PCC Patching

Rigid pavement patches are used to treat localized slab problems such as spalling, scaling (e.g., reactive aggregate distress, over-finishing the surface), joint deterioration, corner breaks or punchouts. If the problem is limited in depth, then a partial depth patch may be appropriate, otherwise a full depth patch is recommended. If the problem is not localized and affects too large a portion of the slab, or the distress is severe, the entire slab may need replacement.

A high quality patch can be considered a permanent repair, although all patches are treated as a form of pavement distress. Although HMA is sometimes used for emergency patches, PCC should be used for permanent patches. Fast-setting PCC is often used to minimize setting time.


Partial Depth Patch

Partial depth patches (Figure 1) are used to restore localized areas of slab damage that are confined to the upper one-third of slab depth. Generally, this includes light to moderate spalling and localized areas of severe scaling (ACPA, 1995[1]). Partial depth patches are usually small, often only 50 – 75 mm (2 – 3 inches) deep and covering an area less than 1 m2 (10.8 ft2) (ACPA, 1995[1]). The generally partial depth patching process proceeds as follows (ACPA, 1995[1]):

  1. Locate the area to be patched. Extend the patch beyond the damaged area by 75 – 100 mm (3 – 4 inches).
  2. Remove the damaged material. Removal is usually accomplished by sawing and chipping. Small areas can be removed by sawing around the patch edges and then chipping out the interior. The patch should be deep enough to remove all the damaged material.
  3. Clean the area to be patched. Sandblasting or water blasting removes loose particles and creates a rough texture to which the bonding agent can adhere.
  4. Apply a bonding agent. A cementitious grout is used to help the patch material bond to the original slab material.
  5. Place, finish and cure the PCC. The PCC should be placed so that the patch is of the same elevation as the surrounding slab. Finishing the patch from the center to the edges helps push the PCC patch material firmly against the existing slab and increases the potential for a high strength bond.
Figure 1. Partial depth patch used to repair spalling damage.

Full Depth Patch

Full depth patches (Figure 2) are used to restore localized areas of slab damage that extend beyond the upper one-third of slab depth or originate from the slab bottom. Generally, this includes spalling, punchouts, corner breaks, moderate to severe slab cracking and localized areas of severe scaling (e.g., reactive aggregate distress, over-finishing the surface) (ACPA, 1995[1]). Corner breaks and punchouts should almost always be patched to full depth. When deciding between a partial and full depth patch for spalling and slab cracking, realize that joint spalls extending more than about 75 – 150 mm (3 – 6 inches) from the joint are indicative of possible slab bottom spalling. Corner breaks and slab cracking are indicative of structural inadequacies that cannot be addressed with partial depth patching. These problems should be addressed using a full depth patch. Figure 3 shows a full depth patch pour.


Figure 2. Full-depth patch preparation.

Figure 3. Pouring a small full depth PCC patch.

A PCC full depth patching process proceeds as follows (ACPA, 1995[1]):

  1. Locate the area to be patched. If the area to be patched is too close to an existing joint or crack, the patch area should be extended as follows:
    • Patch boundary within 2 m (6 ft.) of an existing undoweled transverse joint. Extend the patch to the transverse joint.
    • Patch boundary on an existing doweled transverse joint. If the other side of the joint does not require repair, extend the patch beyond the transverse joint by about 0.3 m (1 ft.) to remove the existing dowels.
    • The patch boundary falls on an existing crack (CRCP). Extend the patch beyond the crack by about 0.15 m (0.5 ft.).
  2. Remove the damaged material. Usually, full depth saw cuts are used to isolate the repair area from the rest of the pavement. Then, the isolated section is lifted out as a whole or broken up and removed.
  3. Prepare the patch area. The base material and subgrade is compacted, smoothed and dried (Figure 4). Dowel bars holes are drilled into the adjacent slab transverse sections and dowel bars are inserted to provide load transfer across the patch boundary. Slab replacements longer than about 4.5 m (15 ft.) require longitudinal tie bars as well (Figure 5).
  4. Apply a bonding agent. A cementitious grout is used to help the patch material bond to the original slab material.
  5. Place, finish and cure the PCC. The PCC should be placed so that the patch is of the same elevation as the surrounding slab. Vibratory screeds are often used to strike off and finish full depth patches.

Figure 4. Base preparation.

Figure 5. Drilling holes for tie bar placement.



Footnotes    (↵ returns to text)
  1. American Concrete Pavement Association (ACPA).  (1995).  Construction of Portland Cement Concrete Pavements.  National Highway Institute Course No. 13133.  AASHTO/FHWA/Industry joint training.  Federal Highway Administration, Department of Transportation.  Washington, D.C.