1. Hot Mix Asphalt Production Chris Lange PMP, Pr.Tech.(Eng) Director (Technical) Much Asphalt (Pty) Ltd Road Pavement Forum: 10 th April 2006

2. Hot Mix Asphalt Production Plant types and basic components Plant calibration Dust extraction Filler handling and control Aggregate heating Procurement / handling of raw materials Finished product storage Delivery

3. Drum Mix Plant - Conventional HMA made continuously and sent to storage silos Drying and mixing drum Bitumen Tanks Scalping screen to remove oversize aggregate Cold Feed Bins Belt scale Primary dust collector Filter Baghouse Hot Storage Bins Exhaust Fan

4. TWIN DRUM PLANT : COUNTER-FLOW

5. Old Drum Mix Mix Plant:

6. Twin Drum Plant RAP Feed Aggregate feed Drying & heating Drum Coating & mixing drum Finished product storage Plant filler storage and feed Filter Baghouse

7. Parallel-Flow Drum- mixer Zones Combustion Heating Drying Air BIT. Hot Mix Asphalt Mixing

8. Counter-Flow Drum- mixer Zones Aggregate Air Bitumen Hot Mix Asphalt CombustionHeatingDryingMixing

9. Counter-Flow Batch Plant Dryer Zones Hot Aggregate CombustionHeatingDrying Aggregate Air

10. Batch Plant Elements Cold feed bins Dryer Drum Bitumen storage tanks Hot Storage silos Primary collector Filter Baghouse Batch/Mixing tower RAP Feed

11. Hot aggregate travels up bucket elevator Pugmill Aggregate weigh hopper Bitumen weigh pot Hot mix asphalt dispensed into truck / hot-bin Aggregate from dryer Aggregate to screens Screens size aggregate

12. Bitumen Weigh- hopper Aggregate and bitumen weigh hoppers

13. Aggregate Hot Bins

14. Warren Brothers Patent Application Drawing: Original Batch Plant

15. Belt Scale Calibration Cold feed system Belt scale Reference scale

16. Cold Feed Bins and RAP Bin

17. “Graphing the Feeders”

18. Tachometer Mounted on Tail Pulley of Cold Feed Bin Belt

19. “No Flow” Paddle at Feeder Discharge

22. Induced Air Burner

23. Fuel Reticulation and Heating System In-line heater HFO Sampling pt HFO Tank

24. Temperature Profile of Counter-Flow Dryer 150º C 100º C 20º C Gases Aggregates Combustion Heating Drying 150º C 300º F 760º C 120º C 400º C 800º C 0º C Aggregate

25. Drum Flights / Lifters

26. Primary and Secondary Emission Control Drying Drum Primary Dust Collector Secondary Dust Collector Exhaust Fan Filtered Air Fines collected and returned

27. Primary Collector: Cyclone

28. Multi-Tube Collector Outlet tube Spin vanes Inlet tube Valve Collector element Gas inlet

29. Discharge Housing Functions as a Knockout Box Gas flow Air Optional knock down plate Bitumen Fines mix with hot mix asphalt

30. Cutaway Section of a Typical Baghouse

31. Pulse Jet Baghouse Dust screw Exhaust fan Manifold

32. Automatic Damper Controls

33. Cyclone, Screw Collector, and Hot Elevator Batch tower Hot Elevator Cyclone feeding fines directly back

34. Filler Weigh-Pod After Surge Silo

35. Emission Control Summary Remove particulate matter –Primary –Secondary Return fines to the mix –Affects void content –Affects mix stiffness –Difficult to control

36. Batch plant filtration

37. Aggregate storage

38. Aggregate Storage

39. BITUMEN TANKS – ELECTRICALLY HEATED/ 24 HR TEMPERATURE MONITOR AND CONTROL Bitumen Storage

40. Old Style Operating Cabin

41. Plant automation: Modern control cabin:

42. Plant automation

43. Roodepoort Op Screen Plant Automation – Operating System Graphics

44. Batch Plant Schematic

45. Batch Plant Op Screen

46. Laboratory from the past

47. Modern Asphalt Laboratory

48. Quality Control Trends Monitored Binder Content Voids in Mix Filler Content

50. Slat Conveyor Feeding Storage Silos

51. Hot Storage – Skip and Winch System Plant Mixing Tower Skip Bucket Winch

52. Storage Silo: 165 t Capacity

53. Correct Loading Sequence

54. The good old days The End