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When a concrete construction joint or penetration needs to resist water ingress, SikaSwell S-2 provides a hydrophilic polyurethane seal that expands when water reaches it. Use it as a standalone triangular bead or to bond SikaSwell A and P Profiles to prepared concrete.
Why this product exists
Construction joints and penetrations create potential paths for water through concrete. SikaSwell S-2 is placed within the concrete structure so contact with water causes the sealant to swell and seal these details.
The expansion is reversible. In a totally dry state the sealant shrinks towards its original dimensions, then expands again when exposed to water. It is permanently water resistant through wet and dry cycles.
The numbers that matter
In tap water, volume change is less than 25% after 1 day and less than 100% after 7 days. This controlled swelling is the mechanism used to seal the joint when water reaches the installed sealant.
SikaSwell S-2 is recommended for sealing against water pressures up to 2 bar. Above 2 bar it may only be used as a supplementary joint sealing solution.
At +23 °C and 50% relative humidity, curing is approximately 2 mm after 1 day and 10 mm after 10 days. Skinning time is approximately 60 minutes.
Where this product earns its keep
- Concrete construction joints: Forms a swellable seal within the concrete structure where water may track through the joint.
- Pipe and steel penetrations: Seals penetrations through concrete walls and floor slabs.
- Cable ducts: Seals construction joints and penetration details in concrete cable ducts.
- Swellable profiles: Fixes and adheres SikaSwell A and SikaSwell P Profiles to the prepared substrate.
What it's like on site
Apply between +5 °C and +35 °C to a sound, clean substrate that is dry or matt damp. Remove loose particles, release agents, laitance, paint, rust and other poorly adhering material from existing concrete.
When bonding a SikaSwell profile, apply an approximately 12 mm triangular bed and press the profile firmly into the fresh sealant within 30 minutes. Allow at least 24 hours before placing concrete.
When SikaSwell S-2 is used without a profile, bead size increases with structure thickness: 12 mm below 20 cm, 15 mm at 20–30 cm and 20 mm at 30–50 cm.
How it fits in a real system
Place SikaSwell S-2 in the centre of the concrete structure. Maintain at least 8 cm of concrete cover on both sides in reinforced concrete and 15 cm in unreinforced concrete.
During concreting, compact the concrete properly around the sealant to avoid honeycombing and voids. Protect the installed sealant and profiles from rain, process water and ponding water before the concrete is placed.
Choose this when
- When sealing a concrete construction joint where a water-activated swellable seal is required.
- When sealing pipe, steel or other documented penetrations through concrete walls or floor slabs.
- When fixing SikaSwell A or SikaSwell P Profiles to a prepared substrate.
- When the required sealing pressure is up to 2 bar and the installation can provide the specified concrete cover.
Don't use this when
- Not for movement joints: SikaSwell S-2 is specifically excluded from movement-joint applications.
- Not as the sole sealing solution above 2 bar: Above this pressure it is only recommended as a supplementary joint seal.
- Don't expose it to water before casting: Contact with rain, process water or ponding water can start swelling before the concrete is placed.
- Allow for saline conditions: Swelling in salty water is reduced and delayed compared with tap water.
Tested sealing performance
SikaSwell S-2 has documented water pressure resistance and durability testing under BBA Test Certificate No. 13/4994, water-tightness testing under Vattenfall Test Report No. 1278-10, and sealing testing under WISSBAU Test Report No. 2017-313.
Frequently asked questions
What is SikaSwell S-2 used for?
SikaSwell S-2 seals concrete construction joints and penetrations by swelling when it contacts water. It can also fix SikaSwell A and P Profiles to prepared substrates.
How much does SikaSwell S-2 swell?
In tap water, volume change is less than 25% after 1 day and less than 100% after 7 days. Swelling in salty water is reduced and delayed.
Can SikaSwell S-2 be used for movement joints?
No. SikaSwell S-2 must not be used for movement joints. Its documented applications are construction joints, concrete penetrations and fixing SikaSwell A and P Profiles.
What water pressure can SikaSwell S-2 seal against?
SikaSwell S-2 is recommended for sealing against water pressures up to 2 bar. Above 2 bar, use it only as a supplementary joint sealing solution.
How long should SikaSwell S-2 cure before concrete is placed?
Allow at least 24 hours when bonding a SikaSwell profile and 1–2 days when using the sealant alone. For pouring heights above 50 cm, allow at least 3 days.
Applications and benefits
| Application | Key benefit | Primary trades |
|---|---|---|
| Concrete construction joints | Swells when exposed to water to seal the joint, with permanent resistance through wet and dry cycles. | Concreters, waterproofers |
| Pipe penetrations through concrete walls and slabs | Provides a water-activated seal around the penetration within the concrete structure. | Waterproofers, plumbers, concreters |
| Steel work penetrations through concrete | Seals penetration details where water may otherwise track through the concrete interface. | Concreters, waterproofers |
| Construction joints in cable ducts | Provides swellable joint sealing for documented cable-duct construction details. | Civil contractors, concreters, waterproofers |
| Fixing SikaSwell A Profiles | Forms the adhesive bed that holds the swellable profile in continuous contact with the prepared substrate. | Waterproofers, concreters |
| Fixing SikaSwell P Profiles | Adheres the profile to the prepared substrate before concrete placement. | Waterproofers, concreters |
Product limitations
- Not for: Movement joints.
- Water pressure: Recommended for sealing up to 2 bar. Above 2 bar, use only as a supplementary joint sealing solution.
- Concrete cover: Maintain at least 8 cm on both sides in reinforced concrete and 15 cm in unreinforced concrete.
- Water before casting: Protect the sealant from rain, process water and ponding water before placing concrete.
- High pours: For pouring heights above 50 cm, allow the sealant to harden for at least 3 days.
- Salty water: Swelling is reduced and delayed compared with tap water.
- Concrete placement: Compact concrete thoroughly around the sealant to avoid honeycombing and voids.
Substrate guide
The substrate must be sound, clean, dry or matt damp, with preparation matched to the condition of the concrete.
Existing concrete
Surface prep: Remove loose particles, release agents, laitance, paint, rust and other poorly adhering materials by hand or mechanical preparation.
Primer: Not required. The supplied Product Data Sheet does not specify a primer for prepared existing concrete.
Freshly cast concrete
Surface prep: Excessively rough surfaces can be susceptible to leaking. Smooth the area where SikaSwell S-2 will be placed with a batten.
Primer: Not required. The supplied Product Data Sheet does not specify a primer for this application.
Sika SikaSwell S-2 Physical Properties
| Property | Value |
|---|---|
| Composition | 1-part polyurethane, moisture curing |
| Colour | Oxide red |
| Packaging | 300 ml cartridges, 12 cartridges per box; 600 ml unipacs, 20 unipacs per box |
| Shelf Life | 9 months from date of production |
| Storage Temperature | +5 °C to +25 °C |
| Density | 1.24 kg/L at +23 °C |
| Shore A Hardness | 30–50, non-swollen after 7 days at +23 °C and 50% r.h. |
| Change Of Volume | <25% after 1 day in tap water, <100% after 7 days in tap water |
| Sag Flow | <2 mm at +23 °C and 50% r.h. |
| Substrate Moisture | Dry or matt damp |
| Curing Rate | ~2.0 mm after 1 day, ~10.0 mm after 10 days at +23 °C and 50% r.h. |
| Skinning Time | 60 minutes at +23 °C and 50% r.h. |
| Profile Placement Window | Maximum 30 minutes |
| Ambient Application Temperature | +5 °C to +35 °C |
| Substrate Application Temperature | +5 °C to +35 °C |
| Recommended Water Pressure | Up to 2 bar |
| Minimum Cover Reinforced Concrete | 8 cm on both sides |
| Minimum Cover Unreinforced Concrete | 15 cm on both sides |
| 12 mm Bead Yield | 4.1 m per 300 ml cartridge, 8.2 m per 600 ml unipac |
| 15 mm Bead Yield | 3.1 m per 300 ml cartridge, 6.2 m per 600 ml unipac |
| 20 mm Bead Yield | 1.8 m per 300 ml cartridge, 3.6 m per 600 ml unipac |