Recycling Road Building Materials and Experience with Full Depth Reclamation in the Ontario Provincial Highway System.

The Ontario Ministry of Transportation (MTO) has been committed to recycling road building materials as it makes sound economic and environmental sense. Demands are placed on the aggregate industry to find and secure high-quality aggregate materials to renew and restore Ontario highways. Over the past thirty years, there has been a dramatic demand for contractors to recycle and reclaim materials originating from Ontario’s transportation networks. In southern Ontario, the demand for road-building and construction aggregates has increased primarily due to increased economic activity and population expansion in the Greater Toronto Area (GTA). Provincial legislations including the recently approved Greenbelt Plan, the Niagara Escarpment Plan (NEP), and the Oak Ridges Moraine Conservation Plan (ORMCP) have made finding and securing available high-quality aggregates a more significant challenge. In the north, greater hauling distances increase the costs of importing construction aggregates and disposal of recovered materials. Since the early 1970s MTO aggregate specifications have allowed the use of reclaimed materials as a component of unbound aggregate base. From an engineering perspective, reclaimed materials must meet the same requirements as natural aggregates. Specifications based on laboratory testing have been developed to allow the use of recycled materials in order to promote conservation of natural resources. Aggregates in road base/subbase may include up to 50% reclaimed asphalt pavement when used in conjunction with full depth reclamation (FDR). Samples of granular base material were collected from various FDR projects around the province and tested in response to reports that several recently constructed pavements using full depth reclamation have been experiencing premature cracking problems. Samples were subjected to a series of laboratory tests including permeability, California Bearing Ratio, gradation (both before and after testing) and percentage of asphalt coated particles. Test results indicate a clear correlation between the strength and the percentage of asphalt coated particles present in the blend. The results also indicated that samples with the highest percentages of fines (material passing the 75µm sieve) also have the lowest coefficients of permeability. The results from these lab tests provide a better understanding of the properties and long-term performance of reclaimed asphalt pavement incorporated into the granular base.