Concrete Delivery & Preparation

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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Good concrete work is decided before the truck backs in. The order, the ticket, the site and the crew, checked before any concrete goes in.

The big idea

A good pour is decided before the truck arrives. Once the drum starts turning, the concrete is on a clock, the crew is on the clock, and nothing can be undone. This page is the checklist you run before every pour, big or small.

Concrete for houses is ordered and tested to the CSA A23.1 and A23.2 standards, and NBC Part 9 sets the minimums for house concrete. Engineered work follows the drawings and is often stronger.

What you order

The supplier builds the mix from what you tell them. A short, complete order avoids most problems.

• Strength in MPa at 28 days, from the drawings or the Part 9 minimums below.
• Exposure class under CSA A23.1 for freeze-thaw and de-icing salt. The supplier can advise.
• Largest stone size. Commonly 20 mm (3/4 in). Narrow forms or dense rebar may need smaller.
• Slump in mm, and how it will be placed (chute, pump or buggy). See the next page.
• Air content where freeze-thaw applies, such as garage floors, carports and exterior steps.
• Admixtures such as water reducers, retarders or accelerators, only if wanted.
• Quantity, from the Concrete Math page, rounded up a little.

Part 9 minimums for unreinforced concrete

These come from NBC Part 9 as printed in the Vancouver Building Bylaw 2014 (9.3.1.6 and 9.3.1.7). Your province adopts the code with changes, so check your edition. Reinforced concrete is designed, not just minimum strength, and follows Part 4 or the drawings.

Stone size and quantity: two worked examples

Stone size. Part 9 limits the largest stone to 1/5 of the distance between vertical form sides, or 1/3 of the thickness of flatwork. A 200 mm (7 7/8 in) wall form: 200 ÷ 5 = 40 mm (1 9/16 in). A 100 mm (4 in) slab: 100 ÷ 3 = 33 mm (1 5/16 in). So 20 mm (3/4 in) stone suits both.

Quantity. A 4 m × 5 m (13 ft 1 in × 16 ft 5 in) slab at 100 mm (4 in) is 4 × 5 × 0.1 = 2.0 m³ (2.6 yd³). With a 10% allowance that is 2.2 m³ (2.9 yd³). The 10% is only an example. Ask the supplier how they want you to round. Order a little over rather than short.

When the truck arrives: the delivery ticket

Read the ticket before anyone discharges.

• Mix: strength, stone size, air content, slump and exposure class.
• Admixtures listed, and any water added at the plant.
• Batch time and truck number. Concrete has a limited time from batching to discharge. Municipal and project specifications cite CSA A23.1 for a limit of 120 minutes after batching, so a truck batched at 9:05 should finish discharging by 11:05. Hot weather can shorten that, and the specification can change it. Confirm the limit with your supplier.
• Quantity on the truck.

If anything does not match your order, say so before it goes in the form. Rejecting a load is easier than removing one. And never add water to the load yourself. Water raises slump but cuts strength and durability. If the slump is off, the supplier decides what can be done, and written permission is needed before any water goes in.

Site preparation before the pour

• Forms: clean, braced, to line and level, and signed off.
• Rebar: spacing, cover and supports checked, and free of mud and debris.
• Anchors, sleeves and inserts: in place and secured.
• Base: no standing water, no frozen ground, no loose material.
• Access: clear paths for trucks, wheelbarrows and hoses, and ground that will carry a loaded truck.
• People: everyone knows their job and a signal system is agreed.
• Inspection: every required inspection is done and written off before concrete goes in.

Equipment setup

• Pump: boom or line routed, clamps checked, and outriggers on solid pads. In BC, operating a concrete pump or placing boom requires a concrete pump operator certificate, or supervision by someone who holds one (OHS Regulation 20.26.1). Check the rule in your province.
• Power lines: look up before you set up. In BC the minimum distance to a line over 750 V up to 75 kV is 3 m (10 ft) (Table 19-1A), and the power owner must be involved if you cannot keep it.
• Chutes: positioned so concrete is not dropped from a height, because a long free fall can separate the mix. Use a hose or trunk. I did not find a sourced drop limit, so follow the supplier and the drawings.
• Vibrators: fuelled or charged, tested, with a spare.
• Finishing tools: screeds, floats, trowels, edgers and brooms staged and clean.
• Wash water: for tools only, never for the mix.

Testing on site

For engineered work, and most commercial work, a testing lab or the supplier tests the concrete as it arrives.

• Slump (CSA A23.2-5C).
• Air content, pressure method (CSA A23.2-4C), where air is specified.
• Concrete temperature (CSA A23.2-17C), especially in hot or cold weather.
• Strength cylinders made and cured under CSA A23.2-3C, then tested at the ages your specification names, usually 7 and 28 days.

Test numbers are from a CSA test-method list. Edition years change, so check the current edition.

Common mistakes

• Calling the truck before forms and steel are ready
• Adding water on site
• Not reading the ticket
• Too few people for the working time
• No plan for rain, heat or cold
• Soft ground under the truck or pump
• Pump set up near a power line