Crack sealing is often the number one preventive maintenance choice of municipalities to extend the pavement life of parking lots, streets and highways. For optimum results, crews must be educated in the importance of correct application.
The first and perhaps most important aspect of sealant application is timing. During application, both pavement components and sealants react poorly to extreme ambient temperatures. The middle working range for both is between 45 and 65 degrees, making spring and fall the best temperature range for crack sealing. Municipalities in milder coastal areas are able to continue sealing even in winter.
Proper crack preparation is essential. Routing out or saw cutting cracks before application assures a 40 percent greater chance of success. Routing creates a continuous reservoir for sealant and presents straight side walls for the best adhesion. The routing step is often skipped by professionals who go directly to the air cleaning step known as “blow and go.” However, routing and sawing cracks before sealant application is now recommended by the industry and will eventually be specified in most municipal jobs.
Routers are used to widen and deepen cracks in Asphalt Concrete Pavement (ACP). Recommended depths and widths of the routed grove varies depending on traffic use. As a rule, however, a crack should never be routed deeper than 1 inch. Routing should never be executed on cracks that have previously been sealed.
Crack Chasing Saws are used to widen cracks in Portland Cement Concrete Pavement (PCCP). Diamond blades of 5 to 8 inch in diameter allow for easy maneuverability. To ensure proper sealant installation, the cracks should be cut to a depth of 1/2 to 1 inch and typically no wider than 3/8 inch. Sawing is also used in new concrete construction as a preventative to unplanned cracking. New concrete, however, should be cut to a depth of 2 to 3 inches.
Before installing the sealant, the routed or sawed crack must first be cleaned with a high pressure blower to remove loose debris and dust. The prepared crack should then be filled about three quarters full and allowed to cool. While cooling the sealant will shrink in volume about 14 percent. After cooling the crack is then completely filled. Some professionals suggest the over-banding technique, where the sealant is spread approximately 1/2 inch over the pavement on each side of the crack to provide a more efficiently seal from the infiltration of moisture.
Understandably, each municipality has its own methodology. This article puts forth the industry recommended standard believed to bring about the best result. Proper sealant application can extend the life of the road or parking lot surface up to ten years.
