ASTM C494 dosage · US oz/cwt units
Concrete Admixture Calculator: Dosage, Type & Cost (ASTM C494)
Choose Type A through G or ASTM C260 air entrainment, then calculate batch dosage, water reduction, W/C change, PSI gain, cost, brand references, overdose risk, and compatibility.
ASTM C494 admixture types - 30-second guide
5-12% water reduction · General workability, pumping
None water reduction · Hot weather, long haul
None water reduction · Cold weather, early strength
5-12% water reduction · Hot weather pumping
5-12% water reduction · Cold weather + strength
12-30% water reduction · High strength, SCC, precast
12-30% water reduction · Hot weather HRWR
None water reduction · Freeze-thaw resistance
Concrete Admixture Dosage Quick Reference - ASTM C494
cwt means 100 lb of cementitious material. Treat these as planning ranges and verify final dosage with the manufacturer's datasheet.
| Type | Name | Dosage Range | Water Reduc. | Best Use |
|---|---|---|---|---|
| Type A | Water-Reducing | 2-6 oz/cwt | 5-12% | General workability, pumping |
| Type B | Retarding | 2-4 oz/cwt | None | Hot weather, long haul |
| Type C | Accelerating | 16-32 oz/cwt | None | Cold weather, early strength |
| Type D | WR + Retarding | 2-6 oz/cwt | 5-12% | Hot weather pumping |
| Type E | WR + Accelerating | 2-6 oz/cwt | 5-12% | Cold weather + strength |
| Type F | High-Range WR | 4-16 oz/cwt | 12-30% | High strength, SCC, precast |
| Type G | High-Range WR + Retarding | 4-16 oz/cwt | 12-30% | Hot weather HRWR |
| AEA | Air-Entraining Agent | 0.25-2 oz/cwt | None | Freeze-thaw resistance |
Which admixture do you need?
Temperature above 85 deg F: use Type B for set delay, Type D for water reduction plus delay, or Type G for HRWR plus delay.
Temperature below 40 deg F: use Type C or Type E for acceleration. Avoid retarders unless engineered.
Need pumpability, high slump, or SCC: use Type F or Type G HRWR.
Freeze-thaw exposure: add ASTM C260 AEA and verify air content in the field.
Step 1: Concrete batch information
Baseline cementitious weight: 1,692 lb (16.92 cwt).
Step 2: Admixture type
Step 3: Dosage setting
Recommended planning range for Type A: 2-6 oz/cwt. Typical starting dosage: 4 oz/cwt.
Step 4: Project conditions
Results
Type A · 4.00 oz/cwt · 1,692 lb cement
Batch dosage
67.7 fl oz0.529 gal · 2.00 L
Water reduction
8.5%72 lb water saved if reduced
Strength impact
+0 PSINew 28-day estimate: 3,000 PSI
Panel A: Admixture quantity
- Dosage rate
- 4.00 oz/cwt
- Total fl oz
- 67.7 fl oz
- Total gallons
- 0.529 gal
- Total pounds
- 4.85 lb
- Metric volume
- 2,002 mL · 2.00 L
- % by cement weight
- 0.287%
Panel B: Water reduction
- Water without admixture
- 846 lb
- Estimated reduction
- 8.5%
- Water saved
- 72 lb (8.6 gal)
- Water after reduction
- 846 lb
- W/C ratio
- 0.500 -> 0.500
- Slump estimate
- 4.0 in -> 6.0 in
Panel C: Strength impact
- W/C reduction
- 0.000
- 28-day strength gain
- +0 PSI
- New 28-day estimate
- 3,000 PSI
- 7-day planning estimate
- 2,100 PSI
- 56-day planning estimate
- 3,300 PSI
Panel D: Cost analysis
- Admixture cost
- 0.529 gal x $8/gal = $4
- Cement saved
- 0 lb
- Cement cost saved
- $0
- Net admixture cost
- $4
Panel E: Brand SKU reference
| Brand | Product family | Size | Price | Note |
|---|---|---|---|---|
| BASF | MasterPozzolith 200N | 5 gal | ~$85 | Lignosulfonate WR |
| Sika | Plastiment | 5 gal | ~$78 | Standard WR/retarder |
| GCP | WRDA 35 | 5 gal | ~$80 | Hydroxylated polymer WR |
Planning purchase: 1 x 1-gal container is sufficient. Always request the product datasheet for exact dosage rates.
Panel F: Overdose risk check
OK
4.00 oz/cwtDosage within recommended planning range.
Panel G: Project suitability
Suitability
Suitable85 deg F · pump placement · 3,000 PSI target
Panel H: Combination admixture check
Compatibility
Single admixture selectedNo second-admixture compatibility check is needed.
ASTM C494 Concrete Admixture Types: Complete Guide
| Type | Name | Dosage | Water Reduction | Set Effect | Best Application |
|---|---|---|---|---|---|
| Type A | Water-Reducing | 2-6 oz/cwt | 5-12% | Neutral | General workability, pumping |
| Type B | Retarding | 2-4 oz/cwt | None | +1-4 hrs | Hot weather, long haul |
| Type C | Accelerating | 16-32 oz/cwt | None | Faster | Cold weather, early strength |
| Type D | WR + Retarding | 2-6 oz/cwt | 5-12% | +1-4 hrs | Hot weather pumping |
| Type E | WR + Accelerating | 2-6 oz/cwt | 5-12% | Faster | Cold weather + strength |
| Type F | High-Range WR | 4-16 oz/cwt | 12-30% | Neutral | High strength, SCC, precast |
| Type G | High-Range WR + Retarding | 4-16 oz/cwt | 12-30% | +1-4 hrs | Hot weather HRWR |
| AEA | Air-Entraining Agent | 0.25-2 oz/cwt | None | Neutral | Freeze-thaw resistance |
Admixture Dosage Unit Conversion: oz/cwt to mL/100kg to Percent
Conversion formulas
US: oz/cwt = fluid ounces per 100 lb cementitious material.
Metric: mL/100kg = milliliters per 100 kg cementitious material.
oz/cwt to mL/100kg: multiply by 6.505 and divide by SG.
oz/cwt to % by weight: multiply by SG x 0.007489.
| oz/cwt | mL/100kg | % by weight | Common use |
|---|---|---|---|
| 1 oz/cwt | 5.9 mL/100kg | 0.008% | Low AEA |
| 2 oz/cwt | 11.8 mL/100kg | 0.016% | Standard WR |
| 4 oz/cwt | 23.7 mL/100kg | 0.033% | Standard WR |
| 6 oz/cwt | 35.5 mL/100kg | 0.049% | Max WR |
| 8 oz/cwt | 47.3 mL/100kg | 0.066% | HRWR range |
| 16 oz/cwt | 94.6 mL/100kg | 0.132% | HRWR range |
Concrete Admixture Compatibility Matrix
Compatible means common in practice, caution means trial batch first, duplicate means overlapping functions, and avoid means opposing effects.
| Type A | Type B | Type C | Type D | Type E | Type F | Type G | AEA | |
|---|---|---|---|---|---|---|---|---|
| Type A | - | Caution | Caution | Duplicate | Duplicate | Duplicate | Duplicate | Compatible |
| Type B | Caution | - | Avoid | Duplicate | Avoid | Caution | Duplicate | Compatible |
| Type C | Caution | Avoid | - | Avoid | Duplicate | Caution | Avoid | Compatible |
| Type D | Duplicate | Duplicate | Avoid | - | Avoid | Duplicate | Duplicate | Compatible |
| Type E | Duplicate | Avoid | Duplicate | Avoid | - | Duplicate | Avoid | Compatible |
| Type F | Duplicate | Caution | Caution | Duplicate | Duplicate | - | Duplicate | Compatible |
| Type G | Duplicate | Duplicate | Avoid | Duplicate | Avoid | Duplicate | - | Compatible |
| AEA | Compatible | Compatible | Compatible | Compatible | Compatible | Compatible | Compatible | - |
Concrete Admixture Quick Reference - 10 Common Scenarios
| Scenario | Temp | Admixture | Dosage | Water Reduc. | Key Benefit |
|---|---|---|---|---|---|
| Standard driveway | 60-85°F | Type A | 3-4 oz/cwt | 6-8% | Workability, pump |
| Hot weather slab | >85°F | Type D | 3-5 oz/cwt | 6-10% | Retard + WR |
| Cold weather pour | <40°F | Type C | 20-28 oz/cwt | None | Early strength |
| Cold + strength | <40°F | Type E | 3-5 oz/cwt | 6-10% | WR + accelerate |
| High-strength (>4000 PSI) | Any | Type F | 6-12 oz/cwt | 15-25% | Max WR |
| Self-compacting (SCC) | Any | Type F | 10-16 oz/cwt | 20-30% | Flow, no vibration |
| Hot weather HRWR | >85°F | Type G | 6-12 oz/cwt | 15-25% | HRWR + retard |
| Freeze-thaw slab | Any | AEA | 0.5-1.0 oz/cwt | None | 5-7% air |
| Freeze-thaw + WR | Any | A + AEA | 3-4 + 0.5-1.0 | 6-8% | Durability + WR |
| Precast / fast strip | Any | Type C/E | 20-32 oz/cwt | 0-10% | Fast strength |
Concrete Admixture FAQ
What is the dosage of superplasticizer in concrete?+
ASTM C494 Type F high-range water reducer is commonly dosed around 4-16 oz/cwt, where cwt means 100 lb of cementitious material. A practical starting point is often 8 oz/cwt, then adjust using the product datasheet and trial batches.
How much water reducer do I add to concrete?+
For Type A water reducer, use about 2-6 oz/cwt. For an 18 bag batch using 94 lb bags, 4 oz/cwt is about 68 fl oz, or about 0.53 gallons.
What is the difference between Type A and Type F admixtures?+
Type A is a normal water reducer with about 5-12% water reduction. Type F is high-range water reducer or superplasticizer, usually around 12-30% water reduction. Use Type F for high strength, self-consolidating concrete, or long pumping.
When should I use a retarder in concrete?+
Use Type B, D, or G retarders for hot weather, long haul times, or large continuous pours. Avoid retarders in cold weather unless a professional mix design calls for them.
How much air-entraining agent do I need?+
AEA is often dosed around 0.25-2.0 oz/cwt, targeting roughly 4-8% air depending on exposure and aggregate size. Air content must be verified with field testing because it is very sensitive to materials and mixing.
Can I combine multiple admixtures?+
Yes, common combinations include Type A + AEA, Type F + AEA, and Type D + AEA. Avoid opposing effects such as accelerator plus retarder unless tested and approved.
What happens if I add too much admixture?+
Overdose can cause excessive retardation, flash set, segregation, bleeding, unpredictable air content, or strength loss. Start near the low end of the recommended range and verify with the manufacturer datasheet.