Low Temperature Flexibility Asphalt Pavement Sealant

Crack Sealing Benefits and Techniques

WATER IS THE MOST DESTRUCTIVE element to our pavements. If it rained and snowed everywhere but on our roads and bridges, 90 percent of highway and street work would be eliminated. Since that is not likely to happen any time soon, we need to prevent water intrusion into our pavements. Filling or sealing pavement cracks to prevent water from entering the base and subbase will extend the pavement life by three to five years. Filling cracks and joints with asphalt materials (such as AC 20 or asphalt emulsions) is not new. These pavement repair techniques have been commonplace practices for decades. The asphalt materials are intended to fill the crack and keep most of the water out of the pavement. When water is kept out, pavement deterioration is slowed.

DURABLE AND ECONOMICAL PAVEMENTS EXPAND and contract with seasonal temperature changes. Consequently, cracks and joints are expanding and contracting when the pavements move. Fillers do not expand or contract. Sealing the cracks with a flexible rubberized asphalt that bonds to the crack walls and moves with the pavement will prevent water intrusion. Sealing is better than filling. Sealing will last longer and cost less. As part of a pavement management system, crack sealing can reduce pavement deterioration by restricting water penetration into underlying base and subbase layers.

TO ENSURE A MINIMUM STANDARD Performance specifications are written for different movement conditions and pavements. One specification will not cover all crack sealing situations. Before you purchase a sealant, speak with a manufacturer's representative to find out how the sealant was designed to perform. Today's sealants are highly engineered products formulated to perform in some of the most difficult climatic conditions. The ability to produce a material that will not be soft and track in the summer and still be flexible in freezing temperatures requires research.

USING THE RIGHT EQUIPMENT is an important part of any crack sealing program. There are two major areas of consideration: Crack preparation and sealant application. In the same way that a dentist prepares a tooth before filling a cavity, crews must prepare cracks to receive sealants. The better the preparation, the better the chance that the sealant will last and perform. Cracks must be free of all dirt, dust and debris.

SEALANT APPLICATION can be accomplished in a variety of ways. The success of each method is not only determined by configuration but also by cleaning technique and sealant selection. Sealants applied in routed cracks performed longer. A recessed configuration dispenses material into the confines of a routed crack. The sealant can be placed flush with the pavement, slightly below the surface of the pavement or slightly overfilled on the surface. In an over-band configuration, the sealant is placed onto and over an unrouted crack. The sealant can be shaped into a band over the crack using a rubber blade squeegee or a sealing shoe that flattens the sealant over the crack.

PAVEMENT SELECTION is often a forgotten element in determining the success or failure of a crack sealing program. If the road has alligator cracking, high-density multiple cracking, poor subbase drainage or structural damage, crack sealing will not solve the problem. In these cases the damage is too severe. If you try to save a pavement with too much cracking, you will be disappointed with your efforts. The best candidates for crack sealing are newer pavements that are beginning to form cracks.