Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/102915
Applications Innovations Applications && Innovations tion of techniques to become a smooth, sturdy pavement. Knowing what signs to look for and how to best treat the area will help road contractors achieve the best long-term results. "The types of repairs range from slab stabilization to joint-crack resealing," Harrington says. "If multiple repairs are required, the sequence of applications needs to be understood and followed." Let's dicuss eight popular types of concrete repair. 1. Full-Depth Repair For major distress pavement areas, full-depth repairs can provide quality performance for 10 to 15 years if crews use the right materials. These repairs normally consist of castin-place concrete that replaces the full depth of the existing slab, or at least a portion of a slab to the bottom of the concrete. This technique can be used where utility cuts are needed in the roadway, to restore problem areas at airports or at deteriorated cracks and joints on highways. One of the most common types, full-depth repairs are usually a full lane-width wide, say12 feet, and 4 to 6 feet long, says the American Concrete Pavement Association. Key techniques for effective full-depth repairs include having adequate working room (a minimum of 6 feet longitudinally), a uniform/stable platform, full-depth perimeter saw cuts, a longitudinal strike-off and being prepared for changes. The success of this repair also depends on installing it at the proper time with the right design. If the slab could disintegrate when lifting it, crews should remove the patch area with a backhoe, angle the lift pins, position the cables and keep the lift height to a minimum. 2. Partial-Depth Repair When only a small area of deteriorated concrete needs to be removed and replaced, partial-depth repair may be the best option. This method is traditionally used where joint or crack deterioration is in the top third of the slab (if it extends below this, usually a full-depth repair is necessary), Harrington says. There are three types of partial-depth repair: spot repair, long joint/crack repair and bottom-half repair. Ranging from 10 inches to 6 feet in length, spot repairs can be used where existing load-transfer devices are still functional. The saw-and-chip method is the most common, but milling is rising in popularity in some areas, according to Daniel Frentress, Frentress Enterprises. With cracks longer than 6 feet, a long joint/crack repair would be best and is usually done with milling. Workers can For a smooth riding surface, repairs needs to made precisely with an understanding of any post-repair needs. For example, allowing for grinding and/ or grooving, which can leave a "like new" surface. use a small jackhammer for the rest of the patch where the mill can't reach. If the deterioration spreads to the full depth at a short distance, a bottom-half repair can be used on the edges or cross-joint locations that are not longer than 18 inches. Steps for partial-depth repair include determining the repair boundaries, removing the concrete, preparing the area by sandblasting or air blasting, placing a strip of polystyrene or polyethylene compressible material in the joint, coating it with grout, adding patch material, applying curing compound and, finally, sealing the joint. 3. Stitching Longitudinal cracks that are in a moderate or fair condition can be repaired with cross-stitching or slot-stitching. With these methods, crews use tie bars to stop the crack from widening vertically and horizontally. Cross-stitching creates a less-exposed surface area and is less intrusive to the slab, compared to slot-stitching. Neither method is intended for severely deteriorated or transverse cracks. If contractors stitch a transverse crack that serves as an adjacent joint, the stitching will not allow the transverse joint to move. This can cause a new crack to form near the stitched working crack. The concrete may also spall over the reinforcing bars. For less-deteriorated cracks, sealing and maintaining the crack may be enough to repair the road. 4. Joint Sealing Well-constructed joints can prevent random cracks and prevent faulting, so repairing them is important for the overall road success. "Concrete repairs have a lot to do with joints," Harrington says. Better Roads January 2013 31