Investigation of selected properties of specific soil/solid waste mixtures to determine the engineering acceptability in landfill applications

The purpose of this research was to evaluate the suitability of mixtures of a natural clay soil (typical Beaumont clay) and a fertilizer manufacturing waste byproduct (waste gypsum) for use in various types of landfills. A search of the literature revealed the functions required of soils in landfill applications and indicated several laboratory tests that would be useful in evaluating the performance of the mixtures. Samples of the materials were retrieved from the field, dried and mixed in specific proportions. The mixtures were subjected to testing of four properties: (1) Atterberg limits to classify general behavior; (2) moisture-density relationship to evaluate compaction characteristics; (3) permeability to quantify resistance to fluid flow, and (4) unconfined compressive strength. Results indicated the mixtures should be less compressible than natural clay; tend to exhibit less shrinkage when drying; possess less compacted density; have greater moisture retention capability; exhibit good workability; be impermeable, exhibit good strength characteristics. The mixtures would be suitable for most landfill applications and could be used as fill/subgrade for light structures.