About Fosroc Nitofill TH

Fosroc Nitofill TH is a two-component, solvent-free thixotropic epoxy resin injection grout used to structurally repair cracked concrete and masonry by the resin-injection process. It is the non-sag companion to Fosroc Nitofill LV: where the LV grade is a thin, low-viscosity resin designed to wick deep into hairline cracks whose faces are fully sealed, the TH grade is a stiffer, paste-like material specifically engineered to minimise resin drainage from cracks that are incompletely sealed, open at one end, vertical or overhead. This makes it the practical choice on real site conditions in India, where cracks rarely present themselves as neat, two-side-sealed laboratory specimens.

The product is supplied as a measured base resin and a matched hardener that are mixed on site to a homogeneous consistency immediately before use. Once cured it forms a rigid, non-shrink, chemically resistant bond that re-establishes load transfer across the crack. Because it bonds well to both dry and damp concrete and withstands water, frost, dilute acids and alkalis, it suits the damp, variable conditions found in basements, water tanks, sewage and effluent structures, and monsoon-exposed external elements.

It is important to position Nitofill TH accurately. Despite being grouped here under joint treatment, it is a structural crack-injection adhesive, not an elastomeric movement-joint sealant. It is designed to glue a static, non-moving crack back together and carry stress across it, the opposite intent of a flexible sealant such as Fosroc Nitoseal or Thioflex, which is meant to accommodate ongoing movement at a designed joint. Choosing the right family for the right defect is the single most important decision on these works, and Space Arc Engineering advises clients on that distinction before specifying.

Nitofill TH carries a CE mark to EN 1504-5 (the European standard for concrete injection products), which underpins its claimed adhesion, injectability and durability performance. For Indian projects it is routinely specified alongside IS 456 durability requirements and structural consultant repair schedules.

The technical insight

The engineering value of Nitofill TH lies entirely in its rheology. A crack-injection epoxy faces two competing demands: it must be fluid enough to penetrate and fill the full depth of a fine crack, yet stable enough not to run back out before it gels. Fosroc resolves this with two grades. Nitofill LV (low viscosity, roughly 150-450 cps depending on temperature) is the penetration specialist but needs both crack faces dam-sealed so the thin resin does not bleed away. Nitofill TH is thixotropic, meaning it behaves as a stiff non-sag paste at rest but shears thinner under injection pressure, then re-stiffens once flow stops. That property lets it be forced into open-ended, through-cracks and soffit/overhead cracks and hold position while it cures, which a low-viscosity grout cannot do. The trade-off is reduced penetration into very fine hairline cracks, so the practical sweet spot for TH is the wider end of the injectable range. Under EN 1504-5 the cured resin develops bond by slant-shear that produces monolithic (parent-concrete) failure, and its CE data confirm a non-volatile content above 95 percent, a glass transition temperature above 40 C and certified injectability into damp cracks, the reason it performs in water-retaining and below-grade work rather than only in dry interiors.

Where it is used

• Structural re-bonding of flexural and shear cracks in RCC beams, columns and slabs identified by a structural consultant
• Injection of through-cracks and open-ended cracks in shear walls, retaining walls and basement raft/wall junctions
• Repair of cracks in water-retaining structures such as overhead and underground tanks, STP/ETP tanks and reservoirs
• Soffit and overhead crack repair on slabs and bridge decks where a low-viscosity resin would drain out
• Re-bonding cracks in load-bearing masonry and stone in heritage and conventional buildings
• Sealing and bonding cracks in damp or water-bearing concrete in tunnels, basements and lift pits
• Restoring monolithic action across cracks in precast units, parking decks and industrial floors before overlay
• Crack repair as part of a wider Fosroc concrete-repair scheme alongside Renderoc / Nitomortar patch repairs

Key advantages

• Thixotropic non-sag consistency lets it be injected into open-ended, vertical and overhead cracks without draining away
• Develops adhesion to concrete that exceeds the parent concrete’s tensile strength, giving monolithic structural continuity (EN 1504-5 slant-shear, monolithic failure)
• Bonds reliably to both dry and damp concrete, suiting Indian basements, tanks and monsoon-exposed work
• Non-shrink on cure, so no loss of bond or surface contact within the crack
• Solvent-free with high non-volatile content (>95%) and certified low corrosion risk to embedded steel
• Good chemical resistance to most dilute acids, alkalis, water, sea water, frost, oils and greases once cured
• CE marked to EN 1504-5, giving consultants a recognised performance basis for specification
• Part of a complete Fosroc repair system (ports, surface sealant, patch mortars) for a single-source, warrantable repair

Limitations & considerations

• It is a rigid structural adhesive, NOT a flexible movement-joint sealant; it must never be used to seal a working expansion or movement joint
• Thixotropy reduces penetration into very fine hairline cracks; for those, the low-viscosity Nitofill LV is the correct grade
• Effective on essentially static cracks only; live, moving or progressively widening cracks need the structural cause addressed first and often a flexible solution
• Short pot life that shortens sharply with temperature (around 40 min at 10 C, 20 min at 20 C, 10 min at 30 C), demanding small batches and disciplined work in Indian summer heat
• Cracks narrower than about 0.5 mm or wider than about 9 mm fall outside the intended injection range
• Requires correct surface preparation, port spacing and crack-face sealing; poor technique causes blow-out, voids or incomplete fill
• Best applied at substrate/ambient temperatures of roughly 5-25 C; very hot or very cold conditions need adjustment or hot/cold-weather practice
• Skilled, trained applicators and proper injection equipment are needed to achieve full-depth, void-free results

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Nitofill TH

Within Fosroc’s range, Nitofill TH sits in the structural crack-injection family rather than the movement-joint sealant family, and that distinction defines its positioning. Its direct sibling is Fosroc Nitofill LV, the low-viscosity grade for fine, fully sealed cracks; together with Nitokit Surface Sealant (crack-face sealing) and epoxy patch mortars such as the Nitomortar / Renderoc range, they form a complete injection-and-repair system. It should not be confused with Fosroc’s true joint sealants, the gun-grade polyurethane Nitoseal range, the polysulphide Thioflex 600, or the pourable hot/cold floor-joint sealant Colpor 200PF, all of which are flexible and designed to accommodate movement, the opposite of what Nitofill TH does. Among competitor brands available in India, the closest equivalents to Nitofill TH are crack-injection epoxies such as Sika Sikadur-52 / Sikadur-31 (and the broader Sikadur injection range), MBS (Master Builders Solutions) MasterInject epoxy resins, and STP / Dr. Fixit structural epoxy injection grouts; note that genuine movement-joint sealants like Sikaflex, MasterSeal/MasterFlex or STP elastomeric sealants are a different product class and are not interchangeable with it. The honest summary: specify Nitofill TH when a structural consultant has identified a dormant crack that must be re-bonded to restore load path, especially when that crack is wide, open-ended, overhead or in damp concrete, and reach for a flexible Fosroc sealant whenever the detail is actually a working joint.

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