Sika SikaSwell A
A hydrophilic acrylic profile that expands on contact with water to seal construction joints and penetrations in watertight concrete structures.
What is it?
A rectangular acrylic swellable profile (formerly sold as MSeal 910) that expands in contact with water to seal non-moving construction joints and penetrations in concrete.
Where is it used?
Cast into cold joints of basements, water tanks, sumps, retaining walls, lift pits and around pipe, cable-duct and steel penetrations.
Why use it?
It replaces bulky embedded waterstops, is fast to fix, and re-seals itself through repeated wet-and-dry cycles, filling small voids the concrete cannot.
How is it applied?
Bonded to the prepared substrate with SikaSwell S-2 adhesive along the joint centreline, then cast into the second concrete pour with adequate cover on both sides.
About Sika SikaSwell A
SikaSwell A is Sika’s hydrophilic swelling waterstop for the joints that are almost impossible to seal any other way: the cold joints where yesterday’s pour meets today’s, and the tight gaps around pipes, conduits and steelwork passing through walls and slabs. It is a solid rectangular profile made from an acrylic polymer that reacts to moisture. When ground water or seepage reaches it, the acrylic absorbs the water and grows in volume, pressing hard against the surrounding concrete and closing off the leak path. In a dry spell it shrinks back close to its original size, and the next time water arrives it swells again, which is what makes it dependable in structures that flood and dry out season after season. On many older Indian projects the same product was specified as MSeal 910, so the two names describe one and the same profile.
For a site team, the appeal is how little it disturbs the pour. A conventional PVC dumbbell waterstop has to be threaded through congested reinforcement and held dead-centre in the shutter, which is slow and easy to get wrong. SikaSwell A is simply glued down the middle of the first cast face with SikaSwell S-2 adhesive, the reinforcement is fixed as normal, and the second lift is poured over it. The profile does the sealing from inside the joint. It is supplied in several cross-sections and roll lengths so the size can be matched to the joint width and the expected head of water, and it bonds to concrete, steel and most common construction substrates. Space Arc Engineering supplies SikaSwell A with its matched adhesive across Delhi NCR and Pan-India, along with the placement guidance that keeps it performing.
The technical insight
The seal is driven by osmosis, not by any chemical cure. The acrylic polymer carries hydrophilic (water-loving) groups bound into its structure, so when water contacts the profile it is drawn in and the material swells. Against demineralised water it reaches roughly 50 percent volume increase in three days, about 130 percent at seven days and around 150 percent at thirty days, developing a swelling pressure that can exceed 10 bar in a stiff, well-compacted concrete section. That confinement is the whole point: the pressure only builds if the surrounding concrete is dense and gives the profile something to push against. This is why Sika calls for the profile to sit in the centre of the section with a minimum concrete cover of about 8 cm each side in reinforced work and 15 cm in unreinforced work. Honeycombing, low-density concrete or thin cover lets the profile expand into the void instead of sealing, so it never generates useful pressure. Because the hydrophilic groups are locked into the polymer rather than leached out, the swell-and-shrink cycle repeats over the life of the structure. One caveat sits at the heart of the chemistry: saline or sea water slows and reduces the swelling, which is why coastal and marine joints call for the SikaSwell A Maritim grade instead.
Where it is used
- Sealing horizontal and vertical construction (cold) joints in basement rafts, walls and podium slabs
- Watertightness around pipe, conduit and steel penetrations through walls and floor slabs
- Joints in water-retaining structures such as tanks, reservoirs, sumps and treatment works
- Lift pits, machine foundations and below-grade service rooms subject to ground water
- Construction joints in cable ducts, service tunnels and utility trenches
- Connection joints where new concrete is cast against existing or hardened concrete
- Secant-pile and diaphragm-wall basement junctions where reinforcement is too congested for embedded waterstops
- Small residential and commercial basements needing a fast, reliable cold-joint seal
Key advantages
- Self-sealing action fills small cracks and voids that rigid waterstops bridge over but never close
- Re-swells through repeated wet-and-dry cycles, so seasonal water-table movement does not defeat it
- Far quicker to fix than embedded PVC waterstops, needing only adhesive and no threading through rebar
- Compact cross-section frees up space in congested, heavily reinforced sections
- Bonds to concrete, steel and most substrates, so one product handles joints and penetrations alike
- Supplied in several profile sizes and roll lengths to match joint width and water head
- Resistant to a range of chemicals and stays effective as a permanent in-joint seal
- Conforms with LEED v4 material-ingredient disclosure, useful on green-rated projects
Limitations & considerations
- Only for non-moving construction joints; it must not be used in movement or expansion joints
- Swelling is not instantaneous and takes several hours to activate, so it gives no immediate barrier
- Recommended for water pressures up to about 2 bar; higher heads need an alternative or supplementary Sika joint system
- Needs dense concrete with adequate cover on both sides, since honeycombing or low cover stops it developing pressure
- Standard grade underperforms in saline or sea water, where the SikaSwell A Maritim version is required
- Must be kept dry and protected from rain between fixing and the covering pour, or it swells prematurely
Selection & best practice
Start with a sound, clean substrate that is dry or only matt-damp, and never fix into a joint holding standing water. Level rough or uneven concrete first, either with extra SikaSwell S-2 or a Sika levelling mortar, so the profile makes continuous contact. Lay a triangular bed of SikaSwell S-2 adhesive, roughly 12 mm wide and 12 mm tall, down the centreline and press the profile firmly into the fresh adhesive within 30 minutes, keeping full, unbroken contact along its length. Position the profile in the middle of the section, holding the minimum cover of about 8 cm each side in reinforced concrete and 15 cm in unreinforced concrete. Let the adhesive harden at least 12 hours before pouring, and at least 24 hours where the pour height exceeds 50 cm. Protect the fixed profile from rain and site water until it is cast over, and compact the covering concrete thoroughly around it so there are no voids or honeycombing at the joint. Keep application between +5°C and +35°C substrate and ambient temperature.
Specifications
| Chemical base | Acrylic polymer (hydrophilic swellable profile) |
| Product form | Rectangular pre-formed sealing profile, formerly MSeal 910 |
| Density | ~1.50 kg/l at +23°C |
| Volume change (demineralised water) | ~50% at 3 days, ~130% at 7 days, ~150% at 30 days |
| Swelling pressure | >10 bar in an ideal concrete structure |
| Sealing capacity | Recommended for water pressure up to 2 bar |
| Service temperature | -20°C to +50°C |
| Application temperature | +5°C to +35°C (ambient and substrate) |
| Shelf life | 12 months from production, in dry conditions +5°C to +35°C |
Industry use cases
Water & wastewater
Cold joints in reservoirs, tanks, sumps and treatment works where a continuous, self-sealing joint is critical to watertightness.
Commercial & residential basements
Raft-to-wall and wall construction joints in below-grade parking and plant rooms, especially in high-water-table zones across Delhi NCR.
Infrastructure & tunnelling
Joints in cable ducts, service tunnels and utility trenches, and junctions in secant-pile or diaphragm-wall basements too congested for embedded waterstops.
MEP & penetrations
Sealing around pipes, conduits and steelwork passing through walls and slabs, where conventional waterstops cannot be formed.
Repair & extension
New-to-old concrete connection joints when casting against existing structures during refurbishment or capacity additions.
Frequently asked questions
Is SikaSwell A the same as MSeal 910?
How much does SikaSwell A swell and how long does it take?
Can I use it in an expansion or movement joint?
What water pressure can it hold?
Which adhesive fixes it and how much cover does it need?
Does it work in coastal or marine structures?
How we position Sika SikaSwell A
SikaSwell A is best specified as a system with its dedicated SikaSwell S-2 adhesive, which levels the substrate and holds the profile in place before the pour; the two are designed to work together. For coastal, marine or high-chloride ground water, move up to SikaSwell A Maritim, which keeps swelling reliably in saline conditions. Where a joint moves or a very high water head is expected, look instead at Sika’s PVC waterbar and movement-joint sealant range rather than a swellable profile. On the Fosroc side of our shelf, Supercast SW is the direct equivalent hydrophilic swellable waterstop, offered in matching 5×20 mm and 10×20 mm sections, and is a natural alternative when a project is already standardised on Fosroc’s Supercast joint system. For the wider waterproofing envelope around these joints we also stock membrane and crystalline systems from Fosroc, Dr. Fixit and STP, so the cold-joint seal ties into a complete below-grade specification.
Fosroc Supercast SW — Choose Supercast SW when the project is already standardised on Fosroc’s Supercast joint system, or where the matching 5×20 mm and 10×20 mm swellable sections and Supercast SW adhesive simplify procurement.
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