A concrete supply bid looks simple from a distance: quote the mixes, quote the yardage, quote the truck. What 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.
On the S-sheets, not in 03 30 00
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 real price list for the job, and it's easy to miss simply because it isn't where the section number suggests. Three more clauses travel with it, all outside 03 30 00:
- 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 refused at the chute, on the clock, with the crew standing around.
- SCM and chloride limits. Fly ash or slag percentage caps, often seasonal and 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 — the first load adjusted in the field without a clear record of who authorized it is the first dispute.
What 03 30 00 covers
- Ready-mix supply per the specified mixes — every mix property the documents specify prices directly: strength class, exposure class, air entrainment, slump or slump-flow, aggregate size, cement type, and SCM limits. The part of the bid every supplier gets right, because it's the part 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 here 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 the 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. Seasonal cost the specification sets directly, easy to under-price on a bid written in a different season than the pour is scheduled for.
Two arguments before you quote
Pumping sometimes sits inside the supply contract and sometimes belongs to the placing contractor, and there's 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 the last job's answer, and flag it explicitly when the documents are silent.
Specialty mixes carry the second argument. 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 especially) that reads like an engineering deliverable rather than a supply line item. These 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 instead of trusting the schedule to list every mix that gets poured.
What ends at the chute
- 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 that work turns out to be.
- Formwork and reinforcing — separate trades entirely, priced and contracted independently of the mix that fills them. The one genuine overlap is the chloride-ion limit protecting the steel, a mix constraint rather than a reinforcing one.
- Field testing — sampling and cylinder testing is normally the owner's testing agency, not the supplier's. The real exposure sits at the point of discharge, where the supplier typically supports sampling — 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.
The other end of the truck
| 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 — 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. Read like logistics paragraphs; 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 checking against the pump that's booked, not assumed compatible. |
Read 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 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.