Lesson 3/Learning Event 1
The breaking of a localized section of pavement under traffic with ejection of subgrade soil in a soft and
soupy condition is called frost boil. It is caused by the melting of segregated ice.
Pavement pumping is a problem after free water has collected under the pavement. Water and soil is
ejected through joints, cracks, and along the edges of pavement when the slab is pressed down by heavy
Effect of Frost Action on Pavement Surface
The most obvious surface effect is random cracking and roughness as the result of differential frost
heave. For airfield pavements, it is essential that uncontrolled cracking be reduced to a minimum
because the resulting debris may damage jet aircraft and engines.