Bituminous road construction

A brief description of bituminous road construction

1. Transportation Engineering CE 6014(R15) Dr. Anitha Jacob Lecturer in Civil Engineering Govt. Polytechnic College, Chelakkara , Thrissur Bituminous Road Construction

2. CE 6014 (R15) – Transportation Engineering Module II Road Construction: Construction of bituminous road Flexible pavement & Rigid pavement Prime coat & tack coat – premix Macadam & penetration Macadam – Seal coat Bituminous Macadam road maintenance using cutback/emulsion and hot pre-mix Macadam 2

3. What is a pavement ? A structure to carry vehicle wheel load s afely smoothly at a faster rate w ithout any deformation 3

4. Types of Pavement RIGID FLEXIBLE 4

5. 5 Composition of Pavement

6. Wheel Load Granular structure Load transfer mechanism Rigid Pavement Flexible Pavement 6

7. Comparison 7

8. BT. SURFACE BASE SUB - BASE SUB – GRADE Bituminous Pavement – Typical Cross section

9. Bituminous Pavement Construction 9

10. Bituminous Pavement Construction Properties of Bitumen 10

11. Bituminous Pavement Construction Hot mix technique – Bitumen require proper heating to attain viscosity before mixing with aggregates Cold mix technique – Cutback and emulsion do not require heating of the binder 11

12. General Construction Procedure Formation of subgrade soil Soil exploration to check the dry density of soil For week soil up to 50 cm depth should be replaced with good soil (2 layers of 25 cm thick is compacted) Criteria –95 % of proctor density should be achieved Proper longitudinal slope for drainage Proper camber is provided 12

13. General Construction Procedure ( Contd ) Preparation of Sub-base course Granular Sub-Base (GSB) Broken stone (60 mm down), quarry dust and water 100 mm to 150 mm Wet Mix Macadam (WMM) Broken stone (40 mm down), quarry dust and water Properly mixed, laid and compacted 150 mm to 200 mm Static compactors are used 13

14. General Construction Procedure ( Contd ) Preparation of base course Prime Coat Tack Coat Bituminous Macadam Preparation of wearing course Tack Coat Seal coat or Bituminous Concrete Explained in next slides 14

15. Bituminous pavement construction techniques 15

16. Types of bituminous construction 16

17. Interface treatment To provide necessary bond between old and new pavement layers Prime Coat First application of low viscosity bitumen is used To plug the capillary voids To bind loose mineral particles on the existing porous pavement 24 hours curing Rate of application is 7.3 to 14.6 kg/10m 2 17

18. Prime coat over WMM Check for rate of spread 18

19. Interface treatment ( Contd ) b) Tack Coat Viscous bituminous material over existing impervious pavement surface (bituminous or CC) Rate of application is 4.9 to 9.8 kg/10m 2 19

20. Bituminous pavement construction techniques 20

21. Penetration Type Penetration Macadam Used as a base course Broken stones are dry compacted Hot bituminous binder is sprayed at the top Bitumen penetrate into the voids of aggregates and bind the aggregates together Full grout and Half grout 21

22. Penetration Type Built-up spray grout Two layers of composite construction rolled aggregates Each layer of compacted crushed stone is applied with bituminous binder at a rate of 12.5 to 15 kg/m 2 After the second application of binder, key aggregates are spread and rolled An initial tack coat is applied before the first layer of coarse aggregates 22

23. Bituminous pavement construction techniques 23

24. Premix pavement Bituminous Macadam (BM) Used as a base course Crushed aggregates premixed with bitumen in a hot mix plant at specified temperature Laid at hot in compacted thickness of 75 mm or 50 mm thickness Depending upon the gradation, it can be open graded or semi dense BM 24

25. Bituminous Macadam (BM) 25

26. Premix pavement Bituminous Concrete (BC)/Asphaltic Concrete (AC) Used as a pavement surface course of high quality Mix design for a dense mixture of coarse aggregate, fine aggregate, mineral filler and bitumen 40 mm thick AC surface course for highway pavement (IRC) 26

27. Bituminous Concrete (BC ) 27

28. Premix pavement Mastic Asphalt (MA) Used as a pavement surface course of high quality for bridge deck Mixture of fine aggregate, mineral filler and bitumen Each component is heated and cooked at a temperature of 200 to 223 o C for over 5 hrs. On cooling, it hardens to semi-solid or solid state Without compaction itself an impervious surface can be obtained 25 mm to 50 mm thick 28

29. Mastic Asphalt (MA) 29

30. Bituminous pavement construction techniques 30

31. Bituminous Surface Dressing (BSD) To provide a thin wearing coat over existing pavement Application of Bituminous binder followed by spreading of aggregate cover and rolling Functions To serve as thin wearing course To water proof pavement surface To make surface dust free 31

32. Bituminous Surface Dressing (BSD) Seal Coat Very thin surface dressing Provided over an existing black top 9 mm thick using 6mm stone Functions To seal the surface to prevent water ingress To provide skid resistant surface 32

33. Dumping Of Subgrade Material 33

34. Grading Of Subgrade Material 34

35. Rolling Of Subgrade Material 35

36. Field Density Testing Of Subgrade Material 36

37. Tandem vibratory roller Static roller 37

38. SHEEP FOOT ROLLER 38

39. Pneumatic roller 39

40. Small vibratory roller Plate compactor 40

41. Vibratory roller 41

42. WATER SPRAY BAR 42

43. GOOD TRANSVERSE PROFILE 43

44. Bituminous pavement construction techniques 44 HOT MIX METHODS

45. Cold Mix Techniques Bituminous emulsions A mixture of emulsifiers and fine bitumen droplets(as suspended particles) in water. Emulsifiers add charge to droplets and keeps them in suspension Bitumen droplets having high affinity to aggregates, make a quick and strong bond with aggregates, once applied on road surface Water then evaporates 45

46. Cold Mix Techniques ( Contd ) Bituminous emulsions – Types Based on setting time Slow setting (SS) Medium setting (MS) Rapid setting (RS) Based on surface charge Anionic Bitumen Emulsion Cationic Bitumen Emulsion 46

47. Cold Mix Techniques (Contd.) Bituminous emulsions – Advantages Can be used in wet weather even if it is raining. Eco-friendly as it is water based. Used in soil stabilization in desert areas. No need of extra heating while placing. No wastage in placing and laying of bitumen. Anti-stripping properties. Rapid setting type of emulsion are used in surface of roads. Medium setting type of emulsion are used in premixing of bitumen emulsion and coarse aggregate. Slow setting type of emulsion are used with fine aggregates as the surface area is large and requires time for uniform mixing. 47

48. Cold Mix Techniques (Contd.) Cutback bitumen Bitumen dissolved in volatile solvents of petroleum distillates like gasoline, naptha , kerosene Curing time depends on type of solvent Quantity of solvent controls the viscosity of bitumen After laying, solvent get evaporated leaving behind the bitumen to bind with the aggregate 48

49. Cold Mix Techniques (Contd.) Cutback bitumen – Types Depending on the solvent used Rapid curing Medium curing Advantage over emulsion Compared to Emulsion, the residual percentage of bitumen is more in the case of cutback bitumen 49

50. Maintenance of bituminous pavement Patch Repair Pot holes cut open to rectangular shape Affected material removed, cleaned and recoated with bitumen (emulsion or cutback) Premix is filled and compacted well. Finished level of patch is slightly higher than normal road surface 50

51. Maintenance of bituminous pavement 2. Surface treatment Suitable for bleeding pavement Blotting material such as sand is spread and rolled 51

52. Maintenance of bituminous pavement Resurfacing For total damage of pavement Additional surface course is provided Overlay roads are provided 52

53. Summary Flexible and Rigid Pavements Bituminous pavements – Construction procedure Maintenance of bituminous roads 53

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