A blowup is a localized upward movement of a concrete curb or slab, usually at a joint or crack.


Diagnosis: Cracking and subsequent deviation from the straight plane of a concrete element due to forces imposed by thermal expansion.

Cause: The thermal expansion of concrete is around 5.5 millionths of an inch per degree Fahrenheit. Expansion joints are incorporated in designs to take up this linear dimensional change. The problem occurs when the movement is underestimated, not allowed for, or when correctly sized joints become contaminated with material that is not compressible.

Prevention: Provide joints to accommodate the anticipated movement, that incorporates a compressible filler and gland, seal, or cover that will prevent the intrusion of dirt, water or other non-compressible material.

Possible concrete repairs: Strategic cutting should provide temporary dimensional relief and allow gravity to return the concrete to a flat plane. Install an expansion joint, grout repairs and plane flat. Also, it should be noted that it is often quicker and easier to remove and replace an affected section of concrete.