A lack of bond between pavement layers due to insufficient tack coat can lead to which of the following issues?

The presence of a proper bond between pavement layers is crucial for the structural integrity and longevity of asphalt pavements. When the tack coat, which is a layer of adhesive emulsion, is insufficient, it results in a weak interface between layers. This lack of bonding can cause slippage cracks, which are characterized by horizontal cracking that occurs when the upper layer of asphalt slides over the underlying layer.

Slippage cracks arise specifically from this inadequate bond, as the layers can move independently under traffic loads, leading to stress concentrations that ultimately fracture the surface. This phenomenon can exacerbate further pavement deterioration, as water infiltration through slippage cracks can weaken the underlying layers and contribute to other issues down the line, such as potholes or fatigue cracking.

Recognizing the critical role that an adequate tack coat plays in ensuring good adhesion between asphalt layers helps to mitigate the risk of slippage cracks and enhances the overall performance of the pavement structure.