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Reclamation of Phosphatic Clay Waste Ponds by Capping. Volume 2: Centrifugal Modeling of the Consolidation Behavior of Phosphatic Clay Mixed with Lime or Gypsum

02-030-061Final

Abstract

This part of the research investigates the use of lime and gypsum as additives which might enhance the consolidation of the waste clays.

The results reveal that the pH test provides a rapid method for determining the minimum lime content required for strength producing clay-lime reactions. Lime percentages of approximately 12% were required to achieve the pH level for the clays tested. Miniature vane shear tests showed 28-day strength gains of 3 to 5 times that of untreated clay when 12% lime was added while relatively small strength increases occurred for lower lime contents. In the case of gypsum, the pH test was unsuitable for determining the target gypsum content. Gypsum/clay ratios as high as 12:1 produced practically no strength improvement.

Centrifugal model tests revealed that addition of lime hindered the consolidation magnitude of the clays. In the case of gypsum addition, the consolidation magnitude was enhanced. Consolidation occurred more quickly, and final effective clay solids contents approached those of untreated clay. The behavior of clay/gypsum mixtures is similar to that for sand/clay mixes.

Reclamation of Phosphatic Clay Waste Ponds by Capping.
Other Volumes

FIPR Publication No. 02-030-056
Volume 1: Centrifugal Model Evaluation of Reclamation Schemes for Phosphatic Waste Clay Ponds. University of Florida. April, 1988.

FIPR Publication No. 02-030-062
Volume 3: Evaluation of the Use of Geotextiles for Capping Phosphatic Waste Clay Ponds. University of Florida. April, 1988.

FIPR Publication No. 02-030-063
Volume 4: Piecewise Linear Computer Modeling of Large Strain Consolidation. University of Florida. April, 1988.

FIPR Publication No. 02-030-075
Volume 5: Centrifugal Model Evaluation of the Consolidation Behavior of Phosphatic Clays and Sand/Clay Mixes. University of Florida. March, 1989.

FIPR Publication No. 02-030-073
Volume 6: Consolidation Properties of Phosphatic Clays from Automated Slurry Consolidometer and Centrifugal Model Tests. University of Florida. February, 1989.