A concrete supply bid looks simple from a distance: quote the mixes, quote the yardage, quote the truck. What actually sets the price is almost none of that — it's a set of constraints written by the structural engineer, in the structural drawings, that a supply-only read of Division 03 will never surface on its own. Exposure class, maximum water-cementitious ratio, SCM limits, chloride limits, minimum strength at a stated age: none of it is optional, all of it is enforceable at the cylinder break, and most of it doesn't live where the section number says it should.
This is a working list of where concrete supply scope actually gets decided, built from what shows up across real Canadian ICI tenders — schools, health facilities, transit and institutional work. Not a mix-design textbook. A list of the specific documents worth cross-checking before a mix gets quoted.
What's reliably yours
- Ready-mix supply per the specified mixes — every mix property the documents actually specify prices directly: strength class, exposure class, air entrainment, slump or slump-flow, aggregate size, cement type, and SCM limits. This is the part of the bid every supplier gets right, because it's the part that's genuinely written down as a mix.
- Mix design submittals and substantiating data — trial batch data or field performance history submitted well ahead of first placement. The lead time on this is a real constraint, not a formality: a mix design rejected two weeks before a scheduled pour is a schedule problem for everyone on the job, not just the supplier.
- Admixtures required by specification — air entrainers, water reducers, retarders, accelerators and corrosion inhibitors, whether the spec names a product or states a performance requirement. Named-product clauses are worth flagging on their own, since they remove a supplier's usual flexibility to substitute.
- Hot and cold weather supply requirements — concrete temperature limits at discharge, heated water and aggregates, ice, and cooling measures. This is seasonal cost the specification sets directly, and it's easy to under-price on a bid written in a different season than the one the pour is actually scheduled for.
Where the fight actually happens
Pumping and conveying
Pumping sometimes sits inside the supply contract and sometimes belongs to the placing contractor, and there is no reliable convention across tenders — it genuinely varies job to job, and sometimes it isn't stated cleanly at all. The cost isn't trivial: line pumping a small-aggregate or self-consolidating mix through a boom is a different operation, with different scheduling and standby cost, than a chute discharge into a wall form. Extract the assignment as written rather than defaulting to whichever answer was true on the last job, and flag it explicitly when the documents are silent.
Specialty mixes and the premium nobody flags
Self-consolidating concrete, fibre-reinforced mixes, shrinkage-compensating concrete, high-early-strength mixes and mass-concrete pours requiring a thermal control plan all carry real premiums over a standard structural mix — sometimes a large one, and sometimes attached to a requirement (the thermal control plan, in particular) that reads like an engineering deliverable rather than a supply line item. These callouts hide easily inside a general note or a single mass-pour detail rather than the mix schedule itself, which is exactly why they're worth a dedicated pass rather than trusting the mix schedule to list every mix that actually gets poured.
The other half: what isn't yours, even when it looks close
- Placement, finishing and curing — supply ends at discharge. Getting the concrete into the forms, screeding and finishing the surface, and curing it afterward belong to the placing and finishing trade, even though the mix you supplied has a direct effect on how forgiving or unforgiving that work turns out to be.
- Formwork and reinforcing — forms and rebar are separate trades entirely, priced and contracted independently of the mix that fills them. The only place supply and reinforcing genuinely overlap is the chloride-ion limit protecting the steel, which is a mix constraint, not a reinforcing one.
- Field testing — sampling and cylinder testing is normally the owner's testing agency, not the supplier's. Where the real exposure sits is at the point of discharge: the supplier typically supports sampling there, and when a set of cylinders trends low, it's the mix — and the relationship with the mix designer — that ends up under scrutiny, whatever the paperwork says about who technically ran the test.
Five things that hide outside Division 03 30 00 entirely
- Exposure class tables in structural general notes. The exposure or durability table — C-XL, C-1, C-2, or the F/S/W/C classes, with maximum w/cm and minimum strength attached — is almost always on the S-sheets or in structural general notes, not in the concrete supply section. It is, in every practical sense, the actual price list for the job, and it's easy to miss simply because it isn't where the section number suggests.
- Air content ranges and tolerances. Air percentage is tied to aggregate size and exposure class, with acceptance tolerances that carry real rejection risk on every exterior mix — a load that tests outside the range is a load that gets refused at the chute, on the clock, with the crew standing around.
- SCM and chloride limits. Fly ash or slag percentage caps — often seasonal, tighter in winter — and chloride-ion limits for reinforced or post-tensioned work constrain which mix designs are even legal to submit, let alone which ones are cheapest.
- Delivery time and temperature limits. A maximum time from batching to discharge — the 90-minute rule and stricter project-specific variants — plus discharge temperature windows, sets real plant-to-site feasibility. A supplier whose closest plant can't make the clock on a hot day isn't a supplier who can bid the job at all.
- Mix-specific placement restrictions. Clauses like "no added water on site," fixed rules for slump adjustment at the truck, and washout location requirements read like site logistics but are ticket-level obligations that turn into disputes the first time a load gets adjusted in the field without a clear record of who authorized it.
Who you're actually sharing the pour with
| Trade | What to reconcile before you price |
|---|---|
| Concrete placer & finisher | Order timing, pour rates, slump adjustments at the truck, and who has authority to accept a borderline load — this is the daily interface, and it needs an answer before the first pour, not during it. |
| Testing agency | Sampling at point of discharge, cylinder custody, and the process when strength results trend low — confirm before a low break becomes a dispute about whose mix or whose curing caused it. |
| General contractor | Site access, truck routing, staging and washout locations. These read as logistics paragraphs but they're real supply costs on a congested urban site. |
| Pumping contractor | Line size and mix pumpability — an SCC requirement or a small-aggregate mix changes the mix price, and it needs to be checked against the pump that's actually booked, not assumed compatible. |
The pass that catches most of this
Read the structural general notes and the S-sheets for the exposure class table before pricing a single mix off the concrete section alone — that table, not Division 03, is what actually constrains the design. Then check delivery time, discharge temperature and pumping assignment against the site conditions this specific job implies, not the assumptions carried over from the last one. The mix schedule tells you what to supply; the boundary clauses scattered across the structural drawings tell you what that supply is actually going to cost once winter, distance and exposure class all apply at once.