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Full Depth Reclamation

Full Depth Reclamation. Current Practice Testing Variability Presented To: Canadian User Group for Asphalt Sunday, November 15, 2009 Delta Beausejour Hotel Moncton, New Brunswick Tom Dziedziejko AME Materials Engineering. FDR.

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Full Depth Reclamation

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  1. Full Depth Reclamation Current Practice Testing Variability Presented To: Canadian User Group for Asphalt Sunday, November 15, 2009 Delta Beausejour Hotel Moncton, New Brunswick Tom Dziedziejko AME Materials Engineering

  2. FDR • Rehabilitation Technique that processes the full depth of asphalt pavement and a predetermined portion of the underlying base materials • Uniformly pulverizes and blends to provide an upgraded and homogeneous material

  3. FDR Equipment • Pulverizing drum rotates in an up-cut direction or opposite to the forward direction of travel. • Including some underlying granular helps cool cutting tools and enhances pulverization action • Allows simultaneous injection of stabilizing agents.

  4. Pug-Mill and Expansion Manifold Screen Deck FDR Equipment Belt Scale Crusher • Paver Laid FDR • Recycling Trains • Pulverize, Wind row, Pick up

  5. Distresses That Can Be Treated • Cracking • Age, Fatigue, edge, slippage, block, longitudinal, reflection, continuity • Ride Quality • Bumps, Localized Depressions, Cross fall correction, • Permanent Deformation • Rutting, Shoving, Wash Boarding • General Deterioration • Raveling, Potholes, Stripping, Delamination, etc. • Inadequate Structural Capacity

  6. Candidates for FDR • Good Candidate • Good But Approach with Caution • Potential serious underlying problems • Enhancement likely required

  7. Candidates for FDR • If existing pavement structure is adequate for loads then simple pulverization and regrading may be all that is required before applying surface. • Corrective aggregate may be required to ensure adequate drainage and mechanical properties of the treated material. • If structural enhancement is required then stabilizing agents can be added • Type of agent used should be selected based on the properties of the material present.

  8. Types of Stabilizing Additives • Bituminous • Foamed Asphalt • Asphalt Emulsions • Chemical • Portland Cement • Lime • Fly Ash Types C and F • Kiln Dust (Lime/LKD or Cement/CKD), Cement, Lime Blends • Combinations of the above • Bituminous additives blended with Chemical additives

  9. Types of Stabilizing Additives • Popularity of Recycling is spawning interest in new stabilizers and additives • Foam Enhancing additives • Pine Tar Emulsions

  10. Bituminous Additives • Asphalt Emulsions • Coats all aggregates with emulsion • Emulsion breaks leaving particles cemented together with bitumen • Paving can not proceed until emulsion break is complete • Days? Weeks? Cement sometimes added to accelerate break of emulsion

  11. Bituminous Additives • Foamed Asphalt • Fast becoming the most popular choice for FDR • Small amount of water added to hot asphalt results in foam • Pulverized material needs fines present up to 20% • Foam mixes with fines present in material to form a mastic binder • Mastic spot welds to larger aggregate in material to form bonds that hold mix together • Aggregates with PI as high as 15 treated successfully with no special processes • Typical delay before paving - two days

  12. Additive Selection for FDR • FDR is a Soil Stabilization Technique • When Bituminous Additives are used the process becomes a Hybrid Asphalt and Soil product • Asphalt products provide a binder system • Produces a flexible material with properties that resist fatigue and adds flexibility to the processed mat. • Additives used provide some enhancement to asphalt interaction with soils but also impacts soil properties similar to soil stabilization techniques.

  13. Chemical Additives • Lime • Most often used where soil has high PI (>10) • Benefits • Mitigates effect of reactive clays • Reduces PI of soil after application and reduces swelling potential • Decreases susceptibility to moisture damage (stripping) • Increases tensile and compressive strength of mix • Typical addition 1% to 3%

  14. Chemical Additives • Portland Cement • Most often used where soil has low PI (<10) • Primarily adds strength to weak materials • Benefits • Increases compressive strength of mix. • Strength increase over time • Impact on moisture susceptibility variable (stripping) • Typical addition 1% to 2% • Excessive addition results in potential cracking of the stabilized soil

  15. Chemical Additives • Fly ash • Fly ash is a pozzolan typically requiring presence of lime or hydrating cement to gain strength • Some clays can react with calcium oxide in Type C Fly ash alone resulting in strength gain. • Some fly ash has percentage of lime present that allows some hydration • Potential to Mitigate effect of reactive clays - Lime • Slower strength gain than cement but carries on longer • Excessive addition results in potential cracking of stabilized soil Data Source: Job Report Cold Recycling WR 2500: Foam recycling in Estes National Park, Colorado /USA

  16. Pre Engineering • Rule of Thumb Engineering is the Most Costly Form of Design • Proper Engineering Assessment should be carried out to identify the best choice of additive. • Must consider : • Amount of strength enhancement required. • Pavement Structural Design – Traffic? • Type and quality of base materials present • Drainage Characteristics • Presence of Clays and Silts • Plasticity Index • Pavement Drainage • Ditching • Sub drains

  17. Pre Engineering • Thickness of existing pavement • Optimize percent of pulverized pavement in process depth • + 60% RAP • Identify excessively thick areas • Over 200mm pavement depth could be a problem to process due to equipment capacity • Consider Pre-milling Options to reuse excess in other parts of project. – Shoulder stabilization

  18. Pre Engineering • Proper Mixture Design • Pre tender laboratory design trials to confirm additive selected will work is advisable. • Mix design before construction is compulsory

  19. Internal = 34oC Surface = 28oC Internal = 26oC Surface = 24oC Testing Variability • Accurate Test Results Dictate Acceptance • Stabilized Sample Temperature is Critical Temp = 25 C: Strength = 360 Temp = 26 C: Strength = 340

  20. Test Variability • Strength Change with Varying Conditioning Temperature

  21. Testing Variability 2 Hrs Room Curing 24 Hrs Room Curing 4 Hrs Room Curing

  22. Testing Variability • Optimum Moisture – Field Sample – AC 2.8% • Strength Varies with moisture content at time of compaction

  23. Conclusions • Select FDR based on engineering design • Selected process and enhancement should be based on existing conditions. • Chemical treatments should be established using Material requirements • Ensure Quality Verification Testing is completed accurately • Sample Temperature significantly influences results

  24. Thank YouQuestions ?

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