Crack Sealing Treatments

While treating any crack may ultimately provide some benefit to the underlying pavement structure through the reduction of moisture intrusion, the most advantageous applications for crack sealing are block, longitudinal, reflection, and transverse cracks. Unless the crack treatment is done in early-stage distress development, crack treatments for fatigue cracking do not substantially improve pavement performance; however, the treatment may reduce further deterioration of the pavement. 

Reference - NCHRP Report 784 - Best Practices for Crack Treatments

Crack density is a factor to help identify a pavement’s condition and determine whether routing is appropriate when designing a crack treatment. Crack density is calculated by assessing the linear footage of cracks that are present per square feet of pavement area. The percentage of crack density helps indicate potential movement of the cracks that are present, which in turn impacts the sealant selection. Typically, the higher the crack density, the more cracks that are present in the pavement and therefore less movement is anticipated. The lower the crack density, the less cracks that are present in the pavement and therefore higher movement is anticipated. 

It should be noted that there are two fundamental reasons to rout the pavement prior to crack sealing. The first reason is to prepare and clean the edges of the pavement so that there is better adhesion and therefore a better seal that will last longer.  When routing, the operator should remove one-eighth inch from each side of the crack to remove deteriorated asphalt and enable good bonding of the sealant to the asphalt that is still in good working condition.  The second reason is to create a defined reservoir that holds an amount of sealant to accommodate the anticipated annual thermal movement.  The defined reservoir has specific dimensions on width and depth in the pavement depending on climate and other factors which will be detailed later.  

When pavements have a lower crack density, <20%, the pavement condition is typically appropriate to rout the cracks and then seal to accommodate the anticipated movement. In this case, routing prepares the edges for sealing and developing a defined reservoir.  

When pavements have a higher crack density, >20%, the pavement condition is typically not able to sustain a defined reservoir.  In this case, if the pavement can accept the routing without additional spalling, the crack is routed to prepare the edges for sealing and long life. Crack density should be used as a general guideline to help guide appropriate routing. The unique circumstances of each project may determine that routing is or is not appropriate outside of these guidelines. 

Crack sealing is generally conducted in the winter months when cracks are at their widest.  Depending on what climate region you are in, you will need to select the correct crack sealing material.