Experts agree: For long-lived asphalt pavements and overlays, bond them with a well-placed bond or “tack” coat. But in practice, they’re not applied consistently, compromising the long-term performance of the bituminous surfacing.
Understanding and correct placement of bond or tack coats is essential for long-lived asphalt pavements. New research underscores the importance of bond coats, and new materials are changing how these essential placements are formulated.
They’re better known as tack coats, but “bond coats” better describes their function. The purpose of a bond coat is to “glue” an asphalt overlay to the asphalt layer below.
Today – according to the Asphalt Pavement Alliance – some 94 percent of America’s roads are surfaced with asphalt. But if a strong bond is not created between the layer on which the asphalt driving course is placed, be it asphalt or concrete, the new asphalt surface is at risk of failure.
Bond, or “tack” coats provide the adhesive that binds the asphalt layer to the substrate, adding strength the same way flimsy, thin laminates of lumber are glued together to create strong plywood boards.
