavement structures for roadways including subgrades, aggregate layers, and full depth reclamation of asphalt, chip seal and granular roadways.
The project included a thorough literature review of relevant products and processes across Canada and internationally. A detailed survey was also prepared and distributed to agencies, consultants and contractors to collect information on current stabilization practices and product evaluation procedures used across Canada and internationally. Suppliers of stabilization products were also surveyed to develop a database of current stabilization products and their use and performance.
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