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Introduction to Concrete Engineering by Crystallisation

1. What is the "XYPEX Concrete Waterproofing By CrystallisationTM" process?

XYPEX is a chemical treatment for the waterproofing and durability enhancement of concrete. XYPEX is composed of Portland cement, very fine silica sands and proprietary ingredients. In the presence of moisture and in a reaction involving many by-products of cement hydration, including various mineral salts [potassium included], metal oxides, calcium hydroxide, silica hydrates and, regardless of the cement type or blend, partially hydrated cementitious particulate, the XYPEX catalytic reaction gives rise to a secondary hydration process wherein the entrained moisture is converted into an almost equal volume of dense, quartz-like dendritic fibres and crystalline structures of an inorganic and insoluble nature.

This 1000x magnification SEM photograph shows the dense XYPEX crystal
development from the wall of a bleed tract, ultimately preventing the further
ingress of moisture as well as densifying the concrete

2. How Does XYPEX Work?

When a cement particle hydrates there is a reaction between water and the cement that causes it to become a hard, solid mass. There are also chemical by-products created which lie dormant in the concrete. When we combine the by-products of cement hydration and moisture in the presence of XYPEX, a chemical reaction takes place and the product of this reaction is a very dense, insoluble, inorganic, dendritic crystalline structure.

The development of this crystalline structure can only take place where moisture is present and thus XYPEX tends to form this crystalline material in the bleed water tracts, capillary tracts and shrinkage cracks in concrete. Wherever water goes, XYPEX will form.

3. How Do XYPEX Chemicals React Within Concrete?

The waterproofing effect of XYPEX is due to two reactions: one chemical, and one physical.

When XYPEX is being used as a coating for waterproofing, or other remedial work, on existing concrete structures, in order to get the chemicals from the coating into the concrete, we rely on the physical reaction, diffusion. Diffusion occurs when chemicals in solution of high density migrate through a solution of lower density until the two equalise.

Crystals will grow up to .45 metres into the concrete from an external specified application, subject to water presence. Growth rates are approximately 50 mm for the first three weeks and 10 mm per week thereafter, depending on presence of moisture.

4. Is The XYPEX Process Ongoing?

Since the process is catalytic, the crystalline structure can re-activate many years after the original application, to seal, or re-seal, defects which might occur in the concrete at a later time providing, cracks do not exceed 0.4 mm. It should be noted that XYPEX products are not fluid and as such may not be suitable for sealing live structural cracks on a stand alone basis.

5. How Is XYPEX Applied?

Concrete can be treated with XYPEX by 4 methods:

1. Within the concrete, in the initial mix, using XYPEX Admix.
2. As a “Mud Slurry” of XYPEX Concentrate beneath new Concrete
3. Applied over a finished structure on the outer surfaces, at any period of the structures life, using XYPEX Concentrate and/or XYPEX Modified.
4. Applied to green concrete as a dry shake powder which is trowelled into the concrete, using XYPEX DS1.

6. Is A XYPEX Coating Waterproof?

A coating of XYPEX Concentrate and/or Modified is never waterproof in itself. The coating is only the source of XYPEX chemicals which are progressively drawn from the coating into the matrix of the concrete during the initial curing process. If required, the XYPEX coating itself may be removed after 4 to 5 weeks as the waterproofing (i.e. the crystalline growth) is deep into the concrete by this time.

7. What are the advantages to using XYPEX over membranes?

  • XYPEX does not require dry weather, costly surface priming or leveling prior to application.
  • XYPEX does not require a dry surface, in fact, a wet surface is necessary.
  • XYPEX cannot puncture, tear, rupture or come apart at the seams.
  • XYPEX does not restrict site access or require protection during back filling, placement of steel, wire mesh or other materials.
  • XYPEX does not require costly sealing, lapping and finishing of seams at corners, edges or between membranes.
  • XYPEX is cheaper to purchase and apply than most membrane applications.
  • XYPEX waterproofs and protects the whole of the structure, not just the surface.

8. Are There Additional Benefits Using XYPEX?

  • Yes, self healing capacity for cracking up to approximately 0.4mm in width.
  • Yes, corrosion protection
  • Yes, neutralised chloride ion activity.
  • Yes, chemical resistance.
  • Yes, reduced carbonation
  • Yes, prevention of alkali aggregate reaction.
  • Yes, gains in concrete design strength.
  • Yes, reduced water cement ratios.
  • Yes, accelerated early and ultimate strength.

9. How Long Does It Last?

A XYPEX application, unlike most other systems, is permanently reactive to the presence of water. The fibrous crystalline growth, due to its unique composition, will not deteriorate under normal conditions.

10. How Does It Stand Up In Harsh Conditions?

When applied in accordance with the Specifications, XYPEX functions at 100% efficiency within the following conditions:

pH Range
- 3.00 to 11.0, in constant contact.
- 2.0 to 12.0, in periodic contact.
Temperature Range
- + 130C to -32C constant
- +1530C to -185C periodic
- No effect
- No effect
Oxygen Level (Oxidisation)
- No effect

11. Is XYPEX Non-Toxic?

XYPEX is approved for use on structures that contain potable water or foodstuffs by many agencies, including:

  • NSF 61 “Drinking Water System Component - Health Effects”, NSF International, Ann Arbor, Michigan
  • Drinking Water Inspectorate - DWI - (UK Authority responsible for product approval re potable water), London, England
  • Sirim Malaysia [98 KL0427]
  • Singapore Institute of Standards and Industrial Research
  • Japan Food Research Laboratories (Water Quality Test according to Tap Water Act) Tokyo, Japan
  • Australian Water Quality Centre (Authority for approval of all products in contact with potable water) Bolivar, South Australia
  • State Health Institute & Center For Drinking Water, State Health Institute,
    (Prague, Czech Republic)
  • Federal Department of Health, Division of Chemicals
    (Berne, Switzerland)
  • National Institute of Occupational Health, Register of Substances and Materials (Copenhagen, Denmark)
  • Mairie De Paris, Research Center for the Control of Water,
    (Paris, France)

© RNC Integral Concrete Technology (M) Sdn. Bhd 2004 - 2018