Lesson 3/Learning Event 1
FIGURE 17. DETERMINATION OF FREEZING INDEX
Frost Susceptible Soil
To a large extent, the size of voids in a soil determines its susceptibility to frost. Most inorganic soil.
containing three percent or more grains finer than 0.02mm in diameter by weight are frost susceptible
for pavement design purposes. Gravels, well graded sands, and silty sands which contain 1-1/2 to 3
percent grains finer by weight than the 0.02mm size should be considered possibly frost susceptible and
should be subjected to a standard laboratory test. Sandy soils with as much as ten percent of their grains
finer than 0.02mm by weight may not be frost susceptible, but their tendency to be imbedded with other
soils makes it impractical to consider them separately.
Frost susceptible soils are susceptible to a process called ice segregation. The ice segregation process
occurs as follows: Water in very small void spaces remains liquid below the normal freezing
temperature of water. A strong