Ready-Mix Concrete Ordering: How to Specify Quantity, Strength, Slump, Delivery, and Placement
Accurate ready-mix concrete ordering requires more than estimating cubic volume. This practical guide explains how to define the mix, calculate quantities, schedule trucks, prepare access, and coordinate placement.
Ready-mix concrete ordering is more than calling a supplier and requesting a number of truckloads. The order must match the approved design, the required performance, the available access route, and the crew’s ability to place and finish the material within the working window. A clear order reduces the risk of shortages, rejected loads, cold joints, idle trucks, and last-minute changes.
For additional background when comparing concrete products and supply considerations, review these ready-mixed concrete resources from Heidelberg Materials. The project engineer, specification, and local supplier should remain the final authorities for mix design, testing, and delivery limits.
What ready-mix concrete ordering involves
Ready-mixed concrete is batched at a plant and transported to the project in mixer trucks. Because the material begins its delivery and setting process before it reaches the formwork, ordering and placement must be coordinated closely. The purchaser normally needs to confirm:
- Required concrete volume and the number of loads
- Specified strength class or compressive strength
- Slump or workability requirement
- Maximum aggregate size and any special aggregate requirements
- Cement type, supplementary cementitious materials, fibres, or admixtures
- Delivery date, arrival intervals, and expected pour duration
- Discharge method, such as chute, wheelbarrow, crane bucket, or pump
- Testing, ticketing, curing, and acceptance requirements
Do not select a mix solely because it has a higher strength or appears easier to place. A change in strength, water content, admixture, aggregate size, or setting time can affect finishing, shrinkage, heat development, pumpability, and cost.
Step 1: Confirm the concrete design and project requirements
Begin with the structural drawings, specifications, project standards, and engineer’s instructions. Identify each element that will be poured, because a foundation, suspended slab, column, pavement, retaining wall, and architectural surface may require different concrete properties.
Strength and exposure requirements
Strength is usually stated as a specified compressive strength at a defined testing age, or as a strength class under the applicable standard. The order should use the same terminology and units as the approved documents. Also check requirements related to exposure, permeability, freeze-thaw conditions, sulphates, chlorides, fire performance, durability, or maximum water-to-cement ratio.
Ordering a stronger mix than specified is not automatically a safe substitute. It may have different cement content, heat generation, shrinkage behaviour, finishing characteristics, or approval requirements. If the supplier proposes a substitution, obtain approval from the responsible engineer before delivery.
Slump, aggregate size, and admixtures
Slump describes the consistency or workability of fresh concrete. A low slump may suit certain applications but can be difficult to place around congested reinforcement. A higher slump may improve flow, but it should be achieved through the approved mix design or water-reducing admixture rather than uncontrolled water addition at the site.
Confirm the maximum aggregate size against reinforcement spacing, cover, form dimensions, pump lines, and surface requirements. Ask the supplier to identify any water reducer, retarder, accelerator, air-entraining agent, fibre, colour, or supplementary cementitious material included in the approved design. Admixtures can change setting time and finishing windows, particularly in hot or cold weather.
Step 2: Calculate the quantity to order
Calculate the theoretical volume from the latest drawings, then compare it with the quantity estimated by the supplier or estimator. Use consistent units. For a rectangular element, the basic calculation is:
Volume = length × width × thickness
Convert the result to the supplier’s billing unit, commonly cubic metres or cubic yards. For footings, beams, walls, columns, ramps, and irregular forms, break the work into manageable shapes and add the individual volumes.
| Element | Useful calculation | Important check |
|---|---|---|
| Slab | Length × width × average thickness | Confirm thickened edges, falls, recesses, and steps |
| Wall | Length × height × average thickness | Deduct large openings and account for pilasters |
| Footing | Length × width × depth | Check changes in width, steps, and ground conditions |
| Column | Cross-sectional area × height | Include capitals, haunches, and changes in section |
| Round element | π × radius² × height | Verify diameter and embedment dimensions |
Allowances, difficult geometry, and separate pours
Drawings rarely describe the exact volume that will be discharged into every form. Uneven excavation, irregular subgrade, overbreak, form deflection, spillage, line hold-up, and small measurement differences can affect actual consumption. Apply a reasonable project allowance based on the work and site conditions, but do not use an arbitrary large percentage. Excess concrete creates disposal, cost, and environmental problems.
Separate the order by pour or mix type rather than combining unrelated requirements. A quantity schedule should show the element, mix designation, theoretical volume, allowance, total order quantity, and planned load size. Recheck the calculation after any revision to dimensions, openings, pour limits, or construction joints.
Step 3: Specify the mix clearly
A supplier needs more than the phrase “standard concrete.” Provide a written order or purchase request that can be checked against the specification. Include:
- Project name, delivery address, and site contact
- Pour location and element being constructed
- Total quantity and requested truck capacity or load breakdown
- Strength class or specified compressive strength
- Slump or workability range at discharge
- Maximum aggregate size and aggregate type, if restricted
- Cementitious materials, air content, water-to-cement ratio, or durability requirements where applicable
- Approved admixtures, fibres, pigments, retarders, or accelerators
- Required delivery temperature or special hot- or cold-weather measures
- Testing, delivery ticket, batch traceability, and sampling requirements
When performance requirements need supplier or engineer input
Some projects require a performance-based specification instead of a simple strength and slump instruction. Pumped concrete, self-consolidating concrete, mass concrete, rapid-setting concrete, waterproof concrete, and mixes containing unusual fibres or recycled materials need additional coordination. Ask the supplier to confirm batching capability, approved materials, expected setting behaviour, and compatibility with the placement method.
Do not alter the mix at the site without authorization. Adding water can increase workability but may reduce strength and durability, increase bleeding, and change the approved water-to-cement ratio. If workability is outside the permitted range, contact the supplier and the responsible technical representative before making a decision.
Step 4: Plan truck deliveries and site access
Book the pour with enough notice for the supplier to reserve plant capacity, materials, trucks, and a pump if required. Confirm the booking again before the pour, especially for large placements, remote sites, weekend work, or projects using a specialised mix.
Delivery sequence and pour rate
Estimate the placement rate of the crew and equipment. The interval between trucks should keep concrete arriving continuously without creating a queue that exceeds the site’s discharge capacity. If trucks arrive too close together, they may block access or wait beyond the supplier’s permitted time. If they arrive too far apart, the crew may create unintended construction joints or lose the planned finishing sequence.
Give the supplier a practical arrival window, not just a single time. Confirm the number of trucks, expected quantity per truck, load sequence, contact method, and procedure for reporting delays. Keep the route clear so each vehicle can enter, position, discharge, and leave safely.
Access, waiting space, washout, and weather
Check road width, overhead cables, turning space, ground bearing, gradients, gates, traffic controls, and restrictions on vehicle size or operating hours. Provide a stable position for the truck and identify where washout water and leftover concrete can be managed in accordance with site and environmental requirements.
Weather can affect transport, setting, finishing, and curing. Prepare shade, wind protection, heaters, insulation, water management, or revised timing as appropriate. A weather plan should be agreed before the first truck arrives rather than improvised during the pour.
Step 5: Prepare pumping and placement operations
If the discharge point is beyond the truck chute, coordinate the concrete pump separately. Confirm the pump type, boom reach or line length, access and setup area, ground support, power or washout arrangements, and communication between the pump operator and placing crew.
Pump setup and hose or chute reach
Inspect the proposed route for sharp bends, elevation changes, obstructions, and areas where the line may be unsupported. The pump operator should verify that the selected mix is suitable for the equipment and line configuration. The first material through the line may be primer or grout and should be handled according to the supplier’s and pump contractor’s procedures.
Crew, formwork, reinforcement, and finishing readiness
Do not call the first truck until the site is ready to receive it. Inspect formwork, dimensions, cleanliness, release agent, reinforcement, embedded items, openings, construction joints, access platforms, lighting, and safety controls. Confirm that vibrators, screeds, floats, edging tools, curing materials, test equipment, and backup equipment are available.
Assign responsibilities for directing trucks, checking delivery tickets, sampling, placing, vibrating, finishing, curing, and recording any nonconformance. The placement team should know the planned sequence and how to respond if the pump stops, a truck is delayed, or weather changes.
Common ordering mistakes and how to prevent them
| Common mistake | Likely consequence | Prevention |
|---|---|---|
| Using outdated drawings | Wrong volume or mix specification | Mark the revision used for the order and recheck changes |
| Ordering only the theoretical volume | Shortage before the pour is complete | Review geometry and apply a justified allowance |
| Vague strength or slump instruction | Wrong product or delayed clarification | Use the exact approved designation and units |
| Adding unauthorized water | Reduced performance and rejected concrete | Use the approved mix or obtain technical direction |
| Ignoring truck access | Late deliveries, unsafe positioning, or blocked roads | Complete a route and setup inspection |
| Starting before the crew is ready | Truck waiting, premature setting, or cold joints | Use a pre-pour checklist and readiness confirmation |
Ready-mix concrete ordering checklist
- Verify the latest drawings, specifications, and approved mix design.
- Calculate each pour quantity and document the assumptions.
- Confirm strength, slump, aggregate size, admixtures, and durability requirements.
- Agree on the allowance, load sizes, and number of trucks.
- Book the plant, trucks, pump, testing, and required delivery window.
- Inspect access, truck positioning, pump setup, ground conditions, and washout arrangements.
- Confirm formwork, reinforcement, embeds, joints, equipment, labour, and finishing materials.
- Prepare a weather and contingency plan.
- Check every delivery ticket against the order before discharge.
- Record sampling, test results, placement times, interruptions, and any rejected or adjusted load.
Frequently asked questions
How much ready-mix concrete should be ordered?
Order the calculated volume of the pour plus a justified allowance for geometry, overbreak, spillage, and equipment hold-up. The appropriate allowance depends on the element and site conditions. For critical structural work, have the quantity independently checked before booking.
Can extra water be added to a concrete truck?
Only when the approved mix procedure and responsible technical authority permit it. Uncontrolled water addition can change the water-to-cement ratio and affect strength, durability, bleeding, shrinkage, and finishing. A compatible water-reducing admixture may be the correct solution, but it must be approved and properly documented.
How far in advance should ready-mix concrete be booked?
Book as early as practical for large pours, specialist mixes, restricted delivery windows, remote sites, or periods of high demand. Confirm the order shortly before the pour and provide prompt notice of changes. The supplier can advise on plant capacity, material availability, and minimum notice for the local area.
What should happen if a truck arrives before the site is ready?
Notify the supplier and site manager immediately. Do not discharge into an unprepared location simply to avoid waiting. Follow the supplier’s time and quality procedures, record the arrival and discharge times, and obtain technical direction if the load may exceed its permitted delivery or placement window.