October 9, 2008 Spokane, Washington

1. The Washington State County Road Administration Board Designing for Society: Knowledge, Innovation, and Sustainability Fundamentals of Design and Construction of Full-Depth Reclamation Pavements Gregory E. Halsted, P.E. Program Manager – SC/RCC Pavements Portland Cement Association October 9, 2008 Spokane, Washington

2. Since its founding in 1916, the Portland Cement Association has had the same mission: "Improve and expand the uses of portland cement and concrete." • Divisions • Market Promotion • Research • Technical Services • Codes and Standards • Affiliates • American Concrete Pavement Association • The CTL Group • Cement Association of Canada

3. Regional Promotion Groups

4. Cement-Based Pavement Materials Roller-Compacted Concrete Conventional Concrete Pervious Concrete Soil-Cement No Wearing Course Required Cement- Treated Base Wearing Course Required Cement Content Flowable Fill Full-Depth Reclamation Cast Cement-Modified Soil Rolled Water Content

5. Concrete Soil-Cement • Cementitious Gel or Paste • coats all particles • fills voids • Hydration Products • all particles not coated • voids not filled • linkages bind soil • agglomerations together

6. Soil-Cement Materials in a Pavement Section

7. Cement-Modified Soil (CMS) The objective of CMS is to amend undesirable properties of problem soils or substandard materials so that they are suitable for use in construction. The amount of cement added to the soil is less than that required to produce a hardened mass but is enough to improve the engineering properties of the soil.

8. Reasons to Modify • Improve the properties of the subgrade soil • Reduce volume change caused by moisture • Improve wet strength • Improve compactibility • Expedite construction by improving subgrade support in wet weather • Eliminate muddy construction sites • Create an all-weather work platform It is important to remember that soil modification is different than soil stabilization

9. Benefits of Cement-Modified Soil • Small addition of cement to soils to change properties • Eliminates need for removal/replacement of inferior soils • Low cost soil improvement • Improves pavement support • Forms weather-resistant work platform • Provides permanent non-leaching modification

10. Cement-Treated Base (CTB) CTB refers to an intimate mixture of soils and/or aggregates with measured amounts of portland cement and water that hardens after compaction and curing to form a strong, durable, frost resistant paving material. CTB can be mixed in place using on-site materials, or mixed in a central plant using selected material.

11. What is CTB? • Extremely dense • Intimately blended • Highly compacted • Mixture of • Aggregates or soil or combinations • Portland cement • Water • Base or subbase for either concrete or bituminous surfacing • Stable platform as a building pad • Provides wet-dry and freeze-thaw durability

12. Why Use CTB? • Low first cost and life cycle cost • Allows thinner pavement sections • Can use in-situ materials • Reduces use of virgin aggregates • Reduces moisture susceptibility • Frost resistant • Spans weak subgrades

13. Full-Depth Reclamation (FDR) The FDR process pulverizes the existing asphalt and blends it with underlying base, subbase, and/or subgrade materials, which are mixed with cement to provide a new stabilized base. A new surface is then applied, providing a new roadway structure using recycled materials from the failed pavement.

14. Definition of Reclamation • Method of flexible pavement reconstruction that utilizes the existing asphalt, base, and subgrade material to produce a new stabilized base course for a chip seal, asphalt, or concrete wearing surface. • Alternative Terms: • Full-Depth Recycling (FDR) • Full-Depth Rehabilitation (FDR) • Cement Recycled Asphalt Base Stabilization (CRABS) • Cement-Treated Base (CTB) • Cement-Treated Existing Roadway Materials (C-TERM) • Cement Stabilized Reclaimed Base (CSRB) • Full-Depth Reclamation with Portland Cement (FDR-PC)

15. Challenges FacingAmerica’s Roadways • Continuing Growth • Rising Expectations from Users • A Heavily Used, Aging System • Environmental Compatibility • Changes in the Workforce • Funding Limitations • Combined with large increases in traffic volumes and/or allowable loads often leads to serious roadway base failures!

16. How do you know if you have a base problem and not just a surface deficiency?

17. Examples of Pavement Distress • Alligator Cracking • Rutting • Excessive Patching • Base Failures • Potholes • Soil Stains on Surface

18. Advantages of Reclamation • Use of in-place materials • Little or no material hauled off and dumped • Maintains or improves existing grade • Conserves virgin material • Saves cost by using in-place “investment” • Saves energy by reducing mining and hauls • Environmentally friendly

19. Engineering Benefits • Increased Rigidity • Spreads Loads • Eliminates Rutting • Below Surface • Reduced Moisture • Susceptibility • Reduced Fatigue • Cracking • Thinner Pavement • Section • Retards Reflective • Cracking

20. DESIGN

21. Obtain representative samplesfull length, width, and depth!

22. Laboratory Tests • Sieve Analysis (ASTM C136) • Atterberg Limits (ASTM D4318) • Moisture-Density (ASTM D558) • Durability Tests • Wet-Dry (ASTM D559) • Freeze-Thaw (ASTM D560) • Soluble Sulfates (ASTM C1580) • Compressive Strength (ASTM D1633)

23. PCA Recommended Particle Size Distribution for Full-Depth Reclamation • 100% passing a 3-inch sieve • 95% passing a 2-inch sieve (min) • 55% passing a No. 4 sieve (min)

24. Laboratory Mix Design • Sieve a sufficient quantity of the roadway material through the ¾-inch sieve to determine maximum dry density (MDD) and optimum moisture content (OMC) at various cement percentages (ASTM D558) • Usually about 100 pounds of dry soil is required • Determine MDD and OMC • 4, 6, and 8 percent cement • By weight of dry material • Prepare samples with cement • 9 specimens • 3 at each percentage

25. Strength Determination • Unconfined Compressive Strength Testing • ASTM D1633 • Used by most State DOT’s and the FAA • Simple and quick procedure • 7-day strengths ranging from 300 psi to 400 psi are generally recommended • Proven strength (support) under heavy traffic conditions • Proven durability (performance) in both wet-dry and freeze-thaw environments

26. Please keep in mind that strength and durabilityare NOT the same thing! The purpose of the mix design procedure is to select the correct additive that most closely balances both strength AND performance for the roadway materials!

27. Determining the thickness ofFDR pavements Commonly used methods include those based on layer coefficients for the different pavement materials and those based on a more mechanistic-empirical approach. ?

28. Thickness Design • AASHTO • Use layer coefficients 0.12 to 0.30 • Compare with granular base 0.06 to 0.18 • Design Equation: • Structural Number = a1D1+ a2D2+…+ anDn a1 Layer Coefficient D1 a2 D2 a3 D3 3-Layer Pavement Section

29. 5.75 in Thickness Design • PCA • Empirical method • Based on subgrade strength, material type, axle loads, and frequencies • Publication EB068: Thickness Design for Soil-Cement Pavements

30. CONSTRUCTION

31. An easy construction process whencontrolled by good specifications! • Processing • Compacting • Finishing • Curing • Surfacing

32. Pulverization • Pulverize mat to appropriate gradation • Usually, only one pass is required!

33. Material Removal(if necessary)

34. Cement Spreading • Cement is spread on top of roadway in measured amount in either a dry or slurry form

35. Blending of Materialsand Moisture Addition • Cement is • blended into pulverized, • reclaimed • material and, with the addition of water, is brought to optimum moisture

36. Initial Compaction

37. Grading and Shaping • Material is graded to appropriate Plan line, grade, and cross-sections

38. Final Compaction • Material is compacted • 98% minimum standard Proctor density • 5-test average • None below 96%

39. Curing Bituminous Compounds (cutbacks or emulsions) Water (kept continuously moist)

40. Gradation Moisture Density Primary Testing Requirements A common gradation requirement is for 100% to pass a 3-inch (50 mm), a minimum of 95% to pass a 2-inch (50 mm), and a minimum of 55% to pass a No. 4 (4.75 mm) sieve (ASTM C 136). A common moisture requirement is to be within 2% of the laboratory established optimum moisture content (ASTM D 558). A common density requirement is to be between 95% and 98% of the established laboratory standard Proctor density (ASTM D 558).

41. Traffic Completed portions of FDR base can be opened immediately to low-speed local traffic and to construction equipment, provided the curing material or moist curing operations are not impaired, and provided the FDR base is sufficiently stable to withstand marring or permanent deformation.

42. Surfacing Subsequent pavement layers (asphalt, chipseal, or concrete) can be placed any time after finishing, as long as the soil-cement is sufficiently stable to support the required construction equipment without marring or permanent distortion of the surface.

43. Energy Use and MaterialsReclamation -vs- New Base Based on 1.6 km of 7.3 m-wide, 2-lane road, with a 150 mm base

44. More Advantages • Minimizes inconvenience for both homeowners and businesses • Less construction and transportation equipment • Can apply local traffic almost immediately • Fast operation • Worldwide availability • Familiar to engineers • 25% to 50% cheaper than removal and replacement!

45. The BIGGEST Advantage! • Versatility through use of portland cement • Stabilizes many materials • HMA or surface treatments • gravel or crushed stone bases • sands, silts, and plastic clays • combinations of all materials “Portland Cement is probably the closest thing we have to a universal stabilizer.” Chemical Stabilization Technology for Cold Weather United States Army Corps of Engineers September 2002

46. for additional information, please visit the PCA website at www.cement.org/pavements

47. Thank You! ghalsted@cement.org