The load leaves the plant already spending its window
A ready-mixed load leaves the plant as a proportioned material with a water-cement ratio someone signed for, an air content someone specified, and a workability window sized for the distance to the job. Everything between the plant gate and the finished lift either preserves that or spends it. Drum revolutions, ambient temperature, waiting time at the gate, and the pressure the mix meets in a pipeline all draw on the same account, and none of them appear on the delivery ticket except as a batch time you should be reading before the driver backs in.
Specifications cap the interval between batching and complete discharge. ASTM C94/C94M Standard Specification for Ready-Mixed Concrete sets a default limit expressed both as elapsed time and as drum revolutions; EN 206 Concrete — Specification, performance, production and conformity leaves the equivalent to the producer's declared workability retention, and AS 1379 Specification and Supply of Concrete states its own. Whichever governs your job, that number is a ceiling rather than a target. Loads arriving with twenty minutes left have no tolerance for a boom that still needs repositioning, and the crew ends up choosing between a cold joint and a retempered load.
Water added on site is the most common quiet breach of a mix design. C94 permits a single controlled addition when a load arrives below the specified slump, provided the maximum water-cement ratio is not exceeded and the drum turns enough revolutions at mixing speed to redistribute it uniformly. A hose flicked into the hopper between trucks satisfies none of that. If the load will not pump without more water, the honest options are an admixture redose authorised by the supplier or a rejected load.
Proving the load at the discharge point
Acceptance happens once, at the location the specification names, and that location should be argued before the pour rather than after a low break. Sampling to ASTM C172/C172M, slump to ASTM C143/C143M, air content to ASTM C231/C231M — or ASTM C173/C173M where lightweight aggregate rules out the pressure method — and temperature to ASTM C1064/C1064M make up a routine sequence. The sampling point is not routine. Concrete taken at the truck chute and concrete taken at the end of a hundred metres (330 ft) of boom line are not the same material, and nobody should discover that mid-pour.
Flowable and self-consolidating mixes need a different measurement entirely, because a slump cone that empties completely tells you only that it emptied. Spread diameter, the time to reach the 500 mm (20 in) circle, and the visual stability rating recorded alongside them separate a sound SCC from a mix that has already begun to segregate in the hopper. ASTM C1611/C1611M Standard Test Method for Slump Flow of Self-Consolidating Concrete covers the test; ACI 237R Self-Consolidating Concrete covers what the result means for how the material will behave once it is under pressure.
Rejecting a load at the chute is the cheapest decision available at that moment. Every alternative — placing it and hoping, watering it and pumping it, or splitting it between two elements to dilute the problem — moves the cost downstream into a defect that has to be cored, assessed and either accepted with a concession or removed.
Spread and T50 are the numbers the pump crew and the supplier will argue about at the chute, so working out where this load actually sits against the specified range belongs here, while the truck can still be turned away.
The first of two perpendicular spread diameter measurements.
The second perpendicular spread diameter measurement.
The time in seconds for the concrete to reach the marked spread circle.
Average slump flow
26.5 in
Flowability class: SF2. Viscosity class: VS2 (more viscous, better segregation resistance).
- Diameter spread between the two readings
- 1 in
- T50 spread time
- 3 s
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Concrete Slump Flow Test Calculator (ASTM C1611): 26.5 in — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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This result is a specification — 26.5 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The two readings are averaged whatever the gap between them. ASTM C1611 treats a difference of more than 50mm between the perpendicular diameters as grounds to discard that test and repeat it, so a 700/620mm pair is not a 660mm SF2 mix — it is a test that has not yet produced a usable number, and this page lowers its confidence rather than withholding the average.
- Flowability is not passing ability. A mix can spread to SF2 or SF3 on an open base plate and still arch and block between closely spaced bars, which is why passing ability is measured separately with a J-Ring (ASTM C1621) or an L-box, comparing an obstructed spread against this free one. Nothing entered here describes bar spacing, cover or maximum aggregate size.
- T50 describes how the mix behaves while it is still moving, not whether it stays uniform once it stops. Static segregation — coarse aggregate settling through a deep lift, a mortar-rich layer forming at the top — is judged by a column or sieve segregation test and by the visual stability rating of the patty, none of which this page calculates, so an SF2/VS2 pair is not by itself evidence of a stable mix.
- The viscosity class is a hard cut at exactly 2 seconds, and T50 is hand-timed from the cone clearing the concrete to the spread first touching the 500mm circle. Half a second of operator variation moves a mix from VS1 to VS2, so readings either side of 2s are one borderline band rather than two different mixes.
- A flow class is a target chosen for a particular element, not a grade to be maximised, and it says nothing about what the mix does to the formwork. SF3 is specified for heavily congested or complex sections rather than being an improvement on SF1, and self-consolidating concrete of any class can act on the form at close to full hydrostatic pressure, which is a separate calculation from anything on this page.
Priming, and what happens to the first metre
Steel that has never carried concrete strips mortar off whatever touches it first. Priming lays a lubricating film along the whole line — cement grout, a proprietary priming compound, or a sponge ball driven ahead of the concrete — and the volume required scales with line length and bore, not with the size of the pour. Short primes cause first-load blockages more often than any other single error, and the crew that guesses at half a bag spends the following hour breaking couplings.
Primed material is not structural concrete and must never reach the works. It discharges into a skip, a barrow or a designated waste area, and the first genuine concrete behind it goes the same way whenever there is any doubt about where the grout ended. ACI 304.2R Placing Concrete by Pumping Methods treats prime disposal as a placement-plan item rather than a driver's decision, which is the right level to settle it — in writing, before the first truck arrives.
Prime quantity follows the bore and the length of the string rather than the size of the pour, so the internal volume of the line you have actually laid out is the figure to batch against.
The pipe's inside diameter, not the nominal or outside size.
The total length of pipe run.
Estimated pipe volume needed
0.7573 gallons
- Volume (liters)
- 2.87 liters
- Volume (in³)
- 174.95 in³
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Pipe Volume Calculator: 0.7573 gallons — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- The figure is the contents of a straight bore and nothing else. Fittings, valve bodies, meters, strainers and any water standing in a cylinder or tank at the end of the run are not counted, and the pipe wall is excluded — so this is not the volume of pipe material, and not the space the pipe occupies in a chase or trench.
- Volume scales with the square of the bore, so an inside diameter that is 9 per cent out produces a volume 19 per cent out. Published inside diameters differ by material, schedule and class for the same nominal size, and the calculator takes whatever figure you type at face value — it has no way of knowing that a half-inch pipe was entered at half an inch.
- It assumes the run is completely full of liquid over its whole length. Gravity drains, waste stacks and sewers are designed to flow part full, and a system that has not been purged holds air at its high points, so both contain less than this number says.
- It answers how much the run holds, not how long the wait is. Turning that volume into a hot-water delay needs the fixture's flow rate as well, and the real delay runs longer because the first hot water gives up heat to the pipe wall and to whatever surrounds it. No time calculation happens on this page.
- Nothing here is a sizing or a support check. Velocity, friction loss and pressure drop are separate calculations, and a long run that holds a comfortable volume can still be too small to deliver flow. The contents also weigh whatever that volume of water weighs, which bears on hanger spacing and is not assessed.
What the line charges the concrete to travel
Every metre of pipe, every bend and every metre of vertical rise takes pressure out of the pump before concrete reaches the form. Static head from a vertical column is unavoidable arithmetic. Friction along the horizontal run depends on bore, mix rheology and delivery rate, and each elbow behaves like a substantial extra length of straight pipe. Keeping the calculated peak pressure inside the pump's rated output and, separately, inside the rating of the weakest pipe, coupling and hose in the string is a pre-pour task, not something to establish by watching the gauge.
Two questions decide the layout: whether the pump can sustain the placement rate the finishers need, and whether the line will still be within rating when the mix stiffens late in the pour. High-rise placements, long ground lines to a raft, and any run where a smaller bore was chosen because it is easier to handle all deserve the calculation. Mixes carrying a supplementary cementitious component frequently pump at lower pressure than a plain portland mix of the same slump — that is a design lever pulled at the plant, not a site adjustment.
Line length, bore, bend count and vertical rise decide whether this layout is a pour or a blockage, so the pressure arithmetic belongs at the point where the crew is still free to reroute the pipe or change the pump.
The total horizontal length of pump line.
The total vertical rise the line must pump concrete up.
How many feet of horizontal-equivalent pressure one foot of vertical lift costs.
Your pump/mix's friction loss rate, in psi per 100 ft of horizontal line — enter it in that unit whichever measurement system the page is set to.
Estimated total pressure loss
89.1 psi
The friction loss rate you entered is the biggest source of uncertainty here — it varies by mix design, pipe diameter and condition, and pump output, so confirm it against your pump manufacturer's chart or a field trial rather than treating the default as universal.
- Equivalent horizontal pumping distance
- 297 ft
- Static head of the concrete column
- 34.38 psi
They open the calculator with your figures already in it
Concrete Pump Line Friction Loss Calculator: 89.1 psi — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 89.1 psi — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- No fitting in the line is counted. Every bend, reducer, coupling, flexible end hose and boom section carries its own equivalent-length penalty that this model leaves out, so a line with real geometry in it needs a margin on top of this figure or the pump supplier's full equivalent-length chart.
- Pipe bore, slump, aggregate size, pump output and the condition of the pipe are not inputs — all of them are folded into the single friction-loss rate you type. Change the line size or the mix and the correct rate changes with it, and this calculator has no way to tell you the new one. Take it from the pump manufacturer's chart or a field trial.
- Vertical lift is handled only by the 3-4x equivalency ratio, a rule of thumb calibrated against typical friction rates. The static weight of the concrete standing in the riser is not added as a separate term, so at the low end of the rate and ratio ranges the vertical share can come out below the pressure needed just to hold that column up.
- This is a pressure estimate, not a pump selection and not a pressure rating for the line. It says nothing about whether your pipe, couplings, clamps and end hose are rated for the pressure it reports, and a coupling that lets go under pump pressure is a serious injury risk. Have the pumping contractor confirm the pump and the whole delivery line.
- Blockages, priming the line with slurry, pumping downhill, cleanout, and concrete left standing while a pour is paused all sit outside this model. None of them scale with length and lift, and any one of them can stop a pour the pressure arithmetic said was fine.
Bends, reducers and the anatomy of a blockage
Blockages form wherever the mix is forced to change shape faster than its paste can carry the aggregate: abrupt reducers, tight bends, worn pipe grooved on the outside of every elbow, and the joint where rubber hose meets steel. Aggregate top size relative to bore matters here — pumping guidance in ACI 304.2R Placing Concrete by Pumping Methods limits nominal maximum size to a fraction of the internal diameter, and to a smaller fraction for angular crushed stone than for rounded gravel. Steel or macro-synthetic fibre dosed too high, or tipped into the hopper instead of dispersed at the plant, balls at exactly the same restrictions.
Clearing a blocked line is the most dangerous routine operation on a concrete pour. Pressure stays trapped in the pipe after the pump stops. The correct sequence is to reverse the pump to relieve it, confirm the gauge has fallen, and only then break a coupling, with nobody standing in line with the open end and nobody looking into it. Crews that skip the reverse stroke because the blockage is obviously near the hopper are the ones who find out the whole line was still loaded.
Downtime is a mix problem as much as a schedule problem. Concrete standing in a hot line stiffens against the wall and against itself, so a stoppage running past a few minutes should be met with slow intermittent strokes that keep the column moving. Waiting it out produces a harder restart, a higher starting pressure, and often the blockage the crew was trying to avoid.
The end of the line: air, drop and free fall
Air content leaves a pumped mix more readily than slump does, and the losses concentrate at the discharge end. A boom dropping concrete through a long free vertical section, or an end hose hanging straight down with nothing restraining the column, pulls the material apart and strips entrained air that the admixture was dosed to deliver. Where freeze-thaw exposure governs — ACI 318 Building Code Requirements for Structural Concrete, or the exposure classes in EN 206 — air lost at the hose changes the durability of the finished element, not merely a test result.
Folklore about free fall outlasts the evidence for it. ACI 304R Guide for Measuring, Mixing, Transporting, and Placing Concrete draws the distinction that actually matters: concrete falling cleanly into the form and striking nothing on the way tolerates considerable height, while concrete clipping a bar, a form tie or a form face segregates at almost any height. Congested columns and deep walls earn a drop chute or a hose taken down inside the form; open slab work generally does not.
Displacement placements sit in their own category. Concrete placed through a tremie under water or under support fluid depends on the pipe staying embedded in the fresh column for the entire pour, and a lost embedment contaminates the element rather than blemishing it — a rework problem measured in whole piles.
On a displacement pour the only question that matters at the discharge end is how far the pipe may still be raised before the seal breaks, and it has to be answered against the depth already placed rather than against marks painted on the string.
The horizontal cross-sectional area of the shaft or excavation being poured.
How deep the concrete already placed currently measures, from the base of the pour.
The full length of the tremie pipe currently in the shaft.
Safe pipe withdrawal available
5.079 ft of pipe safely withdrawable
The pipe can be raised by up to this amount and still keep at least 1.5 m (5 ft) of embedment in the placed concrete.
- Concrete volume placed so far
- 5.98 yd³
- Remaining pipe length above pour surface
- 23 ft
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Tremie Pipe Safe Withdrawal & Embedment Calculator: 5.08 ft of pipe safely withdrawable — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- Embedment is taken to be the whole depth of concrete placed, which only holds while the pipe's discharge end is still sitting at the base of the shaft. There is no input for the current tip elevation, so once the pipe has been raised the withdrawal figure is too generous by exactly the height the tip has already travelled.
- The volume line is a plain prism, cross-sectional area multiplied by depth, and it is never reconciled against the concrete actually delivered. It therefore cannot reveal overbreak, sidewall collapse or loss into a permeable stratum, each of which shows up as a shaft taking more concrete than the calculated rise accounts for.
- Embedment is only half of what keeps a tremie flowing. The concrete head inside the pipe has to stay above the water or slurry head outside it, and a mix that stiffens between loads can plug the pipe or let slurry in with embedment still well above 1.5 m (5 ft). None of that is checked here.
- The 1.5 m (5 ft) embedment is a hardcoded constant rather than an input, and it is the common minimum, not the design value for a particular shaft. Many specifications require deeper embedment on deep or slurry-supported shafts, and some also cap the rate of withdrawal; the governing figure is the one in the project specification rather than the one built into this page.
- The depth entered is counted as sound concrete throughout. The top of a tremie pour carries laitance and slurry-contaminated material that has to be overpoured and cut off, and neither that cut-off allowance nor the extra concrete it consumes appears in the volume shown.
Into the formwork: layers, lifts and the joint you did not plan
Placement sequence decides whether the pour becomes one element or several. Layers want to be shallow enough for the vibrator to reach through into the layer below — commonly in the 300 to 500 mm (12 to 20 in) range, adjusted for head diameter and reinforcement congestion — and each layer has to go down before the one beneath it takes initial set. Working outward from a corner with an advancing face, rather than dumping piles and dragging them together, keeps the mortar and the coarse aggregate arriving in the same place.
Concrete is never moved laterally with a vibrator. Dragging a poker sideways floats mortar ahead of the stone and leaves an aggregate-rich pocket behind — a defect the finishers will never see and a core drill will find immediately. Rakes, come-alongs and shovels move concrete; vibrators consolidate it. Placement rate is the other live constraint, because a wall filled faster than the assumed rate of rise loads the formwork beyond what the falsework design checked.
Rate of rise turns into lateral pressure on the forms, so establish what the intended placing speed actually demands and hand that ceiling to the pump operator instead of discovering it as a blowout.
The fresh concrete's unit weight.
How fast the concrete surface rises at this form location, in feet per hour.
The temperature of the fresh concrete at placement, in °F.
ACI 347R Table 2.2 chemistry coefficient for the cement/admixture combination used.
The total vertical height of the wall being poured.
Maximum lateral formwork pressure
970 psf
Wall pressure is rate-limited rather than height-limited. Because a wall is filled over a long period, the concrete at the base normally stiffens before the top arrives, and the pressure envelope caps out well below full hydrostatic.
- Unit weight coefficient Cw
- 1 (dimensionless)
- Full hydrostatic ceiling
- 1,500 psf
They open the calculator with your figures already in it
ACI 347 Wall Formwork Rate-of-Placement Pressure Calculator: 970 psf — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 970 psf — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The rate-based reduction depends on the concrete stiffening as expected. Retarders, cold weather and high cement replacement all delay that and raise the pressure.
- Excludes wind load on the form face, which on a tall free-standing wall form can govern the bracing even though it does not affect the ties.
- Does not address the uplift and lateral load at a construction joint, or the loads from the placing equipment resting on or against the form.
Consolidation: the last operation that can undo the mix
Vibration fails in both directions, and both failures are expensive. Too little leaves honeycombing at form faces, voids beneath horizontal bars, and bond that never develops. Too much drives coarse aggregate downward, brings a laitance layer to the surface, and in air-entrained concrete collapses the bubble structure the durability specification was written around. ACI 309R Guide for Consolidation of Concrete sets out the technique that avoids both: vertical insertion under the head's own weight, a short hold, slow withdrawal, and insertion points spaced so their radii of action overlap.
Withdrawal cues are physical rather than procedural. The surface levels and closes around the head, large bubbles stop rising, and a mortar sheen appears — that is the moment to pull out, not thirty seconds afterward. Vibrating against reinforcement or formwork puts energy where it is not wanted and can shift bars already tied to tolerance. A spare vibrator on site is not a luxury, since a poker dying mid-lift produces a cold joint along the drawing's worst possible line.
The finishing window and the handoff to curing
Bleed water rising to a slab surface is normal behaviour; troweling it back in is not. Any finishing pass made while free water stands on the surface raises the water-cement ratio of the top few millimetres and produces the dusting, crazing and scaling that appears in the first service year. The crew waits for the sheen to leave, and on a hot, dry or windy day the wait may leave almost no window at all.
Evaporation rate drives that window, and it responds to concrete temperature, air temperature, relative humidity and wind speed together rather than any one of them. ACI 305R Guide to Hot Weather Concreting presents the relationship and the widely cited threshold beyond which plastic shrinkage cracking becomes likely; past it, evaporation retarders, fog misting, windbreaks and earlier curing stop being optional. Cold placements invert the problem, and ACI 306R Guide to Cold Weather Concreting addresses protecting the concrete's own heat rather than shedding it.
Curing starts the moment finishing ends, and jurisdiction sets the duration. ACI 301 Specifications for Structural Concrete, CSA A23.1 Concrete Materials and Methods of Concrete Construction, BS 8500 Concrete — Complementary British Standard to BS EN 206, and AS 1379 each carry their own curing and acceptance requirements. The project specification governs on the day; the parent standard explains why the number is what it is, which matters when a curing regime has to be varied on site.
Four site readings decide whether a finishing window exists at all, and none of them says anything useful alone — put them together here, while there is still time to rig a windbreak or bring the start forward.
The temperature of the fresh concrete, not the air.
The ambient air temperature at the job site.
The relative humidity at the job site.
The wind speed across the concrete surface during placement and finishing.
Estimated evaporation rate
0.11 lb/ft²/hr
Below the critical threshold under these conditions — standard curing practices should be adequate, though conditions can change during a long pour, so re-check if temperature or wind picks up.
- Critical threshold
- 0.2 lb/ft²/hr
They open the calculator with your figures already in it
Concrete Evaporation Rate Calculator: 0.11 lb/ft²/hr — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 0.11 lb/ft²/hr — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Solar gain is not in the model. The equation reads concrete temperature, air temperature, humidity and wind only, so a slab in full sun and the same slab in shade return an identical rate from identical readings. If the sun is on the pour, take the concrete temperature off the finished surface rather than off the chute, or the answer comes back low.
- Bleed rate is not modelled. Plastic shrinkage cracking is evaporation outrunning the bleed water rising to replace it, and this calculates only the evaporation half. Low-bleed mixes - low water-cement ratio, silica fume, heavy fly ash replacement, high-range water reducers - can crack plastically at rates below the threshold this page flags.
- Nothing about the slab itself is an input. Thickness, subgrade moisture and absorption, restraint from reinforcement and edge conditions, finishing timing, and the curing method actually applied all govern whether cracks form, and none of them reach the calculation.
- This is one moment at one spot. Wind, humidity and temperature move across the hours of a placement and vary across a large slab - funnelled between buildings, faster over a hot deck, calmer behind a windbreak. Re-run it against readings taken at slab level during the pour, not against a forecast from the nearest airport.
- The threshold is a screening line, not a pass/fail verdict and not a curing specification. A rate below it is not a guarantee against cracking and a rate above it is not a prediction of it; the number tells you when to have fogging, evaporation retardant and windbreaks ready, and it does not replace the hot- or cold-weather concreting requirements in your project specification or the supplier's guidance for the mix being placed.
Conditions are favorable for a standard cure, but evaporation risk can change quickly if wind picks up or humidity drops during a long pour — recheck this calculator against updated conditions if the placement runs long.
What the cylinders will say three weeks later
Specimens made badly convict good pours. ASTM C31/C31M Standard Practice for Making and Curing Concrete Test Specimens in the Field governs how test specimens are consolidated, the initial curing temperature band, and their protection before transport — every step performed on site by someone already doing three other jobs. Cylinders left on a slab edge in the sun overnight break low, and the dispute that follows outlasts the pour by months.
When a result comes in under strength, the questions run backwards along the route the concrete travelled: ticket time and any water added, acceptance tests at discharge, the line and anything flushed into it, consolidation, curing, and finally the specimens. Documented checks at each of those points reduce the argument to a short conversation. Missing records escalate it to coring, evaluation under ASTM C42/C42M Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete, and a structural review nobody allowed for.
Before the first truck backs in
Checks that belong to the pump crew and the placing foreman, settled while the line can still be changed.
- Pipeline pressure rating versus calculated peak — Rate the whole string — the weakest coupling, reducer and end hose govern, not the pump.
- Prime volume matched to line length and bore — Batched, and a designated place to waste it that is not the formwork.
- Aggregate top size against internal bore — Angular crushed stone needs more margin than rounded gravel at every reducer.
- Concrete temperature and evaporation conditions at placing — Recorded at discharge; it decides the finishing window before the finishers do.
- Spare vibrator, spare head, power source proven — A poker failing mid-lift writes a cold joint you did not choose.
- Agreed sampling point in writing — Truck chute or end of line — fix it before the pour, not after a low break.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.