Use of styrofoam under concrete sidewalks

From 1971 to 1974, a study was made of the freezing characteristics under an insulated and uninsulated sections of a sidewalk. A 1 1/2 inch layer of styrofoam insulation was placed under a newly constructed sidewalk which replaced a one year old sidewalk that was failing from displacement by frost heaving. Temperature recordings were made during three winter seasons. Soil densities and moisture contents were monitored during the second season. The insulation was successful in eliminating heaving and cracking of the sidewalk for the three years which included a maximum freezing index of 1000 degree days as the most severe winter. The uninsulated control section and adjacent city walks and concrete aprons heaved during each of the three winter seasons the mildest of which had a freezing index of 577 degree days. Due to differing permeabilities of soil layers and limited and variable recharging of water to the soil, a correlation with the overall heat flow equation could not be tested. Factors were identified that tend to limit the growth of ice lenses. The effectiveness of an insulation barrier is evaluated in terms of time and prevailing air temperature.