What effect does insufficient tacking have on pavement durability?

• A. It enhances durability
• B. It has no effect
• C. It reduces durability
• D. It slightly increases durability

Answer: (C)

Insufficient tacking can significantly reduce the durability of pavement. Tack coat is a bonding layer applied between the existing pavement and the new overlay or asphalt layer. Its primary purpose is to enhance the adhesion between these layers, which is crucial for maintaining the structural integrity of the pavement over time.

When there is insufficient tack, several issues can arise:

1. Delamination: Without an adequate bond, the new asphalt layer is prone to delaminating, which means that the layers can separate under stress, leading to cracks and surface failures.

2. Water Infiltration: A poor bond allows water to infiltrate between the layers. Water plays a major role in the deterioration of asphalt surfaces, as it can lead to weakening of the materials and create voids when it freezes and expands.

3. Reduced Load Transfer: Insufficient tack diminishes the ability of the pavement to transfer loads effectively. This can result in uneven wear and increased stress concentrations that may accelerate pavement distress.

By reducing the overall bond and effectiveness of the layers, insufficient tacking compromises the durability of the pavement, making it more susceptible to various forms of distresses such as cracking, rutting, and eventual failure. Thus, proper application of tack coat is