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Cement content per batch, from the mix design.
Carried through unchanged. Cement is batched dry and is not corrected for moisture — cement that has taken up moisture has already started hydrating and is a defect rather than an input.
The water the design calls for, with aggregates at saturated surface-dry.
This is the figure that sets the water-cement ratio, and the whole point of the correction is that it is NOT the volume to put in the mixer. Water carried in on wet sand counts against it; water absorbed by dry stone adds to it.
Sand per batch as the design states it, at saturated surface-dry.
Sand is where most of the correction comes from. It holds far more free water than coarse aggregate — a damp stockpile at 5% is ordinary — and it is the reason a volume-batched mix goes wrong even before moisture is considered.
Measured moisture in the sand as delivered, percent of oven-dry mass.
Measured by drying a sample to constant mass and comparing. It varies with the weather and with depth in the stockpile — the top of a pile after a dry day and the bottom of the same pile are different materials for this purpose.
The sand's own absorption at SSD, percent of oven-dry mass.
A property of the aggregate, not of the weather, so it does not change between batches. Get it from the supplier's test certificate. The default here is typical for natural sand and is not a substitute for the figure for yours.
Stone per batch as the design states it, at saturated surface-dry.
Coarse aggregate usually carries less free water than sand but more absorption capacity in absolute terms, so on a dry stockpile it is the bigger of the two corrections and it runs the other way.
Measured moisture in the stone as delivered, percent of oven-dry mass.
Set this BELOW the absorption figure to model a dry stockpile. The correction then reverses: the stone takes water out of the mix and the calculator adds water rather than removing it.
The stone's own absorption at SSD, percent of oven-dry mass.
Normal-weight gravel and crushed stone are commonly between 0.5% and 2%. Lightweight aggregate is far higher and is a different problem entirely, because it keeps absorbing during mixing rather than reaching equilibrium first.
Corrected mixing water
293 lb
The aggregates bring 61.8 lb of water with them, so the mixer takes 293.2 lb rather than the design's 355.0 lb. Batch the aggregates at their as-is weights, not the design weights.
- Sand, as-is batch weight
- 1,622.25 lb
- Coarse, as-is batch weight
- 2,449.25 lb
- Cement, unchanged
- 705 lb
- Sand free moisture
- 4 %
- Coarse free moisture
- 0 %
- Water carried in by aggregate
- 61.8 lb
- Design water-cement ratio
- 0.5
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Concrete Aggregate Moisture Correction Calculator: 293 lb — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Free (surface) moisture is total moisture content minus absorption, both expressed on the oven-dry mass — the definitions in ASTM C70 for surface moisture in fine aggregate and ASTM C127/C128 for absorption of coarse and fine aggregate
- Mix designs are stated for aggregate in the saturated surface-dry condition, so batch weights are adjusted by TOTAL moisture and batch water by FREE moisture — the correction sequence set out in ACI 211.1
- Absorption values used as defaults are typical rather than measured: normal-weight gravel and crushed stone commonly fall between 0.5% and 2%, natural sand between 0.5% and 2%. Your own aggregate's absorption is a measured property and the supplier or a test governs it, not these figures
Inputs used
- Cement in the design
- 705 lb
- Design mixing water
- 355 lb
- Fine aggregate (sand), SSD
- 1545 lb
- Sand total moisture
- 5
- Sand absorption
- 1
- Coarse aggregate, SSD
- 2425 lb
- Coarse total moisture
- 1
- Coarse absorption
- 1
Intermediate steps
- Sand, as-is batch weight
- 1,622.25 lb
- Coarse, as-is batch weight
- 2,449.25 lb
- Cement, unchanged
- 705 lb
- Sand free moisture
- 4 %
- Coarse free moisture
- 0 %
- Water carried in by aggregate
- 61.8 lb
- Design water-cement ratio
- 0.5
Confidence note: The aggregates bring 61.8 lb of water with them, so the mixer takes 293.2 lb rather than the design's 355.0 lb. Batch the aggregates at their as-is weights, not the design weights.
What this calculation does not cover
- The moisture percentages are inputs, not measurements. This corrects a design for numbers you supply; it does not tell you what your stockpile is carrying, and a guessed moisture content produces a confidently wrong batch.
- Aggregate moisture changes between batches. A stockpile drains and dries from the top, so a figure measured in the morning is not the figure at the end of the day, and rain between loads invalidates it entirely.
- Absorption is assumed constant and reached. Lightweight and highly porous aggregates keep absorbing during mixing rather than equilibrating first, so the free-moisture model here does not describe them.
- Admixture water is not included. Water carried in with a liquid admixture counts toward the water-cement ratio and has to be accounted for separately.
- This does not design a mix and does not check yield. It corrects the batch you give it; whether that batch makes the volume intended, and whether its ratio meets a specification, are separate questions.
- No allowance is made for water lost to evaporation, to a dry mixer drum, or absorbed by a dry substrate. Those are real on site and none of them is a property of the aggregate.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-15 · v1.0.0
Regulatory standards & verification citations3
- Free (surface) moisture is total moisture content minus absorption, both expressed on the oven-dry mass — the definitions in ASTM C70 for surface moisture in fine aggregate and ASTM C127/C128 for absorption of coarse and fine aggregate
- Mix designs are stated for aggregate in the saturated surface-dry condition, so batch weights are adjusted by TOTAL moisture and batch water by FREE moisture — the correction sequence set out in ACI 211.1
- Absorption values used as defaults are typical rather than measured: normal-weight gravel and crushed stone commonly fall between 0.5% and 2%, natural sand between 0.5% and 2%. Your own aggregate's absorption is a measured property and the supplier or a test governs it, not these figures
Which documents these citations point at
Standards referenced: ASTM C70, ASTM C127 (ASTM International, United States); ACI 211.1 (American Concrete Institute, United States).
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