Toward Performance-Based Acceptance of Asphalt Mixtures in Ontario: Industry (O-MAP) Preliminary Findings

ABSTRACT
Research efforts are being undertaken in North America, to improve methodology for designing asphalt mixes through incorporating reliable laboratory tests and procedures into material specifications. Some of these efforts have further demonstrated that implementing performance tests can improve the longevity of asphalt pavements and reduce risk of premature pavement deterioration. The Ontario Asphalt Pavement Council (OAPC – A Council of Ontario Road Builders’ Association, ORBA) is particularly interested in this focus, as potential means of addressing concerns on premature cracking of asphalt mixes. Considering this, the Ontario Asphalt Expert Task Group (OAETG) – Ontario - Mix Asphalt Program (O-MAP) study, commissioned by the OAPC, has been conducted to examine issues and challenges related to the performance of typical Ontario Superpave asphalt mixtures.

Further to the industry’s readiness to identify any issues and challenges involving performance of typical Ontario Superpave asphalt mixtures, this paper summarises the findings, recommendations, and next steps from round-one of O-MAP Testing. Throughout this round, two SP 12.5 mixes designed specifically for highest Traffic Category (“E”) were studied. The evaluated mixes were Plant-Produced Lab Compacted (PP-LC) prepared using Performance Graded Asphalt Cement (PGAC) 70-28XJ, meeting Ontario Provincial Standard Specification (OPSS) 1101. The results indicated that the success of adopting performance testing in Ontario is reliant on the ability of both the owner-agency and industry to establish and meet performance criteria related to test methods including, but not limited to: Hamburg Wheel Tracking Device (HWTD), Semi-circular Bend Test (SCB), and Disk-Shaped Compact Tension (DCT) array of tests. The round-one results were further incorporated into Performance Space Diagram (PSD) to better characterize the mixes based on performance testing conducted.

Based on the identified study limitations and results analyzed and verified by the O-MAP’s Oversight Study Team (OST), there are still areas requiring further investigation in order to better understand the factors that may affect the interpretation of results. To this end, different mix properties, testing parameters, testing equipment/fixtures, or a combination of all these factors, including the effect of changing height on the reliability of Superpave Gyratory Compactors (SGCs) used in the province, and their differences as a significant source of variation related to "within" and/or "interlaboratory" Coefficient of Variation (COV) should be further investigated.