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ACI 211.1 · absolute-volume method
Absolute-volume mix design yield
Convert a set of batch masses into the volume of concrete they actually produce, and the cement content per cubic metre that specifications are written against.
Verified engine
What the engine returns
The batch yield tells you what volume this quantity of material will actually produce, and the cement content converts the batch to the per-cubic-metre basis a specification is written in. Compare that cement content against the durability class you are designing to: if it lands below the minimum, the mix needs more cement or less yield, not a rounder number.
Inputs the result is built from
Cement mass
Cement specific gravity
Water mass
Water specific gravity
Fine aggregate mass
Fine aggregate specific gravity
Coarse aggregate mass
Coarse aggregate specific gravity
How the result is derived
MethodAbsolute-volume method
StandardACI 211.1 — Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete
GuardSpecific gravities outside the ordinary range for their material are refused rather than computed. A transposed digit produces a plausible-looking yield, and a plausible-looking wrong yield is worse than no answer.
How the batch yield moves with the water mass
Yield and richness, side by side
What absolute-volume yield means
A concrete mix is specified by mass — so many kilograms of cement, water, fine and coarse aggregate. Masses cannot be added to get a volume, because a kilogram of cement and a kilogram of water occupy very different amounts of space.
The absolute-volume method converts each ingredient to the volume it actually displaces, using its specific gravity, and adds those volumes. The total is the batch yield: the volume of concrete the batch will produce. It is called "absolute" volume because it counts only solid and liquid material, with no allowance for entrapped or entrained air.
Cement content follows directly. It is the cement in the batch expressed per cubic metre of concrete produced, which is the figure specifications, durability classes and cost models are all written against.
Absolute-volume method
When this calculation is used
- Proportioning a trial mix before a batching plant run.
- Checking that a supplied mix design actually yields the volume it claims.
- Converting a laboratory batch to a per-cubic-metre specification.
- Diagnosing a short pour, where the delivered volume fell below the ordered volume.
Worked example
A trial batch is proportioned with 300 kg of portland cement, 180 kg of water, 700 kg of fine aggregate and 1100 kg of coarse aggregate, at typical normal-weight specific gravities.
The batch yield tells you what volume this quantity of material will actually produce, and the cement content converts the batch to the per-cubic-metre basis a specification is written in. Compare that cement content against the durability class you are designing to: if it lands below the minimum, the mix needs more cement or less yield, not a rounder number.
The figures are produced by the certified engine when the calculator loads, from this pack’s own declared example. Nothing on this page is a stored answer.
What each input represents
Cement mass
Total cementitious material in the batch. Where supplementary materials are used, each needs its own specific gravity — blending them into one figure is a common source of yield error.
Cement specific gravity
How dense the cement is relative to water. Portland cements sit in a narrow band; blended and pozzolanic cements sit lower, and using the portland figure for a blend overstates yield.
Water mass
Total mixing water in the batch, including any water carried in by admixtures.
Water specific gravity
Essentially unity for potable water. It appears as an input because recycled process water carries suspended solids and is measurably denser.
Fine aggregate mass
Sand in the batch, at the moisture condition the specific gravity below refers to.
Fine aggregate specific gravity
Normally quoted saturated-surface-dry. Mixing an oven-dry gravity with an as-batched mass is one of the most frequent yield discrepancies in practice.
Coarse aggregate mass
Stone in the batch, on the same moisture basis as its specific gravity.
Coarse aggregate specific gravity
Varies with rock type; lightweight and heavyweight aggregates fall well outside the normal-weight band.
Assumptions and limits
- Air content is not deducted. Real concrete contains entrapped air, and air-entrained concrete contains a great deal more, so an as-placed yield will exceed this figure. Use the air-adjusted calculation when air content is specified or measured.
- Every specific gravity must be quoted on the same moisture basis as the mass beside it. The method cannot detect a mismatch — it will return a confident number for inconsistent inputs.
- Admixture volumes are ignored. At normal dosage this is negligible; at high dosage it is not.
- The result is a batch yield, not a delivered volume. Losses in the truck, the pump line and the formwork are separate allowances.
What the guards protect against
- Specific gravities outside the ordinary range for their material are refused rather than computed. A transposed digit produces a plausible-looking yield, and a plausible-looking wrong yield is worse than no answer.
- Every mass and specific gravity must be positive. Zero cement is not a lean mix; it is a mistake in data entry.
- A very rich mix raises a warning rather than a refusal. It is unusual, it is not invalid, and in mass concrete it carries a real heat-of-hydration risk worth flagging.
Provenance
ACI 211.1 — Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete
Absolute-volume method · Neville, A. M., Properties of Concrete
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