Fosroc Thioflex 555
Two-part, self-levelling polysulphide sealant for horizontal concrete joints in roads, runways and fuel-handling pavements — fast-curing, fuel-resistant and rated for 35% movement on butt joints.
What is it?
A two-component, cold-applied polysulphide joint sealant of the self-levelling (pouring) type, supplied in a fast-setting Hand Grade and an ultra-fast-setting Machine Grade for horizontal concrete pavement joints.
Where is it used?
Expansion and contraction joints in concrete roads, runways, taxiways, aprons, hardstandings, parking decks and cargo areas — especially zones exposed to fuel, oil and hydraulic fluid such as aircraft fuelling bays, oil terminals and fuel-station forecourts.
Why use it?
It combines high movement accommodation (35% on butt joints) with proven fuel, oil and jet-blast resistance, fast trafficking times and long service life, so pavement joints stay sealed under heavy wheel and aircraft loading.
How is it applied?
Joints are cleaned and dried, faces primed with Fosroc Primer 7E, a bond breaker / backer rod inserted to control depth, then the mixed base-and-hardener is poured (Hand Grade) or machine-metered (Machine Grade) and self-levels to the joint.
About Fosroc Thioflex 555
Fosroc Thioflex 555 is a two-part, cold-applied polysulphide sealant engineered specifically for horizontal movement joints in concrete pavements. It belongs to the same Thioflex family as the general-purpose Thioflex 600, but is purpose-built for the demands of trafficked roads, airfields and fuel-handling areas where ordinary building sealants fail. The product is a self-levelling (pouring grade) sealant: once the base and hardener are mixed, the material flows and finds its own level inside the joint, producing a smooth, flush surface without tooling. It is supplied in two reactivity grades. Hand Grade is a fast-setting version mixed and poured by hand for smaller areas, road repairs and joints typically up to about 15 mm wide. Machine Grade is an ultra-fast-setting version metered through specialist twin-feed application equipment, used by trained applicators for large runways, taxiways and continuous paving works where rapid re-opening to traffic is critical. Both grades cure chemically rather than by air-drying, so the seal forms reliably even at depth and in cool conditions, and both retain elasticity across the wide temperature swings seen on Indian pavements. The standard supply colour is grey (white base with a black hardener that blends on mixing). The polysulphide chemistry gives Thioflex 555 its defining property for this market: resistance to spilt aviation fuel, diesel, oils and hydraulic fluids, combined with high stress relaxation so the sealant relieves stress rather than tearing the joint arris. For Space Arc Engineering’s clients — airport authorities, NHAI and state highway contractors, refinery and depot operators, and industrial-paving specialists across Delhi NCR and Pan-India — it is a specification-grade answer for joints that must stay watertight and fuel-tight under constant trafficking.
The technical insight
The engineering value of Thioflex 555 lies in the behaviour of its polysulphide polymer. Polysulphides exhibit high stress relaxation — under sustained strain the internal stress decays, so a joint held open at the cold extreme does not keep pulling on the bond line and the sealant does not creep-tear at the arris. This is why the product carries a 35% movement accommodation on butt joints and holds that figure through temperature extremes: it neither hardens and cracks in winter nor slumps and softens excessively in summer heat. The two-part cure is the second key point. Unlike single-part sealants that skin from the surface inward and depend on atmospheric moisture, Thioflex 555 cures throughout its full depth by chemical reaction between base and hardener, which is what allows the deep, poured sections needed in pavement joints to set predictably. The grade choice is essentially a cure-speed decision tied to logistics: Machine Grade reaches a trafficable set in roughly 10 minutes at 35–40°C and about 60 minutes at 5°C, letting a runway re-open in an operational window; Hand Grade is deliberately slower (about 60 minutes at 35–40°C, extending to many hours near 5°C) to give hand crews working time. Crucially, both are self-levelling and therefore only suitable for horizontal or near-horizontal joints — there is no thixotropic gun grade in the 555 line for vertical work, where a non-sag sealant such as Fosroc Nitoseal or a gun-grade Thioflex would be specified instead.
Where it is used
- Transverse and longitudinal expansion and contraction joints in concrete roads and highways
- Runway, taxiway and apron joints at airports and airbases
- Aircraft fuelling bays, hydrant pits and ground-equipment hardstandings where jet fuel spillage occurs
- Oil terminals, refinery roads and fuel-depot pavements exposed to diesel and hydraulic fluids
- Service-station and garage forecourts subject to fuel and oil drips
- Parking decks, container yards and cargo-handling hardstandings under heavy wheel loads
- Concrete hardstandings and loading areas at industrial and logistics facilities
- Floor and pavement joints in warehouses and plant areas requiring chemical-resistant sealing
Key advantages
- High movement accommodation — 35% on butt joints, retained through hot and cold temperature extremes
- Excellent resistance to aviation fuel, diesel, oils and hydraulic fluids — ideal for fuelling areas
- Jet-blast resistant, making it suitable for active taxiways and aprons
- Self-levelling pouring grade gives a smooth, flush, tool-free finish in horizontal joints
- Two-part chemical cure sets fully through the joint depth, not just at the surface
- High stress relaxation and resilience reduce arris tearing and bond-line stress
- Resistant to stone and dirt pick-up, keeping trafficked joints clean and durable
- Two grades available — fast-set Hand Grade for repairs, ultra-fast Machine Grade for large airfield paving
- Long proven service life under continuous heavy trafficking
Limitations & considerations
- Self-levelling only — unsuitable for vertical or overhead joints; use a gun-grade non-sag sealant there
- Two-component product requires accurate full-pack mixing; part-mixing risks under-cure
- Concrete joint faces must be primed with Fosroc Primer 7E for reliable adhesion
- Machine Grade demands specialist twin-feed metering equipment and trained applicators
- Short working time, especially Machine Grade in hot weather, leaves little margin for delays
- Joints must be genuinely clean and dry; moisture, dust or laitance will compromise the bond
- Pot life and cure are temperature-sensitive, so placement must be planned around ambient and substrate temperature
- Not intended for glazing, structural sealing or potable-water contact applications
Selection & best practice
Design the joint before you seal it. For a self-levelling polysulphide, control the sealant depth with a closed-cell backer rod or a bond-breaker tape so the sealant bonds only to the two joint faces and not the base — this two-sided adhesion is what lets the seal stretch and compress without tearing. Follow Fosroc’s width-to-depth guidance (typically around a 2:1 width-to-depth ratio for wider movement joints, with a sensible minimum sealant depth) rather than over-filling, which wastes material and stiffens the joint. Always prepare the joint to bare, sound, dry concrete — saw-cut or rake out, remove laitance, dust and any old sealant, and prime both faces with Fosroc Primer 7E within the primer’s working window. Mix complete base-and-hardener packs to a uniform grey with no streaks; never split a pack by eye. Match grade to job: Hand Grade for smaller areas, repairs and joints up to about 15 mm; Machine Grade, applied by specialist metered equipment, for large runway and taxiway runs needing rapid re-opening. Place only when ambient and substrate temperatures are within the recommended range and rising, account for the faster set in hot weather by planning shorter pour runs, and keep traffic off until the relevant grade has reached its trafficable set. Confirm the live movement accommodation factor, primer and joint dimensions against the current Fosroc TDS for the specific grade on every project.
Specifications
| Product type | Two-component, cold-applied polysulphide joint sealant |
| Grade / consistency | Self-levelling (pouring); Hand Grade (fast-set) and Machine Grade (ultra-fast-set) |
| Movement accommodation | 35% on butt joints, retained through temperature extremes |
| Cure type | Chemical cure of base + hardener (cures through full depth) |
| Hand Grade set time | Approx. 60 min at 35–40°C; 2 hr at 30°C; 4 hr at 20°C; 12 hr at 10°C; 36 hr at 5°C |
| Machine Grade set time | Approx. 10 min at 35–40°C; 15 min at 30°C; 30 min at 20°C; 60 min at 10°C; 90 min at 5°C |
| Standard colour | Grey (white base + black hardener) |
| Primer | Fosroc Primer 7E on concrete joint faces |
| Specific gravity at 20°C | Base 1.36–1.44; Hardener 1.68–1.76 |
| Application temperature | 5°C (rising) to ~50°C; material 15–40°C recommended |
| Joint width (Hand Grade) | Suited to joints up to ~15 mm with ‘G’ gun; consult Fosroc above 50 mm |
| Pack sizes | 5 L, 30 L and 400 L (grade-dependent) |
| Key standards | BS 5212; FED-SPEC SS-S-200E (fuel-resistant); polysulphide to ISO 11600 principles |
| Chemical resistance | Resistant to fuel, oil and hydraulic fluid; jet-blast resistant |
Industry use cases
Airports & Defence Airfields
Sealing runway, taxiway and apron joints, and fuelling-bay hardstandings, where 35% movement, jet-blast resistance and fuel resistance are all required; Machine Grade enables overnight re-opening of active pavements.
Highways & Roads (NHAI / state PWD)
Transverse and longitudinal expansion/contraction joints in concrete carriageways and toll plazas, using fast-set Hand Grade for repairs and Machine Grade for continuous concrete paving.
Oil, Gas & Fuel Logistics
Joint sealing on refinery roads, oil-terminal pavements, depot hardstandings and tanker-loading bays exposed to diesel, fuel and hydraulic-fluid spillage.
Retail Fuel & Automotive
Forecourt and workshop pavement joints at petrol stations, bus depots and vehicle yards where chronic fuel and oil contact would degrade ordinary sealants.
Industrial & Logistics Pavements
Heavy-duty floor and hardstanding joints in warehouses, container yards and cargo terminals subject to constant forklift and trailer trafficking.
Frequently asked questions
Is Fosroc Thioflex 555 a polyurethane or polysulphide sealant?
What is the difference between Hand Grade and Machine Grade?
How much movement can the joint accommodate?
Does it need a primer and a backer rod?
Can Thioflex 555 be used on vertical joints or façades?
Is it suitable for areas with fuel and oil spillage?
How we position Fosroc Thioflex 555
Within the Fosroc joint-sealant range, Thioflex 555 is the specialist horizontal pavement and airfield sealant — the fuel-resistant, fast-curing, self-levelling polysulphide chosen when joints in roads, runways and fuelling areas must survive heavy trafficking and chemical spillage. It sits alongside Thioflex 600, the general-purpose two-part polysulphide for building and civil movement joints, and Fosroc Nitoseal, the polyurethane/gun-grade family used for vertical and non-sag work; for very heavy-duty, high-movement pavement joints Fosroc Colpor (a polyurethane pavement sealant) is the related premium option. Choosing between them is mainly a question of joint orientation, movement and chemical exposure — Space Arc specifies 555 where fuel resistance and airfield-grade performance are the deciding factors. Credible alternatives in the Indian market include Sika’s Sikaflex pavement and PU sealants, MBS / Master Builders Solutions MasterSeal joint sealants, and STP (Shalimar/Pidilite) joint-sealing systems; the right pick depends on the specified standard, movement class, fuel-resistance requirement and applicator capability. As an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, Space Arc Engineering supplies Thioflex 555 in both Hand and Machine grades with the correct Primer 7E and ancillaries, and can provide trained metered-application crews for large airfield and highway projects.
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