About Sika Injection-306

Sika Injection-306 belongs to the acrylate (polyacrylic) family of injection resins, a class chosen specifically when water needs to be stopped in wet, moving, or hard-to-reach conditions. Unlike a structural epoxy that glues a dormant crack shut, this material is a waterproofing gel: it is designed to flow like water, react in the presence of water, and remain flexible for the life of the structure. The mixed resin carries a viscosity of roughly 3 to 11 mPa·s at 20 degrees C, which is why site engineers reach for it on leaking basements and tunnels where the leak path is a network of fine, damp fissures rather than a single wide crack.

The system is supplied in components that are blended on site and pumped at a fixed 1:1 ratio through a twin-line pump. What makes it practical for Indian site conditions is control: the reaction (gel) time is adjustable from about 10 to 60 minutes simply by changing how much accelerator is metered in, so the applicator can set a fast gel for a heavy active leak or a slow gel to travel deep into a large hidden void before it sets. It cures into an elastic gel that can absorb and release water, keeping the seal alive through the wet-and-dry cycling that below-ground structures endure through the monsoon.

The technical insight

The performance of Injection-306 comes down to two linked properties: extreme low viscosity and water-compatible chemistry. Because the mixed resin behaves almost like water (about 3 to 11 mPa·s), capillary and pump pressure carry it into cracks and pores that a 200 to 1000 mPa·s epoxy would simply bridge over and leave leaking. Being a polyacrylic system it is not disturbed by the water already sitting in a wet crack; instead it displaces and travels with it. Once the resin and hardener solution meet in the correct ratio, an in-situ polymerisation forms a soft, cohesive gel rather than a rigid solid. That gel is the seal, and its elasticity is what lets it accommodate the small thermal and hydrostatic movements a basement or tunnel lining experiences without debonding. The adjustable accelerator is the control lever: more accelerator shortens the gel time so the resin sets before it is washed out of a fast-flowing leak, while less accelerator buys travel time to fill a large volume. This tunability, combined with the ability to inject behind the structure (curtain injection) into saturated soil to build a waterproof skin on the earth side, is what separates an acrylate gel from ordinary crack fillers.

Where it is used

• Sealing water-bearing cracks in below-ground concrete such as basements, lift pits and water tanks
• Curtain (external) injection through the wall into water-saturated soil to form a waterproof barrier on the earth side
• Repair of damaged single- and double-layer waterproofing membranes by injection between the layers
• Activating and re-sealing injection hoses cast into construction joints
• Waterproofing of tunnels, shafts, culverts and underground service ducts
• Sealing construction and limited-movement joints against water ingress
• Filling and sealing fine, damp fissures that thicker epoxy or PU resins cannot penetrate
• Stopping active seepage in retaining walls and diaphragm walls

Key advantages

• Ultra-low mixed viscosity (~3 to 11 mPa·s) penetrates hairline cracks and damp micro-pores
• On-site adjustable gel time from roughly 10 to 60 minutes gives full control over travel and set
• Cures to a permanently elastic gel that accommodates minor movement without cracking
• Water-compatible chemistry allows injection into wet and actively leaking cracks
• Solvent-free formulation, better for confined below-ground and enclosed work areas
• Suitable for curtain injection behind the structure into saturated soil
• Simple, consistent 1:1 by-volume metering through a two-component pump
• Long 12-month shelf life in sealed packaging supports project stocking

Limitations & considerations

• Not a structural repair — it seals against water but does not restore load-bearing crack strength like a structural epoxy
• Requires a two-component injection pump and trained applicators; not a DIY or pour-in product
• Application is restricted to a substrate and ambient temperature window of +5 degrees C to +40 degrees C
• The elastic gel handles only minor movement, not the large cycling of a dedicated expansion joint
• Multi-component on-site mixing and accelerator dosing demand accurate metering to hit the intended gel time
• Correct packer spacing, drilling and pressure are essential; poor injection technique leaves untreated leak paths

Selection & best practice

Specifications

Industry use cases

How we position Sika Injection-306

Sika Injection-306 sits in the acrylate-gel tier of Sika’s injection range: choose it for waterproofing wet, fine or moving cracks where flexibility matters. When the job is instead structural — bonding a dormant crack back to full strength — move up to a low-viscosity epoxy injection resin such as Sika Injection-451, and for reactive foam sealing of a heavy gushing leak a hydrophobic polyurethane like the Sika InjectoCem/Sika Injection PU family is the better fit. Space Arc pairs this material with Sika packers, injection hoses and pump cleaner, and can supply matching acrylate and PU systems from other brands we distribute (Fosroc, Dr. Fixit and MC-Bauchemie) so specifiers can standardise across a project.

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