About Fosroc Nitoseal PU800

Fosroc Nitoseal PU800 (formerly Expoflex 800) is a two-component, gun-grade epoxy-urethane joint sealant engineered for the toughest internal floor joints rather than the moving facade or expansion joints that most polyurethane sealants target. It arrives as a white base paste and a grey curing-agent paste; once power-mixed and gun-applied, it cures chemically to a light-grey seal that is hard but retains a controlled degree of flexibility. Where conventional one-part PU and polysulphide sealants prioritise high movement capability and stay relatively soft, Nitoseal PU800 deliberately trades movement range for mechanical robustness: a high modulus, a Shore A hardness of 65-80 and genuine abrasion resistance.

That positioning makes it a floor-joint and protective sealant first. In factories, warehouses, distribution centres and cold stores, the joints between concrete slabs take repeated point loading from forklifts and pallet trucks, hard-wheeled trolleys and, in retail podiums and shopping centres, stiletto heels. Soft sealants in these joints tear at the arrises, extrude under load or get dragged out. Nitoseal PU800 resists this physical abuse and, because it is hard and bonds tenaciously, it also resists picking and vandalism – which is why Fosroc lists it for secure environments such as prisons, where it seals internal partitions, cell doors and windows, fittings and furniture against tampering.

The product is also a chemical and spillage barrier. It withstands occasional spillage of fuel oils, kerosene, mineral acids (around 25%), alkalis, alcohols, mineral oil, hot detergent solutions and even short exposure to 60% live steam, so it suits process areas, washdown bays and industrial kitchens where the joint, not just the slab, needs protection. It accommodates joints from 5 mm up to 50 mm wide, with a movement accommodation factor (MAF) of 10% to BS 6093 for butt joints – a figure that defines its scope: this is a limited-movement sealant for stable, fully or partly restrained joints, not a 25%-class building-movement product.

For Indian contractors, consultants and procurement teams, Nitoseal PU800 fills a specific gap in the Fosroc range: a heavy-duty, abrasion-resistant, chemically robust floor-joint sealant that sits between flexible movement sealants (Nitoseal MS, Thioflex 600) and the trafficked cold-applied joint sealants (Colpor 200PF). Space Arc Engineering supplies and applies it across Delhi NCR and Pan-India as an authorised Fosroc distributor and applicator.

The technical insight

The defining number is the 10% MAF (BS 6093) for butt joints. Because epoxy-urethane chemistry gives a high-modulus, hard (Shore A 65-80) seal, joint design must keep total movement within that 10% band – this is why Fosroc recommends sealing new slabs only at the final construction stage once temperatures have stabilised and initial drying shrinkage is complete. Get the depth right: for joints under 25 mm on solid backing, seal 10-15 mm deep; over a resilient backer, a 20 mm minimum depth is needed; wider joints prefer a square cross-section rather than the 2:1 width:depth ratio used for soft, high-movement sealants. Pot life is only 1 hour at 25 C, so in Indian summer conditions mix in small batches, load the G-gun immediately and apply above 5 C to avoid prolonged cure. Priming with Fosroc Primer MS2 is mandatory only where the joint will be submerged or permanently damp, with sealant applied 30 minutes to 4 hours after priming – on normal dry internal floors no primer is specified, which speeds installation.

Where it is used

• Construction and contraction (saw-cut) joints in industrial concrete ground-bearing and suspended floor slabs
• Heavy-duty internal floor joints in factories, warehouses, distribution centres and logistics hubs
• Forklift, pallet-truck and MHE traffic lanes where joint arrises take repeated point loading
• Shopping-centre floors, podiums and concourses subject to stiletto-heel and trolley traffic
• Cold-store and process-area joints requiring chemical, detergent and steam-cleaning resistance
• Anti-pick sealing of internal partitions, cell doors/windows, fittings and furniture in prisons and secure facilities
• Washdown bays, plant rooms and industrial kitchens exposed to fuel, oil, mineral acid and kerosene spillage

Key advantages

• Cures to an exceptionally tough, abrasion-resistant seal that survives forklift and hard-wheel point loading
• High modulus and Shore A 65-80 hardness resist extrusion, tearing and picking/vandalism
• Broad chemical resistance – fuel oils, kerosene, mineral acids (25%), alkalis, alcohols, hot detergents and short live-steam exposure
• Handles a wide joint range, 5 mm to 50 mm wide, with a single product
• Gun-grade, non-sag paste that tools off flush for a clean, low-trip-hazard finish
• 100% solids, no shrinkage on cure and a high (>65 C) flash point
• Primer (Fosroc Primer MS2) only needed for submerged/permanently damp joints, simplifying typical dry internal applications
• Trafficable quickly – light traffic at 24 h, full traffic at 48 h (20 C)

Limitations & considerations

• Limited movement only – 10% MAF (BS 6093); not suitable for high-movement expansion or building-facade joints (use Nitoseal MS, Thioflex 600 or Colpor 200PF instead)
• Two-part product with a short 1-hour pot life at 25 C – demands accurate batching and fast application, especially in Indian summer heat
• Not a primary waterstop; for water-retaining/below-ground movement joints use a dedicated waterstop or hydrophilic system
• UV exposure causes some surface discolouration and slight surface hardening, so it is intended for internal use
• Requires power mixing (300-500 rpm with a Fosroc paddle) and a follower-plate G-gun – not a simple cartridge product
• Apply above 5 C; low temperatures prolong cure and impair mixing
• Hard cured finish means it is not the choice where soft, flush, paintable movement sealing is the priority

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Nitoseal PU800

Within the Fosroc joint-sealant range, Nitoseal PU800 occupies the heavy-duty, hard-wearing end of the spectrum. It is not a like-for-like alternative to the flexible movement sealants – for general building, facade and high-movement joints you would specify a low-modulus MS-polymer or polysulphide such as Fosroc Nitoseal MS (and the MS range) or Thioflex 600, which offer much higher movement capability but a softer, less abrasion-resistant seal. For wide, trafficked expansion joints in pavements and floors, Fosroc Colpor 200PF is the cold-applied, fuel-resistant counterpart. Nitoseal PU800’s niche is the tough, high-modulus, abrasion- and chemical-resistant floor joint – and as an anti-pick sealant in secure facilities. Among competitor products, Sika’s Sikaflex and Sikadur-Combiflex systems, BASF/MBCC MasterSeal joint sealants, and STP (Choksey/Pidilite) industrial floor-joint sealants address overlapping applications; the correct choice depends on movement, hardness, chemical exposure and traffic. As an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, Space Arc Engineering supplies genuine Nitoseal PU800, the matching Fosroc Primer MS2 and application accessories, and provides specification support to ensure the joint design, depth and primer choice match site conditions.

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