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Advanced Study on the Rheological Behavior of a Composite Binder Treated Recycled Aggregate (Asphalt Emulsion and Cement)

mar, 06/12/2018 - 19:41
Advanced Study on the Rheological Behavior of a Composite Binder Treated Recycled Aggregate (Asphalt Emulsion and Cement)
by Paquin,Y; Proteau,M.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P18 - MAIN

The 2001 Canadian Asphalt Exchange Program (CAEP) - 2001 Summary

mar, 06/12/2018 - 19:21
The 2001 Canadian Asphalt Exchange Program (CAEP) - 2001 Summary
by Beshara,M.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P17 - MAIN


This report documents the results of the 2001 Canadian Asphalt Exchange Program. Nineteen agencies participated in the 2001 Canadian Asphalt Exchange Program. The exchange provides an opportunity for participants to compare their test results with those of other laboratories in order to provide a mechanism for reviewing and refining existing test procedures. The exchange also provides information to participants on their individual test procedures and equipment. Five types of binder material were tested in the 2001 exchange; a 150-200A asphalt cement, an MC-250 asphalt cutback, an HF 150S asphalt emulsion, an HF 150P polymer modified asphalt emulsion and a SHRP binder PG 58-28. All participants were given identical material samples to evaluate. The test result analysis was based on ASTM E691-92 “Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method”. This procedure was used to evaluate the repeatability and reproducibility standard deviations for the different test procedures performed in the asphalt exchange. This information was used to determine the 95 % repeatability and reproducibility limits for each test procedure. The analysis procedure also provided information for each participant to determine if their test results were consistent with those of the other laboratories.

The 2002 Canadian Asphalt Mix Exchange Program - 2002 Summary

mar, 06/12/2018 - 19:15
The 2002 Canadian Asphalt Mix Exchange Program - 2002 Summary
by Beshara,M.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P16 - MAIN


Fifty-one Canadian engineering organizations participated in the 2002 CANADIAN ASPHALT MIX EXCHANGE PROGRAM. The exchange provides an opportunity for participants to compare their test results to those of other laboratories. It provides a mechanism for review and refinement of existing test methods and equipment. The exchange evaluates the volumetric and mechanical properties of an asphalt-aggregate mixture using Marshall Mix Design procedures, the gyratory compactor, and the ignition oven. This report documents the test results for the year 2002 Canadian Asphalt Mix Exchange Program.

Construction of Durable Longitudinal Joints

mar, 06/12/2018 - 18:37
Construction of Durable Longitudinal Joints
by Scherocman,JA.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P15 - MAIN


The durability of longitudinal joints in asphalt concrete pavements is a major problem at many locations across North America. After a short period of time under traffic, these joints tend to ravel. In some cases the raveling is severe enough to completely erode the mix at the joint leaving a gap between the lanes. There are a number of factors during construction that directly affect the durability of a longitudinal joint. The first is the compaction of the unsupported edge of the first lane of mix placed. The second is the amount of overlap of mix on the second lane over the top of the first lane. The third factor is related to the raking of the mix at the joint. The final factor is the compaction of the mix at the joint. The construction of a longitudinal wedge joint is discussed. The need for the application of a tack coat on the joint, for cutting back the unsupported edge of the first lane and for paving in echelon in order to construct a hot joint are also discussed. Construction of a durable longitudinal joint is a question of good workmanship by the contractor using proper construction techniques.

Development of Flexible Pavement Roughness Prediction Models for Use in Network-Level Programming

mar, 06/12/2018 - 18:22
Development of Flexible Pavement Roughness Prediction Models for Use in Network-Level Programming
by Ningyuan,L; Kazmierowski,T; Sharma,B.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P14 - MAIN


This paper describes the performance of flexible pavement observed on Ontario's highway network and the roughness prediction models developed for use in the Ministry of Transportation of Ontario’s (MTO’s) second generation Pavement Management System (PMS2). The PMS2 is used primarily for providing the Ministry’s senior management (decision makers) with a series of analysis reports and information related to pavement management, including annual pavement condition assessment, network pavement maintenance and rehabilitation needs analysis, cost-effective pavement preservation programming, and optimal investment strategy. A critical review of the Ministry's network level pavement performance database is presented, emphasizing pavement condition surveys, prediction models and main factors influencing assessment of long-term pavement performance. Several key issues related to quality control and quality assurance (QC/QA) of the pavement roughness measurement protocol are discussed with reference to roughness measurements and verification techniques used by the MTO. In addition, the paper discusses a pavement evaluation index in terms of International Roughness Index (IRI) and its application in needs analysis, multi-year pavement maintenance and rehabilitation projects programming.

Challenge of Permafrost Degradation Impact on Airport and Road Pavements

lun, 06/11/2018 - 18:48
Challenge of Permafrost Degradation Impact on Airport and Road Pavements
by Uzarowski,L; Musial,M; Rizvi,R.
2018.
TAC 2018: Innovation and Technology: Evolving Transportation - 2018 Conference and Exhibition of the Transportation Association of Canada.
CA6 ARH_10 2018A5168 - INTERNET


A large part of northern Canada is in the discontinuous or scattered and discontinuous permafrost zone. It has been observed at airports and on roads, that due to disintegrating permafrost the pavements in the above zones exhibit rapidly progressing degradation. This paper describes cases where pavement failures due to melting or melted permafrost were investigated. Large settlements or slippage of airport pavements were observed. The pavements became very rough, posing a safety hazard to moving aircraft, particularly on runways. Similar settlement may occur on aprons and taxiways. In some cases airport buildings, including terminal buildings, may differentially settle/heave and require urgent expensive repairs. Relocation of buildings and airside groundside facilities may be necessary. Three cases are described in this paper where airport and road pavements exhibited serious problems due to permafrost degradation. It presents the method of investigation of permafrost presence and condition including visual condition inspection, geotechnical investigation and laboratory testing, temperature monitoring using thermistors and extent of permafrost using OhmMapping. The considered methods of addressing the issue of pavement failures included identifying the location and severity of the problem, addressing the drainage issues, emergency pavement repairs, soil replacements and pavement insulation, structural repairs using geosynthetics, and reconstruction including soil improvement or replacement, and relocation.

Towards Developing Environmental Sustainability Performance Measures for Pavement Asset Management Practice

lun, 06/11/2018 - 18:21
Towards Developing Environmental Sustainability Performance Measures for Pavement Asset Management Practice
by Achebe,JC; Tighe,SL.
2018.
TAC 2018: Innovation and Technology: Evolving Transportation - 2018 Conference and Exhibition of the Transportation Association of Canada.
CA6 ARH_10 2018A5167 - INTERNET


The functionality of performance measurement approach is valuable in Pavement Management Systems (PMSs) to account for different criteria in the decision-making process. However current paradigm of asset management decisions made within pavement management systems only prioritizes resource allocation polices that maximizes the serviceability performance of the road network with no consideration of the environmental sustainability. This is the essence of incorporating environmental sustainability into pavement management The reduction of material consumption and greenhouse gas emission when maintain and rehabilitating road networks can achieve added benefits including improved life cycle performance of pavements, reduced climate change impacts and human health effect due to less air pollution, improved productivity due to optimal allocation of resources and reduced road user cost. The growing awareness of the impacts of road transportation networks on the ecosystem, demands accountability for environmental performance, thus there is need to incorporate environmental performance measure into pavement asset management practices. To address this challenge, this present work focuses on developing a core set of environmental sustainability performance measures for pavement management. The ultimate goal is to develop a framework to incorporate environmental sustainability in pavement management systems for network-level maintenance programming. In order to achieve this goal, this paper present the first step, intention is to review the previous studies for environmental sustainability indicators, as well as the suitability of the indicators for the evaluation of the sustainability in pavement management. A next step will involve an industry and agency survey to identify the state-of-practice trends in environmental performance measurement, highlight data available and data needed, and propose the framework to incorporate measures into network-level sustainable maintenance and rehabilitation programming.

Developing Shear Resistant Asphalt Mixes for Roundabout Pavements

lun, 06/11/2018 - 17:32
Developing Shear Resistant Asphalt Mixes for Roundabout Pavements
by Uzarowski,L; Rizvi,R; Henderson,V; Tighe,S.
2018.
TAC 2018: Innovation and Technology: Evolving Transportation - 2018 Conference and Exhibition of the Transportation Association of Canada.
CA6 ARH_10 2018A5166 - INTERNET


On roads that carry heavy traffic and where higher speed is allowed on the roundabout, conventional mixes may not work well. In the roundabout approach zone the forces due to braking can be very significant. On the roundabout itself, shear stress due to centrifugal forces can be high and regular asphalt mixes may not be able to cope with them. The pavements may shove in the roundabout approach zone and deform and shove and crack within the roundabout. Frequent maintenance including emergency repairs may be required. Frictional characteristics of the pavement in the approach zone can also be of concern. The asphalt mixes to be used at roundabouts should offer better resistance to horizontal shear force than those used in other conventional roadway applications. Unfortunately, the shear resistance testing method for asphalt mixtures is limited in both laboratory and field work. An advanced asphalt technology developed for race track pavement appears to address high shear stresses successfully. A team including the University of Waterloo, Greater Toronto Airport Authority (GTAA) and Golder Associates Ltd. is carrying out a research project on evaluating airport asphalt mixes that can offer superior shear resistance. At minimum, the team will use a Uniaxial Shear Tester (UST). The above mentioned research is focused on optimizing three main components that impact shear resistance: characteristics of asphalt cement; gradation of aggregates; and aggregate angularity. At the same time the mix is also required to offer good frictional characteristics. It is anticipated that as the results of this research, a mix design procedure can be developed that will allow the design of cost effective asphalt mixes that will offer superior shear resistance which could be beneficial to the performance of pavements at roundabouts.

Reducing Urban Heat Island Effect by Using Light Coloured Asphalt Pavement

lun, 06/11/2018 - 17:20
Reducing Urban Heat Island Effect by Using Light Coloured Asphalt Pavement
by Uzarowski,L; Rizvi,R; Manolis,S.
2018.
TAC 2018: Innovation and Technology: Evolving Transportation - 2018 Conference and Exhibition of the Transportation Association of Canada.
CA6 ARH_10 2018A5165 - INTERNET


Light Colour Asphalt Pavement (LCAP) is a process of designing and constructing asphalt pavements that meet the Leadership in Energy and Environmental Design (LEED) Solar Reflective Index (SRI) requirement, as outlined in Credit 7.1 entitled “Heat Island Effect: Non Roof.” Credit 7.1 requires that at a minimum 50 percent of the hardscape (roads, sidewalks, courtyards, and parking lots) be constructed using materials having a Solar Reflectivity Index (SRI) value of 29 or higher. LCAP is a process of designing and constructing asphalt pavements that meet this SRI requirement. The purpose of the development of LCAP is to provide developers looking to achieve LEED certification with a paving alternative that provides performance that is equivalent to conventional asphalt pavement, but that will also meet the requirement of LEED Credit 7.1. LCAP process includes aggregate selection, asphalt mix modification, placement of asphalt mix, stripping of surface asphalt film from new pavement, and evaluation of reflectivity of aggregates, mixes, and in-place pavements. The very light colour aggregate from Coco’s Badgley Island Quarry is a suitable material for LCAP. Conventional new asphalt pavements have an SRI of about 5, and weathered asphalt pavements have an SRI of about 10. There are coatings and epoxy binder mixes available in the market that can be used to increase the SRI of asphalt pavements; however, these technologies are quite expensive, approximately five times more expensive than conventional asphalt. In the LCAP process, the required SRI should be achieved at somewhat increased cost for the final lift of asphalt only, significantly lower than current technologies available on the market.

Safety Evaluation of Signalized Restricted Crossing U-Turn Intersections

sam, 06/02/2018 - 20:33
Safety Evaluation of Signalized Restricted Crossing U-Turn Intersections
by Hummer,JE; Rao,S.
2017.
US1 DTH680 2017S36 - MAIN


This study evaluated restricted crossing U-turn (RCUT) intersection and was conducted by the DCMF program for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. RCUT is defined as a three-approach or four-approach intersection where minor street left-turn and through movements (if any) are rerouted to one-way downstream U-turn crossovers. RCUTs are also known as superstreets, J-turns, reduced conflict intersections, and synchronized streets. Previous research has shown that unsignalized RCUTs are generally safer than conventional options. However, there are no known studies specific to the safety of signalized RCUTs. The objective of this effort was to collect and analyze crash data to develop a crash modification factor (CMF) for signalized RCUTs. This study collected and analyzed crash data before and after conversion of 11 intersections from conventional to RCUT design. The intersections were in suburban areas on four- or six-lane arterials. For most individual sites and groups of sites examined, odds ratio tests showed that there were high-quality comparison sites available, and regression to the mean was not an issue. The project team recommends a CMF of 0.85 for overall crashes and 0.78 for injury crashes for the conversion of a conventional intersection to an RCUT intersection. Based on those CMFs, the project team produced an estimated benefit-to-cost ratio of 3.6 to 1.0 when considering safety and operations or 2.6 to 1.0 considering safety only.

Safety Evaluation of Edge-Line Rumble Stripes on Rural Two-Lane Horizontal Curves

sam, 06/02/2018 - 20:25
Safety Evaluation of Edge-Line Rumble Stripes on Rural Two-Lane Horizontal Curves
by Himes,S; Gross,F; Persaud,B; Eccles,K.
2017.
US1 DTH680 2017E26 - MAIN


The Development of Crash Modification Factors (DCMF) program conducted safety evaluations of edge-line rumble stripes (ELRSs) on rural two-lane horizontal curves for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the application of ELRSs on rural two-lane horizontal curves. ELRSs are a variation of common shoulder rumble strips used to alert drowsy or distracted drivers when they are leaving the travel lane to the right. ELRSs are installed with the edge-line pavement marking placed directly over the rumble strip. Geometric, traffic, and crash data were obtained at treated rural two-lane horizontal curves in Kentucky and Ohio. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before–after analysis was conducted using reference groups of untreated rural horizontal curves with similar characteristics to the treated sites. The analysis also controlled for changes in traffic volumes over time and time trends in crash counts unrelated to the treatment. Owing to a small sample for the reference group in Kentucky and a simultaneous statewide curve warning sign upgrade program in Ohio, alternative reference sites were used to account for annual trends. The results for Kentucky indicated statistically significant reductions for total, injury, run-off-road (ROR), and nighttime crashes, with crash modification factors (CMFs) of 0.75, 0.64, 0.74, and 0.63, respectively. The results for Ohio indicated statistically significant reductions for all crash types, with total, injury, ROR, nighttime, and nighttime ROR CMFs of 0.79, 0.79, 0.78, 0.75, and 0.71, respectively. The two States’ results could not be combined because of the statewide curve signing program in Ohio. It is important to note that all crash types considered in this research excluded intersection-related and animal crashes. Benefit–cost (B/C) ratios were estimated to be 331:1 for Kentucky and 477:1 for Ohio. If ELRSs were used as a curve-specific treatment, the B/C ratio would likely be much smaller because of the higher installation cost; however, these results suggest that the treatment can be highly cost effective.

Ontario Must Prepare for Vehicle Automation Part 2: How Skilled Governance Can Influence its Outcome

sam, 05/26/2018 - 05:35
Ontario Must Prepare for Vehicle Automation Part 2: How Skilled Governance Can Influence its Outcome
by Grush,B; Niles,J; Schlecter,B.
2017.
CA6 ARG750 2017O55 Part.2 - MAIN|INTERNET


This report recommends that our regional and municipal bus transit authorities move from an acquire-and-operate mode to one of specify-and-regulate. There are two key and menacing drawbacks to an acquire-and-operate approach. First, we are entering an era in which technology is changing faster than any government agency can respond, meaning that the risk associated with choosing, acquiring and deploying rapidly innovated automated transportation systems becomes untenable. A March 2017 staff report from the Toronto Transit Commission illustrates this, as detailed in this report. Second, the cost of new systems, new infrastructure and attrition of existing systems is out of taxpayer reach without commercial involvement if we are to move dramatically away from household car ownership. Finally, this report recommends a way to specify and regulate growing fleets that is focused entirely on optimization and inclusion. This involves licensing regulated operators to manage fleets under government social-performance criteria. These fleet operators would be free to innovate vehicles, services and prices — subject to safety, privacy and security certification. Beyond performance criteria and certifications, this approach represents an all-digital market system managed via fees and subsidies based entirely on social performance metrics. It is critical that all segments of urban society be served by this “new mobility.”

Ontario Must Prepare for Vehicle Automation: Automated vehicles can influence urban form, congestion and infrastructure delivery

sam, 05/26/2018 - 05:35
Ontario Must Prepare for Vehicle Automation: Automated vehicles can influence urban form, congestion and infrastructure delivery
by Grush,B; Niles,J; Baum,E.
2016.
CA6 ARG750 2016O55 Part.1 - INTERNET


The purpose of this report is to look at why and how government agencies and public interest groups can and should influence the preferred types and deployment of automated vehicles and the implication of related factors for planning.

Safety Evaluation of Multiple Strategies at Stop-Controlled Intersections

ven, 05/25/2018 - 05:33
Safety Evaluation of Multiple Strategies at Stop-Controlled Intersections
by Le,T; Gross,F; Persaud,B; Eccles,K; Soika,J.
2018.
US1 DTH680 2018S12 - MAIN


The Development of Crash Modification Factors program studied the safety performance of various stop-controlled intersections for the Evaluation of Low-Cost Safety Improvements Pooled Fund Study. This study evaluated the safety effectiveness of multiple low-cost treatments at stop-controlled intersections. Improvements included basic signing and pavement markings. This strategy is intended to reduce the frequency and severity of crashes at stop-controlled intersections by alerting drivers to the presence and type of approaching intersection. Geometric, traffic, and crash data were obtained at three- and four-legged, two- and four-lane major road, and urban and rural stop-controlled intersections in South Carolina. To account for potential selection bias and regression to the mean, an empirical Bayesian before–after analysis was conducted, using reference groups of untreated intersections with similar characteristics to the treated sites. The analysis also controlled for changes in traffic volumes throughout time and time trends in crash counts unrelated to the treatments. The aggregate results indicate reductions for all crash types analyzed (i.e., total, fatal and injury, rear-end, right-angle, and nighttime). The reductions are statistically significant at the 95-percent confidence level for all crash types. For all crash types combined, the crash modification factors (CMFs) are 0.917 for all severities and 0.899 for fatal and injury crashes. The CMFs for rear-end, right-angle, and nighttime crashes are 0.933, 0.941, and 0.853, respectively. The benefit–cost ratio estimated with conservative cost and service life assumptions is 12.4 to 1 for total crashes at unsignalized intersections. The results suggest that the multiple low-cost treatments, even with conservative assumptions on cost, service life, and the value of a statistical life, can be cost effective

The Road to Vision Zero: Zero Traffoc Fatalities and Serious Injuries

jeu, 05/24/2018 - 04:36
The Road to Vision Zero: Zero Traffoc Fatalities and Serious Injuries
by Calibaba,J.
2017.
CA7 FAT150 2017R58 - MAIN


Vision Zero is a priority road safety framework for Canada, as outlined by the Canadian Council of Motor Transport Administrators (CCMTA) in the release of their Road Safety Strategy 2025 (RSS 2025). The strategy, released in 2016, focuses on the long term of ensuring Canada’s roads are the safest in the world, while adding a greater focus on the vision of “towards zero” serious injuries and fatalities on the roadways. The Vision Zero Advocate Institute, supported by ATS Traffic, is the market leader in Vision Zero. Current studies point to a clear disparity in municipal comprehension and implementation of Vision Zero initiatives. The Vision Zero Advocate Institute closes that gap. (from the introduction)

Evaluation of Maintenance Costs for the Roadway Maintenance and Rehabilitation Analysis Application (RoMaRa) in the Province of Alberta

sam, 05/12/2018 - 20:00
Evaluation of Maintenance Costs for the Roadway Maintenance and Rehabilitation Analysis Application (RoMaRa) in the Province of Alberta
by Cowe Falls,L; Tighe,S.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P13 - MAIN


Maintenance management systems can identify the most cost-effective maintenance treatments at the most appropriate time in the pavement life cycle. Pavement maintenance models can be developed to determine the impact and cost of the treatments and their impact on pavement serviceability. Agencies are examining the cost effectiveness of maintenance and its role in life cycle cost analysis (LCCA). Privatization has made maintenance activities a ‘line item’ in the operating budget, highlighting maintenance costs and providing a mechanism for tracking activities. The implementation of the Infrastructure Management System (IMS) and Roadway Maintenance and Rehabilitation Application (RoMaRa) in Alberta has resulted in surface condition data and maintenance work orders being allocated to the same highway kilometer point for the first time. This paper explores the potential for modeling of maintenance costs as a function of a pavement performance index. While RoMaRa can be used to calculate maintenance costs as part of the Life Cycle Costs of competing rehabilitation alternatives, no location based data was available until recently. Various trends in performance will be presented. The methodology could be applied to other areas in Canada considering calibrated maintenance cost models as a function of pavement performance indices.

Stone Mastic Asphalt (SMA) – A Solution to Mitigate Rutting at Heavy Traffic Intersections and Bus Lanes

sam, 05/12/2018 - 19:40
Stone Mastic Asphalt (SMA) – A Solution to Mitigate Rutting at Heavy Traffic Intersections and Bus Lanes
by Anderson,P; MacInnes,K; Moore,G.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P12 - MAIN


Stone Mastic Asphalt (SMA), used in Ontario since 1990, is suitable for pavements needing superior rut-resistance. In 1999, the City of Hamilton initiated a project in a high traffic volume industrial corridor to evaluate the production, placement, and performance of SMA. Traditional hot mix asphalt (HMA) had rutted at this site within a year of paving. In 2001, based on the successful completion of this project, the City of Hamilton placed SMA on a bus lane that had rutted within a few months of paving with traditional HMA. This paper describes the methodology used to design the SMA mixtures as well as practical experience gained from the production and laydown of the material. A comparison of mix properties of SMA generated by Marshall and SuperpaveTM Gyratory compaction methods is reported. Field testing and monitoring included coring to compare nuclear density tests and in-place core density results, skid resistance, and surface deformation determination. A comparison of SMA skid data with historical data of various surface mixes is provided. Successful production and placement of SMA can be achieved on urban road projects despite the need to deal with relatively small quantities of mix and handwork around utility covers.

Expanded Asphalt Stabilization on the Trans-Canada Highway in Ontario

sam, 05/12/2018 - 18:58
Expanded Asphalt Stabilization on the Trans-Canada Highway in Ontario
by Lane,B; Kazmierowski,T.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P11 - MAIN


The first Ministry of Transportation Ontario contract using expanded or “foamed asphalt” involved recycling 22.5 km of flexible pavement on Highway 17, south of Wawa, in 2001. Expanded asphalt was selected as the rehabilitation treatment due to a lack of aggregate availability in the area. An end result specification for expanded asphalt stabilization was developed for this demonstration project. The existing hot mix asphalt (HMA) and granular base were reclaimed, re-graded and compacted. Expanded asphalt stabilization was carried out to a depth of 150 mm. The expanded asphalt operation proceeded well, providing a smooth, hard, uniform surface suitable to accommodate detour traffic. Following a two-day curing period, the stabilized base was overlaid with 80 mm HMA. Falling weight deflectometer (FWD) testing was carried out prior to and following construction. Normalized deflections were compared and the structural capacity of each pavement layer was evaluated by back-calculating the results. The expanded asphalt stabilization was found to have a resilient modulus of 1395 to 1645 MPa and a granular base equivalency of 1.50 to 1.58. This paper presents the innovative design and construction details of this demonstration project and discusses quality assurance, FWD test results and short term post-construction monitoring.

In-Service Rut Performance Investigation of Saskatchewan Highways and Transportation Asphalt Concrete Mixes

sam, 05/12/2018 - 18:33
In-Service Rut Performance Investigation of Saskatchewan Highways and Transportation Asphalt Concrete Mixes
by Carlberg,M; Berthelot,CF; Richardson,N.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P10 - MAIN


The objective of this research was to investigate the effect that percent fractured coarse aggregate particles has on the rutting performance of dense-graded asphalt concrete pavement. Higher “fracture” asphalt concrete is usually more costly to produce in Saskatchewan, which has mostly glacial gravel deposits. Ten pavements that had been designed with “rut-resistant” volumetrics were selected from mix design records for further investigation in the field. The pavements selected were of varying age and had varying degrees of fracture. Each pavement was cored between the wheel paths and in the outer wheel path, and rut measurements were taken at each sampling location. The cores were then analyzed to determine post-construction and present-day aggregate gradation, fracture, fine aggregate angularity, asphalt content, air void content, Voids in Mineral Aggregate (VMA) and Voids Filled (VF). Traffic data for each site was calculated and used to determine the number of Equivalent Single Axle Loads (ESALs) that had passed over the pavement. A linear regression analysis was performed to relate rut depth to the post-construction properties noted above. No significant relationship between fracture and rutting performance was found. Significant factors in rutting performance were found to be historic traffic, asphalt content, voids filled percentage, and density.

Mechanisms of Instability Rutting in Hot Mix Asphalt Pavements

sam, 05/12/2018 - 18:22
Mechanisms of Instability Rutting in Hot Mix Asphalt Pavements
by Birgisson,B; Roque,R; Drakos,C; Novak,ME; Ruth,BE.
2002.
Proceedings of the Forty-Seventh Annual Conference of the Canadian Technical Asphalt Association (CTAA): Calgary, Alberta.
CA6 AIH___ 2002P09 - MAIN


Instability rutting may be characterized by either shoving of the material at constant volume (plastic deformation/shear), or a combination of traffic densification and plastic deformation, with failure located within the top one to two inches (25-50 mm) of the pavement layer. Measurements of tire contact stresses under several truck tires, integrated into three dimensional finite element models, have shown that radial truck tires induce high transverse contact stresses on pavements, resulting in high near surface shear stresses. The older bias-ply type tires tend to have lower transverse contact stresses, resulting in zones of maximum shear stresses that are deeper in the pavement. Coarse-graded mixtures rely on compaction to develop the aggregate-to-aggregate interlocking needed to provide adequate rutting resistance, whereas the rutting resistance of fine-graded mixtures tends to be governed more by the overall aggregate structure and composition of the mastic. Recent work has shown that air voids in the top inch (25 mm) of most pavements tend to be higher than for the rest of the pavement. Critical high temperature and air void conditions, combined with critical stress states immediately under the tire, may control pavement rutting.

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