Air-Entraining Admixtures: Wood-Derived and Synthetic Types, Dosage and ASTM C260

Air-entraining admixtures are surfactants that stabilize microscopic air bubbles, about 0.01 to 1 mm (0.0004 to 0.04 in) across, in concrete during mixing, so that concrete resists damage from freezing and thawing and from deicing salts. Which chemistry, how much and which standard does a mix need?

The same products are sold as air entraining agents, air entrainers or AEAs, and EN 934-2 calls them air entraining admixtures. ACI PRC-212.3-16 sorts concrete admixtures into 12 groups, and air entrainment is one of them.

Two chemistry groups do the work: wood-derived acid salts, which lose air with haul time, and synthetic surfactants, which can gain air when water is added late. Each percentage point of air costs about 3 to 5 % of 28-day compressive strength, and two US data sheets give a typical product range of 7 to 391 mL/100 kg (0.1 to 6.0 fl oz/cwt) of cementitious material. ACI CODE-318-25 sets 3.5 to 7.5 % target air by exposure class and aggregate size, and ASTM C260/C260M-24, EN 934-2:2009+A1:2012 Table 5 and IS 9103:1999 classify the products.

Each value is traced to its source: standards and codes to their issuing body, product values to the data sheet named with them, prices to the dated source beside them (methodology and fact-checking).

What Is an Air-Entraining Admixture?#

An air-entraining admixture is a surfactant added during mixing that develops a system of microscopic, spherical air bubbles in the cement paste, which raises resistance to freezing and thawing and to deicer scaling and improves workability (FHWA-HIF-20-085).

ACI PRC-212.3-16 Table 1.2 lists air-entraining admixtures under ASTM C260/C260M and AASHTO M 154. The same table names four exposure purposes, durability in freezing and thawing, deicer, sulfate and alkali-reactive environments, and adds improved workability as a fifth.

Entrained air vs entrapped air#

Entrained air is small, spherical bubbles of about 0.01 to 1 mm (0.0004 to 0.04 in) developed on purpose, while entrapped air is irregular voids larger than 1 mm (0.04 in) present without any admixture (FHWA-HIF-20-085).

Entrapped air usually occupies 1 to 2 % of the concrete volume and sometimes 3 to 4 % (FHWA-HRT-06-117). EN 206-1:2026 (clause 3.3.6) defines entrained air as microscopic bubbles intentionally incorporated during mixing, 10 to 300 µm across. That European range, 0.01 to 0.3 mm, sits inside the lower part of the FHWA range.

What is air-entrained concrete?#

Air-entrained concrete is concrete made with an air-entraining admixture to a target air content that the governing code sets by exposure class and maximum aggregate size. The target is a percentage of concrete volume, reached by trial dosing. Non-air-entrained concrete still holds entrapped air but has no stabilized bubble system.

How Do Air-Entraining Admixtures Work?#

Air-entraining admixtures do not generate air; they lower the surface tension of the mixing water and coat each bubble formed in mixing with a water-repelling shell that resists coalescence. The shell also anchors each bubble to cement and aggregate particles. The mixer forms the bubbles, and the admixture decides whether they survive as a stable system of fine, separate voids (FHWA-HIF-20-085).

How surfactants stabilize bubbles during mixing#

An air-entraining admixture molecule has a non-polar hydrocarbon tail that repels water and an anionic polar head that attracts it, so the molecules collect at the air-water surface and lower its surface tension (FHWA-HIF-20-085).

The collected molecules then form a water-repelling shell around each bubble. That shell resists coalescence, so small bubbles do not merge into large ones, and it anchors each bubble to cement and aggregate particles (FHWA-HIF-20-085).

Why air voids relieve freezing pressure in saturated paste#

Water expands about 9 % by volume as it freezes, and the empty entrained voids give that water a place to go before hydraulic and osmotic pressure cracks the paste. The voids stay largely unsaturated, and the protection holds while the paste stays below a critical degree of saturation of about 86 % (range 75 to 91 %, FHWA-HIF-17-009). Above that level, damage can occur in a single freeze-thaw cycle irrespective of the air volume.

Void spacing matters as much as air volume. FHWA-HIF-17-009 gives a spacing factor of at most 0.20 mm (0.008 in) as the usual criterion for moderate exposure, with a specific surface of at least 24 mm²/mm³ (600 in²/in³), both measured on hardened concrete by ASTM C457/C457M-24. EN 934-2:2009+A1:2012 Table 5 applies a spacing factor of at most 0.200 mm (0.0079 in), measured by EN 480-11, to admixture test mixes. Exposure classes and test methods for freeze-thaw damage and air voids are covered on their own page.

Types of Air-Entraining Admixtures: Wood-Derived, Synthetic and Air-Detraining#

Air-entraining admixtures belong to 2 chemistry groups, wood-derived acid salts such as Vinsol resin and wood rosin and synthetic surfactants such as alkyl sulfates and sulfonates, while air-detraining admixtures do the opposite job and remove air.

Table 1 compares the two air-entraining groups and the air-detraining group by examples, ACI material class, behavior in the mix and hazard line.

Wood-derived vs synthetic air entrainers in the mix#

Wood-derived air entrainers lose air with time and haul distance, while synthetic air entrainers, on the market since the mid-1980s, can gain air when water is added late (FHWA-HIF-20-085).

Supply has shifted inside the wood-derived group: FHWA-HIF-20-085 (2020) reports that, because of supply issues, wood rosins have replaced Vinsol resins in most markets. Performance also differs at similar air. In study FHWA-HRT-06-118 (Tanesi and Meininger 2007), Vinsol mixes reached higher freeze-thaw durability factors than synthetic mixes at comparable air contents; the values appear under durability factor below.

Retempering is a third difference. Adding water to concrete made with a non-Vinsol air entrainer can cluster air voids around coarse aggregate and lower strength (FHWA-HIF-17-009). The chemistry group therefore belongs in the mix submittal next to the target air content.

Air-detraining admixtures and defoamers#

Air-detraining admixtures remove entrained or entrapped air, the reverse of an air entrainer, and ACI PRC-212.3-16 section 16.5 lists tributyl phosphate, dibutyl phosphate, polydimethylsiloxane, alcohols and polypropylene glycols among them. ACI files them in chapter 16 with the miscellaneous admixtures, apart from the chapter 5 air-entraining group.

Defoamers also sit inside some finished products: some polycarboxylate (PCE) superplasticizers contain a defoamer that lowers air (ACI PRC-212.3-16). An air-entrained mix with a PCE water reducer is therefore set by trial with both products in the batch.

What Does Air Entrainment Do to Concrete?#

Air entrainment makes fresh concrete more workable and less prone to bleeding and segregation and makes hardened concrete resistant to freezing and thawing. The cost is about 3 to 5 % of 28-day compressive strength for each percentage point of air (FHWA-HIF-20-085).

Table 2 lists each effect of entrained air with its value and the type of source behind it.

Workability, bleeding and segregation#

Entrained air improves workability and reduces bleeding and segregation of fresh concrete (FHWA-HIF-20-085). These fresh-state gains also explain why air is entrained in mortar: EN 934-3:2009+A1:2012 Table 2 covers an air-entraining/plasticizing class of mortar admixture. Other ways to raise concrete workability are compared on their own page.

Compressive strength loss per percentage point of air#

Each percentage point of entrained air lowers 28-day compressive strength by about 3 to 5 % (FHWA-HIF-20-085). Air above the target costs about 5 % strength per excess point, and a spacing factor below 0.10 mm (0.004 in) can cut strength below the intended value (FHWA-HRT-04-150). On that rule, a batch that overshoots its target by 2 points loses about 10 % of strength (2 × 5 %).

High-strength mixes pay more: air entrainment reduces the strength potential of high-strength concrete more than that of conventional concrete (NRMCA CIP 33). Strength and air are therefore proven together in trial batches at the specified air content.

Durability factor with and without entrained air#

Entrained air raised the freeze-thaw durability factor from 14.4 % for non-air-entrained concrete to 85.7 to 93.5 % for Vinsol mixes at 2.7 to 4.7 % air in study FHWA-HRT-06-118 (Tanesi and Meininger 2007). The study mixes had a w/c of 0.45 and 356 kg/m³ (600 lb/yd³) of cement, and the Vinsol mixes reached those factors even with a spacing factor above 0.36 mm (0.014 in).

Synthetic air-entrained mixes in the same study, at 2.5 to 4.5 % air, mostly stayed below a durability factor of 80 % (FHWA-HRT-06-118). Equal air content did not give equal durability in this study. Paving practice in the same report pairs total air with void spacing: 6 ± 1 % total air with a spacing factor below 0.20 mm (0.008 in).

Air-Entraining Admixture Dosage: Typical Ranges and Dose Basis#

Air-entraining admixtures are dosed as a small volume per mass of cementitious material, and two US data sheets give a typical product range of 7 to 391 mL/100 kg (0.1 to 6.0 fl oz/cwt) of cementitious material, as supplied. By mass, the order of magnitude is about 0.05 % by mass of cement (FHWA-NJ-2001-021, report value). ACI FAQ 659, citing ACI PRC-211.1-22, sets the target from the paste side: about 9 % air in the mortar fraction (passing 4.75 mm, No. 4) for a spacing of about 0.2 mm.

Table 3 compares the three dose bases with the type of value behind each.

1 fl oz/cwt = 65.2 mL/100 kg. The final dose is set by trial to the specified air content.

The worked example below converts one dose inside the typical product range into a batch quantity (calculated from the study mix above and the product range).

• Input: 356 kg/m³ (600 lb/yd³) of cement, dosed at 65.2 mL/100 kg (1.0 fl oz/cwt).
• Metric batch: 3.56 × 65.2 = 232 mL of admixture per m³.
• US batch: 6 cwt × 1.0 = 6.0 fl oz per yd³.

Trial batches then move the dose up or down until the specified air content is reached. Other doses and units run in the admixture dosage calculator.

What changes the air-entraining admixture dose#

Nine material and production factors change the dose or the air-void system a given dose produces. The nine factors, with the effect of each, are listed below (FHWA-HIF-20-085, FHWA-HIF-17-009).

• Fly ash carbon: carbon in fly ash in concrete raises the dose.
• Silica fume: raises the dose.
• Fine slag: raises the dose.
• Finer cement: raises the dose.
• Higher cement alkali: lowers the dose.
• Larger aggregate: raises the dose.
• Sand content: a higher sand content lowers the dose.
• Hot concrete: raises the dose.
• PCE water reducers: some give large, widely spaced bubbles and unstable air, so the void system needs checking at the same dose.

ASTM C618-26 Note 1 states that finely divided materials may reduce entrained air, so air is checked by test and the admixture dose raised. Slag cement contains no carbon, so the fly ash carbon effect does not carry over to it (Slag Cement Association). With rounded aggregate, about 1 percentage point less air may suffice (FHWA-HIF-17-009). Placement moves air too: FHWA-HIF-17-009 reports that 1 to 2 % air is commonly lost in pumping and consolidation.

AEA demand and the foam index test (ASTM C1827)#

ASTM C1827-20 (active), Determination of the Air-Entraining Admixture Demand of a Cementitious Mixture, measures how much admixture a given binder combination needs, as a foam-index-type test. It compares binder sources, such as two fly ash supplies, before trial batches.

Batching and dispensing air-entraining admixtures#

ACI E4-12 adds accelerators with the mixing water, apart from the air-entraining admixture, and sets a dispensing tolerance of 3 % of the required volume or the minimum recommended dose per unit of cement, whichever is greater. Air entrainers ship as liquids in drums, intermediate bulk containers or bulk, and as powder in water-soluble bags.

For self-compacting concrete, the 2005 European Guidelines add the air-entraining admixture before the superplasticizer when consistence is low, never onto dry materials, and do not pre-blend admixtures. Formulated air-entraining admixtures carry their own hazard information: see the product safety data sheet.

Selecting Air-Entrained Concrete by Exposure, Application and Climate#

Air-entrained concrete is selected wherever concrete freezes while saturated, and the target air content follows the governing code, the exposure class and the maximum aggregate size. ACI CODE-318-25 Table 19.3.3.1 sets 6.0 % for Exposure Class F1 and 7.5 % for F2 with 9.5 mm (3/8 in) aggregate, falling to 3.5 % and 4.5 % at 75 mm (3 in).

Table 5 compares nine applications by the role air entrainment plays in each.

Code air content requirements in the US, UK and Europe#

Three code families set air content for freezing exposure: ACI CODE-318-25 for Exposure Classes F1 and F2, BS 8500-1:2023 for XF3 and XF4 in the UK, and EN 206-1:2026, which leaves limiting values to national choice. ACI CODE-318-25 (publication year 2025, 702 pp.) keeps Exposure Classes F0, F1 and F2 and removes F3. EN 206-1:2026 (CEN approval 2026-01-19, dated March 2026) supersedes EN 206:2013+A2:2021 and makes its Annex F limiting values informative, a national choice. ACI 201.2R-16 recommends higher air contents than ACI 318; they reach US readers as reprinted in FHWA-HIF-17-009.

Table 4 compares the code and guidance values by document, exposure and aggregate size.

Two documents tighten or cap air for specific work. ACI SPEC-301-20 4.2.2.4(b) limits specified air to not more than 3 % for slabs that receive a hard-troweled finish. Paving runs higher: FHWA-HRT-06-118 gives 6 ± 1 % total air with a spacing factor below 0.20 mm (0.008 in), and most DOTs target 5 to 7 %, often with a tolerance of ± 2 points (FHWA-HRT-06-117). Pressure, volumetric and SAM methods for checking these targets are compared under air content tests.

Air entrainment in hot and cold weather#

Hot concrete needs more air-entraining admixture for the same air content (FHWA-HIF-20-085), and UK ready-mix guidance (BRMCA, July 2020) treats 30 °C (86 °F) as the appropriate maximum for air-entrained concrete. The same guide sets 35 °C (95 °F) as its default maximum for other concrete.

Cold weather shifts the risk to young concrete. NRMCA CIP 27 calls for 24.1 MPa (3,500 psi) before air-entrained concrete faces repeated freeze-thaw cycles.

Which Standards Classify Air-Entraining Admixtures?#

Three product standards classify air-entraining admixtures side by side: ASTM C260/C260M-24 in the US, EN 934-2:2009+A1:2012 Table 5 in Europe and IS 9103:1999 in India. ACI PRC-212.3-16 chapter 5 gives guidance without requirements.

ASTM C260/C260M-24, Standard Specification for Air-Entraining Admixtures for Concrete (active), covers materials proposed for use as air-entraining admixtures added to concrete in the field. It sets requirements for initial and final time of setting, compressive and flexural strength and length change relative to a reference concrete (ASTM store abstract), and the products are tested by ASTM C233/C233M-24 (active). AASHTO M 154 is listed with ASTM C260 in ACI PRC-212.3-16 Table 1.2.

NRMCA's 2026 guide specification (2PE004-26) lists air-entraining admixtures under ASTM C260/C260M. In India, IS 9103:1999 is active, reaffirmed 2018, with two amendments (BIS), and covers 5 admixture types including air-entraining.

Table 6 compares the standards and reports by region, edition, status and role.

How air-entraining admixtures are tested against a control concrete#

EN 934-2:2009+A1:2012 Table 5, harmonised under CPR 305/2011, requires test mix air at least 2.5 % by volume above the control mix and total air of 4 to 6 %. The same table sets a spacing factor of at most 0.200 mm (0.0079 in) by EN 480-11 and a 28-day compressive strength of at least 75 % of the control mix.

IS 9103:1999 doses the air-entraining admixture to give 3.5 to 7 % air (cl. 6.2.2) against a control made with the reference admixture. A relative durability factor of at least 80 applies when the purchaser asks for the Annex B test. ASTM C260/C260M-24 follows the same control-concrete logic through ASTM C233/C233M-24, with the requirement categories listed above.

Complete List of Air-Entraining Admixture Materials#

ACI PRC-212.3-16 Table 1.2 names 9 material classes used as air-entraining admixtures, from salts of wood resins and tall oils to synthetic detergents and alkylbenzene sulfonates.

Table 7 lists the 9 classes in ACI order with the chemistry group where a source names one.

Classes as listed in ACI PRC-212.3-16 Table 1.2; groups as named by FHWA-HIF-20-085; "not assigned" where no source names one.

Quotes for an air-entraining admixture compare by specification and declaration: the standard claimed (ASTM C260/C260M, AASHTO M 154, EN 934-2 Table 5 with a declaration of performance, or IS 9103), the chemistry group, the form (liquid or powder) and the dose basis printed on the data sheet. A product counts as conforming only with its declaration or test report in hand.

When Should You Not Use Air-Entrained Concrete?#

Air-entrained concrete is avoided or capped in 2 cases named in the sources: slabs with a hard-troweled finish and high-strength mixes. ACI SPEC-301-20 4.2.2.4(b) caps specified air at 3 % for slabs receiving a hard-troweled finish, and high-strength mixes lose more strength potential to entrained air than conventional concrete (NRMCA CIP 33).

Repair of scaled surfaces and sealers for scaled slabs are outside the scope of this page. Air-entraining cement, where the agent is added at the cement mill, is a cement product and not covered here.

What are the downsides of air-entrained concrete?#

Air-entrained concrete has 3 downsides: lower strength, an air content that shifts in production and a 3 % cap on hard-troweled slabs. Strength falls by about 3 to 5 % per percentage point of air (FHWA-HIF-20-085). Air shifts with fly ash carbon and hot concrete, wood-derived products lose air with haul time and synthetics can gain air with late water (FHWA-HIF-20-085). FHWA-HIF-17-009 adds that 1 to 2 % air is commonly lost in pumping and consolidation.

Is an air-entraining admixture the same as a foaming agent?#

No: an air-entraining admixture stabilizes small dispersed voids in structural concrete, while a foaming agent makes a preformed foam for low-density cellular concrete. Foam generation and density control are covered under foaming agents for concrete. Air-entrained concrete holds its 0.01 to 1 mm (0.0004 to 0.04 in) voids at the 3.5 to 7.5 % targets of ACI CODE-318-25.

Does entrained air make concrete shrink more?#

Only slightly: entrained air raises drying shrinkage by not more than 10 % for air contents up to about 5 % (ACI 224R-01, citing Carlson 1938). ACI Committee 224 still carries the 1938 Carlson data in chapter 3 of its 2001 report on drying shrinkage.

Do water reducers change entrained air?#

Yes: some PCE water reducers give large, widely spaced bubbles or contain defoamers, and 7 of 19 lignosulfonate retarders in HRB Bulletin 310 (1962) entrained more than 5 % air without any air-entraining agent. The PCE bubble effect comes from FHWA-HIF-17-009, and the defoamer content from ACI PRC-212.3-16.

Air content is therefore checked by trial whenever a water reducer joins or leaves an air-entrained mix. Normal, mid-range and high-range types are compared under water-reducing admixtures.