A contractor we work with in the Lachenaie sector called us mid-project last November. They had compacted the subgrade on a new commercial access road, but the on-site density readings were inconsistent. The clayey silt from the Mascouche formation was proving trickier than the borings suggested. We recommended a laboratory CBR test on remolded samples compacted at the target moisture content. The result came back at 5.2%, well below the 8% minimum the pavement design required. That single data point triggered a lime stabilization protocol that saved the client from a premature pavement failure. In Terrebonne’s variable soil conditions, the CBR test is not just a number on a report; it is a direct measure of how the subgrade will perform under repeated loading, and it often decides whether the structural section gets built as designed or requires modification. We complement this testing with in-situ density checks when verifying compaction compliance on site.
A 2% difference in CBR can mean an extra 50 mm of granular base — across a 500-meter road, that decision moves budget line items by tens of thousands of dollars.
Methodology applied in Terrebonne
Local geotechnical conditions in Terrebonne
Terrebonne’s population has grown over 15% in the last decade, and the pressure to open new residential and commercial accesses means construction schedules are tighter than ever. The risk of skipping a laboratory CBR test is not theoretical: we have seen compacted subgrades that passed density tests but failed under traffic within two freeze-thaw cycles because the soaked bearing capacity was never verified. The ASTM D1883 procedure is deliberate — compactive effort, moisture conditioning, and 96-hour soaking each contribute to a design value that reflects long-term performance, not just the conditions on compaction day. For projects funded under provincial or municipal programs, the MTQ and most Terrebonne engineering consultants require a minimum soaked CBR of 8% for local residential streets and 15-20% for arterial roads. Without that verified number, the pavement design is essentially an assumption, and an assumption that fails means reconstruction costs far exceeding the price of a single test suite.
Our services
Our laboratory CBR test is one component of a broader geotechnical testing program for Terrebonne projects. The three services below are typically contracted alongside CBR when the project scope includes pavement design, embankment construction, or subgrade improvement.
Standard and Modified Proctor Compaction
Determines the maximum dry density and optimum moisture content for the soil to be used in CBR specimen preparation. We run both standard (ASTM D698) and modified (ASTM D1557) compactive efforts depending on the pavement layer specification.
Grain Size Analysis and Atterberg Limits
Sieve and hydrometer analysis plus liquid and plastic limit testing classify the soil according to the Unified Soil Classification System (USCS). This classification is required input for the MTQ pavement design method used across Terrebonne.
In-Situ Density Testing
Sand cone and nuclear gauge testing on compacted subgrade and granular layers to verify that field density meets the percentage of maximum dry density specified in the project compaction requirements.
Questions and answers
What does a laboratory CBR test cost in Terrebonne?
For a single-point CBR test on a remolded specimen, including compaction and 96-hour soaking, the fee ranges from CA$180 to CA$260 per specimen. A complete design suite with three compaction points and corresponding CBR specimens typically falls between CA$700 and CA$1,100, depending on the number of moisture-density points required.
How long does it take to get CBR results from your lab?
The standard turnaround is 5 to 7 business days. The 96-hour soaking period mandated by ASTM D1883 accounts for most of that time. We can accommodate expedited requests for an additional fee, but the minimum soaking period cannot be reduced without compromising the validity of the soaked CBR value used in pavement design.
Do you test undisturbed samples or only remolded specimens for CBR?
We can test both. The standard ASTM D1883 procedure uses remolded specimens compacted at a target moisture content, which is the method required for most pavement design work. If the project requires a CBR on an undisturbed Shelby tube sample to evaluate in-situ bearing capacity, we can follow ASTM D4429 or a modified D1883 protocol. The remolded method is far more common for road and parking lot design in the Terrebonne area.