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Dowsil 888 Silicone Joint Sealant: A Product Overview
Dowsil 888 is a non-sag, one-part silicone joint sealant purpose-built for concrete pavement joints where movement, weather exposure, and durability are constant challenges. With proven movement capability of +100% extension and -50% compression, it flexes with slab movement instead of tearing apart—so your joints stay sealed through seasonal shifts and heavy use. It extrudes in conditions from cold mornings to extreme heat, giving you job-site flexibility without fighting the material. The result is predictable performance, fewer failures, and no costly callbacks when sealing critical pavement joints first-time-right.
≥1000%
Ultimate elongation delivers extreme flexibility under load
Key Features of Dowsil 888 Silicone Joint Sealant
- Movement capability +100% / -50%: absorbs joint expansion and contraction without failure—no cracking, no callbacks
- Ultimate elongation ≥1000%: stretches under stress and returns without damage, keeping joints sealed long-term
- Non-sag formulation: stays where you place it, even in vertical or irregular joints for cleaner application
- Wide application range (-20°C to 49°C): keeps working across Australian climates, from cold starts to hot pavements
- UV and weather resistant: holds performance in harsh outdoor exposure without breakdown
- Unprimed adhesion to concrete: bonds directly to Portland cement surfaces when clean—cuts prep time and labour cost
- Fast skin-over (≈1 hour): allows efficient workflow and early protection from contaminants
The Dowsil 888 Silicone Joint Sealant Advantage
- Handles real joint movement without failure, protecting against water ingress and structural damage
- Reduces labour time with primer-free adhesion on clean concrete—faster installs, better margins
- Reliable in tough site conditions, so you keep moving instead of waiting on materials
- Built for pavement work where durability matters—confidence the job will last, not come back
Adheseal tips for using Dowsil 888 Silicone Joint Sealant
Scenario: Applying to damp or contaminated concrete
Potential Outcome: Poor adhesion leading to sealant debonding and joint failure.
Adheseal Best Practice: Only apply to clean, dry, frost-free concrete. Proper prep ensures full adhesion and predictable performance—no rework later.
Scenario: Incorrect joint depth or no backer rod
Potential Outcome: Three-sided adhesion causes stress build-up and tearing.
Adheseal Best Practice: Install correct backer rod and follow depth ratios. This allows proper movement and prevents failure—first-time-right sealing.
Applications in Practice: Trade Scenarios
For Civil Contractors (On-Site Applicators): Pavement joint sealing
The Professional's Challenge
Concrete slabs expand and contract constantly. Standard sealants crack or debond, leading to water ingress and joint deterioration.
The Adheseal Solution
Dowsil 888 flexes with slab movement thanks to its high elongation and movement capability. Apply into correctly prepared joints with backing rod to allow full movement. Success means durable, sealed joints that hold under real traffic and weather conditions.
Best Practice Note
Keep sealant recessed 9–13 mm below surface as per joint design. This protects the seal and maintains performance after surface grinding.
For Maintenance Teams (Remedial Specialists): Joint repair work
The Professional's Challenge
Existing joints are irregular, with minor spalling and inconsistent widths—hard to seal properly with rigid materials.
The Adheseal Solution
Dowsil 888 accommodates non-uniform joints while maintaining adhesion and flexibility. Its non-sag consistency allows controlled placement even in difficult repairs. Success means reliable sealing without needing perfect joint geometry.
Best Practice Note
Ensure old sealant is fully removed and joint is clean before installing new material. This prevents contamination and ensures long-term bond strength.
Frequently Asked Questions
What is Dowsil 888 silicone joint sealant used for?
Dowsil 888 is used for sealing concrete pavement joints. It provides flexible, weather-resistant sealing that handles joint movement and prevents cracking or water ingress.
How much movement can Dowsil 888 handle?
Dowsil 888 handles +100% extension and -50% compression. This high movement capability allows joints to expand and contract without failure, delivering predictable performance.
Does Dowsil 888 require a primer on concrete?
Dowsil 888 does not require a primer on clean Portland cement concrete. This unprimed adhesion speeds up application and reduces labour without compromising bond strength.
Can Dowsil 888 be applied in cold or hot conditions?
Dowsil 888 can be extruded from -20°C to 49°C. This wide application temperature range keeps you working across varied site conditions without delays.
Uses & Benefits
Where to Use
- Roadway concrete pavement joints (sawn or formed)
- Airport taxiways, aprons, and tarmacs
- Fuel station forecourts and refuelling pads
- Concrete loading docks and warehouse drive-ins
- Bridge decks and kerb expansions
- Remedial joint resealing in grind-back overlays
Key Benefits
- Outstanding joint movement performance: +100% / -50%
- No primer required on most clean concrete surfaces
- Fast skin-over and long open time for tooling flexibility
- Resists UV, weathering, and short-term fuel exposure
- Low modulus – prevents edge cracking and stress failure
- Compliant with ASTM D5893, FAA P-605, EN 14187-5
Applying DOWSIL™ 888 Silicone Joint Sealant: Enhanced Protocols & Best Practices
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1. Surface & Joint Preparation
Clean the joint thoroughly using wire brushing and high-pressure air. Remove all dust, laitance, curing compounds, and contaminants. Ensure the substrate is dry and frost-free before applying the sealant.
Method A: New Concrete
Allow concrete to cure properly. Saw-cut joints and remove dust with compressed air. Ensure the surface is free of all contaminants.
Method B: Remedial/Grind-Back Joint
Grind and remove old sealant. Clean with abrasive method and air blowout. Ensure surface is recessed and uniform before installation.
Timing: Do not apply during rain or when concrete is damp. Surface must be fully dry before starting.Pro Tip: Use solvent or mechanical prep on heavily soiled or fuel-contaminated surfaces. -
2. Backer Rod Installation
Insert closed-cell backer rod to control sealant depth and prevent three-sided adhesion. Select appropriate diameter to allow compression during insertion.
Standard Method
Place backer rod to a depth that allows sealant thickness of 6–13 mm depending on joint width. Use joint width-to-depth ratio of approximately 2:1.
Grind-Finished Joint
Account for expected grinding depth — place rod slightly deeper (up to 12.7 mm) so final profile sits correctly below the surface.
Timing: Install backer rod immediately prior to sealant application to avoid contamination.Pro Tip: Never puncture or split the backer rod — air pockets can cause sealant failure. -
3. Sealant Application
Dispense DOWSIL™ 888 using a manual, pneumatic, or bulk pump gun. Apply in a continuous motion to avoid air entrapment.
Cartridge Application
Cut nozzle to match joint width and extrude steadily. Tool immediately to avoid skin formation.
Bulk Pump Application
Use an air-powered system for large jobs. Maintain consistent pressure and flow rate above 72 mL/min.
Timing: Tool within 5–10 minutes. Skin forms in ≤1 hour. Avoid rain exposure during early cure.Pro Tip: Use masking tape on joint edges for cleaner lines and remove before skin-over begins. -
4. Finishing, Curing & Cleanup
Tool the sealant to form a concave profile recessed 9.5 to 12.7 mm below the slab surface. Protect from moisture for 8–24 hours. Clean tools using solvent or mechanical wiping before curing completes.
Curing Conditions
Allow 21 days at 25°C / 50% RH for full cure. Cooler temps will extend curing time.
Tool Cleanup
Wipe uncured material using xylene or suitable solvent. Do not use water-based cleaners.
Timing: Protect sealant from rain for at least 8 hours after placement.Pro Tip: Do not disturb or traffic over sealant until full cure is reached to avoid damage.
Limitations & Safety Information
Not for Immersed or Wet Surfaces
DOWSIL™ 888 must only be applied to clean, dry, frost-free surfaces. It is not suitable for use in permanently immersed joints or those exposed to standing water prior to cure.
Not for Asphalt or Bitumen
Do not apply to bituminous or oily substrates. For such joints, consider alternative polyurethane-based or hybrid sealants suited to flexible pavements.
Avoid 3-Sided Adhesion
To maintain proper movement capability, always install a backer rod or bond-breaker tape to prevent adhesion on three sides of the joint.
Storage & Shelf Life
Store in original, sealed packaging below 32°C. Use within the shelf life printed on packaging (typically 12 months from manufacture). Protect from freezing.
Material Safety
Contains moisture-curing silicone polymers. Emits methanol vapours during cure. Use in well-ventilated areas. Avoid inhalation or skin contact with uncured product.
Personal Protective Equipment (PPE)
Wear nitrile gloves, safety glasses, and suitable protective clothing. In enclosed areas, use adequate respiratory protection if ventilation is poor.
Disposal
Dispose of uncured product and contaminated materials according to local environmental regulations. Do not pour into drains or watercourses.
First Aid Measures
In case of skin contact, wash with soap and water. For eye exposure, rinse immediately with water and seek medical attention. Refer to SDS for detailed guidance.
Dowsil 888 Silicone Joint Sealant Application Guide
Concrete (Portland Cement)
Surface Preparation
Ensure concrete is clean, dry, and frost-free. Remove dust, debris, oils, and old sealant residues before application.
Primer Requirements
No primer typically required
Dowsil 888 adheres directly to properly prepared concrete, reducing prep time and improving job efficiency.
Download Dowsil 888 Silicone Joint Sealant Documents
| Document | Type | Download |
|---|---|---|
| Dowsil 888 Technical Data Sheet | TDS | |
| Dowsil 888 Safety Data Sheet | SDS |
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