When we core existing asphalt on Davis Drive or Yonge Street in Newmarket, the base layer often tells a story of differential heave that traces back to the Holland Marsh silts and the Oak Ridges Moraine sands beneath. Flexible pavement design here is not just about traffic loading. It is about how the subgrade responds to freeze-thaw cycles that penetrate over a meter deep, and how the aggregate interlock holds up after a spring thaw that saturates everything. We approach each project by first characterizing the insitu subgrade with CBR testing and then layering the granular base and asphalt thicknesses to meet the minimum structural number required by the Ontario Provincial Standard Specifications.
A pavement section designed without a soaked CBR test on the actual subgrade is just a guess wrapped in asphalt.
Methodology and scope
Local considerations
Newmarket's development arc since the 1970s pushed subdivisions into areas where the Oak Ridges Moraine meets the Holland Lowlands. Older arterial roads were built on compacted fill that was placed long before modern compaction specifications existed. When we design a flexible pavement overlay for these corridors, the biggest uncertainty is what lies beneath the existing asphalt: sometimes it is a sound granular base, other times it is a thin layer of screenings over uncompacted sandy silt. We mitigate this risk by performing dynamic cone penetration testing at regular intervals to map the base stiffness profile before finalizing the structural number. Ignoring this step leads to alligator cracking within three to five years, which we have seen repeatedly in parking lots where the original geotechnical investigation was skipped to save cost.
Applicable standards
OPSS 350 (Material Specification for Asphalt Concrete), ASTM D698 / D1557 (Proctor Compaction), ASTM D1883 / AASHTO T-193 (CBR Test), AASHTO 93 (Pavement Structural Design), MTO Laboratory Testing Manual LS-200 Series
Associated technical services
Subgrade Assessment and CBR Testing
We sample the subgrade at grade elevation, perform soaked CBR tests in our ISO 17025-accredited lab, and classify the soil according to the Unified Soil Classification System. This data feeds directly into the structural number equation.
Granular Base and Asphalt Thickness Design
Using the AASHTO 93 method and OPSS 350 material specifications, we calculate the required thicknesses for Granular B, Granular A, and each asphalt lift. We provide a pavement cross-section drawing with compaction requirements.
Forensic Pavement Evaluation
For rehabilitation projects on existing roads, we extract cores, log the layer thicknesses, test the remaining asphalt modulus, and identify the failure mechanism—whether it is subgrade rutting, stripping, or fatigue cracking—before proposing the overlay design.
Typical parameters
Frequently asked questions
What is the typical flexible pavement section for a residential street in Newmarket?
A typical local residential street with low truck traffic might use 40 mm of HL3 surface course over 50 mm of HL8 binder course, placed on 150 mm of Granular A and 300 mm of Granular B Type II. However, this must be confirmed by a CBR test on the subgrade. Soft silty soils may require a thicker granular base or a geotextile separator.
How much does a flexible pavement design package cost for a site in Newmarket?
A full pavement design package, including subgrade investigation, CBR testing, and a stamped design report, typically ranges from CA$2,210 to CA$7,110 depending on the number of test pits and the project area. Smaller infill lots fall at the lower end, while larger commercial sites with multiple boreholes and traffic analysis are at the upper end.
Do you use the AASHTO 93 method for pavement design?
Yes, we use the AASHTO 93 empirical method as our primary design framework, calibrated with local Ontario materials. We input the soaked CBR to derive the resilient modulus of the subgrade, select the layer coefficients for asphalt and granular materials per MTO practice, and compute the required structural number for the 20-year ESAL projection.
How do you account for frost action in Newmarket pavement design?
Frost penetration in the Newmarket area can exceed 1.2 metres. We follow Ontario Provincial Standard Drawings for frost protection, specifying a combined pavement and granular thickness that prevents frost-susceptible subgrade from freezing. We also check the soil's frost susceptibility classification from grain-size data and recommend non-frost-susceptible Granular B where needed.
What is the difference between Superpave and Marshall mix designs?
Superpave is a performance-based system that uses the Superpave gyratory compactor and considers the project's traffic level and climate. Marshall is an older volumetric method still referenced in some smaller municipal specifications. For Newmarket roads, we typically specify Superpave with a PGAC 58-28 binder, which handles our winter lows and summer highs better than a generic Marshall mix.