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Lime-Cement Columns: Mix Design and Laboratory Testing

Lime-Cement Columns: Mix Design and Laboratory Testing. Jesse Jacobson, George Filz, and Jim Mitchell. Lime-Cement Columns: Mix Design and Laboratory Testing. Introductory comments Issues at I-95/Route 1 interchange Laboratory test procedure Results for I-95/Route 1 soil

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Lime-Cement Columns: Mix Design and Laboratory Testing

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  1. Lime-Cement Columns:Mix Design and Laboratory Testing Jesse Jacobson, George Filz, and Jim Mitchell

  2. Lime-Cement Columns:Mix Design and Laboratory Testing • Introductory comments • Issues at I-95/Route 1 interchange • Laboratory test procedure • Results for I-95/Route 1 soil • Results for Route 33 soils • Soil water to cement ratio versus strength • Key findings

  3. Introduction Lime-Cement Column Technology • Adding dry lime and cement to clay reduces compressibility and increases strength • Less expensive than “wet” deep mixing, jet grouting, or drilled shafts • More expensive but faster than surcharging with wick drains • Equipment designed for soft ground • No spoil

  4. Introduction Lime-Cement Column Rig

  5. Introduction LCC Mixing Tool – 32” Diameter

  6. Introduction LCC – Finished Column

  7. Introduction LCC – Exposed 32” Diameter Column

  8. Introduction LCC Applications for Embankments on Soft Ground • General applications: • Reduce settlement • Improve stability • Shorten construction time • Particular applications: • Widen existing embankments on soft ground to reduce differential settlement between old and new embankment • Reduce the bump at the end of the bridge

  9. I-95/Rte 1 Issues I-95/Route 1 Interchange

  10. I-95/Rte 1 Issues Reasons for Using Deep Mixing • Schedule requirements • Protect existing features Proposed Embankment Existing Embankment DM Columns Soft Clay Firm Ground

  11. I-95/Rte 1 Issues Problems and Issues at I-95/Route 1 • Different results for laboratory tests performed by two engineering consulting firms • Surprising impact of lime on I-95/Route 1 soil • Poor performance of LCC test columns in a highly organic zone

  12. I-95/Rte 1 Issues Different Labs Produced Different Results

  13. I-95/Rte 1 Issues Surprising Impact of Lime

  14. Lab Procedure Laboratory Test Procedure Based On: • Swedish Geotechnical Society procedure • Procedures of two consulting firms • A few details developed by Virginia Tech

  15. Lab Procedure 35-Step Laboratory Test Procedure Covers: • Storage and handling of soil sample • Soil preparation • Lime and cement preparation • Mixing soil and stabilizer • Forming specimens • Curing specimens • Compression testing • Data reduction and presentation

  16. Lab Procedure Laboratory Equipment and Procedure

  17. I-95/Route 1 Tests Characteristics of I-95/Route 1 Soil Samples • USCS Classification: OH, Organic Silt • LL = 69, PL = 38, PI = 31 • Natural water content = 67% • Organic content = 6% • Clay fraction = 38% • Composition of clay fraction: • 55% montmorillonite • 15%kaolinite • 15% vermiculite • 10% mica • 5% chlorite

  18. I-95/Route 1 Tests Effects of Parameter Variations for I-95/Route 1 Tests • Lime Type: Hydrated and quick lime gave about the same results • Cement: Type I/II and Type II cements gave about the same results • Curing Temp: 28-day strengths increased as the curing temperature increased from 10 to 20 to 40 deg C. • Initial Water Content: 28-day strengths decreased as the initial water content of the soil increased from 52 to 67 to 82 percent.

  19. I-95/Route 1 Tests Effect of Soil Drying on Mixture Strengths • 28-day strengths were lower for soils that were dried and then restored to natural moisture content than for soils that were never dried. • The effect was more pronounced for oven drying than for air drying. • Drying the I-95/Route 1 soil reduced its plasticity and pH

  20. I-95/Route 1 Tests Effect of Soil Drying on Mixture Strengths Never Dried Air Dried Oven Dried

  21. I-95/Route 1 Tests Effect of Soil Drying on Mixture Strengths • We restored the pH of the air-dried and oven-dried soils to about 7 using CaOH • Atterberg limits were unaffected by pH restoration • Mixture strengths were unaffected by pH restoration • Tentative explanation: Drying affects organics, reducing plasticity and making organics more soluble. Widely dispersed soluble organics interfere with cementitious reactions

  22. I-95/Route 1 Tests Effect of Dose Rate andLime-Cement Ratio for I-95/Route 1 Tests • Dose Rate: 100, 150, 200, 250 kg/m3 • Lime-Cement Ratio: 0-100, 25-75, 50-50, 100-0 • Use a contour plot to present test results

  23. I-95/Route 1 Tests Contour Plot of 28-day Strengths Lime Dose Rate (kg/m3) Cement Dose Rate (kg/m3)

  24. I-95/Route 1 Tests Contour Plot of 28-day Strengths Lime Beneficial Lime Dose Rate (kg/m3) Lime Detrimental Cement Dose Rate (kg/m3)

  25. I-95/Route 1 Tests Comparison of H&A, URS, and VT Results

  26. I-95/Route 1 Tests Comparison of H&A, URS, and VT Results • URS samples dried before tests, H&A and VT samples did not • URS reconstituted their samples to higher water content than the natural water contents used by H&A and VT • URS cured samples at 15°C, VT at 20°C, and H&A at 25°C • H&A used a different definition of dose rate that puts more cement in the mixture than URS and VT

  27. Rte 33 Tests Characteristics of Route 33 Zone 1 Soil • USCS Classification: OH, Organic Silt • LL = 109, PL = 52, PI = 57 • Natural water content = 92% • Organic content = 7% • Clay fraction: 65% • Composition of clay fraction: • 55% montmorillonite • 20%kaolinite • 15% vermiculite • 10% mica • 0% chlorite

  28. Rte 33 Tests Characteristics of Route 33 Zone 2 Soil • USCS Classification: OH, Organic Silt • LL = 209, PL = 129, PI = 80 • Natural water content = 120% • Organic content = 15% • Clay fraction: 52% • Composition of clay fraction: • 60% montmorillonite • 20%kaolinite • 3% vermiculite • 15% mica • 2% chlorite

  29. Rte 33 Tests Contour Plots of 28-day Strengths Zone 1 Lime Dose Rate (kg/m3) Zone 2 Cement Dose Rate (kg/m3)

  30. Soil Water to Cement Ratio versus Strength

  31. Key Findings • Laboratory procedure controls critical test variables • Contour plots are a useful way to present results • Increase in curing temperature increases strength • Increase in soil water content decreases strength • Drying and re-hydrating a soil prior to mixing can decrease the mixture strength • Lime can be detrimental to mixture strength for some soils at some dose rates • For L:C::0:100, the mixture strength decreases as the soil water to cement ratio increases

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