### **ITEM P-210 CALICHE BASE COURSE**

DESCRIPTION

**210-1.1** This item shall consist of a base course composed of
caliche, caliche-gravel, caliche and limestone, or material of similar
characteristics, constructed on the prepared underlying course in
accordance with these specifications and in conformity to the dimensions
and typical cross section shown on the plans.

MATERIALS

**210-2.1 MATERIALS**.  The base course material shall consist of
caliche, caliche-gravel, caliche limestone, or similar materials
obtained from sources approved by the Engineer prior to use of the
materials.  All acceptable material shall be screened, and the oversize
shall be crushed and returned to the screened material in such manner
and proportions that will produce a uniform product.

The gradation of the material, as finally processed and blended, shall
meet the following requirements when tested in accordance with ASTM C
136.

Sieve Designation Percentage by Weight

(Square Openings) Passing Sieves

2 inch (50.0 mm) 100

No. 40 (0.425 mm) 15-35

No. 200 (0.075 mm) 0-15

That portion of the material, including the blended filler, passing a
No. 40 (0.425 mm) mesh sieve shall be known as soil binder and shall
have a liquid limit of not more than 35 and a plasticity index of not
more than 10 as determined as ASTM D 4318.

If necessary, the Contractor shall blend or combine materials so that
the final processed material meets all of the requirements of these
specifications.  The Contractor shall make such modifications in
materials and methods as are necessary to secure a material that is
capable of being compacted into a dense and well-bonded base.

**210-2.2 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 sieve, or for correcting the
gradation to the limitations of the specified gradation, it shall be
uniformly blended with the base course material on the runway, at the
crushing plant, or at the mixing plant.  The material for such purpose
shall be obtained from sources approved by the Engineer.

CONSTRUCTION METHODS

**210-3.1 OPERATION IN PITS**.  All work involved in clearing and
stripping pits, including the handling of unsuitable material, shall be
performed by the Contractor at his/her own expense.  The pits shall be
operated in such a manner that a clean and uniform material will be
secured.  The base course material shall be obtained from approved
sources.

**210-3.2 EQUIPMENT**.  All equipment necessary for the proper
construction of the work shall be on the project, in first-class working
condition, and approved by the Engineer before construction is permitted
to start.

**210-3.3 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 caused by
improper drainage conditions, hauling, or any other cause, shall be
corrected at the Contractor\'s expense.

**210-3.4 PLACING AND SPREADING**

**a.**  The aggregate base material that has proportioned or processed
shall be placed on the prepared underlying course and compacted in
layers to the thickness shown on the plans.  The depositing and
spreading of the material shall commence where designated and shall
progress 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 that shall spread the aggregate in the required
amount.  The base material shall be spread and shaped the same day as
placed.

**b.**  If the travel plant method is used for mixing, the base material
shall be placed on the underlying course in windrows parallel to the
centerline of the runway.  Sufficient quantity and proportions of
materials shall be placed in the windrow to provide a base mixture
conforming to the specified grading and compacted thickness.  The
windrow shall be shaped to a uniform section and left undisturbed until
measuring and sampling are complete.  After mixing and before spreading,
the mixture shall be examined by the Engineer, who shall determine
whether the mixing is complete and satisfactory and whether the proper
moisture content is maintained for spreading.  No spreading shall be
done, except when authorized.

After the mixing has been completed, the base material shall be spread
to the required depth and width 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, disced, and dragged if necessary until a smooth,
uniform surface is obtained true to line, grade, and cross section.

**c.**  When the base materials are to be proportioned and mixed or
blended in-place, the different layers shall be spread and placed as
follows with the relative proportions of the components of the mixture
designated by the Engineer.

The base aggregate shall be deposited and spread evenly to a uniform
thickness and width.  Then the binder or filler or other admixture shall
be deposited and spread evenly over the first layer.  As many layers of
materials as the Engineer may direct shall be added to obtain the
required base materials.

When the required materials have been placed, they shall be thoroughly
mixed and blended by means of approved graders, discs, harrows, or
rotary-tillers, supplemented by other suitable equipment, if necessary. 
The mixing shall continue until the mixture is uniform throughout. 
Areas of segregated material shall be corrected by the addition of
binder or filler material and shall be uniformly applied, prior to and
during the mixing operations if necessary, to maintain the material at
the proper moisture content.  When the mixing and blending have been
completed, the material shall be spread in a uniform layer which, when
compacted, will meet the requirements of thickness and typical cross
section.  Hauling over material that has not been mixed and shaped shall
not be permitted, except when necessitated by the placing of successive
layers of materials.  Layers of base material allowed to become
partially compacted shall be scarified and disced before placing binder
material or before blading and shaping for rolling.

**d.**  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.  Unless otherwise permitted by the Engineer,
the aggregate 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 placing and spreading, sufficient caution shall be exercised
to prevent the incorporation of subgrade, subbase, or shoulder material
in the base course mixture.

**210-3.5 COMPACTION**.  Immediately after completion of the spreading
operations, the mixture shall be thoroughly compacted.  The number,
type, and weight of rollers shall be sufficient to compact the mixture
to the required density.

The field density of the compacted material shall be at least 100
percent of the maximum density of laboratory specimens prepared from
samples of the material delivered to the jobsite.  The laboratory
specimens shall be compacted and tested in accordance with **\[ \]**. 
The in-place field density shall be determined in accordance with ASTM D
1556 or ASTM D 2167.  The moisture content of the material at the start
of compaction shall not be below nor more than 1-1/2 percentage points
above the optimum moisture content.

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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).**

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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 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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The course shall not be rolled when the underlying course is soft or
yielding or when the rolling causes undulation in the base course.  When
the rolling develops irregularities that exceed 3/8 inch (9 mm) when
tested with a 16-foot (4.8 m) straightedge, the irregular surface shall
be loosened, then refilled with the same kind of material as that used
in constructing the course, and again rolled as required above.

**210-3.6 FINISHING**.  The surface of the base course shall be finished
by blading or with automated equipment especially designed for this
purpose.

In no case will the addition of thin layers of material be added to the
top layer of base course to meet grade.  If the elevation of the top
layer is 1/2 inch (12 mm) or more below grade, the top layer of base
shall be scarified to a depth of at least 3 inches (75 mm), new material
added, and the layer shall be blended and recompacted to bring it to
grade.  If the finished surface is above plan grade, it shall be cut
back to grade and rerolled.

**210-3.7 SURFACE TOLERANCE**.  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.

**210-3.8 THICKNESS CONTROL**.  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).  Where the thickness is deficient by more than 1/2 inch (12
mm), the Contractor shall correct such areas at no additional cost by
excavating to the required depth and replacing with new material. 
Additional test holes may be required to identify the limits of
deficient areas.  The Contractor shall replace, at his/her expense, the
base material where borings have been taken for test purposes.

**210-3.9 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.

**210-3.10 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.

METHOD OF MEASUREMENT

**210-4.1**  The quantity of caliche 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
tests or cores taken as directed by the Engineer, 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,
thickness 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 material shall not be
included in any other excavation quantities.

BASIS OF PAYMENT

**210-5.1**  Payment shall be made at the contract unit price per cubic
yard (cubic meter) for caliche base course.  This price shall be full
compensation for furnishing all materials and for all preparation,
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-210-5.1 Caliche Base Course---per cubic yard (cubic meter)

TESTING REQUIREMENTS

ASTM C 136 Sieve Analysis of Fine and Coarse Aggregates

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 1557 Test for Laboratory Compaction Characteristics of Soil Using
Modified Effort

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

END OF ITEM P-210