SL40 Water Repellent

PROSOCO SL40 Water Repellent — Deep-Penetrating 40% Silane Protection for Concrete and Masonry

PROSOCO SL40 Water Repellent is a clear, penetrating silane water repellent formulated as a solution of silane reduced in solvents. Designed for professional contractors treating horizontal and vertical concrete and masonry surfaces, SL40 protects against water intrusion and waterborne contaminants. Its low viscosity and small molecular size allow maximum penetration into the substrate, delivering protection from within rather than relying on a surface film.

Unlike film-forming sealers, SL40 chemically reacts with the substrate to produce a long-lasting water repellent effect while preserving the surface's natural appearance, vapor permeability, and slip resistance. Depth of penetration is directly controlled by the application rate, giving contractors precise control over treatment intensity based on substrate porosity and project requirements.

Technical Specifications

Key Features & Benefits

Long-Lasting Water and Salt Protection

SL40 chemically reacts with the concrete or masonry substrate to deliver durable water repellency rather than a temporary surface coating. This makes it particularly valuable on structures exposed to deicing salts, where ongoing moisture and chloride intrusion can cause serious long-term damage.

Effective Chloride Screen for Reinforced Concrete

SL40 forms an effective chloride screen within the substrate, reducing corrosion of rebar in reinforced concrete caused by water and water-carried salts. For contractors working on parking structures, bridge decks, or other reinforced concrete applications, this protection directly extends service life.

Breathable Treatment — No Trapped Moisture

Treated surfaces retain 90% water vapor transmission (ASTM D6490), meaning moisture already present in the substrate can continue to escape. This prevents the blistering, delamination, and freeze-thaw damage that can result from sealing moisture inside a substrate.

No Surface Film or Gloss

SL40 does not form a surface film or alter surface gloss, keeping surfaces looking natural after treatment. It is also safe for use on surfaces subjected to vehicle traffic and leaves little or no residue on clean window glass, reducing the need for masking or post-treatment cleanup.

Penetration Depth Controlled by Application Rate

Because depth of penetration is controlled by the loading rate, contractors can tailor treatment to the specific porosity and absorption characteristics of each substrate. This flexibility allows appropriate protection levels for both dense and more porous masonry and concrete surfaces.

Reduces Efflorescence, Mildew, and Atmospheric Staining

By blocking water intrusion, SL40 also reduces the conditions that lead to efflorescence, mildew growth, and atmospheric staining. This helps maintain the visual appearance of treated facades and horizontal surfaces over time.

Resists Penetration Over Minor Shrinkage Cracks

SL40 resists water penetration when applied over existing shrinkage cracks of 0.02 inches or less. This provides meaningful protection on surfaces with minor surface cracking without requiring full crack repair before treatment.

Common Applications

Horizontal Concrete Surfaces

Ideal for concrete slabs, plazas, parking decks, and flatwork exposed to water, deicing salts, and vehicle traffic. SL40's vehicle-traffic-safe formulation makes it suitable for areas that cannot be taken out of service for long periods.

Vertical Concrete and Masonry Facades

Provides water repellency on vertical wall surfaces including concrete block, brick, and cast-in-place concrete facades exposed to wind-driven rain and atmospheric contaminants.

Reinforced Concrete Structures

The chloride screen formed by SL40 is particularly beneficial on reinforced concrete structures such as parking garages and bridge decks where rebar corrosion from water-carried salts is a long-term structural concern.

Masonry Walls and Surfaces

Suitable for treating concrete masonry units (CMU), brick, and other masonry substrates to reduce water absorption, efflorescence, and atmospheric staining while preserving the substrate's natural appearance.

New Concrete After Curing

SL40 can be applied to new concrete that has been thoroughly cured for a minimum of 14–28 days, sealing the substrate at the beginning of its service life before damage from water or salts can accumulate.

Compatible Materials

• Concrete (horizontal and vertical)
• Concrete masonry units (CMU / concrete block)
• Brick masonry
• Cast-in-place concrete
• Other masonry substrates (always test natural stone other than limestone, marble, travertine, and calcareous stones)

Limitations

• Not suitable for asphalt or other non-masonry materials
• Not appropriate for use on limestone, marble, travertine, or other calcareous stones — always test other natural stone before full application
• Not recommended for below-grade applications or use under hydrostatic pressure
• Will not prevent water penetration through structural cracks, defects, or open joints
• Not suitable for sale in states and districts with more restrictive AIM VOC regulations (see VOC restriction list above)

Product Documents

• Product Data Sheet
• Safety Data Sheet
• Safety Data Sheet (Spanish)
• SDS Canadian French
• VOC Compliance

Application Instructions

Surface Preparation

1. Protect people, vehicles, property, plants, and all non-masonry surfaces from product, splash, residue, fumes, mists, and wind drift. Divert and/or protect auto and pedestrian traffic.
2. Ensure fresh air entry and cross ventilation during application and drying. Extinguish all flames, pilot lights, and other potential sources of ignition during use and until all vapors are gone.
3. When applying to exteriors of occupied buildings, cover all windows, exterior intakes, and air conditioning vents, and shut down air handling equipment during application and until all vapors have dissipated.
4. If possible, install all caulking, patching, and joint sealants before application. If impractical, test for adhesion and prepare joints as required.
5. Remove all dirt and surface contaminants (including waxes and sealers) with an appropriate PROSOCO cleaner. Do not use raw acids. Rinse thoroughly to remove all cleaning compounds and residues.
6. Let surfaces dry thoroughly before application. Surfaces should be free of dust, surface dirt, oil, grease, and other contaminants that might prevent penetration.
7. Inspect surfaces carefully for dust, dirt, moisture, or other contaminants that can cause the product to react and stain the material.
8. Cap and make the tops of walls watertight prior to application.
9. New concrete must be thoroughly cured for a minimum of 14–28 days before application. Surfaces may be damp but must be absorbent to ensure good penetration.
10. On existing buildings, all caulking, patching, and joint sealants should be in place and cured before application. If SL40 is applied before installation of caulking or sealants, test to verify compatibility.
11. If a chemical curing agent was used on new concrete, conduct a test area just before general application to ensure compatibility. Dissipating-type curing agents are preferred when possible; blanket or water curing is recommended whenever practical.

Safety Data Summary

Hazard Information

• Highly flammable liquid and vapor (Flash Point 35°F / 2°C)
• Harmful if swallowed or inhaled
• Causes skin irritation
• Causes serious eye irritation
• May cause drowsiness or dizziness
• UN Number: UN1866

Personal Protective Equipment

• Wear protective gloves
• Wear protective clothing
• Wear eye protection / face protection
• Use only outdoors or in a well-ventilated area

Safe Handling

• Keep away from heat, sparks, open flames, and hot surfaces — no smoking
• Keep container tightly closed
• Ground/bond container and receiving equipment
• Use explosion-proof electrical, ventilating, and lighting equipment
• Use only non-sparking tools
• Take precautionary measures against static discharge
• Wash face, hands, and any exposed skin thoroughly after handling
• Do not eat, drink, or smoke when using this product
• Avoid breathing dust, fume, gas, mist, vapors, or spray
• Store in a well-ventilated place; store locked up; keep cool
• In case of fire: use CO2, dry chemical, or foam for extinction
• 24-Hour Emergency Information: INFOTRAC at 800-535-5053
• Dispose of contents/container at an approved waste disposal facility

Frequently Asked Questions

Q: Will SL40 change the appearance or gloss of the treated surface?
A: No. SL40 does not form a surface film or gloss, and treated surfaces maintain their natural appearance after application.

Q: Can SL40 be used on surfaces with existing cracks?
A: SL40 resists water penetration when applied over existing shrinkage cracks of 0.02 inches or less. It will not prevent water penetration through structural cracks, defects, or open joints — those should be repaired prior to application.

Q: Is SL40 safe for use on surfaces subjected to vehicle traffic?
A: Yes. SL40 is specifically noted as safe for use on surfaces subjected to vehicle traffic, and it does not form a surface film that would compromise slip resistance.

Q: Can SL40 be used on limestone, marble, or travertine?
A: No. SL40 is not appropriate for use on limestone, marble, travertine, or other calcareous stones. For other natural stone types, a test application should always be performed before full treatment.

Q: How soon after pouring can new concrete be treated with SL40?
A: New concrete should be thoroughly cured for a minimum of 14–28 days before SL40 is applied. If a chemical curing agent was used, a test area is recommended prior to full application to confirm compatibility.

Q: Is this product available for immediate shipment?
A: SL40 is a special order product. Production lead times and quantity minimums may apply. Contact Diamond Tool Store for current availability and lead time estimates.