Integral Waterproofing Admixtures: Crystalline, Hydrophobic and Pore-Blocking Types (PRAH vs PRAN)

Integral waterproofing admixtures are permeability-reducing admixtures added at batching, and ACI PRC-212.3-16 splits them into 2 classes: PRAN, which cuts water absorption without pressure, and PRAH, which resists water under hydrostatic pressure. Which type, how much and which standard does a basement, tank or precast element need?

The same products are sold as permeability-reducing admixtures (PRA), water-resisting admixtures, integral waterproofing compounds and waterproofers. ACI PRC-212.3-16 sorts concrete admixtures into 12 groups, and permeability-reducing admixtures are one of them.

Crystalline powders are dosed at 0.8 to 3 % by mass of cement across current data sheets, and IS 2645:2003 caps any integral waterproofing compound at 3 % by weight of cement. EN 934-2:2009+A1:2012 Table 9 limits capillary absorption to 50 % of the control after 7 days of curing. Makers claim crack sealing up to 0.4 to 0.5 mm (0.016 to 0.02 in), while an independent thesis found healing only up to 0.30 mm (0.012 in) and only with liquid water, and in an Iowa State University test 2 of 5 commercial products fell below 90 % of reference strength.

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 a Waterproofing Admixture?#

A waterproofing admixture is a chemical admixture added to the batch that reduces water absorption, or water penetration under pressure, of the hardened concrete itself, which ACI PRC-212.3-16 calls a permeability-reducing admixture (PRA).

The ACI report places these products in group 15, one of its 12 admixture groups, with 2 subclasses: 15a for non-hydrostatic and 15b for hydrostatic conditions. The same report sets the limit of any admixture in its section 1.1: chemical admixtures are not a substitute for suitable concrete mixture proportions and acceptable construction practices.

Is concrete waterproof without an admixture?#

No: concrete takes up water through its capillary pores and leaks at cracks, joints and penetrations, and an admixture changes only the first of those paths.

A 2019 UK practitioner article puts typical structural concrete at 10 to 40 mm (0.4 to 1.6 in) of water penetration in the EN 12390-8 test. The same article (2019) holds that admixtures alone are very unlikely to substantially improve resistance to liquid water, because leakage occurs mainly at cracks, joints and penetrations. The other route to a tight pore system is a lower w/cm made placeable with superplasticizers, plus supplementary cementitious materials such as silica fume, fly ash and slag cement.

Permeability-reducing, water-resisting and integral waterproofing compound: three names, one family#

The name follows the region: US documents say permeability-reducing admixture (ACI), Europe says water resisting admixture (EN 934-2 Table 9), the UK Concrete Society says water-resisting admixture, and India says integral waterproofing compound (IS 2645). Trade and site usage adds integral waterproofing admixture, waterproofer and damp-proofing admixture. The classification route, not the name, decides what a data sheet must prove.

How Do Waterproofing Admixtures Work?#

Waterproofing admixtures work in 2 ways named in ACI PRC-212.3-16 Table 1.2: PRAN materials give a water-repellent surface and reduced water absorption, and PRAH materials reduce permeability and raise resistance to water penetration under pressure.

Crystalline products, one of the 2 PRAH material groups, contain ingredients that can react with water and components of the cement to form hydrates in the capillaries and microcracks, and the Concrete Society (Fingertips, 2025) calls them essentially pore blockers that may provide some ongoing crack sealing.

Absorption without pressure vs water under pressure (PRAN vs PRAH)#

A PRAN (group 15a) is rated for absorption without pressure, while a PRAH (group 15b) is the class ACI assigns to resistance against water under pressure. ACI PRC-212.3-16 Table 1.2 lists long-chain fatty acid derivatives, soaps and oils, petroleum derivatives and fine particle fillers as PRAN materials, and crystalline materials and hydrophilic polymers as PRAH materials.

Europe draws the same line in two documents. EOTA EAD 260026-00-0301 divides permeability-reducing admixtures into water resisting admixtures, tested for capillary absorption under EN 934-2, and waterproofing admixtures for high hydrostatic pressure, tested for water penetration depth under EN 12390-8. Absorption and pressure are different transport paths, and the water penetration tests that measure them are compared under permeability of concrete.

Why cracks, joints and penetrations still leak#

Cracks, joints and penetrations leak because no admixture treats them, and leakage occurs mainly at those points (practitioner article, 2019).

A crystalline product data sheet limits self-sealing to static cracks: dynamic cracks are not sealed and need a flexible sealant, and moving joints need engineered expansion joints.

A waterproofing admixture lowers the flow through sound concrete between the joints and leaves joint layout, crack control and every pipe or tie penetration to the design, in line with ACI PRC-212.3-16 (1.1) on mixture proportions and construction practice.

Types of Waterproofing Admixtures: Crystalline, Hydrophobic, Pore-Blocking and Polymer#

Waterproofing admixtures fall into 4 material types: crystalline and hydrophilic polymer types in the PRAH class, and hydrophobic (water-repellent) and pore-blocking fine-filler types in the PRAN class (ACI PRC-212.3-16 Table 1.2).

The table below compares the 4 types by ACI class, material, action and hazard line.

Crystalline types: pore blocking and crack-sealing claims#

Crystalline types are pore blockers whose ingredients react with water and cement components to form hydrates in capillaries and microcracks (Concrete Society, 2025). The data sheets of five crystalline products claim sealing of static cracks up to 0.4 to 0.5 mm (0.016 to 0.02 in), and that range is a manufacturer claim, never an independent or standard value.

Independent work sets a lower bar. Roig-Flores, in a 2018 PhD thesis at the Universitat Politècnica de València, found almost complete healing in 2 months of early-age cracks up to 0.30 mm (0.012 in) under water immersion or wet and dry cycles, and no healing at 95 to 100 % relative humidity. The thesis called the results "not drastically different from autogenous healing", with a more stable minimum permeability, and Formagini et al. (2025, Journal of Building Engineering) found limited additional benefit beyond natural autogenous healing in mechanical recovery. Crack healing with and without these admixtures is compared under self-healing concrete.

Hydrophobic and pore-blocking types#

Hydrophobic types use long-chain fatty acid derivatives, soaps, oils and petroleum derivatives to make the concrete water-repellent, and pore-blocking types use fine fillers such as silicates, bentonite and talc (ACI PRC-212.3-16 Table 1.2).

Liquid hydrophobic products are dosed in mL/100 kg (fl oz/cwt) of cementitious material as the product data sheet states. Both types sit in the PRAN class, which ACI rates for absorption, so a below-grade wall under water pressure calls for a product with PRAH classification and pressure test data instead.

Hydrophilic polymer types#

Hydrophilic polymer types are latex, water-soluble or liquid polymers, which ACI PRC-212.3-16 Table 1.2 lists under PRAH next to crystalline materials. Their dose is a product value, and no polymer dose is reproduced here because the report text that carries one is not the current edition.

What Do Waterproofing Admixtures Change in Concrete?#

Waterproofing admixtures change strength, air content and set as well as permeability: in an Iowa State University test of 5 commercial products, 2 fell below 90 % of the reference strength and surface resistivity rose 7 to 30 %.

The table below separates study results from maker claims for each property.

Strength, air and set across five commercial products#

Iowa State University tested 5 of 13 commercial PRAs (2 PRAN, 3 PRAH) at w/c 0.45 with 335 kg/m³ (564 lb/yd³) of cement, at the recommended and double dose. The study, for the FHWA pooled fund TPF-5(205), used no water reducers, air entrainers or SCMs. Two of the 5 fell below 90 % of reference strength, air changed by -1 to +2 points for most products and +4 points for one, and surface resistivity rose 7 to 30 %.

Doubling the dose caused marked set retardation in one product (Iowa State University). Set-time effects of other admixtures are covered under setting time of concrete.

The study proposed acceptance limits: resistivity at least 10 % above the reference, strength at least 90 %, a length-change increase of at most 0.01 % at 28 days and, for PRANs, ASTM C642 voids and C1585 sorptivity at least 10 % lower. These limits are an Iowa State University proposal, not a standard.

Why rapid chloride and resistivity results can mislead#

Rapid chloride permeability and resistivity results can understate a waterproofing admixture's performance because of its ionic content (Iowa State University). The same study found PRA data sheets using CRD-C 48, DIN 1048, BS EN 12390, ASTM C1202, C1556 and C1585, rarely the same test across products, so two data sheets do not compare directly unless they share a method.

ASTM C1202 measures charge passed, and how ionic admixtures shift it is explained under rapid chloride permeability test.

Waterproofing Admixture Dosage: Typical Ranges and Dose Basis#

Crystalline waterproofing admixtures are dosed at 0.8 to 3 % by mass of cement across current data sheets, a typical product range from at least two makers and never a standard requirement.

IS 2645:2003 (Note 1) caps an integral waterproofing compound at not more than 3 % by weight of cement, a standard requirement. Liquid hydrophobic products are dosed in mL/100 kg (fl oz/cwt) of cementitious material as the product data sheet states; the data sheets on record give single-product values only, so no generic range is given here.

The table below lists each dose with its basis and value type.

The final dose is set by trial mixes with the project materials.

Worked example, for a mix with 400 kg/m³ (674 lb/yd³) of cement as the input and the crystalline range as the dose:

• At 0.8 %: 400 × 0.008 = 3.2 kg/m³ (5.39 lb/yd³) of crystalline admixture.
• At 3 %: 400 × 0.03 = 12.0 kg/m³ (20.2 lb/yd³) of crystalline admixture.
• IS 2645:2003 ceiling for this mix: 12.0 kg/m³ (20.2 lb/yd³), equal to the top of the range.

Each data sheet states its own basis, cement or cementitious material. Other doses and units run in the admixture dosage calculator.

Batching powders and liquids#

Crystalline powders go onto the coarse aggregate belt or into the truck drum with part of the water before the rest of the batch, never dry into wet concrete. Central mixers take the powder as a pre-mixed slurry. Liquid hydrophobic products go in with the mix water or after at least 75 % of it, never directly onto dry cement (data sheets of two products).

Liquid hydrophobic products must not freeze: their data sheets give a freezing point of 0 °C (32 °F) and protection below 5 °C (41 °F). Crystalline powders carry a portland cement base, whose hazard line is in the types table, and fresh concrete is caustic and can cause chemical burns (ASTM C494/C494M safety caveat). Handling rules are in the product safety data sheet.

Selecting a Waterproofing Admixture by Exposure, Application and Climate#

A waterproofing admixture is selected by water exposure first: a PRAH type where water stands against the concrete under pressure, a PRAN type where only absorption without pressure matters.

Basements below the water table and water-retaining structures fall in the pressure group, and dry-cast units in the absorption group. In both, the test result is declared for that exposure.

The table below matches each exposure or application to a class and the proof to request.

Water-retaining and below-grade structures#

Water-retaining structures in the US are designed to ACI CODE-350-20, Code Requirements for Environmental Engineering Concrete Structures, with Commentary ACI 350R-20, and the ACI store lists its publication year as 2021. ACI PRC-212.3-16 (1.1) adds that chemical admixtures are not a substitute for suitable mixture proportions and acceptable construction practices. For potable water storage, the data sheets of three crystalline products state NSF/ANSI/CAN 61 certification.

Below-grade walls and slabs follow the same crack rule as tanks. Self-sealing works for static cracks only, according to a crystalline product data sheet, so dynamic cracks and moving joints are designed and detailed as joints, not left to the admixture.

Placing in hot and cold weather#

Temperature changes how crystalline types heal and how liquids must be stored. Roig-Flores et al. (2016, Construction and Building Materials 114) tested a 4 % crystalline admixture with cracks of 0.10 to 0.40 mm (0.004 to 0.016 in) made at 2 days: healing in water was almost perfect at 30 °C (86 °F), lower at 15 °C (59 °F) and insufficient in wet and dry cycles.

Cold weather adds a storage rule: liquid hydrophobic products are protected below 5 °C (41 °F) per their data sheets. Warm weather adds a set check, since doubling the dose caused marked set retardation in one product (Iowa State University).

Low-permeability mixes without a waterproofing admixture#

Four mix measures lower permeability without a waterproofing admixture, and they are listed below.

• A lower water-cement ratio, the w/cm of the mix.
• Silica fume, a supplementary cementitious material: silica fume in concrete.
• Fly ash, a supplementary cementitious material: fly ash in concrete.
• Slag cement, a supplementary cementitious material: slag cement in concrete.

A lower w/cm needs a dispersant to stay placeable, and high-range water reducers supply the water cut. How the water cut is reached and held is covered under superplasticizers.

Which Standards Classify Waterproofing Admixtures?#

Four documents classify waterproofing admixtures, and only 2 of them set numeric limits: EN 934-2:2009+A1:2012 Table 9 in Europe and IS 2645:2003 in India.

ACI PRC-212.3-16 names the PRAN and PRAH classes without limits, and EOTA EAD 260026-00-0301 declares penetration depth without a pass mark. The 76-page ACI report (2016) replaced ACI 212.3R-10, and ACI Committee 212 is working on a revision, with no new edition as of 2026-10-23.

Is there a code for admixtures in the US? ASTM C494/C494M-24, active and last updated 2024-08-06, covers eight types, A to G and S, and US waterproofing products are offered as Type S. The table below sets the documents side by side.

European absorption limits and the EOTA pressure route#

EN 934-2:2009+A1:2012, published 2012-06-12 and harmonized under the Construction Products Regulation 305/2011, defines a water resisting admixture (3.2.9) as one that reduces capillary absorption of hardened concrete. Its Table 9 requires capillary absorption (EN 480-5) of at most 50 % by mass of the control in the 7-day test after 7 days of curing and at most 60 % in the 28-day test after 90 days of curing, 28-day strength of at least 85 % of the control and air at most 2 % by volume above the control. Some crystalline products are declared as water resisting admixtures to Table 9 in their declarations of performance (two makers).

EOTA EAD 260026-00-0301 treats the crystalline powder admixture as a waterproofing admixture for high hydrostatic pressure and states that it is not a water resisting admixture to EN 934-2, because the capillary absorption test is not appropriate for it. The EAD declares EN 12390-8 water penetration depth at 28 days on reference concrete with 300 kg/m³ (506 lb/yd³) of CEM I 32,5 R at w/c 0.60, without and with the admixture, and sets no pass or fail limit. ETA-18/1129 was issued under this EAD for a crystalline powder admixture by DIBt (version 2 dated 2020-05-28; EOTA database, read 2026-10-23). EN 12390-8:2019 is the current edition of the penetration test, after the 2000 and 2009 editions.

Why the US has no waterproofing admixture specification#

The US has no ASTM type defined by permeability: ASTM C494/C494M-24 holds eight types, A to G and S, and waterproofing admixtures are offered as Type S, the specific performance type. In the Type S wording read in C494/C494M-19 (4.1 and 5.4), the purchaser names the performance characteristic and the maker substantiates it on request, and Type S sets no permeability requirement.

ASTM C494/C494M-19 excludes admixtures for dry-cast products (plasticizing, water-repellent and efflorescence-controlling) from Type S. Some crystalline and hydrophobic products are marketed as ASTM C494 Type S (product claims of two makers). The Type S family as a whole is covered under specialty admixtures.

Integral waterproofing compounds in India (IS 2645:2003)#

IS 2645:2003, reaffirmed 2022, is India's specification for integral waterproofing compounds and the only one of the four documents that sets a permeability limit, less than half that of plain mortar. The second revision, active with 0 amendments on the BIS portal, also requires initial set of at least 30 min, final set of at most 600 min, and 3-day and 7-day strength of at least 90 % of plain mortar.

The product's chloride content is declared and is at most 2.0 % by mass of the product, and the dose is not more than 3 % by weight of cement (Note 1). The package is marked with the maximum chloride content, recommended dosage, date of expiry and batch number, and the BIS Standard Mark is optional (IS 2645:2003).

Integral waterproofing compounds fall under IS 2645, not under IS 9103:1999, the Indian specification for concrete admixtures with five types. Sourcing under IS 9103 and BIS rules is covered under concrete admixtures in India.

Complete List of Waterproofing Admixture Materials#

ACI PRC-212.3-16 Table 1.2 names 6 material classes used as waterproofing admixtures, 4 in the PRAN class and 2 in the PRAH class.

The table below lists the 6 classes in ACI order with their class and the page that covers each.

Classes as listed in ACI PRC-212.3-16 Table 1.2.

Supplier quotes compare on three points: the declared test and its method, the dose with its basis, and the approvals such as a declaration of performance, an ETA, IS 2645 conformity or an NSF/ANSI/CAN 61 statement.

What Is the Best Waterproofing Admixture for Concrete?#

No single waterproofing admixture is best: the right one is a PRAH type with a declared pressure test where water stands against the concrete, and a PRAN type where only absorption matters.

The choice rests on test results measured the same way, since data sheets rarely use the same test across products (Iowa State University). Membranes, waterstops, sealers and crystalline slurries applied to hardened surfaces are construction products and are not covered here.

What do you mix with concrete to make it waterproof?#

Three things make concrete resist water: a PRAH or PRAN admixture matched to the exposure, a low w/cm, and joints detailed for movement. The admixture treats the pores, the low w/cm narrows them, and the joints handle cracks and penetrations. The water cut for a low w/cm comes from water-reducing admixtures.

Is a waterproofing compound the same as a waterproofing admixture?#

Yes, when it is added to the batch: India's IS 2645:2003 calls the batch-added product an integral waterproofing compound.

A product brushed or sprayed onto hardened concrete under the same "waterproofing compound" label is a surface product, not an admixture, and IS 2645 does not cover it.

Can a waterproofing admixture be used in mortar?#

Yes: IS 2645:2003 tests integral waterproofing compounds in cement mortar. Waterproofers for site-mixed mortar are compared under mortar admixtures.

What drives the cost of a waterproofing admixture?#

The cost that matters is dose times price per unit of cementitious material, not the price per bag. Approvals such as a CE marking with a declaration of performance, a BIS license or an NSF/ANSI/CAN 61 statement narrow the eligible suppliers, and quotes against one specification put those factors side by side.