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This paper presents the results of a series of tests run on specimens of a low-plasticity clay (LL = 34, PI = 12) with a calcite content of approximately 25 percent by weight. The naturally occurring clay tested is from playa lake deposits in southern Idaho. This test program investigated the strength of labratory compacted specimens as a function of time and curing conditions.
Specimens of 33.3 mm (1.3 in.) diameter were prepared using the Harvard miniature kneading compaction device. Specimens for strength testing were prepared with water contents at optimum (16.5 percent) and 4.5 percent dry of optimum (12 percent). The latter value is approximately the water content of the material as-sampled. After compaction, specimens were allowed to cure under either air-dry or moist conditions prior to strength testing. The unconfined strength [ASTM Tests for Unconfined Compressive Strength of Cohesive Soil (D 2166-66)] of replicated specimens was measured at times ranging from several minutes to three months after compaction.
The results of these tests showed substantial strength gain with loss of moisture. Most of the increase in strength was experienced within the first 8 h of air-drying while the increase was more gradual for the moist cured specimens. The specimens compacted at optimum water content exhibited higher strengths than those compacted dry of optimum after curing. In the as-molded condition, however, the dry-of-optimum specimens were stronger.
calcareous soils, clays, compaction, compresive strength, curing, kneading compaction, lacustrine clay, moisture content, optimum moisture content, shrinkage, unconfined compression tests
Assistant professor, University of Utah, Salt Lake City, Utah
Design engineer, The Land Group, Salt Lake City, Utah