The tickets add up to 42.0 cubic metres. The pump stopped twenty minutes ago, the last truck is washed out, and the transfer beam still wants about a metre and a half. The plant batched exactly what was ordered: the take-off said 42.0, and 42.0 is the volume of the drawn shape — not what a 100 m ground line and seven drums actually consume.
Two of those losses are pure arithmetic. A 125 mm pump line has a cross-section of 3.1416 × 0.125² ÷ 4 = 0.01227 m², so 100 m of it holds 100 × 0.01227 = 1.23 m³ standing in the line when the pump stops; this opening tally assumes none of that is blown back into the placement. Seven drums keeping an illustrative 0.03 m³ each add 7 × 0.03 = 0.21 m³. Total 1.23 + 0.21 = 1.44 m³, gone before anybody made a mistake, and 42.0 − 1.44 = 40.56 m³ reaching the works.
The take-off is geometry and it is usually right. The order is a logistics decision and it is usually a feeling. Order tight and the pour stops mid-element, which is how an unplanned cold joint lands in a transfer beam at eleven at night. Order loose and you pay full rate for concrete that goes back on the truck — usually still charged.
No structural code tells you how much concrete to order; the Philippine structural code and the ACI documents behind it govern concrete once it is in place. Dimensional tolerances sit in a separate tolerance specification, the ACI 117 family, and that document binds only where the project specification incorporates it by reference — the Philippine structural code does not adopt it automatically. Read it for what it is: ACI 117 sets dimensional acceptance limits, not a volume allowance, and several of its limits are one-sided, so they do not translate symmetrically into concrete volume.
Where your contract adopts ASTM C94/C94M, the ready-mixed concrete specification, delivered volume is verified by weighing a load and dividing by its measured density — the gravimetric yield test, ASTM C138/C138M — rather than by nameplate capacity. That adoption is not automatic either: Philippine ready-mix is frequently specified through DPWH or PNS references instead. Note also what the yield provision covers. It governs the supplier's batched volume against the volume you ordered, and it says nothing about the pump line and drum losses on your side of the batcher, which is what the rest of this article is about. Confirm the tolerance in the edition your contract names; the allowance itself is a commercial number you must justify.
The plant sells batched volume, not placed volume, so everything downstream of the batcher is the buyer's. Over-break, form bulge, slab thickness and drum residue recur on every pour of that type and scale with geometry, so they belong in the unit rate, derived from your own delivery records. Priming and unrecovered line concrete are set by line length and diameter, so they belong as a fixed item per pour, not a percentage. Abnormal over-break after heavy rain, emergency loads, returned-concrete charges and rejection are event-driven and belong in contingency.
Philippine public-works measurement is normally on the neat lines shown on the drawings, so unauthorised over-break is not a paid quantity; over-excavation the Engineer directs, typically to reach sound bearing, is normally handled as a variation, often with lean fill measured separately.
One pour: six isolated footings 2.00 m × 2.00 m × 0.45 m cast against earth; six column stubs 0.40 m × 0.40 m × 1.20 m in plywood forms; a 12.0 m × 9.0 m suspended slab 150 mm thick on metal deck; concrete delivered at an illustrative 6 m³ per truck from a plant that batches in 0.5 m³ increments and sets no minimum load. Every figure below is illustrative and must be replaced with your own records.
What this build-up assumes. The slab is treated as a flat prism: the 150 mm is taken as a constant thickness on a flat soffit, and 108 × 0.150 = 16.20 m³ is only right on that reading. Neither the deck profile nor the rib depth is stated, and on a profiled composite deck it matters enormously whether the 150 mm is the overall depth including the rib or the cover above the flutes. If it is the cover, a typical 51 mm trapezoidal profile fills roughly 0.5 × 108 × 0.051 = 2.75 m³ more, about 17 percent of the slab and five times the 0.54 m³ allowed below for thickness — a bigger swing than every allowance in this build-up put together.
The excavation base is assumed cut to level, which is what lets over-break be applied to the four vertical faces alone. Fifty millimetres of base over-dig is routine and would add 4.41 × 0.05 × 6 = 1.32 m³, more than the whole side over-break of 1.11 m³ below. Truck size is an input too, and it drives the truck count, the residue and the entire part-load argument: 5 m³ is common in Philippine practice, and at that size the same order is 30.51 ÷ 5 = 6.10, so seven trucks, residue 7 × 0.03 = 0.21 m³, and the sixth-load economics of the last two steps are replaced wholesale.
Footings 2.00 × 2.00 = 4.00 m², × 0.45 = 1.80 m³ each, × 6 = 10.80 m³. Stubs 0.40 × 0.40 = 0.16 m², × 1.20 = 0.192 m³ each, × 6 = 1.152, say 1.15 m³. Slab 12.0 × 9.0 = 108.0 m², × 0.150 = 16.20 m³. Neat total 10.80 + 1.15 + 16.20 = 28.15 m³.
Assumption: 50 mm average over-cut per vertical face in firm machine-cut ground, base cut to level. Cast plan 2.00 + 2(0.05) = 2.10 m each way. Per footing 2.10 × 2.10 = 4.41 m², × 0.45 = 1.9845 m³; extra 1.9845 − 1.80 = 0.1845 m³. Six footings: 0.1845 × 6 = 1.107, say 1.11 m³. Subtotal 10.80 + 1.11 = 11.91 m³.
Assumption: 5 mm average increase on each plan dimension, so 0.405 m rather than 0.400 m. Per stub 0.405 × 0.405 = 0.164025 m², × 1.20 = 0.19683 m³; extra 0.19683 − 0.192 = 0.00483 m³. Six stubs: 0.00483 × 6 = 0.02898, say 0.03 m³. Subtotal 1.15 + 0.03 = 1.18 m³, almost nothing.
Assumption: 5 mm average extra thickness over the deck. Extra 108.0 × 0.005 = 0.54 m³. Subtotal 16.20 + 0.54 = 16.74 m³.
Boom pump, an assumed 40 m of effective 125 mm line: 3.1416 × 0.125² ÷ 4 = 0.01227 m², × 40 = 0.49 m³ standing in the line. Assume half of it is recovered into the last placement, so 0.49 ÷ 2 = 0.25 m³ lost, plus an assumed 0.25 m³ priming grout batch, charged but never structural: 0.25 + 0.25 = 0.50 m³ per pour. That recovered fraction is an assumption in its own right and it moves the headline: recover nothing, which is what the opening tally assumed of the 100 m line, and the total below becomes 30.75 m³ and the allowance 9.2 percent rather than 8.4. The grout batch is asserted rather than derived, and the 125 mm diameter is an input like any other. Residue at an illustrative 0.03 m³ per truck over six trucks (confirmed in step 7): 0.03 × 6 = 0.18 m³.
11.91 + 1.18 + 16.74 = 29.83 m³; plus 0.50 pump = 30.33 m³; plus 0.18 residue = 30.51 m³.
Allowance over neat 30.51 − 28.15 = 2.36 m³, and 2.36 ÷ 28.15 = 0.0838, or 8.4 percent before truck rounding. The pour does not order 30.51 m³; it orders 31.00, so the figure actually committed is 31.00 ÷ 28.15 = 10.1 percent. Both are outputs of at least eight stated assumptions, not rules, and neither transfers to the next pour.
At an illustrative 6 m³ per truck, 30.51 ÷ 6 = 5.085, so six trucks. Five full loads are 5 × 6.0 = 30.00 m³, leaving 30.51 − 30.00 = 0.51 m³ on the sixth. This plant batches in 0.5 m³ increments and sets no minimum load, so the last load is ordered at 1.0 m³ and the order becomes 31.00 m³. At an illustrative ₱4,850 per cubic metre, 31.00 × 4,850 = ₱150,350, plus an illustrative ₱2,500 part-load charge = ₱152,850.
Now divide that by the right thing. Per cubic metre of neat take-off, 152,850 ÷ 28.15 = ₱5,430, about 12 percent above the headline rate. Per cubic metre actually placed it is a different number: what goes into the works is 28.15 + 1.11 over-break + 0.03 bulge + 0.54 slab thickness = 29.83 m³, because the 0.50 m³ pump loss, the 0.18 m³ of residue and the 0.49 m³ of surplus riding on the part load are never placed. On that basis 152,850 ÷ 29.83 = ₱5,124, about 5.7 percent above the headline rate. Neat take-off, volume placed and volume delivered are three different denominators, and a percentage means nothing until it names the one it was divided by.
Five loads alone would cost 30.00 × 4,850 = ₱145,500, so the sixth part load costs 152,850 − 145,500 = ₱7,350. Against that, running short: the 0.51 m³ shortfall buys an emergency load on the same 0.5 m³ increment, so 1.0 × 4,850 = ₱4,850 plus the ₱2,500 part-load charge = ₱7,350, and standby at an illustrative ₱3,500 per hour for an assumed two hours is ₱7,000: 7,350 + 7,000 = ₱14,350, or 14,350 ÷ 7,350 = 1.95 times the premium. The standby duration is doing much of that work and is an assumption, not a given: one hour gives 10,850 ÷ 7,350 = 1.48 times and four hours 21,350 ÷ 7,350 = 2.90 times. All of it is before joint preparation, the engineer's time, programme slip, or the joint being refused where it landed. A joint agreed in advance, where the design accepts it, is a construction joint; one created by an empty truck at 11 PM usually is not.
Mostly slab: a 480 m² deck at 150 mm. Neat 480 × 0.150 = 72.00 m³. Thickness 480 × 0.005 = 2.40 m³. Pump 0.50 m³. Subtotal 74.90 m³; 74.90 ÷ 6 = 12.48, so 13 trucks, residue 13 × 0.03 = 0.39 m³. Total 75.29 m³, allowance 75.29 − 72.00 = 3.29 m³, and 3.29 ÷ 72.00 = 4.6 percent. Five percent is slightly generous.
Mostly earth-formed footings: twenty footings 2.00 m × 2.00 m × 0.45 m by chute. Neat 20 × 1.80 = 36.00 m³. Over-break 36.00 × 0.1025 = 3.69 m³. Subtotal 39.69 m³; 39.69 ÷ 6 = 6.615, so 7 trucks, residue 7 × 0.03 = 0.21 m³. Total 39.90 m³, allowance 39.90 − 36.00 = 3.90 m³, and 3.90 ÷ 36.00 = 10.8 percent. Five percent gives 36.00 × 1.05 = 37.80 m³, leaving 39.90 − 37.80 = 2.10 m³ short. Same rule, same supplier — the losses attach to surfaces and truck counts, not volume.
The only allowance worth using is one you measured. On every pour record neat volume, batched volume from the tickets, and one line on conditions — earth-formed or formed, pumped or chuted, ground and deck type. After ten or fifteen pours you have an over-break figure for your own ground and crews, better than any published rule of thumb.
If you would rather not keep the arithmetic by hand, the concrete build-up in the RHCES Estimator works the same way: geometry and assumptions in, allowance percentage out.
Decide before the last truck is empty. Measure what is left to place while concrete is still moving, call the plant, and if a joint is unavoidable agree its location with the design engineer while you still have a choice.
Please do not. It is the consequence of at least eight stated assumptions — 50 mm over-cut, 5 mm form bulge, 5 mm extra slab thickness, a 40 m line, a 125 mm line diameter, half the line recovered, a 0.25 m³ grout batch and 0.03 m³ of residue per truck — applied to one mix of elements, with truck size and the plant's batching increment sitting behind the truck count as further inputs. Change the mix and the same assumptions gave 4.6 and 10.8 percent above; recover none of the line and 8.4 becomes 9.2; round up to whole loads and what you actually commit to is 10.1 percent. Any allowance quoted to you as "per code" is common practice, not a mandate: use the method and replace every figure with your own records.