Aggregate Moisture Correction Calculator
Correct concrete batch quantities for fine and coarse aggregate moisture separately, then total the wet batch mass and net free-water contribution. This prevents one of the most common batching mistakes: treating different stockpiles as if they all contain the same amount of water.
Enter the two aggregate stockpiles
Combined moisture correction
| Material | Dry mass | Wet batch mass | Moisture | Absorption | Free water |
|---|
Why each stockpile should be corrected separately
Fine aggregate and coarse aggregate often have different moisture histories, surface conditions and absorption properties. Rain can saturate one material while another continues draining or drying.
Correcting each stockpile independently preserves that information. It also lets a batch plant see which material is responsible for most of the water contribution.
Worked example
Suppose 750 kg of fine aggregate has 5% moisture and 1.5% absorption. It weighs 787.5 kg when batched wet and contributes 26.25 kg free water. A 1,050 kg coarse aggregate with 1.5% moisture and 1% absorption weighs 1,065.75 kg wet and contributes 5.25 kg free water.
Current moisture data matters
ASTM C566 describes total evaporable moisture testing and notes that moisture values can be used for adjusting concrete batch quantities. The usefulness of the correction depends on how representative the test sample is of the stockpile actually entering production.
Use current plant procedures and appropriately representative testing.
Reference: ASTM C566-25.
Common mistakes
One moisture value for all materials: fine and coarse aggregates can differ.
Using moisture without absorption: total moisture is not the same as free water.
Using a negative free-water value incorrectly: below-absorption aggregate can draw water into the particles.
Updating weights but not water: correcting one without the other can disturb the mixture balance.
Limitations
This calculator assumes the moisture and absorption percentages you enter are valid and that an SSD reference basis is appropriate. It does not perform moisture testing or plant control.
Frequently Asked Questions
Why separate fine and coarse aggregate?
Because their moisture and absorption values can be different.
How is wet aggregate weight calculated?
Dry mass × (1 + moisture ÷ 100).
How is free water calculated?
Dry mass × (moisture − absorption) ÷ 100.
What if free water is negative?
The aggregate requires water rather than supplying it under the selected basis.
Can this replace moisture testing?
No. It only processes the moisture values you enter.