Grain Size Analysis (Sieve + Hydrometer) for Ottawa Geotechnical Projects

CSA + ASTM D422 is the traditional combined method covering both sieve and hydrometer portions. ASTM D6913 is the newer standard specific to the sieve analysis part, with clearer guidance on sample splitting, sieve shaking duration, and acceptance criteria for mass loss. Our Ottawa lab follows D6913 for the mechanical sieve component and retains D422 methodology for the hydrometer sedimentation phase, ensuring compliance with both current ASTM requirements and legacy project specifications.

Champlain Sea clays, including the sensitive Leda clay found across central and east Ottawa, typically contain 50 to 80 percent clay-sized particles (finer than 2 µm). A sieve analysis alone cannot distinguish between silt and clay fractions in this range. The hydrometer method, based on Stoke's law settling velocities, quantifies the true clay content, which directly controls the soil's plasticity, compressibility, and sensitivity to remolding. Without hydrometer data, the risk of misclassifying a highly sensitive clay as a ordinary silt is significant.

A standard combined sieve and hydrometer test on a single soil sample typically ranges from CA$150 to CA$220, depending on whether a full hydrometer curve with multiple readings or a single-point hydrometer is requested. Rush turnaround and projects requiring multiple samples may adjust the unit price. All testing is performed in our ISO 17025 accredited Ottawa laboratory.

For granular soils with particles up to 19 mm, a minimum of 500 grams of air-dried material is required. For soils containing gravel up to 75 mm, we need at least 5 kg to ensure a representative split. Fine-grained soils for hydrometer analysis require about 200 grams of material passing the No. 10 sieve. The sample must be sealed in a moisture-tight bag immediately after field collection to preserve in-situ water content if that data is also needed.