A standard CBR mold, a compaction hammer, and a penetration piston—that's what sits on our lab bench when a Saint-Jerome project starts. The California Bearing Ratio test measures how well a soil resists penetration under controlled moisture and density conditions. We compact specimens at optimum moisture from Proctor curves, soak them for 96 hours to simulate the worst-case spring thaw, then push a 49.6 mm piston at 1.27 mm/min. For the silty sands common along the Rivière du Nord terraces, this soaking phase often reveals strength loss that a dry test would miss. That data feeds directly into the flexible pavement structural design, helping engineers set the right asphalt and granular thickness for local freeze-thaw cycles.
A soaked CBR value below 3% on the Rivière du Nord silts means the subgrade needs stabilization before any pavement structure goes down.
Process and scope
Site-specific factors
Saint-Jerome sits at roughly 100 meters above sea level, but the bigger number for pavement engineers is the 1400 mm of annual precipitation that saturates the silty-clay subgrades across the lower Laurentians. A soaked CBR test run on untreated native soil from a Mirabel-adjacent site recently dropped from 8% to 2.7% after the full soak cycle. That kind of collapse under traffic loading leads to alligator cracking within two winters. The NBCC 2020 frost-depth maps put this region at 1.8 meters or deeper, so any pavement section designed without a soaked CBR value risks differential heave and premature failure. Municipal inspectors in the Saint-Jerome area increasingly require both a lab CBR and a gradation analysis before approving subdivision road acceptance.
Reference standards
ASTM D1883-21 (CBR of laboratory-compacted soils), AASHTO T 193-22, CSA A23.3-19 (Concrete and pavement base references), MTQ Laboratoire des Chaussées manual (Quebec supplement)
Other technical services
Soaked CBR on Native Subgrade
We compact specimens at optimum moisture from a standard or modified Proctor, then soak for 96 hours under a 4.5 kg surcharge ring. The penetration curve gives CBR at 2.5 mm and 5.0 mm, plus the swell percentage. This is the base input for the AASHTO 1993 pavement design equation used by Quebec consultants.
CBR on Granular Base and Borrow Materials
For the MG-20 and MG-112 crushed stone layers that sit above the subgrade, we run unsoaked CBR tests at field density targets. This confirms the structural number contribution of each lift and helps the contractor dial in compaction specs before the paving crew arrives.
Typical parameters
Frequently asked questions
How much does a laboratory CBR test cost in Saint-Jerome?
For a single-point soaked CBR on native soil, budget between CA$180 and CA$310 per specimen, depending on whether a Proctor curve is already available and how many compaction points we need to establish. A full pavement package with three CBR points plus Proctor and gradation typically runs higher but gives the engineer everything needed for the structural design.
How long does the lab CBR test take from sample delivery to report?
Standard turnaround is 7 to 10 working days. The four-day soak is what drives the schedule—there is no way to shorten that without compromising the result. If the project is on a tight timeline, we can run the Proctor compaction first and start the CBR compaction while the moisture-density data is still being finalized.
Do I need a field CBR test or a lab CBR test for my Saint-Jerome parking lot?
For design purposes, the lab CBR is the reference method because it controls moisture and density precisely. A field CBR or Dynamic Cone Penetrometer can be useful for quality control during construction, but the structural thickness design should come from a soaked lab value. We often run both when the subgrade is variable across the site.
What sample quantity do you need for one CBR point?
We require a minimum of 35 kilograms of disturbed material per CBR specimen if we are also running the Proctor compaction. If you are supplying Shelby tubes for an undisturbed test, three 75 mm diameter tubes per depth are the minimum. The lab can provide sample bags and instructions for the Saint-Jerome area.
Can you test recycled concrete aggregate with the CBR method?
Yes, ASTM D1883 works for recycled materials as long as the maximum particle size does not exceed 19 mm. For coarse RCA with larger particles, we use a scalping procedure or recommend the large-scale CBR mold. The soaked test is especially important for recycled materials to check for strength loss from unhydrated cement fines.