8 minute read
Choosing the right technique for economical pavement repair
John Roberts
Executive Director International Grooving & Grinding Association West Coxsackie, New York
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oad preservation and maintenance options today have grown to involve different levels of repair, all with the same anticipated outcome of extending the life of the existing pavement. Full and partial depth concrete pavement repairs are two tried-and-true repair options that are used to address areas on a roadway where deteriorated concrete is impacting ride quality or the structural capability of a pavement. Where these types of repairs are performed—full or partial depth—depends upon the extent and the location of the damage.
Full Depth Repair
Full depth repair involves removing a portion of the existing slab and replacing it with new concrete, returning the deteriorated areas to their original state. Performing full depth repairs can improve pavement rideability and structural integrity while extending pavement service life.
A full depth repair is normally performed for the following types of distresses: blowups or corner breaks, D-cracking, alkali-silica reactivity (ASR), full depth joint deterioration, random transverse cracking, random longitudinal cracking, and punchouts. Whether or not a full depth repair is needed depends on the severity and location of the distress.
Full depth repairs should last as long as the adjacent concrete slabs, as long as proper design and construction procedures are followed. Many full depth repairs are made during preservation and restoration projects that include additional measures such as slab stabilization, dowel bar retrofit, diamond grinding and joint resealing. In using these procedures, the surface where the repairs took place is exposed for the life of the repair making it easier to monitor performance. Covering the distress with an overlay does not correct the cause of the problem and oftentimes the distress manifests itself again, usually as a larger, more expensive problem. This also allows the owner to maintain the existing grade so features such as curbs, gutters, bridge clearances, approach slabs and roadside appurtenances do not need adjustment.
Deteriorated concrete is removed from a road using a carbide mill. Nighttime full depth repair on US 52 Rivers Ave.
Case Study: Full Depth Repairs on U.S. Route 52, Charleston, SC
U.S. Route 52, also known as Rivers Avenue, is a multi-lane highway that passes through South Carolina as it travels across the northern, eastern and southeast regions of the United States. The history of this concrete surface dates back to the mid-1930s, when Rivers Avenue was the main corridor to the Charleston Naval Base.
Sections of the highway had been treated with uncoordinated repairs including improperly placed joints from previous road widening over the decades and frequent asphalt patches used in place of concrete. Washouts and voids underneath the roadway were being treated like potholes and filled with asphalt, and many slabs had shifted over the years, causing joint faults.
Given the generally good structural condition of the pavement, a decision was made to rehabilitate the original concrete using a non-overlay solution. The repair consisted of 8-inch fulldepth concrete patching and then diamond grinding the entire length, including crossovers and intersections, cleaning and sealing of longitudinal and transverse joints, and asphalt median milling and resurfacing.
Because of the high traffic volumes, work was performed at night between the hours of 7 p.m. and 6 a.m. to minimize the impact on the traveling public. One of the challenges for the project team was the lack of adequate quantities as bid to do all the necessary repairs. Consequently the full-depth slab replacement quantities were increased by 65 percent to allow for the repair of all intersecting concrete streets, utility cuts, and proper patch length between joints.
The final product completed in December 2010 is a smooth ride with satisfactory results.
Partial Depth Repair
Partial depth repair is a restoration technique that refurbishes localized surface distress, such as spalling at joints and/or cracks in the upper one-third to one-half of a concrete pavement. When spalls are present on a pavement surface, the ride can be rough and eventually other pavement problems can develop. Partial depth patches replace unsound concrete, restore rideability of the pavement, deter further deterioration, and provide suitable edges for effective joint and crack resealing.
One of the identifying factors in partial depth patches is that they are usually small. Each individual patch typically covers an area less than about 1.2 sq. yards and they are often only 2 to 3 inches deep. When installing a partial depth repair, the extent of the deterioration must be determined, the deteriorated concrete removed, the patch area cleaned, the patch material placed, and then the joint system reformed unless using a hot applied polymer resin for the patch material.
Partial depth repair is most commonly used for spalling, but it can also be used for small areas with severe scaling. Spalling is defined as the breaking, cracking, chipping, or fraying of the slab edges that occurs within 2 inches of joints and cracks or their corners. Cracking, on the other hand, is a fracture through most or all of the thickness of the slab. However, when several small spalls exist along a joint or crack, it may be preferable to repair the full length of the spalled area as one patch. Partial depth repair is usually not recommended for visible spalls that extend more than 6 to 10 inches from the joint and are moderately severe. With such spalls it is possible that more deterioration is taking place below the slab surface. These spalls are often caused by material problems, such as D-cracking, ASR, or by corrosion or lockup of dowel bars at transverse joints. Full depth
Workers place concrete on a partial depth repair operation.
Backfill material is placed on a partial depth repair job.
repair is more appropriate, and recommended, for those distresses. If there is no obvious indication of the depth or cause of the spalling, coring is necessary to determine whether deterioration exists below the surface.
Case Study: Partial Depth Repair in Mosinee, Wis.
The Wisconsin Department of Transportation (WisDOT) roadway repair on U.S. Route 153 in Mosinee included a mile and a half of repairs on a four-lane divided highway. The work on the highway consisted primarily of concrete pavement partial depth repair and some full depth repair.
Repairs began in September 2010 and concluded smoothly in midNovember 2010. The quick 2½ month rehabilitation using the PDR technique was appropriate for the type of deterioration suffered by this highway. In this situation, it was a more appropriate repair than doing a full depth repair, as the remainder of the pavement was still in good functioning condition. Avoiding a full depth repair can reduce the costs involved with repairing the roadway and ease traffic control concerns through the work zone due to its quick turnaround.
The contractor milled out the deteriorated pavement sections and placed the patch mix within the removal area. The repair sections were sandblasted clean and a grout was applied prior to the concrete placement and then cure was applied. All existing joints and random cracks have to be reestablished through the full depth of the repair when using cementitious backfill materials.
The repair quickly restored structural integrity, improved ride quality, and extended the service life of a pavement with moderate deterioration at the joints. Additionally, rather than replacing or overlaying an entire road, an otherwise structurally sound road was kept intact. The speed of the repair opened the highway to traffic within a shorter amount of time, reducing the time delay to motorists.
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Conclusion
Both full and partial depth repair are recommended repair techniques for a public works department’s toolbox. Understanding the differences and knowing when to use one over the other is essential, in order to provide a longlasting pavement at the best cost. For more information of full or partial depth repair, contact the International Grooving & Grinding Association (www.igga.net).
John Roberts can be reached at (518) 731-7450 or jroberts@pavement.com.
About IGGA
The International Grooving & Grinding Association (IGGA) is a nonprofit trade association founded in 1972 by a group of dedicated industry professionals committed to the development of the diamond grinding and grooving process for surfaces constructed with Portland cement concrete and asphalt. In 1995, the IGGA joined in affiliation with the American Concrete Pavement Association (ACPA) to represent its newly formed Concrete Pavement Restoration Division. The IGGA/ ACPA CPR Division now serves as the technical resource and industry representative in the marketing of optimized pavement surfaces, concrete pavement restoration and pavement preservation around the world. The mission of IGGA is to serve as the leading promotional and technical resource for acceptance and proper use of diamond grinding and grooving as well as Concrete Pavement Preservation (CPP) and restoration. For more information, visit www.igga.net.
