Crack filling or sealing refers to the process of applying hot asphalt cement binder product to the cracks that form in weathered existing asphalt. Asphalt, being a much more flexible material in comparison to concrete, resists freezing and thawing conditions fairly well, but no material is resistant enough to exist longer than a few decades without eventual deterioration. Given enough time, all asphalt pavements will develop significant cracks and shifting of the base underneath that the usefulness of the pavement and its performance is diminished or completely eliminated. The reason crack filling is done is to reduce or limit the amount of moisture that penetrates through the asphalt mats and works its way into the stone base below only to freeze and thaw (in cold climates) and worsen the crack width and depth.
Also crack filling keeps vegetation from growing through the cracks whose roots can further the asphalt crack damage. Lastly, moisture can erode away at the stone and dirt under the asphalt causing unstable base, rutting, and potholes. Crack filling has been shown to be effective enough to increase the life of an asphalt pavement at a much lower cost that complete replacement, enough so to be valuable in terms of a life cycle cost perspective.
A towable wheel-mounted piece of equipment often referred to as a ‘Tar Kettle’ is typically utilized and can range anywhere from a small manual push unit to a large towed unit equipped with seating.
Prior to the application of the liquid asphalt product, cracks are typically exposed to a blast of air to remove dirt and debris, then hit with a heat lance which dries and prepares the crack for application of material.
A hose is attached with a triggered handle to release the hot liquid onto the cracks. The curing or drying time is typically relatively short depending on the temperature and exposure to direct sunlight. Smaller walk behind units are also available for smaller quantities and crack sizes.