FDR Mix Design


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FDR Mix Design

  1. 1. Full Depth Reclamation (FDR) Engineered Mix Design with Asphalt Emulsion
  2. 2. FDR Mix Design with Asphalt Emulsion <ul><li>Sampling and pre-screening </li></ul><ul><li>Material evaluation </li></ul><ul><li>Mix design </li></ul><ul><li>Quality control </li></ul><ul><li>Constructed projects </li></ul><ul><li>Structural design </li></ul><ul><li>Design method also applies to granular base stabilization (GBS) </li></ul>
  3. 3. FDR Mix Design with Asphalt Emulsion <ul><li>Material evaluation </li></ul><ul><li>Mix design </li></ul>
  4. 4. Sampling <ul><li>Place samples in separate containers / bags - preferably sealed </li></ul><ul><ul><li>Preserve original moisture content if cut dry </li></ul></ul><ul><li>Record location of samples </li></ul>
  5. 5. Sampling <ul><li>Samples combined for composite mix design </li></ul><ul><ul><li>If too varied, individual mix designs to be performed </li></ul></ul><ul><ul><ul><li>If greater than 2” in bituminous surface thickness variation, perform separate designs </li></ul></ul></ul><ul><ul><ul><li>Soil data from borings may determine variability of road & need for individual designs </li></ul></ul></ul><ul><li>The key is to get representative samples to the depth of the planned reclamation along the length and width of the road </li></ul>
  6. 6. Minimum Sampling (SemMaterials Field Engineers & Agency) <ul><li>Samples taken at defined spacing (and / or from quarry) - ASTM D 1452 or D 75 </li></ul><ul><ul><li>Coring, backhoe, auger, etc. (stagger edges & center) </li></ul></ul><ul><ul><li>Must be representative locations (from borings data) </li></ul></ul><ul><ul><li>Minimum of 4 sample areas & 2 samples / mile </li></ul></ul><ul><ul><ul><li>Equally divide between center, edges, and length of road </li></ul></ul></ul><ul><ul><ul><li>50 - 75 pounds from each sample area </li></ul></ul></ul><ul><ul><li>If coring, need no less than 30 cores (6” & 6” deep) </li></ul></ul><ul><ul><ul><li>Core in pairs </li></ul></ul></ul><ul><ul><ul><li>Equally divide between center and edges and length of road </li></ul></ul></ul><ul><li>350-lb minimum for each mix design </li></ul>
  7. 7. Pre-screening <ul><li>Recommendations: </li></ul><ul><ul><li>Sand equivalent (SE) > 25 </li></ul></ul><ul><ul><ul><li>ASTM D 2419, Method B </li></ul></ul></ul><ul><ul><li>Washed passing No. 200 (P200) < 20 % </li></ul></ul><ul><ul><ul><li>ASTM C 117 and C 136 </li></ul></ul></ul><ul><li>Not soil stabilization </li></ul>
  8. 8. Add-rock <ul><li>Virgin aggregate or RAP may be added </li></ul><ul><ul><li>To increase depth of finished structural layer </li></ul></ul><ul><ul><li>To improve gradation </li></ul></ul><ul><ul><ul><li>Cleanliness (P200) & material quality </li></ul></ul></ul>Add rock
  9. 9. Material Evaluation / Preparation <ul><li>Thickness of cores / slabs </li></ul><ul><li>Crush bituminous layer to pre-determined gradation </li></ul><ul><li>1.25 inch maximum size </li></ul><ul><li>SE and washed gradation testing </li></ul><ul><li>Modified Proctor </li></ul><ul><li>analysis – ASTM </li></ul><ul><li>D 1557, Method C </li></ul>
  10. 10. Material Evaluation – Modified Proctor <ul><li>Without emulsion </li></ul><ul><li>OMC is not for compaction in this case, but it is used as a material property to set the moisture content required before emulsion addition </li></ul><ul><li>Removes some </li></ul><ul><li>subjectivity in </li></ul><ul><li>moisture content needed </li></ul><ul><li>before emulsion addition </li></ul>
  11. 11. Material Evaluation – Water content before emulsion <ul><li>If rainfall is ≥ 20 inches: </li></ul><ul><ul><li>60 to 75% of OMC if SE < 30 </li></ul></ul><ul><ul><li>45 to 65% of OMC if SE > 30 </li></ul></ul><ul><li>If rainfall is < 20 inches: </li></ul><ul><ul><li>50 to 75% of OMC if SE < 30 </li></ul></ul><ul><ul><li>40 to 65% of OMC if SE > 30 </li></ul></ul><ul><li>This results in a water content close to in-place moisture content on a sealed / overlaid road </li></ul><ul><li>Moisture mixed with sample and sealed, typically overnight </li></ul>
  12. 12. FDR and GBS Tests Tests run on 150-mm SGC prepared specimens Thermal Cracking Resistance Indirect Tensile Test (IDT) AASHTO TP 9 Relative indicator of quality. Strain or deflection w/ applied load for structural design. Resilient Modulus ASTM D4123 Reliability Construction & QA/QC Requirements Moisture resistance Retained Strength ASTM D4867 Strength Indirect Tensile Strength (ITS) ASTM D4867 Curing Short-Term Strength Cohesiometer ASTM D1560 Performance Parameter Test
  13. 13. Basic Specifications* *To be adjusted based on region Project dependent Project dependent Thermal cracking 120,000 150,000 Res. Mod., psi 20 25 Retained ITS, psi 35 40 ITS, psi 150 175 Short-term strength, g/in. P200 > 8% P200 < 8%
  14. 14. Texas Emulsion FDR Specifications Report Seismic modulus, appendix Report Resilient modulus, T307 80% Retained UCS 150 UCS, Tex-117-E, psi Report Dielectric value, appendix 50 ITS, Tex-226-F, psi Required Test
  15. 15. Texas FDR projects <ul><li>Capable of performing TxDOT tests </li></ul><ul><ul><li>Texas drop hammer </li></ul></ul><ul><ul><li>Percometer (dielectric value) </li></ul></ul><ul><ul><li>Bath apparatus, latex membranes, porous stones </li></ul></ul><ul><ul><li>UCS – Cured. Short-term strength? </li></ul></ul><ul><ul><li>Seismic modulus (FFRC) </li></ul></ul>0.25” in. Expose half of the stone side to the water Ensure that the membrane and the plastic seal the top of the specimen from any evaporation or hydration.
  16. 16. Mix Design – Number of specimens <ul><li>4 emulsion contents </li></ul><ul><li>Typically 2,700 g weight (dry basis) </li></ul><ul><li>8 specimens for STS </li></ul><ul><li>16 specimens for ITS and conditioned ITS </li></ul><ul><li>2 specimens for G mm </li></ul><ul><li>3 specimens for IDT </li></ul><ul><ul><li>Cut two from each </li></ul></ul>
  17. 17. Mix Design - Mixing <ul><li>High energy mixer </li></ul><ul><ul><li>10 to 12 inches in diameter </li></ul></ul><ul><ul><li>Rotates on its axis at 50 to </li></ul></ul><ul><ul><li>75 revolutions per minute </li></ul></ul><ul><ul><li>A mixing paddle which </li></ul></ul><ul><ul><li>makes contact with the </li></ul></ul><ul><ul><li>bottom and side of the bowl </li></ul></ul><ul><ul><li>rotates on its axis at </li></ul></ul><ul><ul><li>twice the bowl rotation rate </li></ul></ul><ul><ul><li>and in the opposite rotation </li></ul></ul><ul><ul><li>direction as the bowl </li></ul></ul>
  18. 18. Mix Design - Mixing <ul><li>High energy mixer </li></ul><ul><ul><li>60 seconds for </li></ul></ul><ul><ul><li>both water and </li></ul></ul><ul><ul><li>emulsion </li></ul></ul><ul><ul><li>Typically non- </li></ul></ul><ul><ul><li>heated materials </li></ul></ul>
  19. 19. Mix Design – Pre-compaction curing <ul><li>After mixing, specimens are cured in plastic cylinder for 30 minutes at 40°C </li></ul><ul><li>Simulates aeration the road gets before final compaction – includes shaping with motor grader </li></ul><ul><li>Slight moisture loss </li></ul>
  20. 20. Mix Design - Compaction <ul><li>Superpave gyratory compactor (SGC) </li></ul><ul><li>150 mm mold </li></ul><ul><li>30 gyrations – simulates field density </li></ul><ul><li>600 kPa, 1.25° angle </li></ul><ul><li>10 second square pressure </li></ul><ul><li>after last gyration </li></ul><ul><li>Un-heated mold </li></ul><ul><li>Moisture will not squeeze </li></ul><ul><li>out if proper water content </li></ul><ul><li>is chosen </li></ul>
  21. 21. Mix Design - Curing <ul><li>STS specimens: </li></ul><ul><ul><li>1 hour </li></ul></ul><ul><ul><li>25°C at 10 to 70% </li></ul></ul><ul><ul><li>humidity </li></ul></ul><ul><li>ITS / resilient modulus: </li></ul><ul><ul><li>25°C testing after: </li></ul></ul><ul><ul><ul><li>72 hours at 40°C </li></ul></ul></ul><ul><ul><ul><li>1 day of cooling </li></ul></ul></ul>
  22. 22. Short-term strength (STS) by cohesion <ul><li>Has been used for a very long time </li></ul><ul><li>Original intent still applies </li></ul><ul><li>Practical method for potentially weak specimen strength testing </li></ul><ul><ul><li>Compression failure with ITS possible </li></ul></ul><ul><ul><li>Handling with resilient modulus difficult </li></ul></ul><ul><li>Modified for larger </li></ul><ul><li>specimens </li></ul><ul><li>Specified torque </li></ul><ul><li>applied to nuts for </li></ul><ul><li>consistency </li></ul>
  23. 23. STS by Cohesiometer Cohesiometer measures early strength; tested after 1 hour cure Load applied Stress on sample Shot in cylinder Great indicator of emulsion curing, in-place early strength, and ability to carry traffic.
  24. 24. Bulk specific gravity <ul><li>CoreLok used for density unless it can be shown absorption is low with SSD method </li></ul><ul><li>Along with G mm , </li></ul><ul><li>air voids are </li></ul><ul><li>determined for </li></ul><ul><li>information </li></ul>
  25. 25. Resilient Modulus <ul><li>Performed before ITS </li></ul><ul><li>25°C, 1 Hz </li></ul><ul><li>Relative quality indicator </li></ul><ul><li>Can be used for pavement </li></ul><ul><li>design </li></ul>
  26. 26. Indirect tensile strength (ITS) <ul><li>Specimens (dry testing) are conditioned at 25°C for two hours </li></ul><ul><li>Conditioned specimens are vacuum saturated a minimum of 55 percent (in most cases) and then soaked 24 hours </li></ul><ul><li>Tensile strength calculated </li></ul><ul><li>Dry and conditioned strength </li></ul><ul><li>at each emulsion content </li></ul>
  27. 27. Thermal Cracking <ul><li>Performed at optimum emulsion content </li></ul><ul><li>Determine crack initiation temperature </li></ul><ul><ul><li>Creep and strength testing in IDT </li></ul></ul><ul><li>Determine required temperature at depth of top of FDR layer – LTPPBind </li></ul>
  28. 28. Quality Control <ul><li>Asphalt emulsion – quality & quantity </li></ul><ul><li>Moisture content – microwave / generator </li></ul><ul><li>Depth control / Width control </li></ul><ul><li>Density </li></ul><ul><ul><li>Reference with Modified </li></ul></ul><ul><ul><li>Proctor or test strip </li></ul></ul><ul><ul><ul><li>Test strip by nuclear </li></ul></ul></ul><ul><ul><ul><li>density or sand cone </li></ul></ul></ul><ul><ul><li>In-place by nuclear </li></ul></ul><ul><ul><li>density or sand cone </li></ul></ul>
  29. 29. Constructed projects <ul><li>Chisago County, MN – various roads </li></ul><ul><li>Mercer County, IL – Ridge Road </li></ul><ul><li>Olmsted County, MN – CR 21 </li></ul><ul><li>Pine County, MN – CR 131 & CR 143 </li></ul><ul><li>Scott County, MN – Spring Lake Twsp </li></ul><ul><li>Shelby County, IA – M47 </li></ul><ul><li>TxDOT US-60 </li></ul><ul><li>Numerous others – GA, CA, CO, IA, NE, MN, IL, MO, OK, TX </li></ul>
  30. 30. Structural Design <ul><li>Coefficients determined by third-party consultants on various projects </li></ul><ul><li>Dependent on original material quality </li></ul>0.25 to 0.28 0.21 to 0.24 0.18 to 0.20 Engineered FDR or GBS High quality material Medium quality aggregate / medium amount of fines Rounded aggregate / high amount of fines
  31. 31. FDR Mix Design SemMaterials, L.P.