Concrete pavements face relentless movement. Thermal expansion, contraction, and heavy loads place extreme stress on joints, demanding a sealant engineered for more than just aesthetics. Dowsil 888 delivers the robust, flexible seal these demanding environments need, directly to concrete, without requiring a primer. It ensures joints remain protected against environmental degradation and differential movement, maintaining integrity over time.

Why this product exists

Dowsil 888 Silicone Joint Sealant is a one-part, cold-applied, non-sag silicone material formulated specifically for Portland cement concrete pavement joints. It cures upon exposure to atmospheric moisture, forming a low-modulus silicone rubber designed to accommodate significant movement. This sealant supports new construction, repair, and remedial applications, even in joints that are not uniform in width or exhibit minor spalling, provided its movement capabilities are not exceeded.

The numbers that matter

Its remarkable movement capability of +100% extension and -50% compression means a 10mm joint can reliably expand by 10mm and compress by 5mm, ensuring joints remain sealed through severe thermal and structural shifts. The low modulus design minimises stress transfer to the bond line, enhancing durability in dynamic applications. Crucially, Dowsil 888 offers unprimed adhesion to Portland cement concrete, simplifying application and reducing installation time and material costs. It remains extrudable across a wide temperature range, from -29°C to 49°C, allowing for application in diverse Australian climates.

What it's like to use

Dowsil 888 is supplied as a one-part, cold-applied, non-sag material, ready to use directly from its bulk container. This eliminates the need for mixing on site. Its workability allows dispensing into joints by hand or with an air-powered pump. Surface preparation is straightforward: surfaces must be clean, dry, and frost-free for optimal unprimed adhesion to concrete. The sealant typically achieves a skin-over in an hour or less under standard conditions. Proper joint design, including the correct placement of a compatible backer rod, like those from the Adheseal range, is critical to prevent three-sided adhesion and ensure sealant performance.

Where this product excels

• Civil Construction: Sealing expansion and contraction joints in concrete highways, airport runways, bridge decks, and other critical infrastructure exposed to heavy traffic and extreme weather.
• Industrial Concrete Slabs: Movement joints in large-scale industrial floor slabs and concrete structures that require durable, flexible sealing against thermal cycles and structural movement.

How it fits in a real system

In concrete pavement joint systems, Dowsil 888 acts as the essential final seal. It is installed after the joint has been properly prepared and a backer rod inserted to control sealant depth and prevent three-sided adhesion. The sealant should be recessed below the pavement surface, with specific depths recommended to account for future grinding operations. This careful placement ensures long-term performance and protection of the concrete structure.

Choose this when

• When sealing movement joints in Portland cement concrete pavements that experience significant thermal and structural movement.
• When the project requires a low-modulus sealant with high movement capability (+100% extension / -50% compression).
• When unprimed adhesion to concrete is a key requirement for efficiency and reliability.
• When the joint will be exposed to weather, UV radiation, and short-term fuel exposure.

Don't use this when

• Not for: Applications involving continuous water immersion.
• Not for: Use in totally confined spaces where the sealant is not exposed to atmospheric moisture.
• Not for: Application with asphalt pavements or during inclement weather conditions (wet or damp surfaces).
• Not for: Spill containment areas of any kind, or medical and pharmaceutical uses.