What type of bonding agent do Ottawa contractors use between old and new asphalt layers?

The bonding agent between old and new asphalt is a critical but often overlooked component of any Ottawa driveway resurfacing job. Without proper bonding, the new overlay can delaminate and separate from the old surface, especially under the stress of our severe winters.

Tack Coat: The Standard Bonding Agent

The most common bonding agent used by Ottawa asphalt contractors is a tack coat, which is a thin application of asphalt emulsion sprayed or brushed onto the existing surface before the new hot-mix is placed. The two main types are:

• SS-1 (slow-setting emulsion): A water-based asphalt emulsion that "breaks" (the water evaporates) and leaves a thin sticky film on the old surface. This is the most widely used tack coat for residential driveways in Ottawa.
• CSS-1 (cationic slow-setting emulsion): Similar to SS-1 but with a positive electrical charge that helps it bond better to aggregate surfaces. Some contractors prefer this for older, more oxidised asphalt.

Both products are applied at a rate of approximately 0.2 to 0.7 litres per square metre, depending on the porosity and condition of the existing surface.

Why the Bonding Agent Matters in Ottawa

Ottawa's climate creates conditions that actively work to separate asphalt layers. When water infiltrates the interface between old and new asphalt and freezes, it expands with tremendous force. Over a typical Ottawa winter with temperatures dropping to -25 or -30 degrees Celsius and dozens of freeze-thaw cycles, any weakness in the bond will be exploited. By spring, you can end up with sections of the new overlay lifting or cracking along the bond line.

The tack coat creates a waterproof, flexible bond that moves with the thermal expansion and contraction of both layers. Without it, the new asphalt simply sits on top of the old surface like a separate slab.

Surface Preparation Before Tack Application

The tack coat can only bond properly to a clean surface. Ottawa contractors should:

Power-sweep the existing driveway to remove all loose debris, sand, and winter grit

Fill any cracks wider than 6 millimetres with hot rubberised crack filler

Remove any oil stains that would prevent adhesion (common in Gloucester and Kanata driveways with older vehicles)

Ensure the surface is dry before applying the tack coat

If these steps are skipped, the tack coat bonds to dirt rather than asphalt, and the overlay will fail regardless of how thick it is.

How to Verify Proper Application

When the tack coat is first applied, it appears brown or dark amber. As the water evaporates (the "breaking" process), it turns black and becomes tacky to the touch. The new asphalt should be placed only after the tack has broken but while it is still sticky. If the tack has dried completely and is no longer tacky, it needs to be reapplied.

Ask your contractor what tack product they use and ensure it is applied before you see hot-mix being placed. A contractor who skips this step is cutting a corner that will cost you dearly within a few Ottawa winters.

Find experienced asphalt resurfacing contractors through Ottawa Driveways who follow proper bonding procedures for long-lasting overlay results.

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Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• Justyn Rook Contracting
• RenoMotion Inc.
• M.O.T. CONSTRUCTION INC.
• Humble Homes - property maintenance
• ALTIOR CONSTRUCTION

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