Freezing‐Point Depressions in Stabilized Soil Aggregates, Synthetic Soil, and Quartz Sand

The freezing‐point method, using a small probe‐type thermistor as the sensing element, was used to study certain factors believed to lower the freezing‐point depression of soil moisture. The factors investigated were aggregate size, particle size, and undercooling temperature. The materials used were homogeneous and consisted of Palouse silt loam obtained from the A 1 horizon, synthetic soil, and quartz sand. The Palouse silt loam was treated with soil conditioner, formed into aggregates, and separated into groups of various sizes. The freezing‐point depression measured on the various groups of aggregates increased with decreasing size of aggregates. This same trend was obtained for different‐sized sand separates. With successive freezing and thawing, the freezing‐point depression decreased for Palouse silt loam aggregates but was relatively unchanged for sand separates. The synthetic soil was made from ground quartz sand and illite clay. Part of the synthetic soil was treated with various rates of soil conditioner and formed into aggregates. The freezing‐point depression, made on aggregates of 1 to 2 mm. diameter, increased with increasing rate of soil conditioner. Different undercooling temperatures had little effect in changing the freezing‐point depression for Palouse silt loam or sands. However, the freezing‐point depression was increased with increasing undercooling temperatures for nonaggregated synthetic acid‐soil.