Evaluation of Tire-Derived Aggregate (TDA) as Embankment Material
In collaboration with Alberta Recycling and Alberta Transportation, the IRRF is investigating the use of TDA as embankment fill. To determine the feasibility of using this recycled material in road construction, 825,000 waste tires, weighing approximately 8,000 tonnes, were processed into TDA and used to construct a test road. The road itself consists of three test sections, each using a different type of TDA as embankment fill: off-the-road (OTR) tires, passenger and light truck tires (PLTT), and a PLTT-soil mixture. This is a long-term project that will see researchers conducting a number of tests on the road’s behaviour over the next several years.
Seasonal Falling Weight Deflectometer (FWD) Testing
In regions like Alberta, pavement is subjected to deep freeze, followed by the thawing season. To determine the effects of climate on our roads, the IRRF has partnered with Alberta Transportation to investigate how the flexible pavement responds to various traffic loads in different seasons. Alberta Transportation has provided the IRRF with seasonal FWD test results executed on a number of the Province’s highways so that researchers may analyze pavement behaviour throughout the year.
Evaluation of Bottom Ash as Pavement Insulation Layer
Traditional road construction in cold regions has relied on Styrofoam to insulate the pavement’s subgrade layer from frost, which can be costly to roadway projects. As an alternative, the IRRF has partnered with the City of Edmonton and Alberta Transportation to investigate an alternate insulation option: waste bottom ash. Bottom ash is a byproduct of burning coal to generate electricity in Alberta, and as a result, is a locally and readily available material. The IRRF has added both Styrofoam and bottom ash layers to its test road, where its performance will be observed over a number of years. The insulated sections and an adjacent control section are instrumented at various depths beyond the frost line to investigate the insulation’s effectiveness in limiting frost penetration and decreasing the negative effects of thawing. The sections are also equipped with multi-depth deflectometers (MDD) to measure frost heaving, which is detrimental to pavement ride-ability in Alberta.
Evaluation of Light-Weight Deflectometer (LWD) Performance
IRRF researchers are working with Alberta Transportation and C-TEP to investigate the effectiveness of light-weight deflectometers (LWD) in evaluating base and subgrade layers quality. Currently, these layers are evaluated with a nuclear density gauge; however, radiation exposure and the gauge’s inability to reflect the pavement’s mechanistic properties hinder its effectiveness. LWDs present a portable and safe alternative in material characterization and construction quality evaluation, and IRRF researchers are working to determine LWDs’ potential for future use in road construction.
Winter Road Maintenance Procedures
Effective winter road maintenance procedures are integral in areas with prolonged winters, such as Alberta. The IRRF has partnered with the City of Edmonton to evaluate commonly used street sanding/ salting and plowing procedures to determine the best application of the City’s resources during varying winter road conditions. Through the application of different levels of sand/ salt and plowing in various combinations, researchers are working to identify the most effective operations for Alberta’s winter weather. The IRRF hopes that this work will not only ensure safer driving conditions in the future, but also help prevent the negative environmental and aesthetic impacts of over-sanding and salting.
Flexible Pavement Response to Environmental and Traffic Loads
The IRRF has joined with Alberta Transportation to investigate flexible pavement’s structural response to dynamic vehicle loading. The IRRF’s test road has been equipped with a variety of sensors that measure the strains experienced at the bottom of the asphalt layer under wheel and FWD loading. So far, researchers have conducted several tests focusing on the impact of various parameters, such as wheel wander and vehicle speed. These and other test results will be used to develop robust 3-dimensional finite element models of the flexible pavement system and enhance mechanistic-empirical (ME) pavement design procedures.
