What is a Shattered Slab?
A shattered slab is a concrete pavement slab that intersecting cracks break into four or more pieces. The FAA maintenance circular names overloading by traffic and inadequate foundation support as the main causes.
How the distress is defined
The PAVER manual for concrete airfields lists the distress as number 72, Shattered Slab/Intersecting Cracks. Overloading, inadequate support, or both break the slab into four or more pieces. The manual calls the high severity level of this distress a shattered slab.
The manual sets the severity from the number of pieces and from the severity of their cracks:
| Level | Pieces | Cracks |
|---|---|---|
| Low | 4 or 5 | Mostly low severity |
| Medium | 4 or 5 | More than 15 percent medium severity, no high severity cracks |
| Medium | 6 or more | More than 85 percent low severity |
| High (shattered) | 4 or 5 | Some or all cracks of high severity |
| High (shattered) | 6 or more | More than 15 percent medium or high severity |
Two counting rules apply:
- Do not count shrinkage cracks when you count the pieces.
- Do not record other distress, such as scaling, spalling or durability cracking, on a slab of medium or high severity. The severity of the intersecting cracks already sets the slab rating.
Other cracked slabs
Cracks that divide a slab into two or three pieces are not a shattered slab. PAVER records them as longitudinal, transverse and diagonal cracks (distress 63). A corner break (distress 62) is one crack that meets both joints within half the slab length from the corner. If all the pieces or cracks lie inside a corner break, PAVER records a severe corner break.
Why it matters on an airfield
- The FAA treats this distress as load-related. The Structural Condition Index counts shattered panels at all severities. An SCI of 80 is the FAA definition of structural failure of a rigid pavement.
- Pavement distress can produce loose material that strikes aircraft propellers or enters jet engines. The FAA calls this foreign object debris (FOD), and says all pavement inspections should address it.
- The PCI survey records the distress. A federally obligated US airport must inspect the pavement in detail at least once a year. A PCI survey per ASTM D5340 may extend that interval to three years.
Repair
The FAA circular lists “repair/replace slab” for cracked rigid pavement. Full-depth repair removes all the damaged concrete. The base and sub-base may also need repair when water and pumping damaged them. The circular gives a procedure for full slab replacement in Appendix A7.
Frequently Asked Questions
- What is a shattered slab?
- A shattered slab is a concrete slab that intersecting cracks break into four or more pieces. The PAVER manual gives overloading and inadequate support as the causes. It gives the distress the code 72, Shattered Slab/Intersecting Cracks, and calls the high severity level of that distress a shattered slab.
- How is a shattered slab different from a corner break?
- A shattered slab has four or more pieces, and a corner break is one crack across a corner. A corner break is one crack that meets both joints within half the slab length from the corner. If all the pieces or cracks lie inside a corner break, PAVER records a severe corner break instead.
- Can a slab with only two or three pieces be a shattered slab?
- No. Cracks that divide a slab into two or three pieces are longitudinal, transverse or diagonal cracks, PAVER distress 63. Shrinkage cracks do not count towards the four pieces.
- How do you repair a shattered slab?
- The FAA maintenance circular lists replacement of the slab as a repair for cracked slabs. Full-depth repair removes all the damaged concrete, and the circular has a procedure for full slab replacement. The base may need repair as well if water and pumping damaged it.
References
- paver-concrete
- PAVER Distress Identification Manual, Concrete Surfaced Airfields US Army ERDC-CERL, for the US Air Force (June 2009)
- faa-ac-150-5380-6c
- AC 150/5380-6C, Guidelines and Procedures for Maintenance of Airport Pavements FAA
- faa-ac-150-5320-6g
- AC 150/5320-6G, Airport Pavement Design and Evaluation FAA
- faa-ac-150-5380-7b
- AC 150/5380-7B, Airport Pavement Management Program FAA
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