The Yamaska River plain left Granby with a mix of till, glaciolacustrine silts, and pockets of Champlain Sea clay that make every job different. A contractor on rue Principale can hit clean sand at two metres, while a project near Lac Boivin encounters fat clay down to seven metres. Getting the particle distribution right from gravel through clay means running both sieve and hydrometer tests under ASTM D6913 and D7928. We combine wet washing over the No. 200 sieve with sedimentation analysis so the gradation curve covers the full range. For jobs where fines content affects the classification, the hydrometer data feeds directly into the USCS group symbol — the difference between an SM and an SC changes the bearing assumptions considerably. About forty percent of the samples we process from the Granby area fall into the silty sand to lean clay spectrum.
A complete grain size curve from 75 mm down to 2 microns tells you more about a soil's behaviour than the blow count alone.
Methodology applied in Granby Quebec
Risks and considerations in Granby Quebec
Granby's winter freeze-thaw cycles are aggressive on fine-grained soils, and a gradation that looks acceptable in August can become a frost-susceptible material by January if the silt fraction exceeds fifteen percent. The MTQ frost criteria tie directly to the percent passing the 80 µm sieve, which is exactly where the hydrometer picks up after the wash sieve. We have seen projects where the grain size curve alone flagged a fill material as frost-susceptible before any expensive physical testing was ordered. Summer humidity in the Eastern Townships also means samples arrive with elevated moisture; we oven-dry at 110°C before the sieve stack to avoid clumping on the finer meshes. For clay-rich samples, the pre-treatment with hydrogen peroxide removes organics that would otherwise skew the sedimentation readings.
Our services
Our Granby laboratory processes the full grain size analysis in-house, from coarse sieving through hydrometer sedimentation, with reporting that matches both ASTM and MTQ formats.
Combined Sieve and Hydrometer Analysis
Full particle distribution from 75 mm down to 2 microns. Includes wet washing, coarse and fine sieving, plus 24-hour hydrometer sedimentation with readings at 0.5, 1, 2, 5, 15, 30, 60, 120, and 1440 minutes.
Wash Sieve Only (Minus 75 µm Determination)
When the project only needs the fines content for classification or frost-susceptibility screening, we run the wash over the No. 200 sieve and report percent passing for MTQ compliance.
Gradation for Road Base and Concrete Aggregate
Coarse sieve stacks per ASTM D6913 with full reporting of uniformity coefficient, coefficient of curvature, and comparison against MTQ granular material specifications.
Frequently asked questions
What is the difference between a sieve analysis and a hydrometer test?
The sieve analysis covers particles retained on the No. 200 sieve (75 µm and larger) using a stack of wire-mesh sieves. The hydrometer test measures the sedimentation rate of particles smaller than 75 µm in a water column, calculating the distribution down to about 2 microns. Together they give the complete grain size curve from gravel through clay.
How long does a full grain size analysis take in your Granby lab?
The sieve portion can be completed in one working day. The hydrometer sedimentation requires a minimum 24-hour settling period after dispersion, plus oven-drying time. We typically deliver the combined report within three to four business days for routine samples.
Do you need a special sample for the hydrometer test?
Yes — we need about 200 to 300 grams of material passing the No. 10 sieve, kept at natural moisture or sealed to prevent drying. If the sample is too small or has dried out, the dispersion behaviour changes and the clay fraction can read lower than the true value.
What does a grain size analysis cost in the Granby area?
A combined sieve and hydrometer analysis typically runs between CA$140 and CA$220 per sample, depending on whether organic pre-treatment or additional wash sieves are needed. Bulk pricing applies for projects with ten or more samples. More info.