Sika Polysulphide Gun Grade
A two-component, non-sag polysulphide sealant built for expansion joints that keep moving, resisting water, fuel and UV while holding a permanently elastic, watertight seal.
What is it?
A two-part, gun-applied polysulphide sealant that cures to a tough yet permanently elastic rubber, engineered for expansion and movement joints in concrete and between dissimilar materials.
Where is it used?
Expansion joints in precast concrete, reservoirs and water-treatment plants, bridges, culverts, tunnels, subways, and the rigid pavements of highways, runways and aprons.
Why use it?
It absorbs cyclic joint movement of up to +/-25%, resists water, fuels, oils and solvents, and stays flexible under UV and weathering, so joints stay sealed for years without cracking.
How is it applied?
Mix Part A and Part B at 92:8 by weight with a slow-speed drill, prime the joint faces where needed, then gun the sealant into a bond-breaker-backed joint and tool to a slightly concave finish.
About Sika Polysulphide Gun Grade
Sika Polysulphide Gun Grade is the workhorse joint sealant that specifiers reach for when a movement joint has to stay watertight through years of thermal cycling, settlement and traffic. Supplied as two components, a grey base and a curing agent, it is mixed on site and gunned into the joint, where it chemically cross-links into a firm but permanently elastic rubber. Unlike a one-part sealant that skins slowly and depends on atmospheric moisture, this two-part chemistry cures right through the section on a predictable timeline, which is what makes it dependable in deep or trafficked joints. The non-sag consistency means it holds its shape in the joint mouth rather than slumping, so it can be tooled cleanly and used in joints that are not purely flat.\n\nFor Indian projects, the appeal is durability under punishing service conditions. The cured sealant shrugs off water immersion, spilled fuels and oils, and the intense UV and temperature swings that break down lesser materials, staying serviceable across roughly -40 C to +80 C. That combination is why it turns up in water-retaining structures, on bridge decks and culverts, and along the expansion joints of concrete pavements at highways and airports. As an authorised distributor and applicator across Delhi NCR and Pan-India, Space Arc supplies genuine, batch-fresh Sika material and can advise on joint design, priming and backing so the sealant performs as the data sheet promises rather than failing early through a detailing mistake.
The technical insight
The performance comes from the polysulphide polymer itself. In the pack, Part A carries the liquid polysulphide polymer and fillers while Part B supplies a curing agent; once mixed at 92:8 by weight, the curing agent oxidises the polymer’s terminal thiol groups and knits the chains into a three-dimensional elastomeric network. Because that reaction is chemical rather than moisture-driven, the sealant cures uniformly through its full depth, roughly 6 hours to skin, about 24 hours to initial set and around 7 days to full cure at 30 C, independent of how thick the bead is. The resulting rubber has an elongation of over 450% and elastic recovery above 75%, so it can stretch and rebound with the joint through repeated cycles and still return to shape, which is precisely what a +/-25% movement rating means in practice. The polysulphide backbone is also what gives the material its standout chemical and fuel resistance, letting it be specified in fuelling aprons and industrial areas where hydrocarbon-based sealants would soften and fail.
Where it is used
- Sealing expansion and movement joints in precast concrete elements and panel construction
- Water-retaining structures including dams, reservoirs and water-treatment plants
- Movement joints in subways, bridges, culverts and tunnels
- Rigid concrete pavements of highways, airport runways, taxiways and aprons
- Trafficked joints in industrial floors and hardstandings subject to vehicular loads
- Joints between dissimilar construction materials where a flexible, watertight seal is required
- Fuelling aprons and areas exposed to spilled oils, fuels and solvents
- Perimeter and construction joints in commercial and residential buildings
Key advantages
- Accommodates cyclic joint movement of up to +/-25% without cracking or losing seal
- High elongation over 450% with elastic recovery above 75%, so it rebounds with the joint
- Strong chemical resistance to water, fuels, oils and solvents for industrial and fuelling areas
- Non-sag consistency holds its shape in the joint mouth and tools cleanly
- Two-part chemistry cures right through the section on a predictable timeline, even in deep joints
- Excellent adhesion to concrete, metal, glass and most common construction materials
- Flame and fuel resistant, meeting BS 5212 Type F / FB requirements
- Conforms to BS 4254, IRC:57 and IS 12118, so it fits Indian infrastructure specifications
Limitations & considerations
- Being two-part, each set must be fully mixed on site at 92:8 by weight; incorrect ratio or under-mixing compromises cure
- Full cure takes about 7 days at 30 C before water immersion, fuel contact or traffic is allowed
- Application is limited to a substrate and air temperature window of +5 C to +45 C
- Damp or wet joints require Sika Primer-3 on the faces; skipping the primer risks adhesion failure
- Not suitable for contact with drinking water or food
- Pot life is only about 90 minutes at 30 C, so mixed material must be placed promptly in warm weather
Selection & best practice
Sound joint detailing matters as much as the sealant. Ensure joint edges are clean, dry and structurally sound; cut back and repair any weak arrises with a suitable mortar before sealing. Set the correct depth with a polyethylene backer rod and apply a bond-breaker tape so the sealant bonds only to the two joint faces and not the base, allowing it to stretch freely. Design cyclic joints to a width-to-depth ratio of about 2:1, respecting minimum depths of 5 mm on non-porous surfaces, 10 mm on porous concrete and 20 mm on trafficked or hydraulic joints. Mix Part A and Part B at 92:8 by weight with a slow-speed drill (300 to 600 rpm) for 8 to 10 minutes to a uniform colour, prime with Sika Primer-3 where conditions are damp, then gun the sealant in without trapping air and tool to a lightly concave profile. Mask the surfaces beforehand and strike off before the skin forms, then allow the full 7-day cure before exposing the joint to water, fuel or traffic.
Specifications
| Chemical base | Cross-linking polysulphide, two-component |
| Mixing ratio | Part A : Part B = 92 : 8 by weight |
| Colour | Grey paste |
| Packaging | 4 kg set (Part A 3.68 kg + Part B 0.32 kg), 2 sets per box |
| Density | 1.6 – 1.7 kg/litre at 30 C |
| Movement capability | +/-25% (IRC:57-2006) |
| Elongation | >= 450% (ASTM D882) |
| Joint width / depth | 5 – 50 mm wide; min depth 5 mm non-porous, 10 mm porous, 20 mm trafficked; 2:1 W/D ratio |
| Cure schedule at 30 C | Skin ~6 hrs, initial set ~24 hrs, full cure ~7 days; pot life >90 min |
Industry use cases
Water & Wastewater
Sealing expansion joints in reservoirs, WTPs and STPs, where the sealant stays watertight and elastic under permanent water contact after full cure.
Roads & Highways
Movement joints in rigid concrete pavements and along bridges and culverts, absorbing thermal cycling and traffic loads to +/-25%.
Airports
Runway, taxiway and apron joints, including fuelling aprons, where its fuel and solvent resistance is a decisive advantage.
Precast & Buildings
Joints between precast concrete elements and perimeter joints in commercial and residential structures needing a durable flexible seal.
Industrial Facilities
Trafficked floor and hardstanding joints in plants and warehouses exposed to spilled oils, fuels and cleaning solvents.
Frequently asked questions
Can Sika Polysulphide Gun Grade be used in water-retaining structures?
Do I need a primer?
How much movement can the joint take?
What is the pot life and how long before it can take traffic?
What joint sizes does it suit?
Which standards does it meet?
How we position Sika Polysulphide Gun Grade
Choose the Gun Grade where the joint is not perfectly flat or needs a non-sag material that holds its shape while tooling; for large horizontal joints in pavements and floors, its sister product Sika Polysulphide Pour Grade is often the more economical, self-levelling choice. Pair either with Sika Primer-3 on damp joint faces and a compatible polyethylene backer rod for correct depth. Where a project calls up polyurethane rather than polysulphide, or needs faster cure and higher movement, Sikaflex construction sealants are the natural step across. Space Arc also supplies equivalent joint sealants from Fosroc, STP and other brands, so we can match whatever a consultant has specified rather than force a single option.
Fosroc Thioflex 600 — A specifier standardising on the Fosroc system, or matching an existing Thioflex-based specification, may prefer this equivalent two-part gun-grade polysulphide for the same movement-joint duties.
Related Sealants & Joint Treatment products
Source Sika Polysulphide Gun Grade for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.