Sika Sikadur-Combiflex Adhesive IN
The two-part epoxy that anchors Sikadur-Combiflex SG tapes into permanently flexible, watertight joints on dry or damp concrete.
What is it?
A two-part, solvent-free, thixotropic epoxy adhesive that bonds Sikadur-Combiflex SG waterproofing tapes to concrete, steel and other substrates.
Where is it used?
Expansion and construction joints, and cracks, in basements, water tanks, treatment plants, tunnels, culverts and precast structures.
Why use it?
It forms a high-strength, water-resistant bond that lets the tape flex with joint movement without letting water through.
How is it applied?
Mix Part A and Part B 2:1 by weight to a uniform grey, trowel onto a sound substrate, then press the Combiflex tape into the wet epoxy and consolidate.
About Sika Sikadur-Combiflex Adhesive IN
Sikadur-Combiflex Adhesive IN is the bonding half of Sika’s well-known Combiflex joint-sealing system. On its own the adhesive does little; its job is to lock a flexible Sikadur-Combiflex SG tape onto the two faces of a moving joint so the finished detail behaves as one watertight, elastic unit. Supplied as a pre-batched two-part epoxy, it cures to a hard, chemically resistant bond that stays intact while the tape absorbs expansion, contraction and settlement across the gap. For Indian sites dealing with monsoon loading, ground-water pressure and daily thermal cycling, that separation of roles matters: the tape handles the movement, the epoxy simply holds firm.
What makes the product practical on real projects is its tolerance of imperfect conditions. It bonds to dry or matt-damp concrete without a separate primer, so waterproofing crews are not stalled waiting for a slab to reach a paper-dry state. The paste is non-sag, which means it holds its shape on vertical tank walls and overhead soffits instead of slumping. It works on internal and external details alike, and once cured it resists water, many chemicals and even root penetration. Because it comes in matched, pre-weighed units, on-site mixing errors are minimised and every batch behaves the way the data sheet promises.
The technical insight
The engineering logic rests on decoupling adhesion from flexibility. A rigid sealant bonded directly across a moving joint concentrates strain at the bond line and eventually tears free; the Combiflex system instead bonds only the tape’s outer edges, leaving a deliberately unbonded central zone free to stretch. Sikadur-Combiflex Adhesive IN provides the rigid, high-strength anchor at those edges, developing tensile adhesion above 2 N/mm2 on dry or matt-damp concrete and on blast-cleaned steel, with compressive strength reaching 55 N/mm2 at 7 days. As the joint opens, movement is taken up by elastic elongation of the loose tape span rather than by peeling the epoxy, so the waterproof seal survives cycles that would fail a conventional bonded sealant. The thixotropic, filled epoxy also fully wets the substrate and the tape’s fleece backing, creating a continuous, void-free bond that leaves no capillary path for water to migrate under pressure.
Where it is used
- Bonding Sikadur-Combiflex SG waterproofing tapes across expansion joints in basements, rafts and podium slabs
- Sealing construction joints in tunnels, culverts and other underground works
- Crack-bridging on water-retaining structures such as tanks, reservoirs and treatment plants
- Detailing joints in sewage and effluent treatment plants exposed to aggressive water
- Sealing joints between precast panels and around pipe penetrations
- Waterproofing roof and terrace movement joints where a flexible, trafficable seal is needed
- Restoring leaking joints during repair and rehabilitation of existing wet structures
Key advantages
- Bonds to dry or matt-damp concrete with no separate primer, keeping the waterproofing sequence moving
- Thixotropic, non-sag paste holds its shape on vertical walls and overhead soffits
- Solvent-free and low-odour, suitable for confined tanks and enclosed underground spaces
- High compressive strength up to 55 N/mm2 and tensile adhesion above 2 N/mm2 on concrete and steel
- Pre-batched 2:1 units remove guesswork and reduce site mixing errors
- Water, chemical and root resistant once cured, extending the life of the joint detail
- Works for internal and external joints across a wide +10 C to +40 C application window
Limitations & considerations
- It is only the adhesive; a watertight joint also needs the matching Sikadur-Combiflex SG tape and correct surface preparation
- Cannot be applied to wet substrates with standing water or against active water flow through the joint
- Roughly 30-minute pot life at +30 C shortens further in large mixed quantities and in summer heat, so mix in small workable batches
- Application is restricted to substrate and ambient temperatures between +10 C and +40 C
- Substrates must be sound, clean and laitance-free; adhesion suffers on weak, dusty or contaminated surfaces
- Not a standalone crack filler or structural bonding grout for wide gaps or load transfer
Selection & best practice
Prepare the substrate first: grind or grit-blast concrete to remove laitance and expose a sound, slightly roughened surface, and blast-clean steel to bright metal. Confirm the surface is dry or only matt-damp with no glistening water. Mix Part A for about a minute, add Part B and blend the full pre-batched unit to a uniform concrete-grey with no streaks, avoiding over-mixing that entrains air. Work only what you can place within the pot life, and in hot Indian conditions keep material shaded and mix smaller lots. Trowel the epoxy onto the bond zones, press the Combiflex SG tape firmly into the wet adhesive so it fully wets the fleece backing, and roller out all air pockets. Keep the central movement zone free of adhesive so the tape can flex. Protect the fresh joint from rain and traffic until cured.
Specifications
| Product type | Two-part, solvent-free thixotropic epoxy adhesive |
| Chemical base | Epoxy resin with selected fillers |
| Mixing ratio | Part A : Part B = 2 : 1 by weight |
| Colour | Part A white, Part B black, mixed concrete grey |
| Density | approx. 1.6 kg/L (mixed, at +30 C) |
| Compressive strength | 55 N/mm2 at 7 days (+30 C) |
| Tensile adhesion strength | >2 N/mm2 on dry/matt-damp concrete and blast-cleaned steel |
| Pot life | approx. 30 minutes (100 g mass at +30 C) |
| Application temperature | +10 C to +40 C (substrate and ambient) |
| Consumption | approx. 1.2 kg/m for 200 mm tape at 1 mm; approx. 1.4 kg/m at 2 mm |
| Packaging | 6 kg pre-batched set (4 kg Part A + 2 kg Part B) |
| Shelf life | 12 months from production in sealed packaging, stored +5 C to +40 C dry |
Industry use cases
Water & wastewater
Sealing expansion and construction joints in RCC tanks, clarifiers and treatment plant channels exposed to constant water and aggressive effluent.
Basements & below-ground
Waterproofing movement joints in basement rafts, retaining walls and lift pits under hydrostatic pressure.
Tunnels & infrastructure
Detailing construction joints in tunnels, culverts and underpasses where a flexible, watertight seal must survive ground movement.
Precast & industrial
Bonding joint tapes between precast panels and around penetrations in industrial floors and process structures.
Repair & rehabilitation
Re-sealing leaking joints and bridging cracks in existing water-retaining structures during refurbishment.
Frequently asked questions
Is Sikadur-Combiflex Adhesive IN a complete waterproofing product on its own?
Can I apply it if the concrete is damp?
What is the pot life and how much can I mix at once?
How much adhesive do I need per metre of joint?
What surface preparation does it need?
What pack size does it come in and how should I store it?
How we position Sika Sikadur-Combiflex Adhesive IN
Sikadur-Combiflex Adhesive IN is never bought alone; it is specified alongside the Sikadur-Combiflex SG tape it bonds, and often with Sikadur-31 or Sikadur-30 epoxy adhesives for related structural bonding on the same job. Where the detail is a straightforward movement joint that needs an elastic gun-grade sealant rather than a full bonded-tape system, a single-part sealant such as Sikaflex is the simpler, lower-cost route. Across our other brands we can pair this system with complementary waterproofing membranes and repair mortars to complete the below-ground or water-retaining scope. Talk to Space Arc for the right combination for your joint width, movement and exposure.
Fosroc Nitoseal MS600 — When a joint only needs a durable, paintable gun-grade movement sealant rather than a full bonded-tape waterproofing system, a specifier may choose the simpler single-part Fosroc MS-polymer sealant instead.
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