Description
Mapei Mapeproof Swell is a one-component, rubber-based hydrophilic sealant paste that expands on contact with water to form a flexible, watertight seal in reinforced concrete. Supplied in a 320ml cartridge and applied with a standard extrusion gun, it's the go-to solution for sealing pipe penetrations, cold joints, construction joints and seeping cracks in basements, tanks, pools and below-ground structures.
Once confined within a joint or crack, Mapeproof Swell increases in volume by at least 100% when it meets water, pressing tightly against the surrounding concrete and resisting considerable hydrostatic pressure. It bonds to slightly damp surfaces, so there's no need to wait for a structure to fully dry out before sealing.
Key Benefits
- Self-sealing on contact with water – minimum 100% volumetric expansion closes the gap as soon as water arrives
- Works on damp substrates – bonds to slightly damp, clean and sound concrete (no standing water)
- Highly flexible – elongation above 700% accommodates movement without losing the seal
- Quick, clean application – gun-applied from a 320ml cartridge, no mixing required
- Works with any infiltrating water – suitable for use with any kind of water that seeps or infiltrates
- Non-corrosive – safe for use around steel pipework and reinforcement
Applications
- Sealing pipework passing through concrete walls and slabs
- Sealing cold joints and construction joints in reinforced concrete
- Sealing cracks where water is seeping through reinforced concrete structures
- Sealing spacers in formwork
- Sealing lights and drainage outlets in swimming pools and water tanks
- Bonding various types of joints
Used by builders, groundworkers, waterproofing contractors, pool installers and basement specialists on new-build and repair work alike.
How It Works & Application Guidance
Mapeproof Swell expands in all three directions, towards the path of least resistance – so it must always be confined within a joint, chase or crack. It is not suitable for surface-only application.
- Remove all dust, loose material and anything that could affect the bond. The surface may be damp, but there must be no water on it.
- On steel pipework, remove all traces of oil and grease with ethanol.
- For cracked concrete or construction joints, break out the sides to a depth of at least 6cm, clean out, apply Mapeproof Swell, then confine it with a suitable repair mortar.
- Where water is actively seeping, stop the flow with a rapid-setting leak plug first, then apply Mapeproof Swell on both sides, ensuring a boundary of at least 5cm.
- Cut the nozzle to suit – cutting at the first line gives the normal 6–13mm bead. Pierce the membrane under the nozzle, load into an extrusion gun and apply a continuous, even bead.
- Wait until the product has fully set before pouring concrete against it.
Compatibility
Suitable for reinforced concrete, prefabricated concrete elements and steel or plastic pipework passing through concrete. Can be applied on damp or uneven surfaces. Do not apply to dirty or weak surfaces, or to surfaces heavily contaminated with acids or solvents.
Technical Specifications
- Product type: One-component hydrophilic (hydro-expansive) sealant paste
- Consistency: Thixotropic paste
- Colour: Light grey
- Pack size: 320ml cartridge
- Coverage: Approx. 3 linear metres per cartridge (6–13mm bead)
- Volumetric expansion in water: Minimum 100%
- Application temperature: +5°C to +40°C
- Surface skin formation: 180–200 minutes
- Polymerisation time: 2mm every 9 hours
- Density: 1.25–1.30 g/cm³
- Dry solids content: 90%
- Shore A hardness (DIN 53505): 32
- Elongation (DIN 53504): >700%
- Load at break (DIN 53504): 2.5 N/mm²
- Tear strength (ISO 34-1): 10 N/mm
- Water sealing: 1 ATM
- Solubility: Insoluble in water; non-corrosive
- Storage: Up to 12 months in a dry place at +15°C to +25°C
Technical data are typical values at +23°C and 50% R.H. Product for professional use.
What's Included
1 x Mapei Mapeproof Swell 320ml cartridge. Extrusion gun not included.
Frequently Asked Questions
What is Mapeproof Swell used for?
It seals pipe penetrations, cold joints, construction joints and leaking cracks in reinforced concrete. It swells on contact with water to block leak paths in basements, tanks, pools and below-ground structures.
Can I apply it as a surface sealant?
No. Mapeproof Swell expands in all directions, so it must be confined within a joint, chase or crack and covered with a suitable repair mortar. It is not designed for surface-only application.
Can it be applied to damp concrete?
Yes. It bonds to slightly damp surfaces as long as they're clean and sound, but there must be no standing water on the surface.
How far does one cartridge go?
Each 320ml cartridge gives approximately 3 linear metres of bead at 6–13mm diameter.
Can I use it on an actively leaking crack?
Stop the water flow first with a rapid-setting leak plug, then apply Mapeproof Swell on both sides of the plug with a boundary of at least 5cm.
How long before I can pour concrete against it?
Wait until the product has fully set. It skins over in 180–200 minutes and cures at roughly 2mm every 9 hours at +23°C.
Millcot supplies genuine Mapei waterproofing and construction chemicals to builders, contractors and tilers across the UK – with trade pricing and fast, reliable delivery.
Download the Mapei Mapeproof Swell Technical Datasheet (PDF)