Ready-mix concrete ordering and delivery field guide

What ready-mix is, and why the order decides the pour

Ready-mix concrete is concrete batched at a plant to a set recipe and delivered to the site in a rotating-drum truck, ready to place. You are not mixing anything. You are ordering a product, taking delivery of it, and getting it into the forms before it sets. That shift is the whole point. With ready-mix, most of what decides whether the pour succeeds happens on the phone and at the chute, not in the forms.

Three things have to be right, and they are separate decisions. The mix has to match the job, which is the mix design and the spec. The quantity has to cover the pour with a little to spare, which is the yardage. The timing has to get the concrete placed before it stiffens, which is the schedule and the discharge clock. Get the recipe right and run short, and you have a cold joint. Order plenty of the wrong mix, and you have a driveway that scales the first winter.

What controls the recipe is covered in the companion mix-design and water-cement-ratio guide, and what you check at the chute is covered in the slump-test guide. This guide is about the order and the delivery: how much to order, what to put on the ticket, and how to take the load without wrecking it.

How much concrete should I order?

Calculate the volume in cubic yards: length times width times thickness, all in feet, divided by 27. A slab 20 ft by 30 ft at 4 in thick is 20 times 30 times 0.333, which is about 200 cubic ft, divided by 27 is roughly 7.4 cubic yards. Convert the thickness to feet first. A 4 in slab is 0.333 ft, a 6 in slab is 0.5 ft. The most common field error is leaving thickness in inches and ordering a fraction of what you need.

Then add a waste allowance, commonly 5 to 10 percent. Use the low end on a clean, machine-placed pour and the high end on hand-poured residential work, irregular shapes, or a subgrade that is not dead flat. Spillage, over-excavation, a form that bows out, and the concrete left in the truck and the pump line all eat into the number. Running 5 percent short on a slab is not a rounding error. It is a cold joint or a second mobilization.

Order in full or half yards, because that is how the plant batches, and round up rather than down. The concrete yardage calculator on this site runs the volume and the waste factor for slabs, footings, and walls. Order a little long. The cost of an extra quarter yard is nothing next to the cost of a truck running dry with the crew standing in wet concrete.

What do I need to specify when ordering concrete?

The plant needs enough to batch the exact mix, not a generic 3000 guess. At a minimum, give the compressive strength (f'c in psi), the slump, the maximum aggregate size, the air content if the concrete sees freeze-thaw, and the mix design number if the project has an approved one. Add the admixtures, the cement type, and any supplementary cementitious material the spec calls for.

If the project has a submitted and approved mix design, order by its number and let that carry the rest. The mix design already fixes the proportions, the water-cement ratio, the admixtures, and the strength. Ordering 4000 psi air-entrained, 4 in slump, 3/4 in aggregate, mix number such-and-such tells the plant exactly what to load. Ordering some 4000 invites a substitution you never approved.

Specify, do not assume. The dispatcher batches what you say, and the ticket becomes the record of what you said. If the spec is in front of you, read the strength, the exposure class, the slump, and the air straight off it. The mix-design guide covers what each of those means and why the supplier set them where they did.

Ordering to the spec and choosing the strength

The right mix for the job is whatever the project specification and the mix design call out, and that is rarely a one-size number. A footing, an interior slab on grade, an exterior driveway, and a structural column can all read 4000 psi and still be four different mixes once you account for exposure, air, aggregate, and admixtures. Order the generic and you may get concrete that meets the strength and fails the durability.

A driveway or sidewalk in a freeze-thaw climate wants air entrainment and often 4000 psi or better for scaling resistance, even though the loads are light. A footing buried below frost may not need air at all. An interior slab wants low shrinkage and a slump you can finish, not the wettest mix on the truck. A structural element follows the engineer's exposure class and strength, full stop.

Strength itself is specified as f'c, the compressive strength the concrete is designed to reach at its test age, usually 28 days, in psi. Most residential flatwork lands somewhere around 3000 to 4000 psi, and exterior work in cold climates trends to the higher end because the air entrainment and the durability come with it. Structural concrete and columns go higher, set by the engineer. Order the strength the spec gives you. Do not round it down to save a few dollars a yard, and do not assume a higher number is automatically safer, because a richer mix shrinks and cracks more.

One point crews miss: the strength on the ticket is the designed f'c, and the concrete is proportioned to exceed it on average so the test cylinders pass with margin. That overdesign lives in the mix design. It is not your license to add water, because the water you add comes straight off that margin. When a mix design exists, order it by number and it carries all of this. The mix-design guide walks through how the exposure class, the overdesign, and the water-cement ratio drive the proportions.

Ordering the slump for the placement

Slump is the measure of how wet and workable the concrete is, and you order it to match how the concrete gets placed, not to make finishing easy. Flatwork that gets screeded often runs in the 4 to 5 in range. A wall or a heavily reinforced section that has to flow around bars and consolidate wants more. A pump mix usually carries a higher slump or a mid-range water reducer so it moves through the line. Confirm the target against the mix design.

The trap is ordering or asking for a wet, soupy load because it spreads easy. A high slump from added water is a low-strength, high-shrinkage load wearing an easy-to-place disguise. A high slump from a water reducer is fine. Same number on the cone, opposite outcome, which is exactly the distinction the slump-test guide draws.

Order the slump the mix is designed for and bring it up with chemistry, not a hose. If the placement genuinely needs a wetter mix, get the supplier to design it that way with a water reducer or a plasticizer, so the water-cement ratio holds while the slump climbs.

Air entrainment for freeze-thaw exposure

Any concrete that gets wet and then freezes, exterior flatwork, driveways, sidewalks, curbs, steps, and exposed structural concrete in cold climates, needs entrained air. Air entrainment puts microscopic bubbles in the paste that give freezing water somewhere to expand, which stops the surface from scaling and keeps the concrete from coming apart over freeze-thaw cycles. Order it, or the first hard winter takes the surface off.

The target air content depends on the exposure and the maximum aggregate size, and it commonly runs in the 5 to 7 percent range for severe freeze-thaw, often specified around 6 percent. The mix design and the spec set the exact number against the ACI 318 exposure class. Confirm it on the order and check it at the truck, because air can be lost to a long haul, overmixing, or pumping.

The common, expensive miss is ordering interior, non-air-entrained concrete for an exterior pour because it was cheaper or it was what showed up. Non-air-entrained concrete outside in a freeze-thaw climate scales and spalls, and there is no fixing it after the fact. The air-entrainment details live in the mix-design guide. On the order, the rule is simple: outside and it freezes, it gets air.

The ready-mix truck and the load

A standard ready-mix truck holds up to about 10 cubic yards, though many plants load 8 to 9 to stay within weight and road limits, and the legal axle weight often caps the load below the drum's geometric capacity. So a 7 yard pour is one truck, and a 25 yard pour is three trucks, planned and spaced. Confirm the capacity with your supplier, because it varies by plant and local weight law.

The drum turns to keep the concrete agitated and uniform on the way to the site, then reverses to discharge down the chute. The mix sitting in the drum is on the clock from the moment water hit the cement at the plant, which is why the batch time on the ticket matters as much as the mix.

For anything past one truck, the order is also a delivery schedule. You tell dispatch the pour rate you can place, and they space the trucks so concrete arrives steadily without trucks lined up at the curb stiffening while they wait. Too few trucks and you run dry between loads, which risks a cold joint. Too many at once and they sit past the discharge limit. The spacing is part of the order, not an afterthought.

What's on a concrete batch ticket?

The batch ticket, or delivery ticket, is the legal record of what was batched and when, and it travels with the truck. ASTM C94 sets what it has to carry. At a minimum, expect the supplier and plant, the date, the truck and ticket number, the mix identification, the cubic yards, the specified strength or mix design, and the time the truck was batched or loaded. Many tickets also list the cement, the admixtures, the design water, and the water withheld.

Read it before the concrete comes off the truck, not after. Check the mix against what you ordered, check the quantity, and write down the batch time, because the discharge clock starts there. If any water is added on site, it gets recorded on the ticket, with the amount and who authorized it. That entry is the difference between a documented tempering and an argument later when the cylinders break low.

Keep the ticket. It is the document that proves the concrete you placed was the concrete you ordered, and it is the first thing pulled when a placement is questioned. A pour with no tickets is a pour you cannot defend.

How long does ready-mix concrete last in the truck?

Traditionally, ASTM C94 set the limit at 90 minutes or 300 drum revolutions from the time water met the cement, whichever came first, to complete discharge. The 2021 edition of C94 changed the default. The time limit is now stated by the purchaser when ordering, and if the purchaser does not state one, the producer sets it, and that limit goes on the delivery ticket. The 90-minute figure is still the common practical benchmark, but confirm the limit on your ticket and your spec.

The reason for any limit is the same. Cement starts hydrating the moment it meets water, and the concrete stiffens whether it is in the forms or the drum. Place it after it has begun to set and you get a weak, poorly consolidated mass with cold joints. Hot weather shortens the usable window because heat speeds hydration, so a load that is fine at 80 minutes on a mild day can be done at 60 on a hot one.

The limit can be waived if the concrete still meets the slump without adding water and can be placed properly, but that is the purchaser's call and it gets recorded. The practical rule: place it before the limit on the ticket, watch it harder in the heat, and the hot-weather guide covers shortening the window further.

Can you add water to ready-mix concrete?

You can add water once, on arrival, only to bring a stiff load up to the design slump, and only if it stays within the mix design's maximum water and water-cement ratio. That is the controlled tempering ASTM C94 allows. Everything past that point lowers strength, and you own the result. The figure to carry: roughly 1 gallon of water per cubic yard raises slump about 1 in and drops compressive strength on the order of 200 to 250 psi, and it cuts freeze-thaw durability on top of that.

Here is the rule, blunt. Do not just add water to make the concrete easier to place. The driver and the crew reach for the hose because soupy concrete spreads itself, and every gallon over the design comes straight off the strength and the durability. A slab you watered to place easy is a slab that cracks, dusts, and scales, and the cylinders will say so.

If the load is genuinely too stiff and you are within the design water, the supplier can add the withheld water once and run the drum 30 revolutions at mixing speed to blend it, recorded on the ticket. If you need it wetter than the design allows, you do not get there with water. You get there with a water reducer the supplier doses, which is the same point the mix-design and slump guides make. Water for slump is the most expensive shortcut on the jobsite.

Scheduling, truck spacing, and large continuous pours

The order is also a clock, and the logistics decide whether the crew ever gets to do its job. Set the start time, tell dispatch the rate you can place in cubic yards per hour, and let them space the trucks to feed that rate. A crew that can place 15 yards an hour does not want four trucks at once. It wants one every 30 to 40 minutes, steady.

Have the crew, the tools, and the forms ready before the first truck rolls. Trucks have a grace period built into the price, and past it they bill standby by the minute while the concrete in the drum keeps aging toward the discharge limit. A truck waiting is money and a risk at the same time. The concrete does not pause for you.

Read the weather into the schedule. Heat and wind shorten the window and speed the set, so on a hot day you pour earlier and space tighter. Rain turns the finish to mush. The pour that starts late and runs into the afternoon heat is the one that finishes badly, so the timing decision gets made the day before, not at the chute.

A big slab, a mat foundation, or a structural deck raises the stakes, because it has to go in as a continuous pour with no cold joints. The order becomes a truck train: enough trucks, spaced tightly enough, to keep concrete arriving at the placement rate from the first yard to the last without a gap that lets the previous lift set. A data-center mat or a large foundation can run hundreds of yards in one continuous pour. Confirm the plant can sustain the yards per hour you need, line up a backup plant for a pour that exceeds one plant's output, and order a retarder to extend the working time across the hours the pour takes.

The failure mode on a large pour is the gap. A 20-minute hole in the supply where no truck shows lets the placed concrete start to set, and the next load lands on a stiffening surface that will not knit. That is a cold joint through a structural element. On a job this size, the supply plan is the pour plan.

Site access, the chute, and the pump mix

A loaded ready-mix truck is heavy, often 60,000 to 70,000 lb gross, and it needs firm, level access to reach the pour. The standard chute reaches only so far, commonly in the 10 to 18 ft range from the truck depending on the rig, so anything beyond the truck's reach needs another method to move the concrete. Sort this out before the truck arrives, not while it idles.

For pours the chute cannot reach, the options are a boom pump, a line pump, a crane and bucket, motorized buggies, or wheelbarrows for small work. A boom pump places concrete over a building or deep into a site. Each method changes the mix you order. A pump line is unforgiving: a pump mix usually needs a higher slump or a mid-range water reducer to move without segregating or plugging, and the maximum aggregate size has to suit the line diameter. Tell the supplier the concrete is being pumped when you order, so they design the mix for it.

The wrong move is to order a stiff mix and then water it on site to make it pumpable, which is the same water-cement problem under a different name. Get the pumpability from the design so the strength holds. A plugged line on a wet, segregating mix stops the pour cold, and clearing it burns the clock on every truck waiting. The pumping guide covers the line, the boom reach, and the mix in detail.

Check that the truck route holds the weight and that you are not sending a loaded truck across a new slab, a septic field, or soft fill. A truck stuck or sunk on site is a pour stopped cold with concrete aging in every drum behind it. Plan the approach, the setup spot, and the washout location as part of the order.

Receiving and QC at the truck

Acceptance happens at the point of placement, not at the plant. When the truck arrives, check the ticket against the order, then test the fresh concrete before it goes in the forms. The standard checks are slump per ASTM C143, air content for air-entrained mixes, and concrete temperature, plus casting strength cylinders per ASTM C31 for the lab to break later.

Sample at the point of discharge, not the first dribble down the chute. Run the slump and compare it to the ticket and the spec tolerance. Check air on any freeze-thaw mix, because it is the number most often lost in transit. Take the concrete temperature, which matters most in hot and cold weather. Make cylinders to the required frequency so there is a strength record if the placement is ever questioned. The slump-test guide covers the procedures.

These tests are your basis for accepting or rejecting the load. A load that fails slump, fails air, or shows up over the temperature limit is a load you can turn back before it is in the forms. Once it is placed, you own it. The whole value of testing at the truck is that the truck can still leave.

When should I reject a load?

Reject a load when it does not meet the order and cannot be brought into spec on the truck. The purchaser has the right under ASTM C94 to refuse concrete that fails the specified requirements. The clear-cut reasons: the wrong mix or strength on the ticket, slump outside the tolerance and not correctable within the design water, air content out of range, concrete over the temperature limit, or a load that has passed its discharge time.

The hard one is the over-watered or aging load. A truck that shows up too stiff and past its time, where the only way to place it is a hose that wrecks the water-cement ratio, is a load to turn back, not to dose and hope. The same goes for a truck that sat too long in traffic and arrives with the slump gone. Placing it to dodge the argument means burying the problem in the forms, where it costs ten times as much to fix.

Make the call before it is placed. Document the reason on the ticket and notify the supplier so the next truck is right. Rejecting a load is expensive and nobody enjoys it, but a rejected truck is cheaper than a failed slab. The slump-test guide covers the acceptance numbers behind the call.

Concrete washout and the environmental rules

Every truck has to wash out the chute, and often the drum, after discharge, and that washwater is caustic. It is an environmental violation if it hits soil, a storm drain, or a waterway. Concrete washout runs high in pH and will kill vegetation and contaminate runoff. On most permitted sites it is a stormwater pollution prevention plan (SWPPP) item the inspector checks.

Set a designated washout area before the pour: a lined pit, a prefabricated washout container, or a bermed and lined area sized for the number of trucks. Keep it away from drains and property lines. The hardened concrete and washout solids get hauled off, not left to leach. On a residential job with no SWPPP, you still do not let a driver rinse into the street or the neighbor's yard.

This is the part of the order people forget until a truck is hunting for somewhere to dump its chute water. Decide where washout goes when you decide where the truck parks. An environmental fine and a cleanup cost far more than a lined washout that takes ten minutes to set up.

Ordering for hot and cold weather

Weather changes the order, not just the schedule. In hot weather, the concrete sets faster and loses slump faster, so order a retarding admixture to extend the working time, ask the plant about chilled water or ice in the mix, and pour earlier in the day to beat the heat. The discharge window shrinks, so tighter truck spacing and a ready crew matter more. The hot-weather guide covers the placement side.

In cold weather, hydration slows and the concrete gains strength slowly, so order an accelerating admixture to speed the set, ask for heated mixing water for a warmer delivery temperature, and consider a richer mix or a Type III cement where the spec allows. Calcium chloride accelerators are limited or banned in reinforced and prestressed concrete because of corrosion, so confirm a non-chloride accelerator where steel is present.

The order and the protection go together. Hot or cold, the admixture buys you time or set, but it does not replace pouring at the right hour and protecting the concrete after placement. Tell the supplier the conditions when you order, so the mix arrives suited to the day, not to a mild morning that has already passed.

Short loads, minimums, and fees

A short load is an order under the plant's minimum, and it carries a short-load fee for the trouble of sending a truck out partly full. The minimum is often somewhere near the truck's full capacity, and the fee for going under it varies by plant and region, commonly a charge per yard under the minimum or a flat add. Ask the dispatcher for the minimum and the short-load fee when you order, because it changes whether a small pour is even worth a ready-mix truck.

The fee changes the math on quantity. If you are close to a half-yard short of clearing a short-load charge, ordering up to the threshold can cost less than the penalty, and you get extra concrete instead of a fee. On the other end, a tiny pour, a few footings or a small pad, may be cheaper in bagged concrete or from a short-load trailer than a full ready-mix truck with a minimum charge.

Partial yards bill as partial yards, but the minimum is the floor. Plan the order around the minimum so you are not paying a penalty to under-order the thing you needed more of anyway.

What to document on every delivery

The tickets and the field tests are the record that proves the concrete you placed matched the concrete you ordered. Keep every ticket, log every test, and note any water added and who authorized it. When a placement is questioned months later, this record is the only thing that answers it.

Common mistakes

• Under-ordering and running short mid-pour, which leaves a cold joint or forces a second mobilization.
• Adding water on site to make placement easy, which raises the w/c ratio and kills strength and durability.
• Ordering non-air-entrained concrete for exterior freeze-thaw work, which scales and spalls the first winter.
• Placing concrete past the discharge time limit on the ticket, after it has begun to set.
• Not reading the batch ticket on arrival, or not keeping it, so there is no record to defend the pour.
• Ordering the wrong slump or mix for the placement instead of the mix design's target.
• Spacing trucks so they wait and stiffen at the curb, or so the crew runs dry between loads.
• Forgetting to designate a washout area until a driver needs one.

Field checklist

Standards and references

ASTM C94, Standard Specification for Ready-Mixed Concrete, is the document that governs ordering and delivery. It sets the delivery ticket requirements, the rules for adding water on site, and the discharge time limits. Note that the 2021 edition replaced the fixed 90-minute or 300-revolution default with a limit the purchaser states at ordering or the producer sets, recorded on the ticket. Confirm the edition and the limit in front of you.

The mix itself is governed by ACI 318, the structural concrete code, which sets the exposure classes and the durability requirements including air content and the maximum water-cement ratio, and ACI 301, the specification for structural concrete. The fresh tests run at the truck follow ASTM standards: C143 for slump, C231 or C173 for air content, C1064 for temperature, and C31 for casting field cylinders. The National Ready Mixed Concrete Association (NRMCA) publishes much of the industry guidance behind this practice.

Above all of these sits the project specification. When the spec is stricter than the standard, the spec controls. The strengths, slumps, air contents, and time limits cited here are common practice and benchmarks. Verify them against the adopted code, the approved mix design, and the contract documents before you order. And the water rule is not a benchmark. Do not add water beyond the design, on any job.

Units, terms, and conversions

Ready-mix is ordered and delivered in a mix of units that show up across the ticket, the spec, and the calculator, so the same quantity can read differently from one document to the next.

Volume is cubic yards in the US, where 1 cubic yard is 27 cubic ft or about 0.765 cubic meters. Strength is psi here and MPa in metric specs, where 1000 psi is about 6.9 MPa, so a 4000 psi mix is roughly 28 MPa. Slump is inches in the US and millimeters in metric, where 1 in is 25.4 mm. Air content and waste are percentages. Aggregate size is given as the nominal maximum, in inches or millimeters.

Ready-mix concrete

Concrete batched at a plant to a set recipe and delivered by truck ready to place

f'c

Specified compressive strength in psi, the design strength at the test age, usually 28 days

Slump

A measure of fresh concrete consistency and workability, in inches or millimeters

Water-cement ratio (w/c)

The mass of water to cement; lower means higher strength and lower permeability

Air entrainment

Microscopic air bubbles added to the paste to resist freeze-thaw scaling and spalling

Batch ticket

The delivery ticket recording the mix, quantity, and batch time; the legal record of the load

Short load

An order below the plant minimum, which carries a short-load fee

Tempering

The one controlled addition of withheld water on site to reach the design slump

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