Penetrating crystalline waterproofing for concrete

How penetrating waterproofing works

Penetrating, or crystalline, compounds are mixtures of Portland cement, fine sand and active chemicals. Applied to water-saturated concrete, they migrate inwards through the moisture in the capillaries and, reacting with the products of cement hydration, form insoluble crystals in the pores, capillaries and hairline cracks. The concrete becomes denser and stops letting water through, yet it is not sealed with a film and remains vapour-permeable.

The main difference from coatings is that the protection forms within the body of the concrete, so it does not delaminate and works from either side — both the positive side, from which the water pushes, and the negative side. This makes penetrating compounds the main tool where the outer face is inaccessible: in basements in service, manholes, pits and lift shafts, tunnels and utility tunnels.

Product forms

Surface coating — a dry mix that is mixed with water and applied by brush, stiff brush or spray to dampened concrete, as a rule in two coats. In the catalogue, these are Xypex Concentrate, PENETRON, SikaTop-501 Seal and Fosroc Brushbond TGP.
Admixture for the concrete mix — added at the batching plant or into the truck mixer, so that crystallisation takes place throughout the entire volume of the structure. The dosage is set as a percentage of the binder mass: 2–3 % for Xypex Admix C-1000 and 0.8–1.0 % for PENETRON ADMIX.
Repair products of the system — rapid-setting mortars for stopping leaks, for example Xypex Patch’n Plug, and stiff mortars for filling chases cut along joints and cracks before the main coat is applied.

Where it is used

foundations, basements and underground car parks — from outside during construction or from inside during repair;
water tanks and vessels, manholes, pumping stations, treatment plants — after checking the documents for contact with drinking water and the resistance to wastewater;
lift shafts, pits, tunnels and utility tunnels, where the water comes from the ground and work is possible only from the inside;
piles and elements that must not be covered with film-forming coatings: ShNK 2.03.11-24 requires concrete with a water impermeability grade of at least W6 for piles and permits their protection with penetrating waterproofing mixes or impregnation, provided this does not reduce the load-bearing capacity;
new cast-in-situ structures, where an admixture in the concrete replaces or supplements external waterproofing.

Capabilities and limitations

Cracks. Crystals fill only static hairline cracks — up to 0.5 mm according to the Xypex and Penetron data sheets. Wider, leaking and moving cracks are cut out and filled following the manufacturer’s procedure, or injected — see “Injection waterproofing”.
Joints. A penetrating compound does not deal with construction and movement joints, pipe penetrations or joints between precast elements — these need waterstops, swelling profiles, injection hoses or sealants, see “Joint waterproofing”.
Substrate. The compound works on concrete and cement mortar with open pores; some materials also allow masonry. It does not work over paint, bitumen, gypsum or concrete with a film of impregnation or curing compound.
Pressure. Most of the compounds in the catalogue are designed for water pressure from both sides, but there are also materials for low heads — for example, Fosroc Brushbond TGP. Where the head is considerable, the solution is selected as part of the design.
Time. Crystallisation needs water and time: watertightness builds up gradually, so the times before filling vessels and before testing are taken from the data sheet.
Aggressive media. For wastewater and aggressive solutions, the data sheets extend the waiting time before filling or require additional protection. Resistance to the specific medium is confirmed by our questionnaire: substance, concentration, temperature and regime.

Substrate preparation

Laitance, dirt, oils, release agent, paint, old coatings and films of curing compounds are removed by water jetting or abrasive blasting to open up the capillaries. Concrete that is too smooth after steel formwork is also treated.
Honeycombing and weak concrete are broken out back to sound concrete; wide and leaking cracks, defective construction joints and pipe penetrations are cut out as a chase of the shape specified by the manufacturer and filled with the system mortar. An active leak is first stopped with a rapid-setting mortar.
Before application, the concrete is saturated with water to a “saturated surface-dry” condition: there must be no puddles or glistening water, and areas that have dried out are dampened again.

Application and curing

The mix is prepared in small batches — as much as can be applied within the pot life given in the data sheet — and is not thinned with water when it stiffens. The first coat is worked into the pores with a brush; the second is applied while the first is still “green”, with dampening between coats. After application, the coating is kept moist for several days and protected from sun, wind, rain and frost: for Xypex Concentrate, fog spraying is carried out for 2–3 days, and for SikaTop-501 Seal the surface is kept moist for 5–7 days. Film-forming curing compounds must not be used — they cut off the water without which crystallisation does not take place. The heat and wind of Uzbekistan are the main enemy: a layer that has dried out will not work, so in summer the work is scheduled for the morning and evening and the dampening is stepped up.

Finishing coats, tiles and plaster are applied within the times and according to the rules given in the data sheet of the specific material: according to the Xypex Concentrate data sheet, for example, other cementitious products are applied after the coating has set, while it is still “green”.

Admixture for the concrete mix

A crystalline admixture is convenient for new construction: the protection is distributed throughout the section, it cannot be damaged during backfilling, and the schedule does not depend on a separate waterproofing stage. But an admixture does not cancel the rules of good concrete practice and does not solve the details:

construction joints, pipe penetrations and movement joints are dealt with separately — with waterstops, swelling profiles, injection hoses;
cracking is limited by reinforcement and curing, and honeycombing and cracks exceeding the tolerance in the data sheet are repaired;
the admixture may affect setting times, so the dosage and the mix design are checked with trial batches using the project materials and agreed with the manufacturer’s technical service;
some admixtures contain an indicator that makes it possible to verify that the admixture has actually been added to the concrete.

Common mistakes

Application to dry concrete or over old paint — the compound does not penetrate and peels off like an ordinary coating.
No moist curing: in hot weather the layer dries out within hours, and crystallisation does not develop.
Expecting the compound to seal moving cracks and movement joints.
Construction joints and pipe penetrations have not been cut out and filled before application — water keeps coming through them.
Too thick a coat in a single pass — cracking and delamination of the coating.
The admixture was added “by eye” on site, without a trial batch and without allowing for the water in the mix.
The vessel was filled before the end of the waiting period given in the data sheet.

What to clarify before ordering

the side of application and the water pressure; whether there are active leaks;
the substrate: concrete or masonry, age, surface condition, width and nature of the cracks;
contact with drinking water — documents recognised in the country of use are required; for wastewater and saline water — the composition of the water;
what will go on top: backfill, tiles, plaster, nothing;
for an admixture — the concrete class and mix design, the method of delivery and placing, a dosage verified by a trial batch.

Materials in the catalogue

Xypex Concentrate — Xypex — crystalline penetrating waterproofing slurry for concrete, positive or negative side.
Xypex Admix C-1000 / C-1000 NF — Xypex — crystalline waterproofing admixture added to concrete at batching, NSF 61.
Xypex Patch’n Plug — Xypex — fast-setting hydraulic cement with crystalline chemistry for stopping active leaks.
PENETRON — Penetron — crystalline penetrating waterproofing for concrete, applied to the positive or negative side.
PENETRON ADMIX — Penetron — crystalline waterproofing admixture for concrete, 0.8–1.0 % by cement weight, NSF 61.
Fosroc Brushbond TGP — Fosroc — crystalline capillary waterproofing for concrete and masonry against shallow water pressure.
SikaTop-501 Seal — Sika — cementitious crystalline waterproofing for positive and negative water pressure.
Penetron — Penetron — Russian-range crystalline penetrating waterproofing for concrete, applied on either pressure side.
Penetron Admix — Penetron — Russian-range crystalline waterproofing admixture for concrete, 1 % by cement weight.

Frequently asked questions

Can a penetrating compound be applied inside a basement?

Yes, this is one of its main advantages: the materials in the catalogue are designed to work on both the positive and the negative side. Active leaks are stopped beforehand, and cracks, joints and pipe penetrations are cut out and filled with the system mortar.

How long does it take for the concrete to become watertight?

Crystallisation proceeds gradually as long as there is moisture in the concrete. The curing time and the waiting periods before filling vessels and before backfilling are set by the data sheet of the specific material — for example, with Xypex Concentrate, tanks are filled no earlier than 12 days after application, and for wastewater and aggressive solutions after 18 days.

Does penetrating waterproofing work on brick?

Only if the data sheet explicitly permits it: crystallisation requires hardened cement paste. Some compounds, for example Fosroc Brushbond TGP, are designed for concrete and masonry; for the others, use on masonry is agreed with the manufacturer before ordering.

Is penetrating waterproofing needed if a crystalline admixture has been added to the concrete?

Usually not: the admixture already works throughout the section. A surface-applied compound is used to repair defects, to treat details and where there are doubts about the quality of placing, but joints and pipe penetrations are dealt with separately in any case.

Rapid-setting compounds for stopping running water before the main waterproofing are in the section Hydraulic plugs.

We will select penetrating waterproofing for your project and calculate the supply — call us or message us on WhatsApp/Telegram: +998 94 094 52 27.