15 March 2001
DISTRESS 61, BLOWUP
3.1. Description. Blowups occur in hot weather, usually at a transverse crack or joint that is not
wide enough to permit expansion of the concrete slabs. The insufficient width is usually caused
by infiltration of incompressible materials into the joint space. When expansion cannot relieve
enough pressure, a localized upward movement of the slab edges (buckling) or shattering will
occur in the vicinity of the joint. Blowups can also occur at utility cuts and drainage inlets. This
type of distress is almost always repaired immediately because of severe damage potential to
aircraft. Blowups are included for reference when closed sections are being evaluated for
reopening. Deduct curves are shown in Figure 3.1. for blowup.
3.2. Severity Levels.
3.2.1. Low (L). Buckling or shattering has not rendered the pavement inoperative, and only a
slight amount of roughness exists (Figure 3.2.).
3.2.2. Medium (M). Buckling or shattering has not rendered the pavement inoperative, but a
significant amount of roughness exists (Figure 3.3.).
3.2.3. High (H). Buckling or shattering has rendered the pavement inoperative (Figure 3.4.).
(Note: For pavements to be considered operational, all foreign material from blowups
must have been removed.)
3.3. How to Count. A blowup usually occurs at a transverse crack or joint. At a crack, it is
counted as being in one slab, but at a joint, two slabs are affected and the distress should be
recorded as occurring in two slabs.