### **ITEM P-213 SAND-CLAY BASE COURSE**

DESCRIPTION

**213-1.1**  This item shall consist of a base course composed of
approved selected material, 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

**213-2.1 SAND-CLAY**.  The materials shall be a mixture of clay and
mineral aggregate.  This mixture shall consist of topsoil, sand-clay,
sand-clay gravel, disintegrated granite, or other approved selected
aggregate, and it shall contain sufficient binder material so blended or
processed as to produce a uniform mixture complying with the
requirements of these specifications.

The materials shall be uniform and free from excess amounts of clay or  
organic matter such as leaves, grass, roots, and other objectionable or
foreign substances.  The coarse aggregate (particles coarser than a No.
4 mesh (4.75 mm) sieve) shall consist of hard, durable pieces or
fragments of stone or gravel.

The gradation of the blended or processed material shall meet the
requirements of one of the gradations given in the following table, when
tested in accordance with ASTM C 136.

Percentage by Weight

Sieve designation Passing Sieves

1-1/2 inch (38.5 mm) 100 100

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

No. 4 (4.75 mm) 45-75 65-100

No. 10 (2.0 mm) 30-60 60-100

No. 40 (0.42 mm) 10-40 20-70

No. 200 (0.075 mm) 2-15 4-25

The fraction passing the No. 40 (0.42 mm) mesh sieve shall be referred
to as binder.  The fraction passing the No. 200 (0.075 mm) mesh sieve
shall be less than one-half the fraction passing the No. 40 (0.42 mm)
mesh sieve.  The material passing the No. 40 mesh sieve shall have a
plasticity index not to exceed 6 and have a liquid limit of not more
than 25, when tested in accordance with ASTM D 4318, for gradation A;
plasticity index shall not exceed 4 and the liquid limit shall not
exceed 25 for gradation B.

**213-2.2 FILLER FOR BLENDING**.  If filler, in addition to that
naturally present in the base course material, is necessary for
satisfactory bonding of the material, or for changing the soil constants
of the material passing the No. 40 (0.42 mm) mesh sieve, or for
correcting the gradation to the limitations of the specified gradation,
it shall be uniformly blended with the base course material.  The
material for such purpose shall be obtained from sources approved by the
Engineer and, when used, shall be of a gradation necessary to accomplish
the specified gradation in the finally processed material.

CONSTRUCTION METHODS

**213-3.1 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 expense.  The base material shall
be obtained from approved pits or other approved sources.  The material
in the pits shall be excavated and handled in a manner that assures a
uniform and satisfactory product.

**213-3.2 EQUIPMENT**.  All equipment necessary for the proper
construction of this work shall be on the project, in first-class
working condition, and approved by the Engineer before construction is
permitted to start.

The processing equipment shall be designed, constructed, operated, and
capable of thoroughly mixing all materials and water in the directed
proportions to produce a base course of the gradation and consistency
required.

**213-3.3 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 before the base course is placed
thereon.  Material shall not be placed on frozen subgrade or subbase.

**213-3.4 PLANT MIXING**.  The base material shall be uniformly blended
and mixed in an approved central or travel mixing plant.  The sand-clay,
together with any blended material, shall be thoroughly mixed with the
required amount of water. After the mixing is complete, the base
material shall be transported to, and spread on, the underlying course
without undue loss of the moisture content.

**213-3.5 PLACING AND SPREADING**.  The base course material that is
correctly proportioned or that has been processed in a plant shall be
placed on the prepared underlying course and compacted in 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 material shall be
spread by spreader boxes, or other approved devices, equipped to
distribute the material in a uniform layer.

When approved, the material may be dumped in piles, but it shall be
spread immediately.  Hauling over the uncompacted base course shall not
be permitted.

**213-3.6 TRAVEL PLANT MIX**.  When the use of a travel plant is
approved, sufficient quantities and proportions of all material
necessary shall be used to provide a base mixture that conforms to the
specified gradation, quality, and thickness.  If a windrow travel plant
is employed for mixing, the sand-clay shall be placed in windrows
parallel to the pavement centerline.  If a traveling plant is used which
mixes previously spread material in-place, the sand-clay shall be spread
to a thickness that may be readily handled by the machine and that will
develop the proper thickness for each layer.  The base material shall be
of a satisfactory moisture content to obtain maximum density.

After 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 and in condition for
compacting.

**213-3.7 MIXED IN-PLACE**.  When the base materials are to be
proportioned and mixed or blended in-place, the different layers shall
be spread and placed in the following manner with the relative
proportions of the components of the mixture designated by the Engineer.

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

After the required materials have been placed, they shall be thoroughly
mixed and blended using approved graders, discs, harrows,
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 then thoroughly remixed.  If necessary,
water in the required amount shall be uniformly applied as directed by
the Engineer prior to and during the mixing operation to maintain the
material at the proper moisture content.  When the mixing and blending
has been completed, the material shall be spread in a uniform layer
which, when compacted, will meet the requirements for thickness and
typical cross section.

**213-3.8 GENERAL METHODS FOR PLACING**.  The base course shall be
constructed in layers not less than 4 inches (100 mm) nor more than 6
inches (150 mm) of compacted thickness.  Each layer shall be measured
for depth.  The material, as spread, shall be of uniform gradation with
no pockets of fine or coarse materials.  Unless otherwise permitted by
the Engineer, the base shall not be spread more than 2,000 square yards
(186 square meters) in advance of the rolling.  Any necessary sprinkling
shall be kept within this limit. 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 placing and spreading operations, sufficient caution shall be
exercised to prevent the incorporation of subgrade, subbase, or shoulder
material into the base course mixture.

**213-3.9 COMPACTION**.  Immediately after completion of the spreading
operations, the base material 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 base 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.  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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**213-3.10 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 mm) straightedge when
applied to the surface parallel with, and at right angles to, the
centerline.

**213-3.11 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 (28 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 refinishing in
accordance with these specifications.  The Contractor shall replace, at
his/her expense, the base material where borings have been taken for
test purposes.

**213-3.12 PROTECTION**.  Work on the base course shall not be
accomplished during freezing temperature nor when the subgrade is wet. 
When the base material contains frozen material 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 fall 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.

**213-3.13 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

**213-4.1**  The quantity of sand-clay 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 (28 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 the 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

**213-5.1**  Payment shall be made at the contract unit price per cubic
yard (cubic meter) for sand-clay 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-213-5.1 Sand-Clay 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 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 and Unit Weight of Soil in Place by the Rubber
Ballon Method

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

END OF ITEM P-213