Applications & Innovations
Better Roads Staff
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 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.
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.
Sealing joints leads to proper joint expansion and contraction and can reduce moisture amounts. This technique also prevents the intrusion of incompressible materials that can cause pressure-related distress such as spalling, buckling and slab shattering.
What material the road contractor selects should be based on their experience level, the traffic level, crack characteristics, climate conditions and cost concerns.
Crews should only place joint sealer when the surface is dry. The sealer is sensitive to temperature, so crews should place it when the pavement and temperature is 40 degrees Fahrenheit or higher.
If the poured joint sealant does not adhere, water or materials can enter the joint and cause poor performance. Problems can also arise if there are poor sealant properties due to over/under heating, the sealant is not sized properly or the joint is too wide.
5. Slab Stabilization
If repairers choose slab stabilization (undersealing) as the mode for repair, they should make sure the joints and working cracks have lost support. If this is not the case, the stabilization is not only wasteful; it could also damage the pavement’s performance.
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