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Quantifying Greenhouse Gas Generation for Roadway Maintenance, Rehabilitation and Reconstruction Treatments


Greenhouse gas (GHG) emission levels in Canada peaked in 2007 at 751 Mt CO2e (carbon dioxide equivalents) and currently these levels are decreasing. Through the Copenhagen Accord, Canada has committed to a 17 percent reduction of 2005 GHG emission levels by 2020 to 607 Mt. To reach this target, any possible reductions to GHG emissions must be made. To reduce GHG emissions generated in roadway construction, it is important to quantify the amount of GHGs produced for various treatments and to identify which aspects of construction contribute the greatest. This paper describes the development of a probabilistic model that quantifies the amount of GHGs generated through maintenance, rehabilitation, and reconstruction treatments for flexible pavement structures and includes the GHG emissions generated from the transportation, production and placement of materials. The maintenance treatments reviewed include: fog seal, slurry seal, micro surfacing, chip seal and ultra thin overlay. The rehabilitation and reconstruction treatments reviewed include: cold in-place recycling, mill and fill, full depth reclamation, and use of offsite recycled and virgin materials for reconstruction. To quantify the GHGs generated for each of these treatments a case study of a typical lane-km (3,700 m2 ) is used. The key parameters that contribute the greatest to the GHGs for each treatment were determined and it was found that material production contributed the greatest to GHG generation. Four primary sensitive parameters were determined for the maintenance treatments including equipment efficiency, the rate at which the treatment is applied and the asphalt cement and aggregate content of the treatment. For the rehabilitation and reconstruction treatments, the sensitive parameters where found to be the emissions value for the production of hot mix asphalt concrete and the amount of Portland cement added. The City of Edmonton has been using foamed asphalt and recycled aggregates for the rehabilitation of roadways for a number of years. A case study quantifying the amount of GHG emissions generated through 33,888 m2 of roadway reconstruction in the neighbourhood of King Edward Park is presented. Through the use of full depth reclamation for reconstruction it is estimated that approximately 52 percent or 700 t CO2e less was generated compared to a traditional remove and replace with virgin materials. 

Conference Paper Details

Session title:
Foth, M.
Berthelot, C.
Climate change