Chemical Admixtures (ASTM C494)
ASTM C494 classifies the common chemical admixtures used to modify fresh and hardening concrete into seven types, A through G. This page is reference material on what each type does — it does not compute an admixture dosage for you.
The seven ASTM C494 types
| Type | Function |
|---|---|
| A | Water-reducing |
| B | Retarding |
| C | Accelerating |
| D | Water-reducing and retarding |
| E | Water-reducing and accelerating |
| F | High-range water-reducing |
| G | High-range water-reducing and retarding |
D, E and G are combination types — they pair a water-reducing function with a set-time modification in a single admixture.
What each function does
Water-reducing admixtures (Types A, D, E) allow a mix to reach a target slump with less mixing water than would otherwise be needed, which can be used either to reduce w/cm at the same workability or to improve workability at the same w/cm. High-range water-reducing admixtures (Types F, G), often called superplasticizers, achieve a much larger water reduction than the normal-range Type A, and are common in flowable, self-consolidating, or high-strength low-w/cm mixes. Retarding admixtures (Types B, D, G) slow the setting time, useful in hot weather or for large placements needing extra working time. Accelerating admixtures (Types C, E) speed up setting and early strength gain, useful in cold weather or where formwork needs to be stripped quickly.
Reference only — not part of this calculator
The US calculator on this site currently has no admixture input field, unlike the calculators for some other regions. This page exists purely as reference material to help you understand what each admixture type does and when it might be relevant to a project — it does not calculate a dosage, adjust the mix proportions, or otherwise feed into the calculator's output. Any admixture use should be based on the product's manufacturer data and confirmed with trial batches.
Frequently asked questions
Does this site's calculator account for admixtures?
No — the current US calculator engine has no admixture input field, unlike some other regions' calculators on this site. This page is reference material to help you understand admixture types; it does not compute an admixture dosage or adjust the mix design for one.
What is the difference between Type A and Type F?
Both are water-reducing admixtures, but Type F is a high-range water reducer (a superplasticizer), capable of much larger water reductions than the normal-range Type A admixture, typically used for flowable or high-strength, low-w/cm mixes.
Can an admixture replace correct mix design?
No. Admixtures modify how a mix behaves or hardens, but they don't substitute for getting the underlying water-cementitious ratio, aggregate proportions, and materials right — they work alongside a sound mix design, confirmed by trial batches.