Lime dust, a waste product from limestone mining, and its admixtures with a silty clay and with fly ash from solid waste incineration were tested for various engineering properties and chemical characteristics to determine the suitability of lime dust as a construction material and as an agent of stabilization. The results indicate that lime dust can be classified as a well-graded silty sand (SW-SM) that has an average maximum dry density of 132.8 pcf (2.12 Mg/m3), average friction angle of 45 degrees, average cohesion of 923 psf (44.2 kN/m2), and average permeability of 1.35 × 10−4 cm/sec. The results also show that the addition of 20–30 percent lime dust to silty clay increases its maximum dry density from 105 pcf to 115 pcf (1.67 Mg/m3 to 1.83 Mg/m3), the friction angle from 29 degrees to 31 degrees, and the unconfined compressive strength from 4,752 psf to 6,912 psf (227.4 kN/m2 – 330.8 kN/m2) but has little effect on permeability. The addition of 20–30 percent lime dust to fly ash increases its maximum dry density from 67 pcf to 80 pcf (1.07 Mg/m3 to 1.28 Mg/m3) and shear strength (computed at a normal stress of 1,000 psf or 47.9 kN/m2) from 970 psf to 1,220 psf (46.4 kN/m2 – 58.4 kN/m2), but has little effect on other properties. Bulk chemical analysis results indicate that lime dust is composed primarily of calcium, silicon, and aluminum oxides whereas magnesium, potassium, iron, and sodium oxides each make up less than 3 percent of the total composition. The results of leachate testing show that the lime dust itself is non-toxic but the leachate generated from lime dust-fly ash mixtures exceeds the Environmental Protection Agency's toxicity limits for lead and cadmium. The combined results of physical and chemical testing suggest that lime dust has potential for use as an effective fill material, as an admixture for cover/liner material for sanitary landfills, and as an additive for soil and waste stabilization.