Xypex FAQ


General FAQ

1. Can Xypex be used against extreme hydrostatic pressure? – Close + Details

Yes. Because Xypex is not dependent upon adhesion to the concrete surface and, instead, becomes an integral part of the concrete mass, it is capable of resisting extreme hydrostatic pressure from either side (positive or negative) of the concrete. Independent laboratory testing in accordance with U.S. Army Corps of Engineers CRD C-48 “Permeability of Concrete” showed that Xypex- treated concrete withstood up to 405 feet (123.4 m) of head pressure (175 psi/1.2 MPa), the limit of the testing apparatus.

2. Does Xypex have any adverse effect on concrete? – Close + Details

No. The Xypex crystalline formation becomes a part of the concrete matrix itself and has no deleterious effect on the concrete. In fact, independent laboratory testing has shown that under most conditions Xypex enhances the strength and durability of the concrete structure.

3. Does Xypex protect concrete against freeze/thaw damage? – Close + Details

Yes. By blocking the intrusion of water into concrete, Xypex helps protect the concrete from the damaging effect of repeated freeze/thaw cycles. Air-entrainment is still recommended for use with Xypex in applications exposed to freezing and thawing.

4. Does Xypex protect reinforcing steel? – Close + Details

Yes. By preventing the intrusion of water, salt water, sewage, and most chemicals, Xypex helps protect reinforcing steel against oxidation and deterioration.

5. How deep does the Xypex crystalline formation penetrate the concrete? – Close + Details

The Xypex chemical reactions that initially take place at the concrete surface will continue deep into the concrete structure. Various factors affect the rate and depth of crystallization within the concrete. Some of these factors are: number of Xypex coats, mix design of the concrete, density, porosity, cement content, exposure to moisture and temperature. Independent testing measured the depth of Xypex crystalline penetration into a cast-in-place concrete block at 30 cm (approximately 12 inches). The test concrete sample was coated on the top surface with Xypex Concentrate and left outside the research laboratory in ambient temperatures for 12 months.

6. How is Xypex different from other products? – Close + Details

The Xypex crystalline system for concrete waterproofing and protection is substantially different from traditional barrier products (membranes, cementitious coatings, etc):

  1. Xypex creates a crystalline structure deep within the pores and capillary tracts of the concrete mass to prevent the penetration of water and aggressive chemicals. In contrast, barrier type products function only at the surface of concrete.
  2. Xypex will seal hairline cracks up to 0.5 mm (0.02 in).
  3. Xypex is not subject to the deterioration problems encountered by membranes.
  4. Xypex is designed to be permanent and reactivates whenever water is present.
7. How long does Xypex last? – Close + Details

The Xypex treatment, unlike most other systems, becomes a permanent part of the concrete matrix. Its unique dendritic crystalline growth will not deteriorate under normal conditions, and the crystalline process will reactivate whenever water is present.

8. How resistant is Xypex-treated concrete to aggressive chemicals? – Close + Details

Based on independent testing according to ASTM C 267 “Chemical Resistance of Mortars”, the Xypex-treated concrete is not affected by a wide range of aggressive chemicals including mild acids, solvents, chlorides and caustic materials. Because Xypex is pH specific (not chemical specific) it will protect concrete from any chemical whose pH range is 3.0 to 11.0 constant contact, or 2.0 to 12.0 periodic contact.

9. In what forms is the Xypex Crystalline Technology available? – Close + Details

The Xypex crystalline technology is available in three forms:

  • As a Coating System (Xypex Concentrate & Modified) for new or existing structures
  • As a Concrete Additive (Xypex Admix C-Series) to be added at time of concrete batching
  • As a Dry Shake material (Xypex DS-1 & DS-2) for fresh horizontal surfaces

These three options will prove an asset to the value-engineering process and to the flexibility of the construction schedule.

10. Is Xypex toxic? – Close + Details

No. Xypex contains no volatile organic carriers (VOCs) and can be applied safely in enclosed surroundings. Xypex is approved by numerous health and water authorities around the world for use on structures that contain potable water or foodstuffs. A few of these agencies are:

  • NSF International
  • Swiss Federal Department of Health
  • Japan Food Research Laboratories
  • United Kingdom (DWI) Drinking Water Inspectorate
  • Australian Water Quality Centre
  • Singapore Institute of Standards and Industrial Research
  • France Research Centre for the Control of Water
  • Czech Republic Health Institute & Centre for Drinking Water
11. Is Xypex used to waterproof cracks, faulty joints and other defects in concrete? – Close + Details

Yes. Xypex has a specific repair system that utilizes its unique crystalline waterproofing technology to stop water flow through cracks, faulty construction joints and other defects. In the case of expansion joints or chronic moving cracks, a flexible sealant is recommended.

12. What are some typical Xypex applications? – Close + Details

Typical Xypex applications include reservoirs, sewage and water treatment tanks, secondary containment structures, tunnels, underground vaults, manholes, concrete pipe, foundations, pools, parking structures and below grade construction.

13. What makes Xypex unique? – Close + Details

Xypex becomes an integral part of the concrete mass itself. Traditional barrier products, on the other hand, rely solely on their performance at the surface of the concrete and are therefore subject to deterioration caused by exposure to the environment, hydrostatic pressure, puncturing, delamination, chemical erosion, and damage during backfilling. Xypex was developed to eliminate these very issues. The Xypex formula is based on the natural characteristics of concrete – the fact that concrete is both porous and chemical in nature. With moisture as the catalyst, Xypex’s proprietary chemicals react with the products of cement hydration to form a non-soluble complex within the pores, voids and capillary tracts of the concrete mass. From this inside position, Xypex renders the concrete impenetrable by water and other liquids from any direction, eliminates the problems normally associated with traditional barriers and, in the process, enhances the quality and durability of the concrete structure.

Admixture FAQ

1. Are there any limitations that affect the performance of Xypex Admix? – Close + Details

Use of Xypex Admix requires a minimum of 10% Portland cement content. Of course, optimum effectiveness will be dependent on a number of factors such as thickness of the concrete, Portland cement content, whether there is sufficient reinforcing steel for strength and crack control, quality of placing and finishing practices, sealing of construction joints etc. Typically, Xypex requires a minimum concrete thickness of 5 cm (2”) and a minimum design strength of 20 MPa (3,000 psi).

2. Can Xypex Admix be used in concrete containing fly ash, micro-silica or slag cement? – Close + Details

Yes. Xypex Admix is very effective when used in modern mix designs that incorporate cementitious replacement materials i.e. fly ash, silica fume and blast furnace slag. The reactions that take place to form the crystalline structure are very complex. During the cement hydration process, Xypex’s active chemicals not only react with calcium hydroxide and unhydrated cement particles but also with various metal oxides and mineral salts, regardless of the cement type used. Consult with a Xypex Technical Services Representative to determine dosage rates for such blended cement mix designs.

3. Can Xypex Admix be used in concrete containing other additives such as a water-reducer, plasticizer or air-entrainment agent? – Close + Details

Yes. Xypex Admix has been used successfully in concrete mix designs containing a variety of other admixtures. However, it should be noted that the use of retarding admixtures at recommended dosage rates may cause further extension of set time when used with Xypex Admix. Consult with a Xypex Technical Services Representative for assistance in determining which version of Xypex Admix to use and the appropriate dosage rate.

4. How are the set time and compressive strength of concrete affected by the addition of Xypex Admix? – Close + Details

The set time of concrete is affected by the chemical and physical composition of ingredients, temperature of the concrete and climatic conditions. Extension of set time may occur when using Xypex Admix. The amount of extended set will depend upon the concrete mix design and the dosage rate of the Admix. Concrete containing Xypex Admix may develop higher ultimate strengths than untreated concrete. Trial mixes should be carried out under project conditions to determine set time and strength of the concrete.

5. Is Xypex Admix available in soluble bags? – Close + Details

Yes. In North America, Australia, S.E. Asia, Europe, the Middle East and Africa, Xypex Admix is now available in soluble bags. Xypex Admix C-500/C-500 NF and C-1000/C-1000 NF are available in a variety of conveniently sized soluble bags to meet specific batching requirements. They enhance quality control and eliminate dust during dosing.

6. What is the difference between the various additives in Xypex’s Admix C-Series? – Close + Details

All variations of the Admix C-Series contain the same amount of reactive chemicals at their prescribed dosage rates and provide the same waterproofing and durability performance characteristics. Xypex Admix C-Series is available in regular or no-fines grades (NF). Xypex Admix C-500/C-500 NF is formulated to have minimal or no effect on setting time. Xypex Admix C-1000/C-1000 NF is formulated for concrete mix designs where a normal or mildly delayed set is desired. Xypex Admix C-2000 is designed for warmer climates and projects where a slower hydration rate is typically required.

7. What is the recommended dosage rate for Xypex Admix? – Close + Details

Xypex Admix is added to the concrete mix at a dosage rate within the range of 2 – 3% by weight of the cement content. Where the “No Fines” (NF) grade is utilized, the equivalent dosage rate is 1 – 1.5%. For assistance in determining the appropriate dosage rate for a particular project, consult Xypex technical literature or contact a Xypex Technical Services Representative.

8. When is Xypex Admix introduced into the concrete mix? – Close + Details

Xypex Admix is added to the concrete mix at time of batching. The sequence for the addition of the Admix powder will vary depending on the type of batching operation and equipment, e.g. ready-mix plant (dry batch operation), ready-mix plant (central mix operation), or precast batch plant.

9. Can the VDS be used in Potable Water projects? – Close + Details

Xypex admixtures containing VDS are NSF 61 certified as safe for use in drinking water.
In the UK, DWI approved.

10. Is the VDS affected by other chemical admixtures? – Close + Details

No interactions or negative effects were found with several common admixtures in lab

11. Will the VDS have an effect on other concrete properties? – Close + Details

No, none. Lab studies showed no interactions. VDS has been included in the admixture
in most countries for over 18 months and no effect on concrete properties was found.

12. Can the VDS be seen on trowelled surfaces? – Close + Details

It is not easy to see the Visual Detection System on a hard-trowelled surface. Find a
formed edge, or get a sample (core, chipped edge).

13. How long can you see the VDS in the field? – Close + Details

The intensity of the dots diminishes with time and they start to grow wide and are more
diffused. UV and weather will degrade the intensity. Ideally, VDS identification should be
done within the first 28 days. As the concrete gets older, it may require removal of a
core or other sample.

14. Does the VDS work on coloured concrete? – Close + Details

The VDS has been tested on concrete with Red Admix, Bio-San, white cement, and
silica fume and was always easily detected.

15. Is the VDS affected by form oil? – Close + Details

Some form oils will cause the dots to grow and become more diffuse. This can actually
make it even easier to see the VDS in many cases but might diminish the VDS faster –
this is one reason why early detection is needed.

16. What do I do if I can’t see the VDS? – Close + Details

First, try looking in reduced light conditions, such as blocking out all daylight. If you still can’t see the VDS it may be necessary to remove cores and send them to the Xypex lab
for testing.

17. What if you can see Xypex in one wall and not another? – Close + Details

Double-check that the wall was supposed to have Xypex. Communicate with concrete
supplier and check batch records. Check surfaces again in darker conditions. If all else
fails, remove cores and send them to the Xypex lab for testing.

18. Can the VDS be seen in the Admix powder? – Close + Details

There is a very faint yellow colour to the Admix powder; when pre-mixed as a slurry,
some yellow colour can be seen bleeding to the top of the mixing bucket.

Coating FAQ

1. Can paint and other finishing materials be applied over a Xypex coating? – Close + Details

Yes. In most circumstances paint, epoxy coatings, cement parge coats, plaster and stucco can be applied over a Xypex coating. For further information concerning the interface of the Xypex coating with paint and other finishing materials, consult with a Xypex Technical Services Representative.

2. Can the Xypex coating be applied to the negative side of a structure? – Close + Details

Yes. Although applied as a coating, Xypex is not relying on its surface bonding capability to achieve its waterproofing effect. By means of diffusion, the reactive chemicals in the Xypex coating migrate through the capillary tracts within the concrete to become an integral part of the concrete mass. Therefore, the Xypex coating can be applied to either the positive (water side) or negative side even against strong hydrostatic pressure.

3. Can the Xypex coating be applied while the concrete is wet? – Close + Details

Yes. In fact, the concrete must be wet or moist before applying the Xypex slurry coat. Xypex requires moisture to generate the crystalline growth in concrete. The presence of moisture is also necessary to ensure proper bonding of the slurry coat to the concrete substrate.

4. How is the Xypex coating system different from other cementitious coatings? – Close + Details

Most cementitious coatings are simply surface treatments and are totally dependent on maintaining a proper bond to the concrete surface. Such coatings usually incorporate a latex modifier which makes the coating less permeable and acts as a bonding agent for better adhesion to the surface. They are surface treatments only, and have the added disadvantage of limiting breathability of the concrete. They do not form crystals within the concrete substrate (contrary to what is sometimes represented) and are not effective when applied against hydrostatic pressure.

5. How resistant is Xypex-treated concrete to aggressive chemicals? – Close + Details

Based on independent testing according to ASTM C 267 “Chemical Resistance of Mortars”, the Xypex-treated concrete is not affected by a wide range of aggressive chemicals including mild acids, solvents, chlorides and caustic materials. Because Xypex is pH specific (not chemical specific) it will protect concrete from any chemical whose pH range is 3.0 to 11.0 constant contact, or 2.0 to 12.0 periodic contact.

6. Is the Xypex affected by temperature, humidity, ultraviolet and oxygen levels? – Close + Details

When applied according to specifications, Xypex performs at 100% efficiency within -25°F to +265°F (-32°C to +130°) constant temperatures or within -301°F to +2786°F (-185°C to +1530°C) periodic temperatures. Humidity, ultraviolet and the oxygen level (oxidation) have no effect on a Xypex coating.

7. Is the Xypex coating suitable for use on surfaces other than concrete? – Close + Details

Xypex is totally compatible with the chemistry of concrete, whether cast-in-place, precast or shotcrete. It is not suitable for application to cut-limestone, clay brick, wood, metals, asphalt or other non-concrete building materials.

8. Is there a preference when choosing between the positive or negative side? – Close + Details

Generally, it is recommended that the Xypex coating be applied to the positive side (water side), if accessible, so as to ensure maximum benefit. Therefore, new construction specifications almost always call for the use of the Xypex coating on the positive side (water side). If, however, the positive side is not accessible e.g. tunneling projects or rehabilitation of existing structures, the Xypex coating will be specified for use on the negative side against the hydrostatic pressure.

9. What are the installation advantages to using a Xypex coating system instead of membranes? – Close + Details

The crystalline nature of the Xypex waterproofing system provides many installation advantages over traditional barrier products:

  1. Xypex does not require a dry surface; in fact, a wet surface is necessary.
  2. Xypex does not require dry weather to be applied.
  3. Xypex does not require costly surface priming or leveling prior to application.
  4. Xypex cannot puncture, tear or come apart at the seams.
  5. Xypex does not require protection during backfilling or during placement of steel, wire mesh or other materials.
  6. Xypex can be applied on either side of a concrete surface – the negative or the positive side.
  7. Xypex does not require sealing, lapping and finishing of seams at corners, edges or between membranes.
  8. Xypex is less costly to apply than most other methods.
10. What is the appearance of a Xypex coating? – Close + Details

A Xypex coating normally produces a grey-colored, cementitious surface. However, Xypex “White” is also available.

Dryshake FAQ

1. How is Xypex DS-2 different from Xypex DS-1? – Close + Details

Xypex DS-2 has been specially designed for dry shake applications on horizontal concrete slabs where greater resistance to abrasion is required. Xypex DS-2 contains the same crystalline waterproofing properties as DS-1, however it also includes a synthetic aggregate hardener which has been crushed and graded to particle sizes suitable for concrete floors.

2. What is the advantage of using the dry shake method? – Close + Details

Because Xypex “dry shake” products become an integral part of the concrete surface, problems often associated with coatings (e.g. scaling, dusting, flaking, delamination) are eliminated. This can be very beneficial for slabs that require a hard surface due to traffic and abrasion. The dry shake method may also provide cost savings, especially on large projects, by reducing material and labor costs and by helping to speed up the construction schedule.

3. When are Xypex Dryshake products (Xypex DS-1 or DS-2) normally used? – Close + Details

The Xypex “dry shake” products are designed specifically for use on horizontal concrete slabs during the new construction phase. By incorporating the dry Xypex powder into the top surface of freshly poured concrete, the active chemicals in Xypex use the bleed water and moisture in the concrete as a migrating medium to generate the crystalline formation throughout the concrete substrate.