2.0 Selection of Candidate Projects
Typically, partial-depth repair is used to repair spalling and popouts on concrete pavement. Spalls may be caused by the infiltration of incompressible materials into joints during cold weather when a jointed concrete pavement contracts and the joints open. During warm weather the pavement expands, closing the joints. However, incompressible materials in the joints prevent the joints from closing and produce high compressive stresses along the joint faces. These compressive stresses can cause spalling of the concrete along the joints.
Force may cause spalling at both top and bottom of the pavements. Dowel bar misalignment may also cause joint spalling Spalls may also be caused by the corrosion of metal joint inserts, dowel bars, and reinforcing steel that has been placed too near the surface. Other clauses of spalls include misaligned dowel bars, D-cracking, alkali-silica reactions, and lack of consolidation of concrete near the joints.
If partial-depth repairs are being considered, coring should be performed at representative joints to determine the depth of deterioration. Spalls greater than the top one-third of the slab caused by misaligned dowel bars or significant D-cracking should not be repaired with partial-depth repairs. In these cases, partial-depth repairs are likely to fail due to high shear stresses. The technique is not appropriate for pavements that will be cracked and seated, broken and seated, or rubberized prior to overlay.
The wetter and colder the climate, the greater the need for timely partial-depth repairs. However, spalling can occur in any climate, and proper partial-depth spall repair will help reduce further deterioration. The damage caused by freezing and thawing cycles is a serious problem in jointed PCC pavements. In wet and freezing climates, the continued presence of water on and in the pavement and the use of deicing salts often makes the damages even worse.
Even in non-freezing climates, any moisture in the concrete can cause corrosion of reinforcing steel in the pavement. Corroding steel creates expansive forces that can lead to cracking, spalling, and debonding of the concrete around it. Reinforcing steel without enough concrete cover is even more likely to corrode. Timely partial-depth repair can protect high reinforcing steel that has not yet corroded and can prevent more serious spalling.
Spalling may also occur in dry and freezing climates. Incompressibles that are trapped in a joint when the adjacent slabs contract during freezing create high compressive stresses in the joint face when the pavements expand during thawing. Early repair of nonfunctioning joint sealing systems, along with any adjacent spalling, can protect the joint from further deterioration.