Concrete Additives: Every Type of Admixture, SCM, Fiber and Pigment and What It Does

Which family solves which problem, at what dose and under which standard?

The same products are sold as additives for concrete, and the trade also uses "admixtures" for the whole group, although ACI and EN keep the terms apart. UK and EU buyers write fibre and colour. This reference covers 11 admixture functions, 9 SCMs, 7 fiber types and 3 pigment oxides.

EN 934-2:2009+A1:2012 caps an admixture at 5 % by mass of the cement. Fly ash replaces 15 to 25 % (Class F) or 20 to 35 % (Class C) and slag cement 20 to 80 % of the cementitious material by mass, macro-synthetic fibers run 1.8 to 12 kg/m³ (3 to 20 lb/yd³), and ASTM C979/C979M-24 caps pigment at 10 % by mass of cement. ConcreteAdditives.net is the independent reference on concrete additives: chemical admixtures, supplementary cementitious materials, fibers and integral pigments, with every value checked against the standard or study that sets it.

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 Are Concrete Additives?#

Concrete additive is a trade umbrella term, defined by no ACI, ASTM or EN document, for any material dosed into concrete to modify it, and this reference splits it into admixtures, SCMs, fibers and pigments. ACI Concrete Terminology (ACI CT-25) defines a chemical admixture as "a liquid, or dispersible powder, used as an ingredient in a cementitious mixture to improve its economy and/or properties in the plastic and/or hardened state." EN 934-2:2009+A1:2012 (3.2.1) limits an admixture to not more than 5 % by mass of the cement content, and EN 206-1:2026 (3.2.1) defines an addition as a finely divided inorganic constituent used in concrete to improve certain properties or to achieve special properties.

The older ACI definition (ACI FAQ 720, citing ACI 212.3R-16) excludes cementitious materials and fiber reinforcement from admixtures, so fly ash and fibers are concrete additives here but not admixtures in the ACI sense. "Mineral admixture" survives as the older ACI and current Indian term for SCMs. Admixture vs additive vs addition turns on these rule books, and the terms are compared under admixture vs additive.

The 4 Families of Concrete Additives and What Each Changes#

The 4 families differ in material and dose basis: admixtures in mL/100 kg or % by mass of cement, SCMs as % replacement, fibers in kg/m³ or % by volume, pigments as % by mass of cementitious material. Table 1 compares the 4 families by material, effect, dose with its basis and product standard.

Doses are ranges with the source type named; the final dose is set by trial batches to the specified property.

Worked example: one mix shows why the basis matters.

• Input: 350 kg/m³ (590 lb/yd³) of total cementitious material with 20 % Class F fly ash, which holds 70 kg/m³ (118 lb/yd³) of fly ash and 280 kg/m³ (472 lb/yd³) of cement.
• Pigment at 3 % of the cementitious material is 10.5 kg/m³ (17.7 lb/yd³), which is 3.75 % of the cement and inside the 10 % cap of ASTM C979/C979M-24.
• An air-entraining admixture at 65.2 mL/100 kg (1.0 fl oz/cwt) is 3.5 × 65.2 = 228 mL per m³ (5.9 fl oz per yd³).

The same pigment reads 3 % on one basis and 3.75 % on the other.

Chemical admixtures: 11 functions dosed in small amounts#

Chemical admixtures are primarily water-soluble substances that modify concrete, mortar or grout in the plastic state, the hardened state or both (ACI PRC-212.3-16, 1.1). ACI PRC-212.3-16 (formerly ACI 212.3R-16) sorts them into 12 groups, from air-entraining and water-reducing to corrosion-inhibiting, lithium and permeability-reducing admixtures. This reference files them under 11 functions: water reducers, retarders, accelerators, air entrainers, shrinkage reducers, corrosion inhibitors, integral waterproofing, viscosity modifiers, foaming agents, mortar admixtures and specialty admixtures. They are not a substitute for suitable mixture proportions and construction practice (ACI PRC-212.3-16, 1.1).

Liquid admixtures are dosed by volume per mass of cementitious material, in mL/100 kg (fl oz/cwt), where 1 fl oz/cwt equals 65.2 mL/100 kg. Others are dosed as % by mass of cement or binder, as supplied or as solids, or in kg/m³ of concrete. Admixture dosage in mL/100 kg, fl oz/cwt and % by mass converts to batch quantities in the admixture dosage calculator.

Supplementary cementitious materials: binders that replace part of the cement#

Supplementary cementitious materials are pozzolanic or latent hydraulic powders, such as fly ash, slag cement, silica fume, metakaolin and calcined clay, that replace part of the portland cement and react to form more binder. Pozzolans react with the calcium hydroxide from cement hydration to form more C-S-H (ACI), while latent hydraulic materials such as slag cement hydrate once activated. Both refine pores, dilute C3A and alkalis and lower heat.

FHWA, citing ACI, gives 15 to 25 % Class F and 20 to 35 % Class C fly ash by mass of total cementitious material. The Slag Cement Association gives 20 to 80 % slag cement, substituted 1:1 by mass. Silica fume runs 5 to 10 % by mass of cement (IS 456:2000 cl. 5.2.1.2; Concrete Society). The 9 materials covered here are fly ash, slag cement, silica fume, metakaolin, calcined clay, natural pozzolans, rice husk ash, ground limestone and ground glass.

Fibers: crack control and post-crack strength#

Fibers are short discrete reinforcement, steel, synthetic, glass, basalt, PVA or natural, that reduce plastic shrinkage cracking at low volume and carry load across cracks at higher volume. ACI FAQ 733 puts synthetic fibers at about 0.1 % by volume for plastic shrinkage cracking and synthetic or metal fibers at 0.3 % by volume or more for toughness and crack width. Micro and macro fibers split at an equivalent diameter of 0.30 mm (EN 14889-2:2006), and microfibers give no post-crack capacity (Concrete Society TR34).

Macro-synthetic fibers run 1.8 to 12 kg/m³ (3 to 20 lb/yd³) (Fiber Reinforced Concrete Association). Steel fibers at 20 to 40 kg/m³ (33.7 to 67.4 lb/yd³) in standard concrete (a manufacturer's FRC handbook) raise post-crack residual strength, not peak flexural or tensile strength. Basalt fits no ASTM C1116/C1116M-23 type and lies outside EN 14889. The steel fiber vs synthetic fiber choice is set out under steel fiber vs synthetic fiber.

Integral pigments: color through the whole section#

Integral pigments are inorganic oxides, such as iron oxides, titanium dioxide and chromium oxide, dispersed through the mix so that the color runs through the full depth of the concrete. ACI PRC-212.3-16 (16.2) lists coloring materials such as iron oxide, chromium oxide, titanium dioxide, carbon black, phthalocyanine and raw burnt umber. Iron oxide pigments carry three identities: red Fe2O3 (CAS 1309-37-1), yellow FeO(OH) (CAS 51274-00-1) and black Fe3O4 (CAS 1317-61-9).

Two vendor guides give a typical product range of 1 to 5 % by mass of cementitious material, while ASTM C979/C979M-24 sets a maximum prescribed dosage of 10 % by mass of cement. EN 12878:2014 is the current EN pigment standard but is not cited in the Official Journal; the EC list still cites EN 12878:2005 with its 2006 corrigendum.

Where to Start: 15 Core Reference Pages and 9 Supporting Sections#

Fifteen pages carry the core of this reference, from the admixture list and ASTM C494 to fly ash, self-compacting concrete and the slump test, and 9 supporting sections cover the rest. Table 2 lists the 15 core pages in reading order; the four family hubs are linked in Table 1.

Table 3 lists the 9 supporting sections and what each covers.

How to Choose a Concrete Additive by Problem#

Start from the problem, not the product: workability, setting time, weather at placement and the durability exposure each point to one family first, and the governing standard or code then sets the number the mix must meet. Table 4 pairs 12 problems with the first family and the number that governs it.

Workability and water demand#

Water-reducing admixtures solve low workability without extra water: ACI PRC-212.3-16 Table 1.2 lists at least 5 % water reduction for normal-range types and at least 12 to 40 % for high-range types. Mid-range types reduce water by 5 to 10 % without retarding initial set. High-range types (ASTM C494 Type F or G) also raise slump and flowability, and the same table names their use in self-compacting concrete.

Do fibers change workability? ACI FAQ 733 states that fibers reduce workability and that the loss is made up with a water reducer or high-range water reducer, never with added water.

Setting time and early strength#

Accelerating admixtures bring setting forward by 1 to 2 hours depending on type, dose and temperature (Concrete Society), while retarding admixtures delay set and reduce water by at least 5 % (ACI PRC-212.3-16 Table 1.2). Accelerators also speed early strength development (ACI PRC-212.3-16 Table 1.2).

Calcium chloride is limited to no more than 2 % flake by mass of cementing material (NRMCA CIP 27), and 2 % regular flake equals 0.98 % chloride ion by mass of cement. ACI CODE-318-25 Table 19.3.2.1 then caps water-soluble chloride ion at 0.15 % for nonprestressed concrete in exposure class C2 and 0.06 % for prestressed concrete, both by mass of cementitious materials.

Placing in cold or hot weather#

Cold weather starts, under ACI 306R-16, when the air temperature has fallen to, or is expected to fall below, 4 °C (40 °F) during the protection period. Concrete needs 3.5 MPa (500 psi) before a single freeze (ACI 306R-16). ACI 306.1-90 (3.4.4) shortens the minimum protection from 3 days to 2 days with Type III cement, an ASTM C494 accelerator or 100 lb/yd³ (59 kg/m³) of extra cement. Accelerators, including calcium chloride at permitted doses, do not prevent freezing (NRMCA CIP 27). ASTM C1622/C1622M-24 covers cold-weather admixture systems for concrete as low as -5.0 °C (23.0 °F) after placement.

Hot weather has its own limit: ACI SPEC-301-20 (4.2.2.5(b)) sets 35 °C (95 °F) as the maximum concrete temperature as delivered, and ACI 305R-20 is the hot-weather guide. Set-retarding admixtures delay set, and extended set-control admixtures, which stop or severely retard cement hydration (ACI PRC-212.3-16 Table 1.2), serve long hauls.

Durability: frost, ASR, sulfates, chlorides and shrinkage#

Five durability problems have a first additive answer: air entrainment for frost, SCMs or lithium admixtures for alkali-silica reaction, SCMs for sulfates, corrosion inhibitors and SCMs for chlorides, and shrinkage-reducing admixtures or fibers for cracking. The five answers and their sources are listed below.

• Air entrainers: improve durability in freezing and thawing and against deicers (ACI PRC-212.3-16 Table 1.2).
• Lithium admixtures (lithium nitrate, carbonate, hydroxide, nitrite): minimize deleterious ASR expansion (ACI PRC-212.3-16 Table 1.2).
• SCMs: refine pores and dilute C3A and alkalis.
• Corrosion-inhibiting admixtures (ASTM C1582/C1582M-24), such as calcium nitrite: reduce the rate of steel corrosion (ACI PRC-212.3-16 Table 1.2).
• Shrinkage-reducing admixtures: reductions of 30 to 50 % in drying shrinkage can be achieved (ACI PRC-212.3-16 Table 1.2).

ACI CODE-318-25 Table 19.3.3.1, as reproduced in NRMCA 2PE004-26, sets 5.0 % air for exposure class F1 and 6.0 % for F2 at 19 mm (3/4 in) nominal maximum aggregate.

Which Standards Classify Concrete Additives?#

Each family of concrete additives has its own product standards, and the US, Europe and India each publish a separate set, with chemical admixtures under ASTM C494 and C260, EN 934-2 and IS 9103. SCMs, fibers and pigments follow the same pattern.

Table 5 sets the product standards of each family side by side, with the edition in force.

The concrete itself is specified under a code: EN 206-1:2026 (CEN approval 2026-01-19) supersedes EN 206:2013+A2:2021 and comes with EN 206-2:2026 and EN 206-3:2026. ACI CODE-318-25 (publication year 2025) is the current ACI building code.

Admixture classes in the US, Europe and India#

ASTM C494/C494M-24 sorts chemical admixtures into 8 types, A to G and S, while EN 934-2:2009+A1:2012 sets requirements in Tables 2 to 13 by function and IS 9103:1999 names 5 types. The ASTM types are 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 and S specific performance. IS 9103:1999 names accelerating, retarding, water-reducing, air-entraining and superplasticizing admixtures.

ASTM C494/C494M-17 and -19e1 Table 1 hold Types F and G to a water content of at most 88 % of the control mix, the same 12 % threshold as ACI PRC-212.3-16, and EN 934-2 Table 3.1 asks high-range water reducers for at least 12 % water reduction. ASTM C494/C494M-24 is active (ASTM store, updated 2024-08-06). EN 934-2:2009+A1:2012 was confirmed at CEN systematic review, and the prEN 934-2 revision was rejected. IS 9103:1999 is active, reaffirmed in 2018 with two amendments (BIS).

EU CE marking and the 2026 assessment systems#

EN 934-2 admixtures and the harmonised SCM standards remain under Regulation (EU) No 305/2011 until new standards are cited under Regulation (EU) 2024/3110, which applies from 2026-01-08.

Delegated Regulation (EU) 2026/1310, published in the Official Journal on 2026-08-28 and in force since 2026-09-17, sets the assessment and verification systems (AVS) listed below; each applies to a family once that family moves under Regulation (EU) 2024/3110.

• Admixtures, all: AVS 2+.
• Additions, pozzolanic or latent hydraulic: AVS 1+.
• Additions, inert and nearly inert: AVS 2+.
• Fibers for structural use: AVS 1.
• Fibers for non-structural use: AVS 3.

Supplier Quotes and Provider Match#

Two request forms turn a specification into quotes or a provider: the supplier quote request for any admixture, SCM, fiber or pigment, and the provider match for mix design, testing or specialty placement. A supplier request names the family, the type or class, the standard required, quantity and packaging, delivery country and plant type. Both forms sit with the calculators and quote tools.

How Every Value on ConcreteAdditives.net Is Checked#

Every number on ConcreteAdditives.net names its source, edition and date, and each value is labelled as a standard requirement, a study result or a typical product value. Standards, codes and regulations are read at their issuing bodies: ASTM, CEN, BIS, ACI and the EU Official Journal. A product value names its data sheet in the same sentence or table cell, and a study value names the study and its year.

A value we cannot trace to its source is omitted rather than hedged. Corrections go to editorial@concreteadditives.net, and the full process is described in our methodology and fact-checking page.

What Does This Reference Not Cover?#

ConcreteAdditives.net covers only what is dosed into concrete, mortar, grout or shotcrete batches and the standards, tests and special concretes built on it, not products applied to finished concrete or additives dosed at the cement plant. Products applied to finished concrete, such as curing compounds, sealers and densifiers, are not covered here. Additives dosed at the cement plant, such as grinding aids, belong to cement making, and asphalt additives belong to paving; neither is covered here.

The site ranks no brands, reviews no products and writes for producers, specifiers, engineers, lab staff and contractors. Who runs the site is set out under about ConcreteAdditives.net.

Is there an additive to make concrete cure faster?#

Yes for strength gain: accelerating admixtures speed setting and early strength development, and calcium chloride is limited to 2 % flake by mass of cementing material. ACI PRC-212.3-16 Table 1.2 lists that function for ASTM C494 Types C and E. Accelerators do not prevent freezing (NRMCA CIP 27), and products applied to the surface for curing are outside this reference.

Which additives reduce cracking in concrete?#

Three additive types reduce cracking: shrinkage-reducing admixtures cut drying shrinkage by 30 to 50 %, synthetic microfibers at about 0.1 % by volume reduce plastic shrinkage cracking, and macro fibers control crack width. The 30 to 50 % range is what ACI PRC-212.3-16 Table 1.2 says can be achieved, and the 0.1 % figure comes from ACI FAQ 733.

Synthetic or metal fibers at 0.3 % by volume or more improve crack width (ACI FAQ 733).

What did the Romans put in concrete to make it stronger?#

Romans mixed volcanic ash, a natural pozzolan, with lime. Seymour et al. (Science Advances, 2023, study result) link hot mixing with quicklime to reactive lime clasts that heal cracks. Today the same kind of volcanic ash is specified as one of the natural pozzolans under ASTM C1945-26b or ASTM C618-26.