highway engineering road construction

1. HIGHWAY ENGINEERING-III
CEng5241
Chapter 1
Part II
1

2. Sub base Course
• Located immediately above the subgrade.
• It has better quality than subgrade.
• When the quality of the subgrade materials
meets the requirements of the subbase
material, the subbase layer may be omitted.
• When suitable subbase material is not available,
the available materials can be treated to achieve
necessary properties (i.e. Stabilization).
2
Construction of Subbase

3. • Sub-base:
–The materials used for the construction of
subbases could be either:
• Natural Gravel
• Cinder Gravel
• Weathered Rock
• Crushed Gravel
• Crushed Rock or Crushed Boulders
• Recycled Pavement Material
• Or any other granular material complying
with the requirements of subbases 3

4. • Sub-base material should be spread on the approved
subgrade by mechanical means without segregation.
• The material should be loosely spread in layers to give
a compacted thickness not exceeding 200mm .
• The final compacted layer should be free from
concentrations of coarse or fine materials.
• The surface of each completed layer should be
moistened prior to the construction of the succeeding
layer.
• Spread and shape the mixture on the prepared
surface in a uniform layer.
4
Construction Method for subbase

5. • The material should be compacted by the use of
rollers progressing gradually from the outside
towards the center of the layer, except on super
elevated curves, where the rolling should begin at
the low side and progress to the high side.
• Rolling should continue until the entire thickness of
each layer is thoroughly and uniformly compacted
to the specified density
• Here the objective is to achieve full compaction
through the full depth of the material (up to the
specified requirement, typically 95 cent of the
maximum dry density).
5
Construction Method for subbase…cont’d

6. Base Course
• Lies immediately above the subbase
• Consists of granular materials (crushed
stone, crushed slag, gravel and sand).
• Specifications are stricter than those for
subbase regarding (gradation, plasticity,
and strength).
• Materials that do not have the required
properties can be used as base course
material if the are properly stabilized with
Portland cement, asphalt, or lime.
6

7. »The material should be laid either by a self propelled paving machine or
by means of a grader
»The equipment should be of adequate rated capacity & in good working
order
»The mixing plant could be either a batch type or continuous type and
equipped with means of accurately controlling the proportions of all
constituent material
»Compaction should be carried out using 8-10 smooth wheel rollers or
multi wheeled pneumatic tyre rollers
7
Construction Procedure

8. »Road base material should be spread by
mechanical means without segregation
»The material should loosely be spread in layers
to give a compacted thickness within
»The surface of each completed layer should be
moistened prior to the construction of the
succeeding layer
»Prior to compaction the moisture content of the
spread material should be adjusted either by the
uniform application of water or drying out to
achieve the OMC
8
Construction Procedure…….cont’d

9. »The surface of the completed layer should
be tightly bound, free from movement
under the compaction plant, and free from
laminations, ridges, cracks, or loose or
segregated materials
»The in-situ density of the completed layer
should achieve the desired MDD @ OMC
»The completed road base layer should not
be used by construction or public traffic
prior to the application of prime coat 9
Construction Procedure…….cont’d

10. »Vehicles used for transporting dense bitumen macadam
base should have tipping bodies capable of discharging
directly into the paving machine
»Dense Bitumen Macadam material should be laid by
spreading/finishing machine capable of laying to the
required widths, thicknesses & cross-sectional profiles
without causing segregation or other surface defects
»The maximum temperature of material during mixing should
not exceed 165°c.
»On discharge from the mixer plant the aggregate should be
completely coated with binder and the fine aggregate should be
evenly distributed throughout the mix
10
Construction Procedure…….cont’d
Dense Bitumen Macadam Base course material

11. »During transport the material should be insulated against
heat loss and protected from the ingress of moisture by
the use of covers
»The temperature of the spread material at the time of
compaction commences should not be less than 135°c.
the compaction should be completed before the
temperature of the laid material falls below 105°c.
»The density achieved in the completed layer should not be
less than 97% of the Marshal Density
11
Construction Procedure…….cont’d
Dense Bitumen Macadam material Base course …….cont’d

12. – Dense Bitumen Macadam Road Base and priming should not be
carried out in the following adverse weather conditions
• During foggy or wet conditions
• When rain is imminent
• when wind is sufficiently strong to cause uneven spraying;
• When the surface on which the layer is to be constructed is wet
• When the temperature of the surface on which the layer is to be constructed
is less than 10°c
• Construction Tolerances
• Level & Grade
• Width
• Thickness
• Cross-Section
12
Construction Procedure…….cont’d
Dense Bitumen Macadam material Base course …….cont’d

13. Construction Procedure…….cont’d
Dense Bitumen Macadam material Base course …….cont’d
13

14. Surface Course
• Upper course of the road pavement and
is constructed immediately above the
base course.
• Consist of mixture of mineral aggregate
and asphaltic materials.
• It should be capable of :
–withstanding high tire pressure,
–Resisting traffic abrasive forces,
–Providing a skid-resistance surface.
–Preventing the penetration of surface
water into the underlying layers
14

15. »Plant & Equipment
• Mixing Plant
• Spreading
equipment
• Paver
• Rollers
• Trucks
15
Construction of Surface Course(AC)
Type of equipment used in AC Construction
General Requirement
Weather conditions
Asphaltic mixes may be mixed and placed only under favorable weather
conditions, and should not be mixed or placed when rain is imminent or
during moist or wet conditions
Moisture
The mixing and placing of asphaltic mixes will not be allowed if:
(i) the moisture content of the aggregate affects the uniformity of temperature;
(ii) free water is present on the working surface;

16. Surface Requirements
•Correction of road base
•Cleaning of Surface
•Prime Coat
•Preparation for placing the
AC mix
16
Construction of Surface Course(AC)
Production & Transport
1.Using batch plants
Heating the aggregate
 The aggregate shall be dried and heated to the required temperature
Batching
 Each fraction of the aggregate and binder shall be measured
separately and accurately in the proportions by mass in which they
are to be mixed
Mixing
 The aggregate filler and binder shall be mixed until a
homogeneous mixture is obtained in which all particles are
uniformly coated

17. Construction of Surface Course(AC)
17

18. Construction of Surface Course(AC)
Fig. Stationary batching plant 18

19. 2.Using drum type mixer plants
•The aggregate and filler shall be accurately proportioned and conveyed into the drum
mixing unit.
•The calibrated amount of binder shall be sprayed onto the aggregates at the correct
position so that no hardening of the binder shall take place.
•A homogeneous mixture and uniform coating of binder must be achieved
19

20. Transporting the mixture
• Loads shall be covered by waterproof canvas or insulated metal
sheets when the haul exceeds 10 km or during cold, windy or
rainy weather
• Any asphalt which has become wet due to rain or any other cause
shall be rejected.
• Hauling over freshly laid material is not permitted.
20
Spreading the mixture
• The mixture shall be delivered to the paver in such a manner that
the paver will never be forced to stop for lack of asphalt
• The temperature of the mixture shall be controlled by measuring
in a random pattern in the truck immediately before emptying
and shall not be more than 10° C below the minimum
temperature specified for mixing
• The addition and removal of material behind the paver shall
normally not be allowed and the paver shall be capable of
spreading the mixture to the correct amounts that will provide the
required compacted thickness

21. 21

22. •The material shall not be excessively displaced in a
longitudinal or transverse direction especially when
changing gears, stopping or starting rollers.
•No cracks or hair cracks shall be formed and the bond with
the underlying layer shall not be broken.
•Rollers shall not be left standing on the asphalt layer
before it has been fully compacted and before the layer
surface temperature has dropped below 60cc
•The mix shall be rolled as soon as possible after it has been
laid by a combination of vibratory and non-vibratory steel-
tired flat rollers and pneumatic-tyred rollers in a sequence
predetermined and approved during the laying of trial
sections 22
Compaction

23. Pneumatic Rubber-Tired Rollers
23

24. Pneumatic Rubber-Tired Rollers 24

25. Smooth wheel rollers 25

26. 26

27. Prime Coats
• For the purpose of adhesion, Applied or spraying asphaltic
Binder materials onto non-asphalt base courses.
• Use low viscous asphalt or tar.
• Asphalt preferred to have high penetrated qualities and
should leave high viscosity residue in the void spaces.
• MC-30 and MC-70 widely used for dense tightly bond
surfaces, and surface with more opened texture.
• Slow setting emulsified asphalts are recommended for
penetrable surfaces.
• Used to:
– Provide a waterproof surface.
– Fill capillary voids in the base.
– Facilitate the bonding of loose mineral particles.
– Facilitate the adhesion of the surface treatment to the
base.
27

28. Tack Coats
• For the purpose of adhesion, it is the
application of bituminous material to an
existing bituminous, Portland cement
concrete, brick, or block surface or base.
• Purpose: Provide adhesion between the
existing surface and the new bituminous
wearing surface.
• Asphalt emulsions are usually used.
• RC-70 through RC-250 are frequently
used. 28

29. Project 1:- [10 Marks for the paper & 5 Marks for
the presentation]
Q1)Take one construction machinery or lab equipment's which
inspires you and present to the class.
– It should includes the type/name, spec., and in what way
it’s different and what is the inspiration and why it is
presented to the class.
– It should be new technology or has different things from
the ordinary construction machinery or lab equipment's.
29
N.B:-
 In each sub-group the number of students should not be more than 6.
 The paper should not be more than 5 pages.
 For the presentation time each members of the group should be
present other wise the total project mark will be zero for the absent
person.

30. The end 
30