About STP ShaliBond Concrete

STP ShaliBond Concrete is the bonding agent engineers reach for when a repair has to act as part of the original structure, not just sit on top of it. It is a two-pack epoxy: Component A is an unpigmented, free-flowing resin and Component B is a black hardener, blended on site at a fixed 2:1 ratio by weight. Because it is 100% reactive and solvent-free, there is no film shrinkage from evaporating solvent and no VOC build-up in enclosed spaces such as basements, tanks and plant rooms, which makes it comfortable to specify for confined-area repairs where solvented primers are a problem.

What sets this grade apart on an Indian site is its long pot life and generous open time. You get roughly three hours of working life from a 100 g mix at 28 degrees C, and a 30 to 45 minute window in which the film stays tacky and ready to receive fresh concrete. That headroom matters when pours are staged, when the weather is hot, or when access is awkward. The product tolerates damp substrates and can even double as a primer where concrete moisture sits between 2 and 5%, so it earns its place across repair, flooring and precast bonding work rather than being a single-trick primer.

The technical insight

The whole value of an epoxy bonding coat is in the interface. When you place fresh concrete against a cured slab, the two never truly knit; the old surface has stopped hydrating, so you get a cold joint that transfers load poorly and lets water track through. ShaliBond Concrete is brushed onto the prepared old surface and left tacky. The epoxy wets into the open pores and surface profile of the substrate, then the fresh concrete is placed into that still-live film. As the epoxy cross-links it develops a continuous adhesive bridge, chemically keyed to the old concrete and mechanically locked into the new. The result is a bond stronger than the concrete either side of it, which is why the ASTM C 882 slant-shear and ASTM 4541 pull-off tests report failure in the parent concrete (>2.5 MPa) rather than at the glue line. The cured epoxy also seals the joint against the acids, caustics and moisture that would otherwise attack a raw construction joint, and because it is solvent-free the film builds to full thickness without the pinholing and shrinkage that solvented primers suffer.

Where it is used

• Bonding freshly placed concrete or repair overlays to hardened, cured concrete slabs
• Adhering new floor toppings and screeds to an existing structural floor
• Structural bonding coat in patch repairs and section-enlargement work
• Steel-to-concrete bonding at repair and strengthening interfaces
• Priming and sealing of roads, bridges, pavements, loading bays and factory floors
• Bonding of joints and construction-joint faces before the next pour
• Use as a damp-tolerant primer where concrete surface moisture is between 2 and 5%
• Sand-extended into a bonding mortar for filling spalled or broken-out areas

Key advantages

• Structural, ASTM C 881-compliant bond that fails in the parent concrete, not at the joint
• Solvent-free and 100% reactive, so no VOCs and no solvent-shrinkage in confined spaces
• Long ~3 hour pot life and 30-45 minute tacky window suit staged pours and hot weather
• Bonds to both dry and damp substrates after correct preparation
• High mechanical performance: >60 MPa compressive, >20 MPa tensile, >22 MPa flexural at 7 days
• Doubles as a low-viscosity primer, cutting the number of products on site
• Can be sand or aggregate extended for thick applications and repair mortars
• Protects the joint against chemical attack from most acids and caustics

Limitations & considerations

• Fresh concrete must be placed while the film is still tacky (within 30-45 minutes); once tack is lost the coat must be re-applied
• Substrate must be sound and fully prepared, free of grease, oil, dust, laitance and residual curing compound, or adhesion will be compromised
• Application temperature must stay within 10-40 degrees C, limiting very cold or very hot placement without site control
• The 2:1-by-weight ratio must be respected; hand-batching by eye or over-extending with sand can under-cure the bond
• As a primer it is limited to concrete moisture of 2 to 5%; free water or heavily saturated surfaces are unsuitable
• Cured or hardened material can only be removed mechanically, so tools must be cleaned with STP Thinner before it sets

Selection & best practice

Specifications

Industry use cases

How we position STP ShaliBond Concrete

ShaliBond Concrete sits in Space Arc’s concrete repair and rehabilitation range as the structural, solvent-free epoxy bonding coat for old-to-new concrete work. Within the same STP ShaliBond family, pair it with ShaliBond TPE where a bituminous or elastomeric bonding primer is called for on flexible or waterproofing interfaces rather than rigid structural joints, and use STP’s ShaliGrout epoxy grouts alongside it when the same repair also needs anchoring or gap-filling. Where a project is written around a single house brand, we also stock equivalent epoxy bonding agents from Fosroc and Sika, so specifiers can match an existing approved-vendor list without changing the repair methodology.

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