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Dowsil 890-SL Silicone Joint Sealant: A Technical Overview
Dowsil 890-SL is a self-leveling, ultra-low modulus, one-part silicone joint sealant designed specifically for horizontal expansion joints in concrete and asphalt pavements. Formulated with high movement capability and excellent adhesion, it delivers long-lasting protection against water ingress, freeze-thaw damage, and joint edge spalling. Its low-modulus chemistry reduces stress at the bond line, making it ideal for roads, highways, airport runways, parking decks, and bridge expansion joints exposed to repetitive vehicle traffic and environmental cycles. The sealant cures with atmospheric moisture, forming a flexible rubber joint that moves with the substrate.
Core Features & Specifications
- Self-leveling formulation — ideal for horizontal joints in trafficable applications
- Ultra-low modulus — reduces stress and accommodates joint movement up to ±25%
- Cures to a durable, flexible rubber that resists UV, ozone, and temperature extremes
- Outstanding adhesion to concrete and asphalt without the need for a primer in most cases
- Fuel-resistant — suitable for airport tarmacs and service station forecourts
- Non-sag, self-leveling — flows easily into joints with no tooling required
- Complies with ASTM D5893, ASTM C920, FAA P-605, and TT-S-00230C (Type II, Class A)
Why Choose Dowsil 890-SL for Pavement Joints?
- Reduces water infiltration and freeze-thaw damage in expansion joints
- Traffic-durable formulation withstands repeated wheel loading
- Backed by Dow’s performance history in major infrastructure projects worldwide
- Wide application temperature range – installs from 4°C to 40°C
- Long service life reduces maintenance and life-cycle costs
±25%
Joint Movement Capability – ASTM C920 Class 25
Best Practices: Do's & Don'ts
Do
- Apply only to clean, dry, sound joints with backer rod or bond breaker tape
- Use closed-cell backer rod to prevent three-sided adhesion
- Protect adjacent surfaces with masking if neatness is critical
Don't
- Do not use in vertical joints or joints with slopes exceeding 3%
- Avoid applying below 4°C or on wet or frosty surfaces
- Do not use in joints subject to hydrostatic pressure or continuous water immersion
Applications in Practice: Trade Scenarios
For Civil Contractors: Highway and Runway Joint Sealing
The Challenge
Pavement joints exposed to traffic and climate cycles require a sealant that can move, resist tearing, and bond reliably to rough concrete surfaces.
The System-Based Solution
Dowsil 890-SL flows freely into horizontal joints, forming a durable, rubber seal that moves with the pavement and protects against joint failure under thermal stress and traffic loads.
Best Practice Note
Apply with a gravity-fed or pressure-assisted bulk dispenser. Ensure joint faces are dry and primed where required. Use bond breaker tape or backer rod to prevent adhesion to joint base.
Performance Comparison: Dowsil 890-SL vs. Traditional Hot-Pour Sealants
| Metric | Dowsil 890-SL | Hot-Applied Sealants | Advantage |
|---|---|---|---|
| Installation Method | Cold-applied | Requires heating kettle | Faster, safer setup |
| Movement Capability | ±25% | ±10% to ±12% | Better flexibility in expansion/contraction |
| Cure Mechanism | Moisture Cure | Thermoset on cooling | More consistent curing in field conditions |
| Tooling Required | No | Yes | Self-leveling saves labour time |
Frequently Asked Questions
What surfaces can Dowsil 890-SL Silicone Joint Sealant be used on?
Dowsil 890-SL Silicone Joint Sealant is formulated for concrete-to-concrete and concrete-to-asphalt pavement joints. It provides excellent unprimed adhesion to Portland cement concrete and asphalt surfaces, even in irregular or spalled joints, making it ideal for infrastructure and road maintenance applications.
How much joint movement can Dowsil 890-SL accommodate?
This sealant offers +100% extension and -50% compression joint movement capability. This ultra-flexible performance ensures long-term durability in concrete and asphalt joints subjected to seasonal expansion, contraction, and dynamic loads.
Can I apply Dowsil 890-SL in wet or damp conditions?
No, the surface must be dry and clean before application. Dowsil 890-SL should not be used on damp or wet asphalt or concrete, as this may compromise adhesion and cure performance.
How long before traffic can pass over the sealed joint?
Under standard conditions (23°C and 50% RH), Dowsil 890-SL will typically become tack-free within one hour. Once skin-over has occurred, light vehicle traffic may resume, but full cure takes up to 21 days depending on temperature and humidity.
Is Dowsil 890-SL suitable for airport runways?
Dowsil 890-SL meets FAA P-605 and is often specified for aviation-related pavements. However, always consult Dow Technical Services for confirmation before using in runway or high-load airfield applications.
Does Dowsil 890-SL require a primer?
No primer is typically required on Portland cement concrete or asphalt. This simplifies installation and reduces labour and material costs. For other substrates, a test patch is recommended or consult with Adheseal technical support.
Applications & Benefits
| Application / Use Case | Key Benefit | Primary Trades |
|---|---|---|
| Concrete-to-concrete pavement joint sealing | Absorbs extreme joint movement and prevents cracking | Civil Contractors, Road Builders, Remedial Specialists |
| Concrete-to-asphalt transitions | Provides durable, elastic seal without stressing asphalt edges | Road Maintenance Crews, Builders, Councils |
| Airfield taxiway and apron joints | Fuel-resistant and compliant with FAA P-605 standards | Airport Maintenance Contractors, Engineers |
| Remedial joint sealing over spalled or irregular joints | Flows into gaps without tooling, restoring watertight seals | Remedial Contractors, Infrastructure Specialists |
| Fast-turnaround roadworks and patching | Skin-over in under an hour allows quicker traffic re-entry | Road Crews, Emergency Repair Teams |
Applying Dowsil 890-SL Silicone Joint Sealant: Enhanced Protocols & Best Practices
-
Surface Cleaning & Joint Preparation
Ensure all joint surfaces are clean, dry, and free of dust, oil, moisture, or loose materials. Remove old sealant and clean to full depth using compressed air or mechanical tools.
Method 1: Mechanical Cleaning
Use a wire wheel or abrasive grinder to expose clean concrete or asphalt joint edges. Recommended for heavy contamination or remedial work.
Method 2: Air Blasting
Use oil-free compressed air to remove fine particles and moisture from saw-cut joints. Ideal for new concrete or routine re-seals.
Timing: Immediately before application, especially in humid or dusty conditions.Pro Tip: Never apply to wet surfaces — allow sufficient drying time after rain or pressure washing. -
Backer Rod Installation
Select a closed-cell backer rod with a diameter 25% larger than the joint width. Insert it to proper depth to control sealant depth and prevent three-sided adhesion.
Shallow Cut Joints
Install rod to a depth that allows for 6–13 mm of sealant, depending on joint width. Refer to Dow’s table for size-specific recommendations.
Deep Cut / Repaired Joints
Use dual-layer or larger rods to maintain consistent sealant thickness and recess even in uneven joints.
Timing: Immediately after surface prep, before applying sealant.Pro Tip: Ensure rod is not twisted or punctured during installation to avoid air pockets under sealant. -
Sealant Application
Apply Dowsil 890-SL directly into the joint using a bulk gun, cartridge, or pump setup. The product self-levels, filling the joint evenly without tooling.
Cartridge Application
Use 857 mL plastic cartridges with a heavy-duty dispensing gun. Ideal for smaller patchwork and on-site repairs.
Bulk Pumping
Use pneumatic or electric pump to dispense from 17 L pails or 189 L drums for large-scale joint sealing projects.
Timing: Apply during dry conditions, between 10°C and 35°C ambient temperature.Pro Tip: Slightly overfill the joint to allow for self-leveling and settling into irregular voids. -
Curing & Traffic Re-Entry
Under normal conditions (25°C, 50% RH), the sealant will become tack-free within 1 hour and cure fully in 21 days. Light traffic may resume once the sealant skins over.
Standard Conditions
Allow at least 1 hour before light traffic exposure. Use signage or barriers to protect fresh joints.
Cool/High-Humidity Conditions
Extend cure and skin time accordingly. Avoid application below -6°C or above 38°C surface temperature.
Timing: 1 hour to skin over; 21 days for full cure at standard temperature and humidity.Pro Tip: For critical applications, verify skin time onsite to avoid premature traffic reopening.
Limitations & Safety
Product Limitations
Not suitable for use in continuously immersed joints, such as water tanks, swimming pools, or fountains.
Do not apply in fully enclosed spaces where moisture cannot reach the sealant to trigger curing.
Avoid use on wet or damp substrates. Joint surfaces must be completely dry before sealant installation.
Not warranted or recommended for airfield runway joints without prior consultation with Dow technical services.
Not tested for use in spill containment zones involving prolonged chemical exposure.
Safety & Handling Requirements
Personal Protective Equipment
Wear chemical-resistant gloves, safety goggles, and long-sleeved clothing to minimise skin and eye contact. Use in well-ventilated areas.
Ventilation Requirements
Ensure adequate ventilation when using bulk sealant indoors or in enclosed structures. Avoid inhaling vapours during application and curing.
Fire & Handling Precautions
Although non-flammable, store away from heat sources and open flames. Follow standard industrial hygiene practices when handling sealant.
Emergency First Aid
Eyes:
Flush eyes immediately with running water for 15 minutes. Seek medical attention if irritation persists.
Skin:
Remove contaminated clothing and wash skin thoroughly with soap and water.
Inhaled:
Move to fresh air. If symptoms such as dizziness or nausea occur, seek medical assistance.
Swallowed:
Do not induce vomiting. Rinse mouth and contact a poison control centre or medical professional immediately.
Seek medical attention immediately in all cases of serious exposure.
Dowsil 890-SL Silicone Joint Sealant Application Guide
Portland Cement Concrete
Surface Preparation
Clean and dry surface thoroughly. Remove all dirt, dust, old sealant, curing compounds, and loose particles. Ensure joints are saw-cut to proper depth with clean edges and no standing moisture prior to application.
Primer Requirements
No primer typically required
Excellent adhesion is achieved without primer under normal conditions. A test patch is advised for unusual concrete mixes or aged surfaces.
Asphalt Pavement
Surface Preparation
Ensure asphalt is fully cured, dry, and free from oils, bitumen bleed, and debris. Do not apply during or after rainfall or when dew or moisture is present. Joints should be cleaned to full depth prior to application.
No primer typically required
The ultra-low modulus formulation is ideal for asphalt's lower tensile strength. Primer-free installation is common but confirm performance via test patch in critical applications.
Spalled or Irregular Joints
Surface Preparation
Thoroughly clean joint area to remove loose aggregate and contaminants. Use a wire brush or mechanical method for edge profiling. Ensure joint width meets minimum movement accommodation guidelines.
Primer recommended for optimal adhesion
In spalled areas, primer may improve bonding to marginal surfaces. Consider Dowsil Primer P when adhesion to eroded or compromised edges is uncertain.
Dowsil Primer PPre-Existing Sealant Repairs
Surface Preparation
Completely remove all old sealant residues and backer rods. Mechanically clean the joint walls using saw-cutting or abrasive methods. Ensure a clean bonding surface is exposed.
Primer recommended for optimal adhesion
If full removal of contaminants cannot be guaranteed, apply primer to ensure adhesion continuity. Especially critical in remedial work with high movement expectations.
Dowsil Primer P
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