Pavement Inspection

LTD Cracking

Longitudinal, Transverse, and Diagonal (LTD) cracks, which divide the slab into two or three pieces, are usually caused by a combination of load repetition, curling stresses, and shrinkage stresses. Low-severity cracks are usually warping- or friction-related, and are not considered major structural distresses. Medium or high-severity cracks are usually "working" cracks, and are considered major structural distresses.

Severity Distress Example Description
Low Close-up photo of a single tight crack in a PCC slab. The crack has no visible spalling. Crack has little or minor spalling (no FOD potential). If non-filled, it has a mean width less than approximately 1/8 in (3 mm). A filled crack can be any width up to 3 in (76 mm), but the filler material must be in satisfactory condition.
Medium Close-up photo of a single medium-severity crack in a PCC slab. The crack appears to be 1/2 in (13 mm) wide and shows areas of spalling. One of the following conditions exists: (1) filled or non-filled crack is moderately spalled (some FOD potential); (2) a non-filled crack has a mean width between 1/8 and 1 in (3 and 25 mm); (3) a filled crack is not spalled or only lightly spalled, but the filler is in unsatisfactory condition; (4) the slab is divided into three pieces by two or more cracks, one of which is at least medium severity.
High Close-up photo of a single high-severity crack in a PCC slab. The crack appears to be greater than 1 in (25 mm) wide and shows areas of spalling with high FOD potential. One of the following conditions exists: (1) filled or non-filled crack is severely spalled, causing definite FOD potential; (2) a non-filled crack has a mean width greater than approximately 1 in (25 mm), creating a tire damage potential; (3) the slab is divided into three pieces by two or more cracks, one of which is at least high severity; (4) a filled crack is wider than 3 in (76 mm).