Abstract: The high cost of handling and the potential reuses of waste foundry sands made the research on waste foundry sands reuse to be attached importance, which is especially beneficial to the improved soil for roadbed. A laboratory testing program was conducted on waste foundry sand and expansive soil-foundry sand mixtures to assess their applicability as improver aimed at the swell-shrink characteristics of the roadbed. The mixtures were compacted in the laboratory at a variety of moisture contents and waste foundry sand content; and the basic physical properties, compaction properties, and mechanical properties were analyzed. The results of the study show that the strength of the mixture is highly dependent on the waste foundry sand content and water content at compaction. Along with increasing waste foundry sand content, plastic index and optimum moisture content gradually decreased; the marginal increment of maximum dry density changed little; and the unconfined compression strength increased at first, then decreased.

Key words: expansive soils, waste foundry sand, improvement, swell-shrink characteristics, maximum dry density, unconfined compression strength