Physical Properties of Fly Ash‐Amended Soils

Abstract Fly ash from a coal‐fired power generating plant was mixed with five California soils at rates of 0, 2.5, 5.0, 10.0, 25.0, and 50.0% by volume. The physical properties related to the agronomic use of fly ash‐amended soils were characterized by determining water‐holding capacity, bulk density, hydraulic conductivity, and modulus of rupture on laboratory compacted soil cores. The moisture release characteristics of each mixture were also determined. Results indicated that a small amount of fly ash added to soils does appear to affect some measured physical properties of soils. At application rates > 25%, there was a consistent increase in water‐holding capacity (except a Domino loam soil), and a decrease in bulk density and modulus of rupture in all soils tested. The hydraulic conductivity increased with small amounts of fly ash, but declined rapidly as fly ash volume increased. Although fly ash application increased the water‐holding capacity of soils, the amount of water available to the plant did not change significantly. At a low applicant rate, fly ash amendment appeared useful in improving certain agronomic properties of soils.