A road job has no delivery address
A building site is a destination. A road is a sequence of them, and the supply plan that worked at chainage zero is being re-made every few hours for the rest of the job. The industry's own delivery guidance assumes the fixed case throughout: the contractor is told to ensure suitable, stable and safe access for the ready-mixed concrete truck, the largest of which may be up to 10.5 metres long, 2.6 metres wide and 3.8 metres high and weigh 32 tonnes when fully loaded. The axle weights in the association's figure beside that text are 7.1, 7.1, 9.51 and 9.51 tonnes, a separate set of figures that the guide does not reconcile with the 32 tonne total. On a road under construction that access is the thing being built: no hardstand at the head of the work, a running surface that is whatever was laid yesterday, and the standing area a 10.5 m vehicle needs to turn and discharge sitting in the part of the road that does not exist yet.
The same guidance states the consequence plainly. Where the truck cannot discharge directly into the works, transport must be provided to move the concrete from the delivery truck to the works: a front shovel or a dumper truck for small volumes, and for larger ones it is usually more efficient to hire a concrete pump. A banksman is required to supervise the safe movement and positioning of the truck. So the honest description of supplying a moving pour front from a fixed plant is not one vehicle arriving at a point. It is a vehicle arriving as close as the ground allows, plus a second machine to carry the concrete the rest of the way, plus a man to get the first one safely into position — repeated at a location that is further from the plant than it was this morning.
Source: the British Ready-Mixed Concrete Association and Mineral Products Association practical guide for site personnel, first published 2017, updated June 2020, section 3.1 on site preparation with the dimensioned figure beside it, and section 3.2 on receiving. The truck dimensions and axle weights are the association's own figures for the largest truck in general use: https://brmca.org.uk/documents/BRMCA_Ready_Mixed_Concrete_Practical_guide_July_2020.pdf
The cycle time that kills it
The allowance is fixed and the haul is not, and that is the whole of the problem. A Californian policy notice governing health-care facility projects requires discharge to be completed within one and a half hours after the introduction of the mixing water to the cement and aggregates, within a maximum of 300 drum revolutions of which no more than 100 may be mixing revolutions. The notice says those limits may not be waived by the producer or by the purchaser, and then sets out the two exits it allows. For unplanned delays, placement may run on if the concrete temperature stays under 90 degrees F, the slump stays in the approved range and no water is added after discharge begins, with the readings documented from 90 minutes onward. Placement ends at 120 minutes. Anything past that needs an alternative compliance method approved by the agency, supported by evidence.
Notice what the clock does not care about. It starts at the mixer, not at the gate, so batching, the outbound run, the wait behind the truck ahead and the discharge itself all come out of one allowance, and placement is last in the queue. British industry guidance sets its limits on the same basis: concrete delivered within two hours after the time of loading when transported in truck mixers or agitators, reduced to one hour where non-agitating equipment is used, unless a shorter time is specified or a longer one permitted by the specifier — limits that, it adds, may be shorter when it is very hot. The ASTM note reproduced in the Californian document is explicit about what should go into choosing one: among other things, projected transportation time between the batch plant and the point of delivery.
On a road job that input is not a constant. It is the one variable the job is deliberately increasing every day, and nothing in a limit agreed on the first morning re-opens it when the run gets longer. That is the difference between a building site, where the haul is set once and stays set, and a linear job, where the haul is a function of how much road has already been built. A supply plan that clears the allowance comfortably in week one can be failing it in week six without a single thing about the concrete having changed. The mix is not what moved; the distance is, and on a linear job it moves in one direction only. How that allowance is set now, and by whom, is the subject of the companion guide on how long a load can stay in the drum.
Source: California Department of Health Care Access and Information, Policy Intent Notice 82, Ready Mix Concrete/Grout Placement Times, effective 10/09/2025, the POLICY section, and its appendix reproduction of ASTM C94/C94M-24d — the ASTM wording is taken from that appendix rather than from the standard itself: https://hcai.ca.gov/wp-content/uploads/2025/10/PIN_82-Ready-Mix-Concrete-Placement-Times-10-02-2025-A.pdf. The two-hour and one-hour figures are from the British guide cited above, section 4.2 on time limits.
Why the last hundred metres costs more than time
Carrying concrete from where the truck can stand to where it is being placed is not a neutral operation, and the guidance is explicit about the penalty. Sampling is normally carried out at the point of delivery; where the concrete is then transported on site by dumper, skip or pump, there will be a reduction in consistence, and that reduction should be taken into consideration when specifying the consistence at delivery. The double handling therefore has to be designed into the mix before the first load is ordered, or the concrete that reaches the pour is stiffer than the concrete that was tested and signed for. Compaction, the same guide notes, is most efficiently achieved if the concrete is placed and vibrated as soon as possible after delivery — which is another way of saying that every metre between the chute and the formwork is charged twice, once to the clock and once to the workability.
Heat compresses this further. Unless otherwise specified, the temperature of the fresh concrete at delivery should not exceed 35°C, and a maximum of 30°C is appropriate for air-entrained concrete, because the stability of the entrained air content is reduced above about 30°C. The Californian notice works to a separate threshold in its own units — concrete temperature under 90 degrees F, rechecked at ten-minute intervals, or every five minutes between 85 and 88 degrees — and no conversion between the two documents has been performed here. Both point the same way. Every extra transfer between mixer and formwork comes out of a margin that warm weather has already spent, and a fixed plant makes that transfer unavoidable at the head of a road job. The margin is gone before anyone on site has made a mistake, which is why it is worth removing the transfer rather than managing it.
Source: the British guide cited above, section 3.3 on sampling and testing for the loss of consistence during site movement, section 4.1 for compaction after delivery, and section 4.3 on concrete in hot weather for the 35°C and 30°C figures. The 90°F threshold and the ten-minute and five-minute recheck intervals are from the Californian policy notice, POLICY section, unplanned-delay procedure. No unit conversion has been performed between the two documents.
What moves with the work
A self-loading mixer changes the geometry rather than the schedule: the batch is made where it is placed, so the plant-to-site leg and the queue behind another truck do not exist to be subtracted. Three things have to travel with the machine for that to be true, and all three are recorded. A self-loading bucket is a verified specification on all six mixer models this site lists. Water is carried on board on all six, in one of two forms: one model has a high-capacity tank with a self-priming system, and the other five have an automatic water-fill controller with an external suction pump. The pattern holds across the wider range as well — fifteen of the sixteen self-loading mixers in our specification file carry an on-board water provision in their equipment list, and the sixteenth list is short of several entries rather than complete and silent on water.
The machine also has to reach the next pour point on its own wheels. A maximum travel speed is verified on four of the six mixer models: 0–23 km/h on the SLM-18, in full-time four-wheel drive, and 0–36 km/h on the other three. Four-wheel drive is verified on those same four. A drum that lifts and rotates through 270° is verified on five of the six, which decides where concrete can be put down without repositioning the machine, and five carry a reversing and drum-monitoring camera as standard. The proportioning is where the record says something a brochure would not: electronic hydraulic weighing is standard equipment on one of the six models and optional on four, and does not appear in the sixth model's lists at all. Without it the bucket is charged by eye — a material difference on work tested against an approved design mix, and no difference at all on a rural access road.
One boundary belongs with that list. The machine supplies a pour; it does not form one. Nothing in the specification record describes forming, screeding, texturing or finishing, and nothing on this page should be read as saying the machine takes the place of whatever does that work on your job. It carries mixed concrete to the point of placement and discharges it there. What shapes and finishes the slab is separate plant with a separate crew, and it stays on the programme.
Source: the specification record we hold for the six mixer models, with a verification status attached to each field — self-loading bucket verified on all six, maximum travel speed and four-wheel drive verified on four, drum rotation verified on five — together with the standard and optional equipment lists held beside them, counted model by model. The fifteen-of-sixteen water count is from our own specification file, counted across the sixteen self-loading mixers it holds; the five crawler dozers keep a different record entirely and are not in that count.
Access along an unfinished road
The head of a road job is the worst access on the site by definition, and it is the only access that matters, because that is where the concrete has to go. Measured overall dimensions exist for ten of the sixteen self-loading mixers in our specification file, and they span 1.60 m to 2.30 m in width and 4.35 m to 7.06 m in length. Read that as a band and not as a claim. Set against the association's 2.6 m truck, the narrowest of the ten leaves a full metre more room and the widest leaves 300 mm — those two subtractions are performed here — so a 2.30 m machine sits much closer to the truck than to the narrow end of our own range. Anyone quoting 1.6 metres as the width of self-loading mixers is quoting one machine as though it were the range.
Height needs a warning that width does not. Only one of the ten records states the posture the machine was standing in when it was measured: the SLM-18, at 2.58 m with the drum in its travelling position and 3.45 m with the bucket raised. The other nine come from a supplier table that does not say which position it measured. On the SLM-18, where both postures are recorded, the gap between them is 870 mm, our own subtraction, so for the nine that difference is real and unrecorded. Width is barely affected by that and stays usable; height is affected, so no travelling height is given here for those nine. Length is the other figure that decides a single-lane formation. The longest of the ten measures 7.06 m — 3.44 m shorter than the association's 10.5 m truck, again our own subtraction — and that machine is the SLM-18, the most completely documented model we publish.
So the best-documented option is also the longest one measured, which is a trade a contractor should be told about rather than left to discover. No turning radius is recorded for any of the sixteen self-loading mixers, so none is stated here. Articulated steering is a verified specification on three of the six mixer models and appears in the standard equipment list of a fourth, but a steering type is not a turning circle and is not presented as one. Two of the ten measured machines have their dimensions published on this site; the SLM-18 is one of them, at 7.06 m long and 2.21 m wide. The full measured list, and what it means for a narrow approach, is in the companion guide on how wide a concrete truck actually is.
Source: our own specification file, which holds real measured overall dimensions for ten of its sixteen self-loading mixers and records the rest as not supplied, with no estimate substituted. Nine of the ten come from a supplier table that does not state the posture the machine was measured in; only the SLM-18 has a dimensioned drawing separating the travelling height from the bucket-raised height. The one metre, 300 mm and 3.44 m clearances are computed here by subtraction from the truck dimensions in the British guide cited above, and the 870 mm posture gap by subtraction between the SLM-18's own two recorded heights. No turning radius is recorded for any self-loading mixer.
What this page does not claim
No output per shift and no metres of road per day. Hourly output is recorded as unverified on all six mixer models, so any daily figure would be manufactured here rather than reported, and the number that would actually govern a road job depends on the haul from your aggregate stockpile, your finishing crew and your formation width rather than on the machine. The same refusal covers loads per shift and any comparison against the size of a crew. What the record supports is a description of the cycle the machine performs — charge the bucket, mix in the drum, drive to the pour point, discharge there — and the arithmetic about your own job is yours to do, with your own distances in it. A figure invented to fill that column would be wrong in a way no reader could check, which is the only kind of wrong that survives into a programme.
One further gap belongs on this page rather than in a footnote. We hold no water-tank capacity for any of the six mixer models, and that is precisely the figure that would tell a road contractor how many batches he gets between refills. It is recorded as unverified, so it is not estimated, and no comparable machine is used to fill it in. A tank size borrowed from a similar machine is exactly the sort of number that gets designed into a water-supply plan and then discovered on site, at the point where the plan is hardest to change. If a written figure reaches us, this page changes. Until it does, the absence is the accurate statement, and it is the one a buyer can act on: ask for the number in writing before it is designed into a programme, from us or from anyone else quoting the same class of machine.
Source: the specification record we hold for the six mixer models, where hourly output and water-tank capacity are both recorded as unverified with no value. No productivity, cycle-count or labour figure exists in our records at all, which is why none is cited.