These cracks, that divide the slab into two or three pieces, are usually caused by a combination of load repetition, curling stresses, and shrinkage stresses. (For slabs divided into four or more pieces, see Shattered Slab.) 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.