The document discusses different types of road bed construction materials and methods. It describes the various layers that make up a road, including: base course, subgrade, and different types of base courses like untreated gravel, treated with asphalt or cement. It provides details on specifications for materials, construction, and maintenance of untreated gravel roads. Treated and stabilized base courses are also outlined. [END SUMMARY]

1. Road Bed
Construction

2. Base Course
•is the materials laid on top
of the subgrade consisting
of crushed stoned or
gravel, sometimes mixed
with asphalt binders.

3. Two types of Base Course
•The granular Base Course or Untreated Base
Course
•Treated Base Course

4. The Granular Base Course is a road surface of
untreated soil mixture describe as gravel road.
Gravel Road consist largely pebbles or crushed rock
particles combined with either, clay, lime, iron oxide or
other fine materials sufficient enough to serve as binder of
the coarse particle.

5. Construction and Maintenance Requirement of Untreated
Gravel Road Surface
1. That the road must be stable to support the supper imposed loads
detrimental deformation.
2. It must shed the large portion of rain that falls on the surface because
water penetrating the sub grade might soften it and loosen the surface
stability.
3. It must be free from large rocks or stones over one inch in diameter
so that it could be regularly maintained by blading or dragging.
4. Gravel Road must possess capillarity properties sufficient enough to
replace the moisture lost through the surface evaporation

6. 5. On dry weather, the moisture film on the clay particles should bind the entire
mass together, and in wet weather the first rain that fall on the surface, should
expand the clay and close the pores to prevent water from entering and
softening of the materials.
6. An excessive amount of highly expansive materials should be avoided
because clay swell and unseat the coarser materials when wet and ultimately
will weaken the stability of road.
7. Gravel Road must be low Cost. Funds for low traffic road is very limited that
most of the time overlooked in the list of appropriation priorities except on
election period.
8. Use local materials. Meaning those materials that could be found nearby the
project

7. Treated Base Course
•To stabilized the base coarse, it is sometimes treated with
either Asphalt, Lime, Portland Cement, or other materials
as binders mixed with the aggregate base course. Treated
Base course is adopted if in the study or analysis of the
highway agency, a better road can be produced at a
minimal over all cost, or when a politician order the
highway office to construct the road with or without study
because it was a commitment during the campaign period.

8. Sand and Asphalt Base Course
• The sand and asphalt base course is composed of either loose beach
sand, dune pit or river sand cemented with asphalt materials. In the
early road construction, sand and clay mixture is not only used as
road surfaces but also for base courses. But lately, the Cutback
asphalt, Emulsified asphalt or Tars have been introduced as
substitute for the clay binders to produce quality base courses for
roads and highways.
• Sand for mixing asphalt should be clean and strong should be clean
and strong, because the surface properties and grain shape must
have the quality to resist displacement under load.

10. Fine Grain
Asphalt Base
• An asphalt stabilized base and
sub-grade constructed with fine
grained has a controlled. Plastic
Index of 6 to 10 respectively.
Aggregates with plasticity Index
up to 30 are processed with
lime. Those with up to 50%
passing the No.200 sieve and
Plastic Index up to 18 can be
stabilized even without pre-
treatment.

11. Soil and Base Course Stabilized with
Cement
• The used of Portland cement in stabilizing soils and aggregates was initially
practiced after world war- 1 in 1914
1. Cement stabilization by mixing natural materials and Portland cement compacted at
optimum moisture content and cured to hydrate the cement is considerably strong and
stable base. It is less susceptible to deformation caused by moisture and temperature
changes.
2. Comparatively, this is less rigid than the Portland cement concrete because its
modulus of elasticity ranges from 100,000 for clay soils with little cement up to
1,000,000 for the strong mixture. Its compressive strength of about 300 psi to 600 psi
with flexural strength of about 20% of the compressive value.
3. Portland cement concrete modulus of elasticity ranges from 3 million to 6 million with
compressive strength of about 3,000 to 5,000 psi.
•

12. The stabilized cement mixture is called “ soil cement” produced by
using abundant native local materials subdivided into three parts:
1. Sandy, and gravelly soils containing less than 25% silt and clay.
2.Sand with lesser amount of fines like beach sand, glacial and
windblown sand.
3. Silty and Clayey Soils.

13. Grading and Maintenance of Untreated Surface
• The cross slope of untreated surface gravel road must be sufficient enough to
drain water to prevent potholes and softening of the roadway; thus:
1. If road materials are sufficiently stable and water tight, one inch per slope is
considered satisfactory although 3/8 to ½ per slope is preferred
2. If the road is steep grade, substantial cross slope is needed to direct the
water into the roadside.

14. • Untreated surface road is seldom constructed in less than 20 cm loose depth.
When compacted, will be compressed to about 15 cm thick. Road development
sometimes adopted the stage construction methods which means, step by step
improvement of the roadway, depending upon the availability of funds and
demand of increased traffic. The sequence of improvement could be as follows:
• First: it might be an earth road surface
• Second: untreated gravel road
• Third: Application of asphalt over the gravel
• Fourth: The use of stone type pavement with gravel as part of the base course

15. DWPH Standard Specification on Aggregate Sub-Base
Course
• The Department of Public Works and Highways
classified the aggregate sub-base course as Item
200 which consists of furnishing, placing and
compacting aggregate sub-base course on a
prepared sub-grade.

16. Item – 200 Material
Requirements
• That, aggregate for sub-base
shall consist of hard, durable
particles of fragments or crushed
stone, crushed slag or crushed or
natural gravel and filler or
natural crushed sand or other
firmly divided mineral matter.
Sieve Designation
Standard Alternate US Standard Mass
Percent
Passing
50 2”
25 1”
10 3/8”
0.75. No.200
100
55-85
40-75
0-12
GRADING REQUIREMENTS FOR ITEM 200

17. Item 201 Material Requirements
CONDITIONS:
1. That the fraction passing the 0.075 mm (No. 200) sieve shall have a mass
percent of wear or to exceed 50.
2. The fraction passing the 0.425mm (No. 40) sieve shall have a liquid limit not
greater than 25 and Plastic Index not greater than 6.
3. The coarse portion retained on a 2.0mm (No.40) sieve shall have a mass
percent of wear no to exceed 50.
4. The materials passing the 20mm (3/4”) sieve shall have a soaked CBR value
of not less than 80%

18. ITEM – 202 Material Requirements
• The portion passing the 0.075mm (No.200) sieve shall not be greater than
0.66 (2/3)of the portion passing the 0.425 mm (No.40) sieve.
• The portion passing the 0.425 mm(No.40) sieve shall have a liquid limit not
more than 25 and Plastic Index not more than 6.
• The coarse aggregate retained on 2.0 mm (No. 10) sieve shall have a mass
percent of wear not more than 45 by L.A. abrasion tests, and not less than 50
mass percent shall have at least one fractured face.
• The material passing the 20 mm (3/4”) sieve shall have a minimum soaked
CBR value of 80%

19. • ITEM 201 CRUSHED
AGGREGATE BASE
COURSES

20. Item- 203 Lime Stabilized Road
Mix Base Course
This item consists of foundation
for a surface course composed of
soil aggregate, lime and water
proportion mixed on site a
constructed on a prepared sub-
grade or sub-base.

22. Preparation of the Soil Aggregate
• Case – I For New Soil Aggregate
• The existing roadbed is scarified lightly and bladed to a uniform grade
according to the plan, then rolled, watered and rolled.
• All depressions appearing on the surface are filled, and the weak portion of
the roadbed is strengthened with new soil aggregate.
• Allow one day for measuring, sampling and testing of the sample for approval
of the quality and gradation before spreading the window for application of
the hydrated lime.

23. Case – 2 Salvage Soil Aggregate
• When materials in the site are to be used for mixing, the surface should be
scarified lightly and bladed to a uniform conforming to the cross section of
the plan.
• The reshaped surface is scarified again to depth required leaving a
foundation of undisturbed material parallel with the profile and cross
section.
• The loosened materials are bladed into a window at the side of the roadway.
The undisturbed materials are then rolled, watered and rolled.

24. Item 204 Portland Cement Stabilized Road Mix Base Course
• This item consist of a foundation for surface course
composed of soil aggregate, Portland cement and water,
proper proportions of road-mixed placed on a prepared sub-
grade or sub-base.
Item 205 Asphalt Stabilized Road Mixed Base Course
• Materials. Asphalt materials should be Anionic or Cationic
Emulsion asphalt of the slow setting type.
• Mixture Proportion. The amount of asphalt material to be
added to the aggregate should be from 4 to 7 mass percent of
the dry aggregate.

25. Item 206 Portland Cement Treated Plant Mix Base
Course
• Travel Plant Mixing Method: The salvage or new aggregate is pulverized until at
least 80 mass percent of all the materials other than stone or gravel passes a 4.75
(No.4) sieve. Any material retained on a 50 mm (2”) sieve and other unsuitable
materials are removed.
• Central Plant Mixing Method: The plant is equipped with feeding and meeting
devices that will introduce the cement aggregate and water into the mixer in
quantities specified. Mixing continue until after a uniform mixture is attained.
• Spreading, Compacting and Finishing: Nor more than 60 minutes should lapse
from the start of mixing to compaction of the laid mixture. After spreading, the
mixture is compacted and finished in accordance with the procedures as
enumerated for lime stabilized road mix base course Item 2-3.

26. Clearing
and
Grubbing

27. • Clearing and Grubbing is categorized under Item – 100 of the
DPWH standard specification. It consists of clearing, grubbing,
removing and disposing of all vegetables matter and debris except
this one objects that are designated to remain in place or are to
be removed in consonance with other provision of the
specifications. It also includes preservation from injury or
defacement of all objects designated to remain.

28. Specification for Clearing and Grabbing provides that:
All surface objects and all trees, stumps, roots and other protruding
obstructions, not designated to remain should be cleared and/or
grubbed including the moving required as follows:
• Removal of undistributed stumps and roots and non-perishable solid
objects with a minimum depth of 90 centimeters below sub-grade or
slope of embankments will not be required.
• Outside the grading limits of cut and embankment areas, stumps and
not perishable solid objects should be cut off not more than 15 cm
above the ground line or below low water level.

29. •In areas to be rounded at the top of cut slope, stumps
should be cut off flush with or below the surface of the final
slope line.
•Grubbing of pits, channel changes and ditches will be
required only to the depth necessary by the proposed
excavation with such areas.
•Burning should be under the surrounding vegetation,
adjacent property, or anything designated to remain on the
right of way will not be jeopardized.

30. Methods of Measurement
• Area Basis- by hectare and fractions thereof acceptably cleared
and grubbed.
• Lump Sum Basis- No measurement of areas will be made for this
item.
• Individual Unit Basis (selective clearing) – The diameter of trees
will be measured at a height of 1.4 meters above the ground.
Trees less than 15 cm diameter will not be measured for payment.

31. Excavation

32. Excavation is the process of loosening and removing earth or rock from its
original position in a cut and transporting it to a fill or to waste deposit.
Roadway excavation is classified int0:
• Unclassified excavation
• Rock excavation
• Common excavation
• Muck excavation
• Borrow excavation

33. • Unclassified Excavation is the excavation and disposal of all materials regardless of its
nature, or not classified and included in the Bill of Quantities under other pay items.
• Rock Excavation consists of igneous, sedimentary and metaphor if rocks that cannot be
excavated without blasting or the use of rippers and all boulders or other detached stones
each having a volume of 1 cubic meter.
• Common Excavation are those that are not included in the Bill of Quantities under rock
excavation or other pay items.
• Muck Excavation consist of the removal and disposal of deposits of saturated or
unsaturated mixture of soils and organic matter not suitable for foundation materials
regardless of moisture contents.
• Barrow Excavation in the excavation and utilization of approved materials for the
construction of a embankment or for other portion of the work obtained from approved
sources in accordance with the following requirements.

34. The Use of Excavated Materials
All suitable materials removed from the excavation area are used in the formation of:
Constructing the Roadbed
• Embankment
• Sub Grade
• Shoulders
• Slope
• Bedding
• Backfill for structures
All unsuitable materials that could not be properly compacted in embankment must must
be disposed of without d lay for it might be included in the work when the engineer turn
his back for a cup of coffee. Borrow materials should not be placed until after the fill
accessible roadway excavation has been placed in the fill.