Stabilization of Fine and Coarse-Grained Soils With Lime-Fly Ash Admixtures

As Part of a Research Project for the Evaluation of Lime Flyash as an Admixture for Soil Stabilization, Laboratory Studies Were Made of Eight Fine and Coarse-Grained Soils From Iowa, Kentucky, New Jersey, Texas and Virginia. The Objectives of This Research Were to Study the Effect of Several Important Variables on the Unconfined Compressive Strength of Lime-Flyash Admixtures on the Standard Proctor Moisture-Density Relationship, the Consistency Limits, and the Ph of Soils, and to Evaluate the Resistance of Lime-Flyash Stabilized Soils to Freezing-and-Thawing and Wetting-and-Drying. Results of This Investigation Indicate That: (1) Maximum Density Decreases and Optimum Moisture Content Increases With the Addition of Lime-Flyash, and Maximum Strength Is Obtained at a Moisture Content Equal to or Slightly Less Than the Optimum, (2) Strength Increases With the Thoroughness of Mixing, (3) Strength Increases With an Increase in the Curing Time, (4) Elevated Temperature Curing Greatly Increases Strength, (5) No Consistent Relationship Was Found Between Strength and Relative Humidity During Curing, (6) Specimens Sealed From Contact With the AIr Gave Greater Strength After Six Months or More Curing Than Did Unsealed Specimens, (7) a Combination of Moist Curing and Immersed Curing Gave Increased Strength for Silty and Clayey Stabilized Soils, (8) the Optimum Ratio of Lime to Flyash and the Amount of Lime-Flyash Additive Needed Varies With the Properties of the Soils Used, (9) Small Percentages of Calcium Chloride Additive Gave Substantial Increases in the Strength of Stabilized Clayey and Sandy Soils, (10) Addition of Lime-Flyash Improved the Consistency Limits and Shrinkage Properties of Soils, (11) if Compacted to Near Standard Proctor Density and Moist Cured at Near 100 Percent Relative Humidity and 70 Degrees F. For 7 and 28 Days, Lime-Flyash Stabilized Soils Do Not Meet Present Durability Criteria for Soil-Cement, However, Further Work Needs to Be Done on the Development of a More Realistic Test for Resistance to the Effects of Freezing-and-Thawing and Wetting-and-Drying, and (12) by Compacting Lime-Flyash Stabilized Soil to a Density Greater Than Standard Proctor Density and by Curing at Temperatures Near 140 Degrees F., the Resistance to Freezing-and-Thawing and Wetting-and- Drying Can Be Greatly Improved. /Author/