11California WMA WorkshopJune 26-27, 2013
2Overview Consider mixture characteristics and costs Review of materials costs Determine the bottom line
3Characteristics to Consider Ability to carry applied stresses Workability – handwork, feathering, compactability Lift ...
4Costs to Consider Cost of component materials Equipment rental or depreciation to addcomponents Drying costs of materi...
5Mix Production CostsDepreciation $1.24Maintenance $1.13Labor $1.79Energy/Drying $2.87Electric Power $0.04Equipment $0.97A...
6Purchase Price of Materials Material $/ton #67 stone 12.70 #78 stone 13.50 #89 11.00 Washed #10s 13.00 Natural sand...
7
8Hidden Costs of Aggregates How much water are you buying? How much does it cost to dry the aggregate? How much materia...
9Cost of Dry Aggregate$/dry ton = ($/wet ton) x (1+w/100)Example:5000 tons of W10’s purchased from a quarry at$13.00/ton. ...
10Handling Costs, Including Loss Handling costs Stockpiling equipment and space Inventory management Loss - all materi...
11Production Costs Depreciation Maintenance Labor Drying Electric Power Equipment
12Drying CostsAstec T-119 Dryer Drum Mixer11.522.533.50 2 4 6 8 10 12 14Moisture Content (%)GallonsofFuelperTonParallel Fl...
13Do Covered Stockpiles Payoff?
14
15
16Moisture 1% increase in moisture increases drying costby 10 to 12% 1% increase in moisture decreases productionrate by...
17Plant Diagnostic Tool http://www.pahotmix.org/images/bobfrank.swf
18Estimated Reduction in Emissions
19Special Equipment for Additives
20Warm Mix Asphalt Cost Additions/Cost Savings: Rules of Thumb Potential Savings Burner fuel Improved in-place density...
21Warm Mix AsphaltProduction of WMA Same plants, may be modified in many cases Same hauling and laydown equipment Same ...
22
23Adequate Baghouse TemperaturesMust be Maintained Low baghouse temperature can cause condensation Corrosion of the bagh...
24Maintaining BaghouseTemperatures Seal air leaks Preheat the baghouse for 15 to 20 minutes Inspect fine return lines f...
25Dryer Flights
26Dryer Flights
27Burner Adjustments Burner may need to be tuned to run efficiently atlower temperatures Improper burner adjustment can ...
28Signs of Unburned Fuel Brown film around coated aggregate Increased susceptibility to rutting Lower dynamic modulus (...
29Differences with WMA Production Addition of the WMA additive or foaming the binder Setting the production temperature...
30Astec Double Barrel GreenFoaming System One pound of water per ton of mix, or about two percent ofthe asphalt flow rate...
31Foaming Warm Mix ProcessExpansion ChamberWater PumpExistingAC PumpCounterflow DrumWater TankFoam Injection pipe runninga...
32WMA Dosing Refer to productmanufacturer fordosage rates Ensure injection systemsare cleaned andcalibrated regularly fo...
33Removing Moisture Increase aggregate retention time Insulate dryer shell Use variable frequency drive (VFD) Reduce s...
34Plant Addition of Aspha-min
35Plant Addition of Sasobit
36Chemical Additives May be added at theasphalt terminal or addedat the plant Dosage rates depend onthe selected additive
37Plant Concerns with WMAPlant burners may not be properly tunedeven for normal HMA productionIncomplete fuel combustion l...
38WMA Production Concerns Amperage on motors for drag slatconveyors, coaters, etc. Incomplete coating of aggregate
39Warm Mix AsphaltPlant Concerns with WMA Condensation in thebaghouse could cause: Mudding of the bags Increase draw on...
40Other Concerns with WMA Activation/melting of RAP orRAS binder at lowertemperatures Additional expense One more mater...
41WMA Mix Test Concerns Lower mix temperatureresults in less aging of thebinder that could result inincreased: Moisture ...
42Combining WMA & RAP Superheating solves baghouse problem without plantmodification or efficiency loss Superheating ass...
43Combining WMA & RAP Superheating solves baghouse problem without plantmodification or efficiency loss Superheating ass...
44Combining WMA and RAP WMA technologies canimprove the ability toproperly coat aggregatesand RAP during production Lowe...
45Rate of Cooling Variables Layer Thickness Air Temperature Base Temperature Mix Laydown Temperature Wind Velocity S...
46Example Paving Temperature DecreaseHot Mix 314 °F Aspha-min Mix 254 °F138.1 pcf 138.5 pcf
47Better Work Environment Studies to quantify fumes have shown that WMA: Reduces Total Organic Material > 90% Drops Ben...
48Better Temperature Uniformity The key is getting densityand getting it uniformly
49Compactive Effort WMA has been seen torequire less compactiveeffort even with the lowertemperatures Changes may need t...
50Temperature Segregation Temperature differentials in the mat can causedensity problems. Temperature differentials exce...
51Infrared (IR) Bar Collects and displayspavement temperaturesacross the mat. Allows for corrections toimprove overallun...
52
53
54Making Field Adjustments to Mixes It is almost a certainty that any mixture will require someadjustments to meet accept...
55Making Field Adjustments to Mixes Maintain current data on stockpile gradations. Thiswill provide a heads up on changes...
56WMA is not a cure for badconstruction practices!
57Additional Resource
58www.ncat.us
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#3 wma production and placement

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Warm Mix Asphalt training documents provided by the National Center for Asphalt Technology (NCAT) for classes held June 26 & 27, 2013 in California, sponsored by the California Asphalt Pavement Association (CalAPA).

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#3 wma production and placement

  1. 1. 11California WMA WorkshopJune 26-27, 2013
  2. 2. 2Overview Consider mixture characteristics and costs Review of materials costs Determine the bottom line
  3. 3. 3Characteristics to Consider Ability to carry applied stresses Workability – handwork, feathering, compactability Lift thickness – t/NMAS ratio, lane drop-off Aesthetics - smoothness and texture Friction Noise DurabilityRefer to NAPA IS128
  4. 4. 4Costs to Consider Cost of component materials Equipment rental or depreciation to addcomponents Drying costs of materials Productivity (tons/hr) Haul/delivery costs Placement and compaction costs Potential of acceptance/pay penalties
  5. 5. 5Mix Production CostsDepreciation $1.24Maintenance $1.13Labor $1.79Energy/Drying $2.87Electric Power $0.04Equipment $0.97Aggregate $11.27Asphalt $20.57Other $0.44Total $40.31DepreciationMaintenanceLaborDryingElec.PowerEquipmentAggregateAsphalt Other
  6. 6. 6Purchase Price of Materials Material $/ton #67 stone 12.70 #78 stone 13.50 #89 11.00 Washed #10s 13.00 Natural sand 10.75 Hydrated Lime 160.00 RAP (4.5% binder) 7.45 PG 67-22 410.00Example
  7. 7. 7
  8. 8. 8Hidden Costs of Aggregates How much water are you buying? How much does it cost to dry the aggregate? How much material is wasted or lost? What is the asphalt demand for the aggregate?
  9. 9. 9Cost of Dry Aggregate$/dry ton = ($/wet ton) x (1+w/100)Example:5000 tons of W10’s purchased from a quarry at$13.00/ton. The W10’s had 5.6% moisture at delivery.$/dry ton = ($13.00/ton) x (1+(5.6/100))$/dry ton = $13.00/ton x 1.056 = $13.73Dry inventory = 5000 tons/(1+w/100)= 4734 tons
  10. 10. 10Handling Costs, Including Loss Handling costs Stockpiling equipment and space Inventory management Loss - all materials purchased do not end up in afinished (sold) product Purchased moisture Yard waste Plant waste Theft
  11. 11. 11Production Costs Depreciation Maintenance Labor Drying Electric Power Equipment
  12. 12. 12Drying CostsAstec T-119 Dryer Drum Mixer11.522.533.50 2 4 6 8 10 12 14Moisture Content (%)GallonsofFuelperTonParallel FlowCounter FlowDouble BarrellWhat is the current cost of fuel?
  13. 13. 13Do Covered Stockpiles Payoff?
  14. 14. 14
  15. 15. 15
  16. 16. 16Moisture 1% increase in moisture increases drying costby 10 to 12% 1% increase in moisture decreases productionrate by 11% Which material stockpiles retain the mostmoisture?
  17. 17. 17Plant Diagnostic Tool http://www.pahotmix.org/images/bobfrank.swf
  18. 18. 18Estimated Reduction in Emissions
  19. 19. 19Special Equipment for Additives
  20. 20. 20Warm Mix Asphalt Cost Additions/Cost Savings: Rules of Thumb Potential Savings Burner fuel Improved in-place density Less wear on plant? Slightly lower asphalt content? Better work environment - improved productivity Higher RAP contents Potential Additions WMA additive Plant modification Anti-strip additive
  21. 21. 21Warm Mix AsphaltProduction of WMA Same plants, may be modified in many cases Same hauling and laydown equipment Same compaction equipment
  22. 22. 22
  23. 23. 23Adequate Baghouse TemperaturesMust be Maintained Low baghouse temperature can cause condensation Corrosion of the baghouse Formation of damp baghouse fines Acceptable baghouse inlet temperatures > 220°F for low-sulfur fuels > 240°F for high-sulfur fuels (reclaimed oils) Varies from plant to plant and mix to mix
  24. 24. 24Maintaining BaghouseTemperatures Seal air leaks Preheat the baghouse for 15 to 20 minutes Inspect fine return lines for buildup Occasionally paint corroded interior surfaces withepoxy-based paint
  25. 25. 25Dryer Flights
  26. 26. 26Dryer Flights
  27. 27. 27Burner Adjustments Burner may need to be tuned to run efficiently atlower temperatures Improper burner adjustment can cause the burner tonot add enough air to burn all of the fuel Expensive Mix contamination
  28. 28. 28Signs of Unburned Fuel Brown film around coated aggregate Increased susceptibility to rutting Lower dynamic modulus (E*) values Increased carbon monoxide (CO) levels Fuel in baghouse
  29. 29. 29Differences with WMA Production Addition of the WMA additive or foaming the binder Setting the production temperature Start production at normal HMA temperatures, thendecrease the temperature to the WMA target29
  30. 30. 30Astec Double Barrel GreenFoaming System One pound of water per ton of mix, or about two percent ofthe asphalt flow rate. This is 0.05% moisture in the mix.
  31. 31. 31Foaming Warm Mix ProcessExpansion ChamberWater PumpExistingAC PumpCounterflow DrumWater TankFoam Injection pipe runningalong side existing AC pipeExisting AC pipe
  32. 32. 32WMA Dosing Refer to productmanufacturer fordosage rates Ensure injection systemsare cleaned andcalibrated regularly foraccurate dosing
  33. 33. 33Removing Moisture Increase aggregate retention time Insulate dryer shell Use variable frequency drive (VFD) Reduce stockpile moisture content
  34. 34. 34Plant Addition of Aspha-min
  35. 35. 35Plant Addition of Sasobit
  36. 36. 36Chemical Additives May be added at theasphalt terminal or addedat the plant Dosage rates depend onthe selected additive
  37. 37. 37Plant Concerns with WMAPlant burners may not be properly tunedeven for normal HMA productionIncomplete fuel combustion leads to: Poor fuel efficiency Fuel contamination of the mix(liquid fuels) Stack emission problems (COand THC) Potential for a baghouse fire
  38. 38. 38WMA Production Concerns Amperage on motors for drag slatconveyors, coaters, etc. Incomplete coating of aggregate
  39. 39. 39Warm Mix AsphaltPlant Concerns with WMA Condensation in thebaghouse could cause: Mudding of the bags Increase draw on exhaustfan motor Formation of corrosiveacids with gases from highsulfur fuelsH2SO4
  40. 40. 40Other Concerns with WMA Activation/melting of RAP orRAS binder at lowertemperatures Additional expense One more material/processto control
  41. 41. 41WMA Mix Test Concerns Lower mix temperatureresults in less aging of thebinder that could result inincreased: Moisture susceptibility Lower tensile strengths TSRs Rutting potential APA Hamburg Flow Number41
  42. 42. 42Combining WMA & RAP Superheating solves baghouse problem without plantmodification or efficiency loss Superheating assures virgin aggregates are dried Provides the greatest economic and environmentalbenefit
  43. 43. 43Combining WMA & RAP Superheating solves baghouse problem without plantmodification or efficiency loss Superheating assures virgin aggregates are dried Provides the greatest economic and environmentalbenefit
  44. 44. 44Combining WMA and RAP WMA technologies canimprove the ability toproperly coat aggregatesand RAP during production Lower productiontemperatures will reducedplant aging of binderswhich may allow forincreased use of RAPwithout grade bumping44
  45. 45. 45Rate of Cooling Variables Layer Thickness Air Temperature Base Temperature Mix Laydown Temperature Wind Velocity Solar Flux
  46. 46. 46Example Paving Temperature DecreaseHot Mix 314 °F Aspha-min Mix 254 °F138.1 pcf 138.5 pcf
  47. 47. 47Better Work Environment Studies to quantify fumes have shown that WMA: Reduces Total Organic Material > 90% Drops Benzene Soluble Matter below detectiblelimitsPictures from paving in YellowstoneNational Park, August 2007HMA WMA
  48. 48. 48Better Temperature Uniformity The key is getting densityand getting it uniformly
  49. 49. 49Compactive Effort WMA has been seen torequire less compactiveeffort even with the lowertemperatures Changes may need to bemade with WMA due tohigher densities Change rolling pattern Decrease binder content Check with non-destructivedevice calibrated to cores
  50. 50. 50Temperature Segregation Temperature differentials in the mat can causedensity problems. Temperature differentials exceeding 30°F can causean 80% reduction in fatigue life (NCAT). TTI recommends keeping temperature differentialsbelow 25°F.
  51. 51. 51Infrared (IR) Bar Collects and displayspavement temperaturesacross the mat. Allows for corrections toimprove overalluniformity
  52. 52. 52
  53. 53. 53
  54. 54. 54Making Field Adjustments to Mixes It is almost a certainty that any mixture will require someadjustments to meet acceptance targets (air voids, asphaltcontent, etc.) Differences between the lab mix design and plant producedmix can be caused by: Changes in the aggregate properties Breakdown of aggregate through the plant Incomplete drying Surges in baghouse fines return Differences in aging and absorption Inaccurate plant calibration Different laboratory equipment Different technicians
  55. 55. 55Making Field Adjustments to Mixes Maintain current data on stockpile gradations. Thiswill provide a heads up on changes from the mixdesign. Make sure plant is “leveled out” before taking a mixsample. For most plants, this takes about 80 to 100tons. Conduct tests to determine Pb, gradation, Gmm, andGmb
  56. 56. 56WMA is not a cure for badconstruction practices!
  57. 57. 57Additional Resource
  58. 58. 58www.ncat.us

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