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Mitigating Pavement Rutting at Intersections

EBA Engineering Consultants Ltd. (EBA) and the University of Alberta (U of A)

1.0 Introduction

EBA Engineering Consultants Ltd. (EBA) and the University of Alberta (U of A) have created a partnership to carry out the project "Mitigating Pavement Rutting at Intersections" for the Centre for Transportation Engineering & Planning (C-TEP). Our proposal has been completed in general conformance with the Limited Call for Research Proposal dated July 17, 2002 and the C-TEP Proposal Rating Form provided on July 25, 2002.

This proposal is based on information provided in the proposal and subsequent discussion with officials for the Cities of Edmonton and Calgary, and Alberta Transportation.

2.0 Background and Rutting Issues

Rutting of asphalt concrete pavement came to be recognized in Canada as a significant distress mechanism in the 1980's. The City of Lethbridge Rutting Study which was funded by Alberta Transportation and the City and carried out by EBA in the early nineties provided new information about the mechanism of instability rutting at urban intersections. As part of a research study carried out by EBA for TAC in 1996 (Guide to the Characteristics, Performance and Selection of Paving Asphalts), a survey of Canadian agencies was carried out at that time and indicated that five provincial agencies (including Alberta) and the two participating cities (Calgary and Edmonton) identified that developing solutions to permanent deformation was their highest priority.

Pavements technology has advanced over the last several years in better defining the mechanisms of asphalt concrete pavement rutting and in providing better design solutions to mitigate rutting, e.g. polymer modified and engineered binders, use of aggregates with higher fractures and manufactured sands, and SMA mixtures. However, the mitigation of rutting at intersections has been proven to be a significant challenge, more so in northern climates where asphalt concrete mix and pavement design and asphalt binder selection is a balancing act between optimizing high temperature (rutting), low temperature (cracking) and durability performance parameters.

This project is to focus on the rutting at intersections in the Alberta context.

What makes intersections special?

  • High traffic means significant user disruption and inconvenience during rehabilitation and maintenance.
  • Truck traffic is concentrated and channelized with much less wheelpath wander.
  • Loading times are very long due to slow vehicle speeds, and the resulting binder stiffness is significantly reduced.
  • Additional shear stresses are imposed due to acceleration and deceleration of vehicles.

Why is a "made-in-Alberta" solution to the mitigation of rutting required?

  • A made-in-Alberta solution doesn't mean it is necessary to re-invent the wheel. It does mean that Alberta's unique climate and materials conditions need to be considered in researching solutions or transferring technology from other jurisdictions.
  • And even within Alberta, High 7-Day Average Temperatures can range from 33

3.0 Past Relevant Project Experience

Members of the EBA/U of A team have had extensive involvement in a wide variety of specialist pavements engineering projects and research assignments. Projects that demonstrate our team's experience and abilities to carry out related research programs include:

City of Lethbridge Rutting Study - An extensive research program carried out between 1988 and 1998 that comprised categorizing existing rutting and developing strategies to mitigate reoccurrence. A series of full scale test pavements were constructed and monitored over a five year period and resulted in changes to aggregate, asphalt and asphalt concrete specifications.

Rutting Trends at C-SHRP LTPP Test Sites - This research studied the rutting performance of 65 C-LTPP test sections across Canada over their first seven to nine years of performance. Transvere profiles measured with a Dipstick Profiler were analyzed to develop Rut Indices to characterize rutting performance.

Validation and Revision of Asphalt Concrete Mix Type Selection and Characteristics (Alberta Transportation) - A network analysis of the rutting performance of over 6,600 km of highways representing 365 paving projects between 5 and 15 years in age formed the basis of the analysis.

Incorporation of Reclaimed Asphalt Pavement in the SUPERPAVE System (NCHRP 9-12) - This project studied rutting, fatigue and low temperature properties of asphalt and mixtures incorporating RAP using SUPERPAVE performance tests including the simple shear, respected shear and indirect tensile tests.

Yellowhead Trail, City of Edmonton - EBA was involved with the investigation and design of a 200 mm thick PCC Inlay at the 127th Street Intersection in 1994.

TransCanada Highway, City of Medicine Hat - The project included a detailed rut survey, subsurface investigation (testholes and trenches) and structural evaluation. The results of the investigation were used with Life Cycle Cost Analysis to provide a recommended strategy for upgrading the facility which included both rigid (PCC) and flexible pavement sections.

City of Calgary - EBA has been involved in several pavement projects including SMA (Glenmore Trail), Superpave (Hwy 22X) and reinforced concrete inlays (Edmonton Trail).

4.0 Methodology

The methodology proposed by EBA/U of A has been developed to achieve the project tasks and deliverables outlined in the RFP.

The primary tasks that form our proposed methodology, and the associated project deliverables follow:

Deliverable 1: Compendium of Research on Mitigating pavement Rutting at Intersections

1.1 Literature Search - Publications will include TRB, Canadian Public Works Association, Canadian Technical Asphalt Association, Institute for Research in Construction, Cement Association of Canada, and Association of Asphalt Pavement Technologists.

1.2 Identify Lead Agencies - Select agencies will be identified through input of the Cities of Calgary and Edmonton and Alberta Transportation, personal contacts and the literature search. The focus will be on urban municipalities sharing similar climate and materials conditions, i.e. Western and Central Canada, and Northern tier States. Information will be gathered on recent and present research, materials/construction specifications and economic analysis of design alternatives.

1.3 Review Recent and Current Investigations carried out by the Cities of Calgary and Edmonton and Alberta Transportation. The investigations include thin and thick concrete inlays, SMA and Superpave mixes, PG and modified binders, asphalt rubber and manufactured aggregates. A meeting would be held with each Participating Agency to review research projects. An analysis of preconstruction design, construction, QC/QA results, mix designs, as-built information and post construction monitoring will be carried out on available information provided by each agency. A review would be carried out of available pavement strength test results (Benkelman Beam, Dynaflex, and FWD). A limited site reconnaissance will also be carried out of each project. Major gaps in information or data will be identified. A summary of each project will be prepared. Other agencies proposed for inclusion are: City of Lethbridge, City of Medicine Hat, and Strathcona County.

1.4 Prepare Compendium Report - It is proposed that this stand alone report would provide Best Practices that would apply to Alberta conditions and a summary of Alberta Research and practices in a format that would facilitate technology transfer across Alberta.

Deliverable 2: Draft Design Guidelines for Mitigating Rutting at Intersections - These guidelines would provide an initial framework for project level design and would be complimentary to the "Research Protocols" for current and future research initiatives to follow.

2.1 Identify inputs and parameters that would apply to the design of (1) the new construction of intersections and (2) the rehabilitation of existing rutted intersections. Develop guidelines for the selection of design inputs. For example, for the rehabilitation of an existing rutted intersection, a guideline for establishing the depth of the "zone of influence" would be established. Identify gaps and research needs required to complete a made-in-Alberta, generic design guideline that could be adapted by individual agencies.

This would be accomplished through a one half day Expert Group Workshop. Experts from the Participating Agencies would be invited to participate.

Deliverable 3: Research Protocols for current and future research initiatives to follow. It is understood that these protocols could be used by Participating Agencies when identifying and constructing trial projects that would facilitate the transfer of technological advances and experience to all agencies in Alberta.

3.1 Develop a generic research approach/methodology in consideration of the following factors:

  • New Construction vs. Rehabilitation
  • The use of common terminology and standards to describe, for example:
- traffic e.g., % trucks, ESALs; and
- rut index.
  • Common standards for characterizing materials properties, e.g. coarse and fine aggregate angularity.
  • Post-construction performance monitoring programs.

3.2 Develop a template that could be used to provide a summary of each research project and a mechanism for storing and sharing data and results.

3.3 Validate and refine these research protocols based on their application to at least one current project from the Cities of Calgary and Edmonton, and Alberta Transportation. Agency PMS data could be used to develop and validate these research protocols.

5.0 Project Team

To carry out this project, EBA and the U of A has assembled a team of pavement specialists and engineering support that represent broad experience and expertise in pavements technology with a focus on Western Canadian practices.

Our team of specialists will work as an Expert Group to brainstorm, identify innovations and direct the overall project, and will maximize the inputs and contributions of our Pavements Specialists.

Dave Palsat, P.Eng., is the Project Manager and Co-Principal Investigator with Professor Soleymani. Dave will be the EBA point-of-contact with C-TEP on administration issues and will lead the preparation of the reports.

Professor Hamid Soleymani, P.Eng., is Co-Principal Investigator. He will lead the development of the Compendium Report and the development of the Research Protocols.

Art Johnston, C.E.T., is the team's Superpave, SMA and Asphalt Specialist and will advise on materials, design and performance issues. He will also contribute to the review of recent and current investigations.

Dave Robson, P.Eng., is the team's concrete specialist and will advise on all concrete materials, design and performance issues.

Cece Dawley, P.Eng., is the Senior Reviewer. He will review all reports and will facilitate the Expert Group Session to develop the draft Design Guidelines.

Graduate Student - The graduate student will be named in early September.

The team will be assisted by Draft and Administrative Support Staff. Resumes of Key Staff are attached.

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