General Xypex FAQ's

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.

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.

Yes. By blocking the intrusion of water into concrete, Xypex helps protect the concrete from the damaging effect of repeated freeze/thaw cycles

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

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.

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 0.4 mm (1/64”).
  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.

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.

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.

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.

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

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.

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.

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.

Coating FAQ's

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.

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.

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

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.

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.

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

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.

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.

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.

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

Additive FAQ's

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).

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.

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.

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.

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.

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/C-2000 NF is designed for warmer climates and projects where a slower hydration rate is typically required

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.

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.