Aggregates and gravel

STA 0+120What "aggregate" means on a job

Civil specifications use a handful of recurring aggregate categories, each doing a different job in the structure:

• Pit run. Unprocessed or minimally processed gravel straight from the pit, used as bulk fill or a base layer where a tight gradation is not required.
• Crushed gravel or crushed granular. Screened and crushed to a specified gradation, used where strength and drainage matter, such as under pavement.
• Granular base and sub-base. Engineered layers under a road or pad, placed and compacted to specific density and often a specific gradation "class" set by the owner's specification.
• Surfacing gravel. The wearing course on an unpaved road, chosen for a balance of binding fines and drainage.
• Riprap and armour rock. Larger, sorted rock sizes used for erosion protection rather than structural support; see marine construction.

The same tonne of crushed rock can be priced completely differently depending on which of these categories it is sold under, because the specification, the testing and the handling differ even when the source pit is the same. See earthworks and excavation for how bulk cut and fill volumes relate to the granular layers described here, and roadbuilding and paving for how base and sub-base fit into a finished road section.

STA 0+240Gradations and specification classes

A gradation describes what proportion of a sample passes through a stack of sieves of decreasing size, from coarse rock down to fine sand and silt. Owners specify a gradation band, not a single number, because a well-graded mix of particle sizes compacts to a denser, stronger, better-draining layer than a single-size material does. Alberta's highway pay items name their specification class directly in the item description, for example "granular base course, design 2, class 25," where the numbers refer to the agency's own gradation and design tables rather than a generic industry standard. Municipal specifications (see municipal infrastructure) set their own gradation classes the same way, and a class from one owner's specification is not automatically interchangeable with another's, even when the material looks similar in a stockpile.

STA 0+360Bulk density: tonnes, cubic metres and trucks

Aggregate is sold by the tonne but placed and measured by the cubic metre, so converting between the two depends on the material's bulk density, and that density changes with moisture and how loosely or densely the material is sitting. As typical planning values, not measurements of a specific pit or stockpile:

These typical values come from a U.S. Army earthmoving field manual¹¹, converted from imperial units, and they should be treated as a planning starting point rather than a test result. A supplier's delivery ticket in tonnes and a specification written in cubic metres of compacted layer are two different units for the same material, and the density used to convert between them belongs in the estimate, not assumed after the fact. The gravel and aggregate tonnage calculator and the swell and shrink converter handle the conversion.

STA 0+480What aggregate costs: 2026 Alberta supply prices

Alberta Transportation and Economic Corridors publishes the average of the three lowest bids on every aggregate-related item it tenders. For contracts tendered between May 2025 and June 2026, the provincial averages were:

Aggregate supply with a gradation option averaged $3.27 per t² per tonne, well above the $1.29 per t² average for supply with no option, which reflects the extra crushing and screening needed to hit a specified gradation. Granular base course (design 2, class 25) averaged $33.65 per t² per tonne, and pitrun gravel priced by the cubic metre in one region averaged $112.46 per m³². These are highway-scale averages on large tendered quantities; a small residential or acreage job pays more per tonne because minimum loads, short-haul mobilization and a smaller negotiating position all push the price up. Use the gravel cost per tonne guide for smaller-job pricing and the unit price index for every item.

STA 0+600Haul economics and axle weights

For most aggregate jobs, hauling the material costs more than buying it, because a tonne of gravel is cheap relative to the diesel, driver time and truck wear needed to move it any real distance. Granular base course prices make the point on their own: the same item varies sharply by region on Alberta's highway program, which is mostly a haul-distance-to-pit signal rather than a difference in the material itself:

Alberta's Commercial Vehicle Dimension and Weight Regulation caps a tandem axle group with eight or more tires at 17,000 kg³, and a single steering axle at 7,300 kg³, before other limits such as tire load, bridge formula or a seasonal road ban apply. Those legal limits, not the truck's rated capacity, usually set how much payload a load can legally carry, which in turn sets how many truckloads a given tonnage works out to. The haul truck cycle time calculator turns a haul distance and cycle time into the number of trucks needed to keep a crusher or a placing crew supplied, and spring road bans covers the seasonal weight restrictions that can cut legal payloads well before the regulation's normal limits.

STA 0+720Sourcing and quality control

Aggregate comes from a pit (unconsolidated sand and gravel deposits) or a quarry (blasted and crushed bedrock), and the source affects both the material's properties and the approvals needed to extract it: pit and quarry operations are themselves regulated land uses, permitted separately from the civil work that consumes their output. Specifications typically call for testing, gradation checks, and sometimes source approval before a pit is accepted for a public contract, particularly where the aggregate will end up in concrete or asphalt rather than as fill. None of that testing regime is standard across every owner, so a contractor pricing supply from a new source should confirm what testing and approval the specification actually requires before assuming a pit is qualified. Recycled sources are increasingly part of the same market: crushed concrete and reclaimed asphalt pavement can substitute for virgin gravel in many granular applications, subject to the same gradation and quality testing as a natural source; see demolition and site clearing for how that material is generated in the first place.

STA 0+840What to send for a price

An aggregate brief that gets a firm number usually includes:

• The material category and, if known, the specification class or gradation required.
• Quantity, in tonnes or cubic metres, and whether that is loose, compacted or bank volume.
• Delivery location and access, including any load or route restrictions.
• Whether supply only, supply and haul, or supply, haul and place is being priced.
• The schedule, including any season-specific haul restriction that might apply.

Ask whether the quoted price is per tonne delivered or per tonne at the pit, since freight is usually the larger share of the delivered cost once haul distance grows past a few kilometres.