|Edwards Jr, James - Jim|
Submitted to: Coal Ash Utilization Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 10/23/1995
Publication Date: N/A
Technical Abstract: Fragipans are naturally occurring subsurface horizons that restrict the depth of root growth to the extent that sustained erosion systematically reduces soil thickness, water storage capacity, and thus productivity. The restrictive nature of these horizons has been attributed to their cementation by amorphous silica, the solubility of which increases rapidly above pH 8.5. Therefore, the addition of a soil amendment with a sufficiently high pH should dissolve cementing agents composed of amorphous silica compounds, and reduce the root restrictive nature of fragipans. Fluidized bed combustion (FBC) ash, at pH 12, was added to the fragipan soil material for this purpose, at rates of 0, 5, 10, and 20 tons per acre. Five replications per amendment rate are to be collected for analysis after equilibration periods of 30, 90, 180, and 365 days. Preliminary results from the 30 and 90 day sampling periods suggest that the addition of ash suppressed the solubility of silica, perhaps due to the chemisorption of Ca, Mg, Fe, and Al to silica surfaces, forming insoluble coatings. The greatest soil strengths were associated with the 5 tons per acre rate. At the higher amendment rates, soil strength gradually declined to a level below that of the unamended soil; however, no definite conclusions can be made at this point in the study.