Crack sealing is highly cost effective and a lot less expensive than other preventive procedures like an overlay, which can cost 8 to 26 times as much. It’s also great for slowing down the reappearance of secondary cracks (caused by problems within the base course) like reflective cracks. Crack sealing, like any other maintenance project, has to be done with proper economic justification, using proper materials and procedures. State maintenance departments bear most of the burden of dealing with cracks and out of several options available to them (slurry, chip sealing, overlays, etc.), they commonly utilize two solutions: crack filling and crack sealing. While these operations have been routinely conducted for many years; their potential benefits as preventive maintenance tools have only been recognized over the last two decades.
The difference between crack filling and crack sealing The terms crack filling and crack sealing though confused as being one and the same, are different. Although little distinction has been made in the past between crack filling and sealing, the purpose of each should be clearly understood so that the most cost-effective and long lasting crack treatment is used.
Crack sealing is the treatment for working cracks which are defined as having horizontal and/or vertical crack movements greater than 0.1 in (2.5 mm). Transverse cracks are a good example of working cracks; however, some longitudinal cracks may also meet the movement criterion. Specialized materials are placed either above or into working cracks using unique configurations to prevent the intrusion of water and debris into the cracks.
Crack sealants are rubberized products, which are used to seal active (working) cracks that continue to extend both in size and severity with time and the ravages of the traffic and weather. Crack sealants have:
• The ability to seal the crack and flex with the pavement’s movement.
• Excellent adhesive and cohesive properties. In other words they firmly adhere to the walls of the cracks and do not tear or split when the cracks widen.
Crack filling is simply filling the cracks that do not show significant movement, due to the close spacing between the edges. They are called non-working cracks, where horizontal and/or vertical movements less than 0.1 in (2.5 mm). They typically include mostly longitudinal, diagonal cracks and some block cracks. Since minimal flexibility is expected, the materials used for crack filling are non-rubberized products, e.g. crumb rubber, AC-3, and asphalt emulsion.
It is easy to conclude that the requirements for crack sealing are more stringent both from material and equipment considerations than crack filling.
Generally, transverse cracks are the first ones to appear in a pavement. Several different types of cracks may appear during the same period. Under such conditions, one material meeting the most demanding type crack may be appropriate. For deciding whether to fill or seal cracks, the expected movement of the cracks in the pavement should be carefully considered. Generally, non-working cracks with moderate to no edge deterioration should be filled and the ones with limited edge deterioration sealed. Experienced personnel can usually identify the crack type; working or non-working and take the appropriate action.