# PART III -- FLEXIBLE BASE COURSES

### **ITEM P-208 AGGREGATE BASE COURSE**

**208-1.1** This item shall consist of a base course composed of
**\[crushed\] \[uncrushed\]** coarse aggregate bonded with either soil
or fine aggregate or both.  It shall be constructed on a prepared
underlying course in accordance with these specifications and shall
conform to the dimensions and typical cross section shown on the plans.

MATERIALS

**208-2.1 UNCRUSHED COARSE AGGREGATE**.  The base course material shall
consist of hard, durable particles or fragments of stone or gravel mixed
or blended with sand, stone dust, or other similar binding or filler
materials produced from approved sources.  All oversized stones, rocks
and boulders occurring in the pit or quarry material shall be wasted;
those of acceptable quality may be crushed and become a part of the base
material, provided the blend meets the specified gradations.  The
aggregate shall be free from vegetation, lumps, or excessive amounts of
clay and other objectionable substances.  The coarse aggregate shall
have a percent of wear not more than 45 at 500 revolutions as determined
by ASTM C 131.

**208-2.2 CRUSHED COARSE AGGREGATE**.  The aggregates shall consist of
both fine and coarse fragments of crushed stone, crushed slag, or
crushed gravel mixed or blended with sand, screenings, or other similar
approved materials.  The crushed stone shall consist of hard, durable
particles or fragments of stone and shall be free from excess flat,
elongated, soft or disintegrated pieces, dirt, or other objectionable
matter.

The crushed slag shall be air-cooled, blast furnace slag and shall
consist of angular fragments reasonably uniform in density and quality
and shall be reasonably free from thin, elongated, or soft pieces, dirt,
and other objectionable matter.  It shall weigh not less than 70 pounds
per cubic foot (1.12 Mg/cubic meter) as determined by ASTM C 29.

The crushed gravel shall consist of hard, durable stones, rock, and
boulders crushed to specified size and shall be free from excess flat,
elongated, soft or disintegrated pieces, dirt, or other objectionable
matter.  The method used in production of crushed gravel shall be such
that the fractured particles occurring in the finished product shall be
as nearly constant and uniform as practicable and shall result in a
minimum of 60% of the material retained on the No. 4 sieve having at
least 2 fractured faces and 75% having at least 1 fractured face.

If necessary to meet this requirement or to eliminate an excess of fine,
uncrushed particles, the gravel shall be screened before crushing.  All
stones, rocks, and boulders of inferior quality in the pit shall be
wasted.

The crushed coarse aggregate shall have a percent of wear not more than
50 at 500 revolutions as determined by ASTM C 131.

All material passing the No. 4 mesh (4.75 mm) sieve produced in the
crushing operation of either stone, slag, or gravel shall be
incorporated in the base material to the extent permitted by the
gradation requirements.

**208-2.3 GRADATION**.  The gradation of the uncrushed or crushed
material shall meet the requirements of one of the gradations given in
Table 1 when tested in accordance with ASTM C 117, ASTM C 136, and ASTM
D 422.

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> **Include testing frequencies for the particle size distribution.**

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**TABLE 1. REQUIREMENTS FOR GRADATION OF AGGREGATE**

  ---------------------- --------------- ------------------ ------------------
  **Sieve Designation**  **Percentage by                    
                         weight passing                     
                         sieves**                           

                                                            

                         **2\'\'         **1 1/2\'\'        **1\'\'maximum**
                         maximum**       maximum**          

                                                            

  2 inch (50.0 mm)       100             \--                \--

  1‑1/2 inch (37.0 mm)   70-100          100                \--

  1 inch (25.0 mm)       55-85           70-100             100

  3/4 inch (13.0 mm)     50-80           55-85              70-100

  No. 4 (4.75 mm)        30-60           30-60              35-65

  No. 40 (0.45 mm)       10-30           10-30              10-25

  No. 200 (0.075 mm)     5-15            5-15               5-15
  ---------------------- --------------- ------------------ ------------------

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> **For frost areas, add requirements for the material finer than 0.02
> mm to a maximum of 3% and the range for the 200 sieve to between 0 and
> 8%.**

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The gradations in the table represent the limits that shall determine
suitability of aggregate for use from the sources of supply.  The final
gradations decided on within the limits designated in the table shall be
well graded from coarse to fine and shall not vary from the low limit on
one sieve to the high limit on the adjacent sieves, or vice versa.

The amount of the fraction of material passing the No. 200 mesh (0.075
mm) sieve shall not exceed one-half the fraction passing the No. 40 mesh
(0.45 mm) sieve. The aggregate blend shall not contain more than 3%
material finer than 0.02 mm unless all materials are produced from
crushed stone.

The portion of the filler and binder, including any blended material,
passing the No. 40 mesh (0.45 mm) sieve have a liquid limit not more
than 25 and a plasticity index not more than 6 when tested in accordance
with ASTM D 4318.

The selection of any of the gradations shown in the table shall be such
that the maximum size aggregate used in any course shall be not more
than two-thirds the thickness of the layer of the course being
constructed.

**208-2.4 FILLER FOR BLENDING**.  If filler, in addition to that
naturally present in the base course material, is necessary for
satisfactory bonding of the material, for changing the soil constants of
the material passing the No. 40 mesh (0.45 mm) sieve, or for correcting
the gradation to the limitations of the specified gradation, it shall be
uniformly blended with the base course material at the crushing plant or
at the mixing plant.  The material for such purpose shall be obtained
from sources approved by the Engineer and shall be of a gradation
necessary to accomplish the specified gradation in the finally processed
material.

The additional filler may be composed of sand, but the amount of sand
shall not exceed 20% by weight of the total combined base aggregate. 
All the sand shall pass a No. 4 mesh (4.75 mm) sieve and not more than
5% by weight shall pass a No. 200 mesh (0.075 mm) sieve.

CONSTRUCTION METHODS

**208-3.1 OPERATIONS IN PITS AND QUARRIES**.  All work involved in
clearing and stripping pits and quarries, including handling of
unsuitable material, shall be performed by the Contractor.  All material
shall be handled in a manner that shall secure a uniform and
satisfactory base product.  The base course material shall be obtained
from sources that have been approved.

**208-3.2 PREPARING UNDERLYING COURSE**.  The underlying course shall be
checked and accepted by the Engineer before placing and spreading
operations are started.  Any ruts or soft, yielding places due to
improper drainage conditions, hauling, or any other cause, shall be
corrected and rolled to the required density before the base course is
placed thereon.

To protect the underlying course and to ensure proper drainage, the
spreading of the base shall begin along the centerline of the pavement
on a crowned section or on the high side of the pavement with a one-way
slope.

**208-3.3 METHODS OF PRODUCTION**

**a. Plant Mix**.  When provided in the proposal, or when selected by
the Contractor and approved by the Engineer, the base material shall be
uniformly blended or mixed in an approved plant.  The mixing plant shall
include bins for storage and batching of the aggregate, pump and tanks
for water, and batch mixers of either the pugmill or drum type.  All
mineral aggregates shall be batched into the mixer by weight.  The
agitation shall be such that a thorough dispersion of moisture is
obtained.  The size of the batch and the time of mixing shall be fixed
by the Engineer and shall produce the results and requirements
specified.  The base course material produced by combining two or more
materials from different sources shall be mixed in a mixing plant
described herein.  The mixture material shall be at a satisfactory
moisture content to obtain maximum density.

**b. Travel Plant**.  When the use of a traveling plant is allowed, the
plant shall blend and mix the materials to meet these specifications. 
It shall accomplish a thorough mixing in one trip.  The agitation shall
be such that the dispersion of the moisture is complete.  The machine
shall move at a uniform rate of speed and this speed shall be regulated
to fix the mixing time.  If a windrow-type of travel plant is employed
for mixing, the aggregate shall be placed in windrows parallel to the
pavement centerline.

The windrow volume shall be sufficient to cover exact areas as planned. 
The windrow contents shall produce a mixture of the required gradation
and bonding qualities.  If a travel plant is used which is of the type
that mixes previously spread aggregates in-place, the material shall
have been spread in such thickness and proportions as may be handled by
the machine to develop a base course of the thickness of each layer and
of the gradation required.  With either type of equipment, the mixed
material shall be at a satisfactory moisture content to obtain the
maximum density.

**c. Materials of Proper Gradation**.  When the entire base course
material from coarse to fine is secured in a uniform and well-graded
condition and contains approximately the proper moisture, such approved
material may be handled directly to the spreading equipment.  The
material may be obtained from gravel pits, stockpiles, or produced from
a crushing and screening plant with the proper blending.  The materials
from these sources shall meet the requirements for gradation, quality,
and consistency.  The intent of this section of these specifications is
to secure materials that will not require further mixing.  The base
material shall be at a satisfactory moisture content to obtain maximum
density.  Any minor deficiency or excess of moisture may be corrected by
surface sprinkling or by aeration.  In such instances some mixing or
manipulation may be required immediately preceding the rolling to obtain
the required moisture content.  The final operation shall be blading, if
necessary, to obtain a smooth uniform surface true to line and grade.

**208-3.4 PLACING**.

**a.** The aggregate base material that is correctly proportioned, or
has been processed in a plant, shall be placed on the prepared
underlying course and compacted in layers of the thickness shown on the
plans.  The depositing and spreading of the material shall commence
where designated and shall progress continuously without breaks.  The
material shall be deposited and spread in lanes in a uniform layer and
without segregation of size to such loose depth that, when compacted,
the layer shall have the required thickness.  The base aggregate shall
be spread by spreader boxes or other approved devices having positive
thickness controls that shall spread the aggregate in the required
amount to avoid or minimize the need for hand manipulation.  Dumping
from vehicles in piles that require rehandling shall not be permitted. 
Hauling over the uncompacted base course shall not be permitted.

**b.**  The aggregate base material that has been processed in a
traveling plant, or mixed and blended in-place, shall be spread in a
uniform layer of required depth and width and to the typical cross
section.  The spreading shall be by a self-powered blade grader,
mechanical spreader, or other approved method.  In spreading, care shall
be taken to prevent cutting into the underlying layer.  The material
shall be bladed until a smooth, uniform surface is obtained, true to
line and grade.

**c.**  The base course shall be constructed in a layer not less than 3
inches (75 mm) nor more than 6 inches (150 mm) of compacted thickness. 
The aggregate as spread shall be of uniform grading with no pockets of
fine or coarse materials.  The aggregate, unless otherwise permitted by
the Engineer, shall not be spread more than 2,000 square yards (1700
square meters) in advance of the rolling.  Any necessary sprinkling
shall be kept within these limits.  No material shall be placed in snow
or on a soft, muddy, or frozen course.

When more than one layer is required, the construction procedure
described herein shall apply similarly to each layer.

During the mixing and spreading process, sufficient caution shall be
exercised to prevent the incorporation of subgrade, subbase, or shoulder
material in the base course mixture.

**208-3.5 COMPACTION**.  Immediately upon completion of the spreading
operations, the aggregate shall be thoroughly compacted.  The number,
type, and weight of rollers shall be sufficient to compact the material
to the required density.

The moisture content of the material during placing operations shall not
be below, nor more than 2 percentage points above, the optimum moisture
content as determined by ASTM **\[ \]**.

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> **If nuclear density machines are to be used for density
> determination, the machines shall be calibrated in accordance with
> ASTM D 2922. The nuclear equipment shall be calibrated using blocks of
> materials with densities that extend through a range representative of
> the density of the proposed base material. ASTM D 3017 may be used to
> determine the moisture content of the material. (See Section 120 of
> the General Provisions for additional guidance)**

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**208-3.6 ACCEPTANCE SAMPLING AND TESTING FOR DENSITY**.  Aggregate base
course shall be accepted for density on a lot basis.  A lot will consist
of one day\'s production where it is not expected to exceed 2400 square
yards (2000 square meters).  A lot will consist of one-half day\'s
production where a day\'s production is expected to consist of between
2400 and 4800 square yards (2000 and 4000 square meters).

Each lot shall be divided into two equal sublots.  One test shall be
made for each sublot.  Sampling locations will be determined by the
Engineer on a random basis in accordance with statistical procedures
contained in ASTM D 3665.

Each lot will be accepted for density when the field density is at least
100 percent of the maximum density of laboratory specimens prepared from
samples of the material delivered to the jobsite.  The specimens shall
be compacted and tested in accordance with ASTM **\[ \]**.  The in-place
field density shall be determined in accordance with ASTM D 1556 or ASTM
D 2167.  If the specified density is not attained, the entire lot shall
be reworked and/or recompacted and two additional random tests made. 
This procedure shall be followed until the specified density is reached.

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> **The Engineer shall specify ASTM D 698 for areas designated for
> aircraft with gross weights of 60,000 pounds (27 200 kg) or less and
> ASTM D 1557 for areas designated for aircraft with gross weights
> greater than 60,000 pounds (27 200 kg).**
>
> **If nuclear density machines are to be used for density
> determination, the machines shall be calibrated in accordance with
> ASTM D 2922. The nuclear equipment shall be calibrated using blocks of
> materials with densities that extend through a range representative of
> the density of the proposed base material. ASTM 3017 may be used to
> determine the moisture content of the material. (See Section 120 of
> the General Provisions for additional guidance)**

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**208-3.7 SURFACE TEST**.  After the course has been completely
compacted, the surface shall be tested for smoothness and accuracy of
grade and crown.  Any portion lacking the required smoothness or failing
in accuracy of grade or crown shall be scarified, reshaped, recompacted,
and otherwise manipulated as the Engineer may direct until the required
smoothness and accuracy are obtained.  The finished surface shall not
vary more than 3/8 inch (9 mm) from a 16-foot (4.8 m) straightedge when
applied to the surface parallel with, and at right angles to, the
centerline.

**208-3.8 THICKNESS**.  The thickness of the base course shall be
determined by depth tests or cores taken at intervals in such manner
that each test shall represent no more than 300 square yards (250 square
meters).  When the base deficiency is more than 1/2 inch (12 mm), the
Contractor shall correct such areas by scarifying, adding satisfactory
base mixture, rolling, sprinkling, reshaping, and finishing in
accordance with these specifications.  The Contractor shall replace, at
his/her expense, the base material where borings have been taken for
test purposes.

**208-3.9 PROTECTION**.  Work on the base course shall not be
accomplished during freezing temperatures nor when the subgrade is wet. 
When the aggregates contain frozen materials or when the underlying
course is frozen, the construction shall be stopped.

Hauling equipment may be routed over completed portions of the base
course, provided no damage results and provided that such equipment is
routed over the full width of the base course to avoid rutting or uneven
compaction.  However, the Engineer in charge shall have full and
specific authority to stop all hauling over completed or partially
completed base course when, in his/her opinion, such hauling is causing
damage.  Any damage resulting to the base course from routing equipment
over the base course shall be repaired by the Contractor at his/her own
expense.

**208-3.10 MAINTENANCE**.  Following the completion of the base course,
the Contractor shall perform all maintenance work necessary to keep the
base course in a condition satisfactory for priming.  After priming, the
surface shall be kept clean and free from foreign material.  The base
course shall be properly drained at all times.  If cleaning is
necessary, or if the prime coat becomes disturbed, any work or
restitution necessary shall be performed at the expense of the
Contractor.

Before preparations begin for the application of a surface treatment or
for a surface course, the base course shall be allowed to partially dry
until the average moisture content of the full depth of base is less
than 80% of the optimum moisture of the base mixture.  The drying shall
not continue to the extent that the surface of the base becomes dusty
with consequent loss of binder.  If during the curing period the surface
of the base dries too fast, it shall be kept moist by sprinkling until
such time as the prime coat is applied as directed.

The Contractor shall remove all survey and grade hubs from the base
courses prior to placing any bituminous surface course.

METHOD OF MEASUREMENT

**208-4.1**  The quantity of **\[uncrushed\]\[crushed\]** aggregate base
course to be paid for shall be the number of cubic yards (cubic meters)
of base course material placed, bonded, and accepted in the completed
base course.  The quantity of base course material shall be measured in
final position based upon depth test, or cores taken as directed by the
Engineer, or at the rate of 1 depth test for each 300 square yards (250
square meters) of base course, or by means of average end areas on the
complete work computed from elevations to the nearest 0.01 foot (3 mm). 
On individual depth measurements, thicknesses more than 1/2 inch (12 mm)
in excess of that shown on the plans shall be considered as specified
thickness plus 1/2 inch (12 mm) in computing the yardage for payment. 
Base materials shall not be included in any other excavation quantities.

BASIS OF PAYMENT

**208-5.1**  Payment shall be made at the contract unit price per cubic
yard (cubic meter) for aggregate base course.  This price shall be full
compensation for furnishing all materials and for all operations,
hauling, and placing of these materials, and for all labor, equipment,
tools, and incidentals necessary to complete the item.

Payment will be made under:

Item P-208-5.1 **\[Uncrushed\]\[Crushed\]** Aggregate Base Course---per
cubic yard (cubic meter)

TESTING REQUIREMENTS

ASTM C 29 Unit Weight of Aggregate

ASTM C 117 Materials Finer than 75μm (No. 200) Sieve in Mineral
Aggregates by Washing

ASTM C 131 Resistance to Abrasion of Small Size Coarse Aggregate by Use
of the Los Angeles Machine

ASTM C 136 Sieve Analysis of Fine and Coarse Aggregates

ASTM D 422 Particle Size Analysis of Soils

ASTM D 698 Moisture-Density Relations of Soils and Soil-Aggregate
Mixtures Using 5.5 lb (2.49 kg) Rammer and 12-in (305 mm) Drop

ASTM D 1556 Density of Soil in Place by the Sand-Cone Method

ASTM D 1557 Test for Laboratory Compaction Characteristics of Soil Using
Modified Effort

ASTM D 2167 Density of Soil in Place by the Rubber-Ballon Method

ASTM D 3665 Random Sampling of Paving Materials

ASTM D 4318 Liquid Limit, Plastic Limit, and Plasticity Index of Soils

**END OF ITEM P-208**