Sika Injection-101
A one-component hydrophilic polyurethane resin that reacts with water on site, foaming inside live cracks and joints to shut down active leaks in basements, tunnels and water-retaining concrete.
What is it?
A single-component, low-viscosity hydrophilic polyurethane injection resin from Sika that cures by reacting with water already present in the crack.
Where is it used?
Actively leaking cracks, construction joints and honeycombed zones in basements, tunnels, retaining walls and underground water tanks.
Why use it?
It chases and seals flowing water where rigid epoxies fail, foaming to fill irregular voids and staying flexible enough to accommodate minor movement.
How is it applied?
Injected through drilled packers with a single-component low-pressure pump; the resin meets water, expands and cures to a closed-cell foam that blocks the leak path.
About Sika Injection-101
Sika Injection-101 is built for one of the hardest problems in waterproofing: sealing a crack that is already leaking. Conventional epoxy injection resins need a dry substrate and set rigidly, so they struggle where water is actively flowing. Injection-101 works the opposite way. It is a one-component, low-viscosity hydrophilic polyurethane prepolymer that treats the water in the crack as its curing agent. As the resin advances through the fissure and meets moisture, it reacts, expands and cures into a closed-cell polyurethane foam that physically obstructs the water pathway, converting a wet, uncontrollable defect into a sealed one.
For engineers and applicators across Delhi NCR and the rest of India, this makes it a practical field tool rather than a lab-condition product. It is used to arrest seepage through basement construction joints, flowing cracks in retaining walls under groundwater head, honeycombed concrete pockets, tunnel-lining joints and underground tank walls. Space Arc Engineering supplies Injection-101 as an authorised Sika distributor, and pairs it with the injection packers and single-component pumps the system depends on, so the material and the method arrive together rather than as two separate procurement headaches.
The technical insight
The mechanism is moisture-triggered polyurethane chemistry. In the drum the prepolymer sits at a low initial viscosity of roughly 150-300 mPas, thin enough to travel deep into fine, water-filled fissures that a thicker grout would bridge over and miss. The moment it contacts water, the isocyanate groups react, generating carbon dioxide that drives expansion. Being hydrophilic, the resin actively pulls in the surrounding moisture rather than repelling it, so it expands toward the leak instead of away from it. Free-foaming expansion is in the order of ten times the liquid volume, which lets a modest injected quantity swell to fill irregular voids, follow the crack around corners and press against wet substrate. The cured product is a flexible closed-cell foam, not a brittle solid, so it tolerates the slight thermal and structural movement that a live joint sees without simply cracking open again. Because water is the catalyst, ambient and substrate moisture directly govern reaction speed and final form; the same resin can finish as a firmer foam or a softer gel depending on how much water it meets.
Where it is used
- Sealing actively leaking construction and cold joints in basement walls and rafts
- Injecting flowing cracks in retaining walls under groundwater pressure
- Filling honeycombed concrete pockets with live water ingress
- Waterproofing tunnel-lining segment and construction joints
- Repairing seeping walls of underground water tanks and sumps
- Curtain and crack injection in lift pits, sumps and below-grade shafts
- Emergency leak arrest where a dry substrate cannot be achieved
- Sealing around pipe penetrations and service entries through wet concrete
Key advantages
- Reacts with water, so it seals cracks that are already wet or actively flowing
- Very low initial viscosity penetrates fine fissures rigid resins cannot enter
- Roughly tenfold expansion fills irregular voids from a small injected volume
- Cured foam stays flexible and accommodates minor joint movement
- Hydrophilic action draws the resin toward the moisture and the leak
- Single-component supply means no on-site mixing ratios to get wrong
- Suited to basements, tunnels and water-retaining structures alike
- Backed by Sika’s system of matched packers and single-component pumps
Limitations & considerations
- Needs contact with water to cure, so it is not a bonding resin for dry, dormant cracks
- Provides sealing and flexibility, not structural strength restoration like an epoxy
- Reaction rate and cured firmness vary with the amount of moisture present, requiring some field judgement
- Requires a single-component low-pressure injection pump and packers, not a caulking application
- Uncured resin is moisture-sensitive; opened containers must be resealed and protected
- For pure structural crack re-bonding a rigid epoxy injection resin remains the correct choice
Selection & best practice
Map the leak first and set packers at roughly 150-200 mm centres, drilling at about 45 degrees so the bore crosses the crack plane inside the section rather than skimming the face. Flush the crack with water if it is not already saturated, since the resin needs moisture to react. Inject with a single-component low-pressure pump, starting at the lowest packer and working upward, holding pressure in the region of 2-5 bar so the resin is driven into the fissure without over-pressurising and spalling the concrete. Watch for resin appearing at the next packer or foaming at the face as the sign to move on. Allow the foam to develop and cure, typically a minimum of 6-8 hours, before removing packers and making good the surface. Keep containers sealed until use and protect the resin from ambient moisture during storage.
Specifications
| Product type | One-component hydrophilic polyurethane injection resin |
| Curing mechanism | Water-reactive (moisture-triggered) |
| Initial viscosity | Approx. 150-300 mPas (before water contact) |
| Free-foaming expansion | Up to approx. 10 times volume on water contact |
| Cured form | Flexible closed-cell polyurethane foam / gel |
| Injection equipment | Single-component low-pressure pump and packers |
| Typical injection pressure | 2-5 bar |
| Pack sizes | 1 litre and 5 litre containers |
Industry use cases
Basements & Below-Grade
Arresting seepage through leaking construction joints and cracks in basement walls and rafts under groundwater head.
Tunnels & Infrastructure
Sealing wet segment and construction joints in tunnel linings where a dry substrate is impossible to achieve.
Water-Retaining Structures
Repairing seeping walls of underground tanks, sumps and reservoirs from the negative or positive side.
Industrial & Utility
Stopping ingress around pipe penetrations, cable ducts and service entries through live, wet concrete.
Repair & Rehabilitation
Emergency leak stoppage on ageing structures where seepage must be controlled before any surface treatment can begin.
Frequently asked questions
Can Sika Injection-101 be used on a crack that is actively leaking water?
Does it restore the structural strength of the concrete?
How much does the resin expand?
What equipment is needed to apply it?
Is it one-component or does it need mixing?
What pack sizes does Space Arc supply?
How we position Sika Injection-101
Within the Sika range, Injection-101 is the flexible, water-reactive answer for live leaks; where a crack is dormant and dry and needs structural re-bonding, a rigid Sika epoxy injection resin is the correct partner product rather than this one. Space Arc typically supplies it alongside injection packers and a single-component low-pressure pump, and follows up leak sealing with a cementitious or crystalline waterproofing coating on the treated face for long-term protection. Buyers weighing the Fosroc equivalent should look at Nitofill UR63, which occupies the same water-reactive PU niche in our Fosroc range.
Fosroc Nitofill UR63 — A specifier standardised on the Fosroc system, or needing an approved-equivalent PU for the same active-leak crack injection, can choose Nitofill UR63 in place of Sika Injection-101.
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