A spalled crack is a crack that shows signs of chipping on either side, along some or all of its width. In the TxDOT’s new PMIS (PA) database, this term is applied to

continuously reinforced concrete pavement (CRCP)

. When occurring in jointed concrete pavement (concrete pavement, contraction design [CPCD]), this distress is known as failed joints and cracks since it may occur at either an intentional joint or shrinkage crack (includes asphalt-patched spalls).

Rating is by number of cracks that show spalling at least 1.0-in. wide for CPCD or 3-in. wide for CRCP, and covering more than 1 ft. of the crack length. Spalling on CRCP or CPCD longitudinal cracks are not rated.

Spalling is due to excessive local pressure at the joint. This pressure may be due to a combination of traffic action, thermal expansion, and/or steel corrosion. The occurrence may be exacerbated by over-finishing/excessive consolidation, where excessive surface paste exists, or improper curing.

If cracks become wide enough to allow the introduction of incompressible materials, subsequent expansion by the slab in warmer weather will cause stress concentrations where these materials are found, resulting in spalling. Also, in areas subject to freeze-cycles, water entering the crack may saturate the concrete around the crack. Freezing temperatures may result in freezing and thawing damage, such as spalling, around the crack. Excessive deflection at the crack from traffic loading may also result in spalling. Finally, if the slab is faulted at the crack, the spalling may be a result of traffic striking at the raised edge of the slab.

As a minimum, corrective action will almost always involve cleaning and sealing cracks/joints, but may also include sawing stress relief joints, slab-jacking, patching using bituminous or polymer patching materials, or a thin bonded portland cement concrete (PCC) or HMA overlay.

A punchout is a full-depth block of pavement, formed at the pavement edge, when one short longitudinal crack forms between two existing transverse cracks. The existing cracks are closely spaced, usually less than 4 ft. apart. The punchout is often rectangular, but some may appear in other shapes. Punchouts must be at least 12 in. long or wide to be rated as a punchout. For punchouts longer than 10 ft., rate one punchout for each 10 ft. of length. Punchouts are most common in continuously reinforced concrete pavements. Where they occur in CPCD pavements, the distress is recorded as a failure. The boundary of the punchout will be severely spalled or faulted.

Formation is usually related to surface moisture infiltrating into the base through the closely-spaced transverse cracks and the adjacent longitudinal joint, followed by erosion/pumping of the base and cantilevering of the small slab. Heavy load applications will connect the transverse cracks with a short longitudinal crack. The punchout progresses with spalling of the cracks, possible rupturing of the reinforcing steel, and eventually settlement of the punchout below the original surface of the pavement. Research has shown that punchouts can be partial depth failures, where horizontal cracking initiates at the reinforcing steel plane due to early age stress in the slab. Longitudinal cracking connecting closely-spaced transverse cracks will form along the axis of longitudinal steel due to traffic loading. Furthermore, locations adjacent to transverse construction joints may be more susceptible to this type of failure because of limitations in slip-form paving in their proximity and consolidation practices at the joint. In some cases, the punchout may become dislodged and present a traffic hazard.

Incorporating a non-erodible base and tied concrete shoulders has been the preferred preventative design strategy. Full-depth PCC patching is generally the preferred method of repair for full-depth punchouts. Half-depth PCC patching is the preferred method of repair for partial-depth failures. Asphalt concrete pavement patches may be used temporarily to address safety issues. Rating is in terms of number of occurrences per mile.

In rigid pavements, full-depth repairs to localized distress are often made using asphalt concrete as an expeditious, temporary fix. Asphalt concrete pavement patches used to address spalls are not counted. As with patching in a flexible pavement, proper patching should always involve saw-cut edges parallel or perpendicular to the direction of traffic, with excavation to the full depth of the slab. Patches should be maintained until such time that a full-depth PCC patch can be placed. Where base erosion was a contributing cause of the original failure, permanent repair measures must address the viability of support under the patch.

Asphalt patches are rated in terms of total number observed, with patches longer than 10 ft. counting as two patches. In the new PMIS (PA) system, asphalt patches are a rated category for CRCP pavements only; when these patches occur in a CPCD pavement, they are rated as a failure. Proper patch construction is discussed in Chapter 10, “Rigid Pavement Rehabilitation.”

Concrete patches are localized areas of newer concrete intended as “longer lasting” repairs of localized surface or structural distress and, as such, should be properly tied in to the existing structure to insure load transfer and longevity. An area sufficiently large enough to include the entire distress-affected area must be removed, leaving clean, square edges prior to patching. Failure to do this will often result in propagation of distress immediately adjacent to the patch.

Currently, TxDOT publishes standards for full-depth, full-lane width patches that must be a minimum of 6 ft. in the direction of travel. Patches placed at joints require a minimum of 38 in. on either side of the joint. The depth and size of half-depth PCC patches will vary based on the conditions of partial-depth failures. Concrete patches are evaluated in terms of total number observed. Width of the patch is not considered. However, long patches are rated as one patch for every 10 ft. Proper patch construction is discussed in Chapter 10, “Rigid Pavement Rehabilitation.”

This evaluation is made on CRCP pavements and is used as a method to obtain the percentage of transverse cracks that are spalled, and to determine whether the slab is behaving as designed. Very small crack spacing (< 2.0 ft.) may be a precursor to punchouts, whereas large crack spacing (> 10.0 ft.) may mean wider crack widths that allow non-compressibles in and may have poor load transfer. A recommended technique to evaluate this condition is to count the total number of transverse cracks in two 200-ft. sections (beginning and end of a typical 0.5-mi. section), and then average the results in terms of ft./crack.

This is a CPCD condition category. Failures are localized areas where traffic loads do not appear to be transferred across joints or cracks. Failures are typically areas of surface distortion or disintegration.

Failures are evaluated in terms of total number observed and include the following distresses:

corner breaks, punchouts

(previously discussed),

asphalt patches

(previously discussed),

concrete patches

(previously discussed),

severe faulting, D-cracking, spalls

(asphalt-filled or not – previously discussed), and

popouts

(> 12 in. wide or long, > 3 in. deep):

This is a CPCD condition category. A shattered slab is a slab that is so badly cracked that it warrants complete replacement. Shattered slabs are formed when a series of cracks intersect to divide the slab into four or more pieces. Although the pieces still remain in their original position, they may settle below the original elevation of the pavement. Also, the intersecting cracks can be accompanied by severe spalling. When five or more failures exist on a single slab, or one or more failures encompass more than half the slab’s area, the slab is rated as a shattered slab.

Slab shattering is primarily due to a lack of subgrade support. The base materials may settle, contain voids, or may be susceptible to erosion, resulting in loss of support. Overloading the concrete slab will create excessive bending stresses where the slab has no support. The result is severe cracking, possible spalling, and settlement. The current department policy requires a non-erodible base beneath all rigid pavements.

This is a CPCD condition category. Longitudinal cracks are cracks that follow a course approximately parallel to the centerline of the pavement. These cracks are generally straight but they may curve slightly back and forth across the length of the pavement. Slabs with cracks that are over half the slab in length and show severe spalling (> 1-in. wide on either side for more than half its length), or are faulted at least 1/4-in., are counted as one slab with longitudinal cracks, regardless of the number of such cracks in the slab.

Causes of longitudinal cracking can be related to environmental conditions or improper construction. One possible cause of such cracks is that the joints were not sawn quickly enough during construction (ideally, such joints should be sawn as soon as the concrete can support the sawing equipment). If the slab is too wide or longitudinal joints were not cut deep enough (refer to “Joints” in Chapter 9), plastic shrinkage and lateral thermal contraction can cause a longitudinal crack to appear. Also, swelling soils or loss of foundation support may cause excessive bending stresses in the slab. Finally, warping and curling stresses may be sufficient to initiate longitudinal cracking.

Working cracks (cracks that open and close due to temperature variations and/or traffic loading) are a structural concern – the origin must be addressed to allow for proper remedy.

This is a CPCD condition category. Some transverse cracks may become so wide that they look and act like joints. The crack must be greater than 1/2-in. wide across the complete width of the lane. These ‘apparent’ joints are important to monitor because they do not have load transfer capability outside of frictional contact and potentially become additional traps for incompressible debris that can cause further damage to the slab. At the network level, the minimum value recordable in the new PMIS (PA) database is 15.0 ft. Rating should be accomplished by evaluating a 200-ft. section at the beginning and end of each 1/2-mi. section and averaging the results in terms of ft./crack (joint).

Apparent joints may form for a number of reasons ranging from excessive loading to poor construction practices to environmental reasons. Construction practice shortcomings can include improperly sawn joints, poor dowel bar alignment, poor paste bond on dirty aggregates, and poor curing practices. Environmental contributors include swelling soils, loss of foundation support, and warping and curling stresses.