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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 – safely – smoothly – at a faster rate – without any deformation 3
- 6. Wheel Load Granular structure Load transfer mechanism 6
- 7. Comparison Flexible • Flexible in nature • Grain to grain load transfer • Multiple layers of Subgrade, sub base, Base course and Surface course • Low initial cost • High maintenance cost • Eg. Bituminous road, WBM Rigid • Rigid in nature • Load transfer by slab action • Slab directly put over subgrade or a sub-base course • High initial cost • Low maintenance cost • Eg. Cement Concrete road 7
- 8. BT. SURFACE BASE SUB - BASE SUB – GRADE Bituminous Pavement – Typical Cross section
- 9. Bituminous Pavement Construction Bitumen • Distillation of petroleum crude oil • Hydrocarbon of high molecular weight • Form can be gaseous, liquid, semisolid or solid Tar • Destructive distillation of coal or wood • More temperature sensitive than bitumen • Carcinogenic material 9
- 10. Bituminous Pavement Construction Adequate Viscosity Low temperature susceptibility Adequate affinity between bitumen and aggregates 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 1. 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) 2. 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) 3. Preparation of base course – Prime Coat – Tack Coat – Bituminous Macadam 4. Preparation of wearing course – Tack Coat – Seal coat or Bituminous Concrete Explained in next slides 14
- 15. Bituminous pavement construction techniques Interface treatment • Prime coat • Tack coat Grouted or penetration • Penetration Macadam • Built up spray grout Premix pavement • Bituminous Macadam • Bituminous Concrete • Mastic Asphalt Surface dressing • Seal coat • Bituminous Concrete 15
- 16. Types of bituminous construction Interface treatment Prime Coat Tack Coat 16
- 17. Interface treatment To provide necessary bond between old and new pavement layers a) 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/10m2 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/10m2 19
- 20. Bituminous pavement construction techniques Interface treatment • Prime coat • Tack coat Grouted or penetration • Penetration Macadam • Built up spray grout Premix pavement • Bituminous Macadam • Bituminous Concrete • Mastic Asphalt Surface dressing • Seal coat • Bituminous Concrete 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/m2 – 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 Interface treatment • Prime coat • Tack coat Grouted or penetration • Penetration Macadam • Built up spray grout Premix pavement • Bituminous Macadam • Bituminous Concrete • Mastic Asphalt Surface dressing • Seal coat • Bituminous Concrete 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
- 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
- 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 223o 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
- 30. Bituminous pavement construction techniques Interface treatment • Prime coat • Tack coat Grouted or penetration • Penetration Macadam • Built up spray grout Premix pavement • Bituminous Macadam • Bituminous Concrete • Mastic Asphalt Surface dressing • Seal coat • Bituminous Concrete 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
- 44. Bituminous pavement construction techniques Interface treatment • Prime coat • Tack coat Grouted or penetration • Penetration Macadam • Built up spray grout Premix pavement • Bituminous Macadam • Bituminous Concrete • Mastic Asphalt Surface dressing • Seal coat • Bituminous Concrete 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 1. 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 3. 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 Hot mix Interface Grouted Premix Surface dressing Cold mix Emulsion Cutback
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