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6-24-97
LIME MODIFICATION OF SOILS
207-R-334
DESCRIPTION: This work shall consist of
upgrading fine grained soils by uniformly mixing lime, as
specified, to aid compaction by drying out wet areas, and to
provide a working platform for subsequent construction.
MATERIALS: Materials shall be in accordance with
the following:
Hydrated lime .......... 913.04.
Water................
913.01.
EQUIPMENT: The machinery, tools and
equipment necessary for proper execution of the work shall be
available on the project site and approved by the Engineer prior
to the commencing of construction operations.
STORAGE AND HANDLING:
- Hydrated lime shall be stored in closed weatherproof
containers until immediately before distribution on
the subgrade. Hydrated lime in bags shall be stored
in weather protected conditions with adequate
protection from ground dampness. The storage facility
shall be approved by the Engineer prior to
commencement of any lime work.
- Each shipment shall be accompanied by a bill of
lading and by a certificate of compliance stating
conformance to the applicable specifications
- The Contractor's safety measures shall comply with
applicable OSHA standards.
MIXTURE COMPOSITION:
- Sample: 50 kg (110 lb), minimum,
samples of the soil to be modified and 5 kg (11 lb),
minimum, samples of the lime to be used shall be
provided least 20 days prior to the use of the lime.
- Mix Design: Lime shall be proportioned
as required by test results of the mixture of lime
and soil on an oven - dry basis. The required
proportion of lime will be established by the
Engineer prior to construction, using samples of soil
and lime, and the Department's laboratory design
procedure for lime modified soil. The Engineer
reserves the right to make such adjustments of lime
proportioning as are necessary during the progress of
the work within the range specified. The Engineer may
add 1% to 2% extra lime if the soils and moisture
content change.
The source or type of lime shall not be changed
during the progress of the work without permission of
the Engineer. However, the Engineer may choose, based
on laboratory test results, to use different types of
lime on different portions of the project. The
different types of lime shall not be mixed in the
same project portions.
CONSTRUCTION REQUIREMENTS:
- Temperature and Weather Limitations:
Lime modification shall be performed only with a
minimum soil temperature, measured 100 mm (4 in.)
below the subgrade, of 7E C (45E F), and with the air
temperature rising. Lime shall not be mixed with
frozen soils or with soil containing frost.
- Preparation of Existing Roadway: All
deleterious material, such as stumps, roots, turf,
etc, and aggregate larger than 75 mm (3 in.) shall be
removed. All soft organic soils shall be removed as
directed by the Engineer.
- Spreading of Lime: The
subgrade shall be scarified or disked prior to
distribution of the lime using a machine of such
design that a visible indication is given at all
times that the machine is cutting to the required
depth. The lime shall then be distributed uniformly
over the surface by means of a cyclone, screw-type,
or pressure manifold type distributor. The Engineer
may reject any procedure which does not provide even
distribution of lime.
- Mixing: The lime, soil, and
water if necessary, shall be mixed by rotary speed
mixers or a disc harrow. The mixing shall continue
until it has been determined by the Engineer that a
homogeneous layer of the specified thickness has been
obtained and such that 100%, exclusive of rock
particles, shall pass a 25 mm (1 in.) sieve and at
least 60% will pass a 4.75 mm (No. 4) sieve. The
loose thickness of a single lime modified layer shall
not exceed 200 mm (8 in.) if a disc harrow is used
and 360 mm (14 in.) if a rotary speed mixer is used.
- Compaction: Compaction of the mixture
shall begin immediately after mixing. If compaction
is to be delayed, the surface of the lime modified
soil shall be crown-graded by either blade dragging
or light rolling immediately after mixing and sealed.
Compaction shall be continued until the lime modified
layer has a density not less than 100 % of the
maximum dry density within the special subgrade
treatment zone or 95% of the maximum dry density
below the special subgrade treatment zone. Maximum
dry densities will be determined in accordance with
AASHTO T 99 or one point proctors in accordance with
AASHTO T 272. If required density can not be achieved
in the field, a one point proctor shall be performed
to verify the target density. The standard dry
density of the lime treated soil shall be obtained by
one point proctor in accordance with AASHTO T 272.
The field in-place dry density will be obtained by
the Engineer in accordance with AASHTO T 191 or T
239.
Aeration by means of further mixing, or the addition
of water and further mixing, may be required by the
Engineer to achieve the required compaction.
- Finishing: When
compaction of the lime modified soil is nearing
completion, the surface shall be shaped to the
required lines, grades and cross section. Compaction
shall then be continued until uniform and adequate
compaction is obtained.
The average compacted thickness of modified subgrade
constructed shall be within 10% of the specified
thickness, except that the thickness at any one place
may be within 15% of that specified.
The Department reserves the right to determine the
actual thickness of the completed and cured layer by
coring, use of a phenolphthalein solution, or by
other means. The Engineer will perform at least one
test every 280 m2 (335 syds) for each
compacted lift to insure that the lime is spread at
the specified rate. All deficient areas shall be
acceptably corrected
METHOD OF MEASUREMENT:
- Measured Quantities: Lime
modified soils will be measured in square meters
(square yards) per the depth specified. The width for
measurement shall be as shown on the plans. Water
will not be measured for payment.
Lime will be measured in megagrams (tons). The lime
may be weighed in trucks or freight cars. If the lime
is shipped in trucks, it may be weighed at the place
of loading, at the place of unloading, or where
otherwise directed. The Engineer may accept original
signed bills in lieu of weighing.
- Contract Quantities: When the
project is constructed essentially to the lines,
grades or dimensions shown on the plans, and the
Contractor and the Engineer have agreed in writing
that the plan quantities are accurate, no further
measurement will be required except when errors are
discovered after work has been started. Corrective
measurements shall then be made.
When the plans have been altered or when disagreement
exists between the Contractor and the Engineer as to
the accuracy of the plan quantities, either party
shall, before any work which would affect the
measurements is started, have the right to request in
writing and thereby cause the quantities involved to
be measured as specified herein.
Should the Contractor's method of construction
require extra earth excavation or embankment due to
requiring more than one lift to construct the lime
modified soil layer as shown on the plans, the extra
earth excavation and embankment will not be measured.
BASIS OF PAYMENT: The accepted quantities of
lime modified soil will be paid for at the contract unit price
per square meter (square yard) for the thickness specified. Lime
will be paid for at the contract unit price per megagram (ton).
PAYMENT WILL BE MADE
UNDER |
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Metric Pay
Unit Symbol
(English Pay Unit Symbol)
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Lime Modified
Soil,_______in
thickness
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......................m2 (SYS) |
Lime
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......................Mg (TON) |
The costs of
removal of deleterious materials, scarification of the subgrade,
spreading of lime, mixing of the lime and soil, sealing of the
surface of the lime modified soils, compaction of the resultant
mixture, shaping the subgrade, work required due to adjustments
of lime proportioning made by the Engineer, additional lime
required due to weather conditions, correction of lime dust
deficient areas, water required for the modification process,
required extra earth excavation and embankment due to method of
construction, and cost of modified subgrade trimming as required
shall be included in the costs of the pay items.
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