Abstract: This technical paper is based on the low cost, environmentally friendly and sustainable improvements that were made to a low volume road that was successfully completed in April 2004. The low volume road of length of about 50 km in a severely deteriorated condition was in an area affected by conflicts that took place during the last two decades in Sri Lanka. The improvements included the construction of a locally available gravel soil base with CBR values ranging from 19-22, that had a surface treatment of prime coat and sand seal. The objective of this paper is to study the feasibility of the replacement of the normal standard design that had a designed aggregate base having a CBR of not less than 80, which however was not locally available, and which was to be followed by a prime coat and a single bitumen surface dressing, with the above mentioned construction. The extensive method described in this paper which has been successful to date, however requires regular maintenance of surfacing and resurfacing once in every six months during the first two years and once in two years thereafter. It is a useful method for the construction of low volume roads in countries where labour is freely available for maintenance.

1. CONTENTS
ABSTRACT
INTRODUCTION
INVESTIGATIONS, DESIGNS AND
IMPROVEMENTS TO ROAD
SOILS FOR CONSTRUCTION
STEPS OF CONSTRUCTION FOR SECTION WITH
AMENDED PAVEMENT STRUCTURE
CONSTRUCTION OF PRIME COAT AND SURFACE
DRESSING (SAND SEALS)
Prime Coat
Surface Dressing (Sand Sealing)
MAINTENANCE OF ROAD
PRESENT STATE OF ROAD
CONCLUDING REMARS

2. Technical Paper to Study the feasibility
Basically for
 To make use of locally available material
 Minimize the estimated cost
 To suit a Low volume road
 Where Labourers freely available for
maintenance.
 Where Regular maintenance is possible
 To Adopt standard design to suit the site
condition .

3. Advantages by adopting design
 Low Cost construction method in Low volume
traffic road
 Least project Cost
 Environmental friendly construction
methods
 Sustainable Improvements to suit
the site conditions
 Achieving Objectives & Goals of Road Devel

4. Replacement of Standard Design
 Standard Design
1. Sub-base of compacted
225mm Gravel layer
(CBR>20)
2. Base of 150 mm ABC
(CBR>80)
3. Priming
4. SBST (surface dressing)
 Modified Design
1. Scarifying & mixing with
gravel to Existing & re-
grading surface to a
compacted thickness of
150 mm
2. Sub-base of 150-300
mm thickness of gravel
(CBR- 19-22)
3. Base with Gravel
compacted thickness of
150 mm (CBR-19-22)
4. Priming
5. Sand Sealing (surface
dressing).

6. Years of Conflict has resulted in theYears of Conflict has resulted in the
deterioration of most of the road infrastructuredeterioration of most of the road infrastructure
in Sri Lanka’s Northern Province and adjacentin Sri Lanka’s Northern Province and adjacent
areas. As a result, some roads have becomeareas. As a result, some roads have become
functionally impassable, through direct damagefunctionally impassable, through direct damage
and/or destruction or due to lack of preventativeand/or destruction or due to lack of preventative
maintenance. The existing roads in these areasmaintenance. The existing roads in these areas
need significant rehabilitation in order toneed significant rehabilitation in order to
facilitate freedom of movement, and revive thefacilitate freedom of movement, and revive the
economy in the area.economy in the area.
INTRODUCTIONINTRODUCTION

7. PROJECT DETAILS Name of Road :- Paranthan-Mullaitivu (A-035)
 Section :- 2.00 km to 52.13 km (50 km)
 TEC :- 50.0 million
 Source of Funds :- GOSL
 Period of Construction
Start :- June -2003
Completion :- April 2004
 Scope of works :- Scarifying existing surface
and mixing gravel & re-grading to a compacted
thickness of 150 mm and gravel sub-base overlay of
compacted thickness of 150mm-300mm and gravel
base overlay of 150 compacted thickness with
priming & sand sealing surfacing

8. Existing Road Condition
Consisting of doubled layers of
50mm single sized aggregate with
extremely large potholes without
aggregate
The available platform width of
road 6-8 m
Carriageway width of 4-5m
Not motor able poor & dilapidated
condition

9. Climate Condition
 Dry Zone
 Annual average Rainfall - <1500 mm
 Ambient Temperature -25-35°C

10. Works Entrusted to ….
 Chief Engineer, RDA Mullaitivu
 No Contractual system was introduced due to
non-availability of competent Road
Experience Contractors
 Entire improvement Works executed by RDA
direct lab our system
 Field Laboratory set-up and attached with
Chief Engineer’s office by Research &
Development Division, RDA/ Ratmalana.

11. Standard Pavement Design
a.) estimating the amount of traffic (and its axle load
distribution) that will use the road over the
selected design life,
b.) assessing the strength of the sub grade soil over
which the road is to be built and that of the
material to be used as sub-base.
c.) taking into account a) and b), selecting the most
economical combination of pavement materials
and layer thickness that will be sufficient to
provide satisfactory service over the design life of
the pavement with only routine maintenance.

12. Investigations & Designs
 Estimated Traffic in 2004 -500 veh /day
 Design Life -10 years
 Axle load traffic – 0.1 million cumulated
standard axles
 Annual Traffic growth rate -4%

13. Standard Pavement Design…….
 Existing Sub-grade CBR varied 3-8 range
 Sub-base gravel 4 days soaked CBR >20
with 225 mm compacted minimum thickness.
 Base with Dense graded aggregate base
coarse with compacted thickness of 150 mm
with 4 days soaked CBR >80
 Prime Coat
 Single Bitumen Seal treatment (SBST)

14. Constraints with standards pavement
Design construction……
 The length of road section -50 km
 Limited funds allocated for improvements -50
million
 Limited Project duration to less than 1 year
 Difficult in handling through RDA direct labour
 DGABC is not readily available locally and to
be transported to a distance of more than
150 km
 No competent bidders in tendering
 No suppliers for DGABC

15. Standard Pavement Design Adopted to …
 Adopted Pavement Design
1. Scarifying & mixing with gravel to Existing
& re-grading surface to a compacted
thickness of 150 mm
2. Sub-base of 150-300 mm thickness of
gravel (CBR- 4 days soaked range 19-22)
3. Base with Gravel 150mm compacted
thickness (CBR- 4 days soaked range 19-
22)
4. Priming
5. Sand Sealing (surface dressing).

16. SOILS FOR CONSTRUCTION
( Four number of Borrow pits selected)
 Gravel for Base, Sub-base Sub
grade & Embankments
considering the followings
1. Maximum Dry Density
2. Engineering Properties
1. CBR
2. Atterberg limits
3. Mechanical Properties
(Particle size Distribution)

17. Engineering Properties of Soils selected….
ID Mark LL PL PI OMC
MAX
DD
CBR
(%)
Kalliyady-1 40 22 18 11.8 1.96 17
Vaddakachchi 33 14 19 10.2 2.01 19
Kalliyady-2 37 19 18 11.2 1.98 21
Kokavil 39 22 17 15.0 1.93 22

18. Step 1- Drainage works
1.Cutting Earth drains
2.Repairs to Existing structures
3. Re-construction of Minor
structures
4.Construction of New minor
structures where ever
required

19. Step 2- Sub Grade Construction
Moistened Existing Damaged
surface & scarified and mixed
with gravel and laid,
spreaded, graded rolled &
compacted to the standard
compaction

20. Step 3- Embankments filling
Wherever road widened to minimum 7.4
m width and raised to the required
levels and this was done by removing the
loose sand and gravel on existing unpaved
road, grass and loose soil on shoulders,
verges and side slopes of embankments.
Then benching the side slopes and road
foundations and compacting of layers of
suitable soils of compacted thickness of
150mm to the required densities

21. STEP 4-Embankment Construction
 where no widening or raising was done,
the top 150mm layer of existing soil was
compacted to 100% standard density.

22. STEP 5-Sub-base Construction
 Over the compacted sub grade to
the full width of carriageway, a sub-
base of thickness 150 to 300mm in
layers of 75 to 150mm compacted
thickness was constructed with
gravelly soil compacted to 100%
standard density

23. STEP 6-BASE CONSTRUCTION
 Over the compacted sub-base to
the full width of the road formation,
a Gravel Soil Base of thickness
150mm was constructed &
compacted to 100% standard
density.

24. STEP 7
 Priming & Surfacing
 Over the compacted base to
the width of carriageway of
5.0m, a prime coat and a
sand seal were applied.

25. Priming
On newly constructed road
bases a prime coat is
required , prior to applying
the surface dressing, to
bind the surface together
and ensure good adhesion
of the binder film.

26. Prime Coat
A prime coat is an application of low
viscosity asphalt to a granular base in
preparation for an asphalt surface
course. The prime coat is designed to
perform the following functions:
1. - To coat and bond loose mineral
particles on the surface of the base.
2. - To harden or toughen the surface.
3. - To waterproof the surface of the
base.
4. - To plug capillary voids.
5. - To provide adhesion between the
base and the next course.

27. Prime Coat GSB was shaped and compacted to the
correct longitudinal and transverse
profile. The compaction was carried out
with standard 8 tonne vibrating and 8-10
tonne smooth wheeled rollers. After
shaping and compaction, dust and loose
materials on the surface were well
brushed and removed. Then the gravel
surface was lightly sprinkled with water to
moisten the surface. The bituminous
material was then sprayed uniformly over
the gravel surface.

28. Prime Coat The material used -CSS-1
 Mixed with an equal amount of water.
 The rate of application of the diluted
emulsion was 1.0-1.5 l/m2.
 The spraying was done at the ambient
temperature of not below 15 ºc by using
a 4000 l bitumen distributor
 Closed for traffic -24-48 hrs min 3 hrs
 After lapse of the period, surface
blinded with Coarse sand as blotting
material with light rolling

29. Surface Dressing (Sand Sealing)
 This is a traditional Sri Lankan periodic
maintenance technique which effectively
SEALS the road surface, but does not
improve its skid resistance. However, Sri
Lankan climate is suitable for good surface
dressing or sand seals with long dry periods
and generally predictable rainy seasons..

30. Surface Dressing (Sand Sealing) A sand seal comprises a thin film of binder,
generally bitumen, which is sprayed on to the
primed road surface and then covered with a
layer of coarse sand and rolling using a
pneumatic tyred roller
 The thin film of binder acts as a water
proofing seal and prevents the entry of
surface water into the road structure.

31. Surface Dressing (Sand Sealing)
 1. Provide a water proof seal to a road
surface, thus preventing the ingress of
surface water to the lower layers of the road
pavement.
 2. Arrest the deterioration of an existing road
surface that is showing signs of distress.
 3. Restore the skid resistance to an existing
road surface.
 4. Provide a dust-free and durable running
surface for a previously untreated
mechanically stable road base.

32. Surface Dressing (Sand Sealing)
 A sand seal was constructed on the primed
gravel surface after a lapse of about 3-4
days.
 This increased the useful life of the road.
 The primed surface was dried, and any loose
material swept and removed from the
surface.

33. Surface Dressing (Sand Sealing)
 Material Used - CRS1
 Temperature - Ambient
temperature>15ºC
 Spray Rate - 0.75-1.00 lit/sq.m
 Covered Sand rate - 8 cu.m/1000sq.m
 Rolling -Std 9 wheeled PTR

34. Damages immediately after
construction
several small patches
surface peeled off

35. Regular Maintenance
 Drainage facilities
 Verges and the side drains

36. Present Road Condition……..
 After completion of 3 years time,
1. Road surface looks satisfactory condition in
more than 95% of the area
2.No edge failures more than 80% of the area
3.Drainage system is under control
4.No inundation
5.Shoulders in more than 90% area is
satisfactory without erosion.
6. Drainage structure are functioning properly
7.During the period all damaged major
structures were newly constructed by
Ministry of Nation Building using Bailey
Bridge Components

37. Performance of road……..
 Road now in good condition
 Replacing by above method gives following
advantages
1. Money savings
2. Time savings
3. Easy maintenance
4. Environmental friendly construction
methods
5. Sustainable developments

38. Overall Benefits by the Construction ……
1. Travel time reduced from 3hrs to 45-60 min
2. Vehicle operating cost considerably reduced
3. National Network in linked by linking district
capitals
4. No detours& passable during rainy seasons
5. Contributed to the great extend of GDP &
Economy growth of the area.
6. Facilitated freedom of movement, andcilitated freedom of movement, and
revived the economy in the area.revived the economy in the area.
7.7. Achieved the Goals & Objectives of RDAAchieved the Goals & Objectives of RDA
8.8. The success of the project inline with VisionThe success of the project inline with Vision
and Mission of RDAand Mission of RDA