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
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
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
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
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