### **ITEM P-153 CONTROLLED LOW-STRENGTH MATERIAL (CLSM)**

DESCRIPTION

**153.1.1** This item shall consist of furnishing, transporting, and
placing a controlled low-strength material (CLSM) as flowable backfill
in trenches or at other locations shown on the plans or as directed by
the Engineer.

MATERIALS

**153-2.1 MATERIALS**

**a. Portland Cement.** Portland cement shall conform to the
requirements of ASTM **\[ \]** Type **\[ \]**. If for any reason, cement
becomes partially set or contains lumps of caked cement, it shall be
rejected. Cement salvaged from discarded or used bags shall not be used.

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> **The Engineer shall specify one of the following : ASTM C 150 - Type
> I, II.**
>
> **ASTM C 595 - Type IP, IS, S, I(PM).**

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**b. Fly Ash.** Fly Ash shall conform to ASTM C 618, Class C or F.

**c. Fine Aggregate (Sand).** Fine aggregate shall conform to the
requirements of ASTM C 33 except for aggregate gradation. Any aggregate
gradation which produces performance characteristics of the CLSM
specified herein will be accepted, except as follows.

**[Sieve Size Percent Passing by weight]{.underline}**

3/4 inch (19.0 mm) 100

No. 200 (0.075 mm) 0 - 12

**d. Water.** Water used in mixing shall be free of oil, salt, acid,
alkali, sugar, vegetable matter, or other substances injurious to the
finished product.

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> **Dyes and other methods of coloring the backfill material may be
> incorporated if desired.**

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MIX DESIGN

**153-3.1 PROPORTIONS.** The contractor shall submit, to the Engineer, a
mix design including the proportions and source of materials,
admixtures, and dry cubic yard (cubic meter) batch weights. The mix
shall contain a minimum of 50 pounds of cement and 250 pounds fly ash
per cubic yard (30 kg of cement and 148 kg of fly ash per cubic meter),
with the remainder of the volume composed of sand, water, and any
approved admixtures.

**a. Compressive Strength.** CLSM shall be designed to achieve a 28-day
compressive strength of 100 to 200 psi (690 to 3 680 kPa)when tested in
accordance with ASTM C 39. There should be no significant strength gain
after 28 days. Test specimens shall be made in accordance with ASTM C 31
except that the samples will not be rodded or vibrated and shall be air
cured in their molds for the duration of the cure period.

**b. Consistency.** Consistency of the fresh mixture shall be such that
the mixture may be placed without segregation. A desired consistency may
be approximated by filling an open-ended three-inch (75 mm) diameter
cylinder, six inches (150 mm) high to the top, with the mixture and the
cylinder immediately pulled straight up. The correct consistency of the
mixture will produce an approximate eight-inch (205 mm) diameter
circular-type spread without segregation. Adjustments of the proportions
of materials should be made to achieve proper solid suspension and
flowable characteristics, however the theoretical yield shall be
maintained at one cubic yard (cubic meter) for the given batch weights.

CONSTRUCTION METHODS

**153-4.1 PLACEMENT**.

**a. Placement**. CLSM may be placed by any reasonable means from a
mixing unit into the space to be filled. Agitation is required during
transportation and waiting time. Placement shall be performed in such a
manner that structures or pipes are not displaced from their desired
final position and intrusion of CLSM into undesirable areas is avoided.
The material shall be brought up uniformly to the fill line shown on the
plans or as directed to the Engineer. Each placement of CLSM shall be as
continuous an operation as possible. If CLSM is placed in more than one
layer, the base layer shall be free of surface water and loose of
foreign material prior to placement of the next layer.

**b. Limitations of Placement.** CLSM shall not be placed on frozen
ground. Mixing and placing may begin when the air or ground temperature
is at least 35 degrees F (2 degrees C) and rising. At the time of
placement, CLSM shall have a temperature of at least 40 degrees F (4
degrees C). Mixing and placement shall stop when the air temperature is
40 degrees F (4 degrees C) and falling or when the anticipated air or
ground temperature will be 35 degrees F (2 degrees C) or less in the 24
hour period following proposed placement.

**153-4.2 CURING AND PROTECTION**

**a. Curing.** The air in contact with the CLSM should be maintained at
temperatures above freezing for a minimum of 72 hours. If the CLSM is
subjected to temperatures below 32 degrees F (0 degrees C), the material
may be rejected by the Engineer if damage to the material is observed.

**b. Protection.** The CLSM shall not be subject to loads and shall
remain undisturbed by construction activities for a period of 48 hours
or until a compressive strength of 15 psi (105 kPa) is obtained. The
Contractor shall be responsible for providing evidence to the Engineer
that the material has reached the desired strength. Acceptable evidence
shall be based upon compressive tests made in accordance with paragraph
153-3.1a.

MATERIAL ACCEPTANCE

**153-5.1 Acceptance.** Acceptance of CLSM delivered and placed as shown
on the plans or as directed by the Engineer shall be based upon mix
design approval and batch tickets provided by the Contractor to confirm
that the delivered material conforms to the mix design. The Contractor
shall verify by additional testing, each 5,000 cubic yards (3,825 cubic
meters) of material used. Verification shall include confirmation of
material proportions and tests of compressive strength to confirm that
the material meets the original mix design and the requirements of CLSM
as defined in this specification. Adjustments shall be made as necessary
to the proportions and materials prior to further production.

METHOD OF MEASUREMENT

**153-6.1 Measurement.** Controlled low strength material shall be
measured by the number of **\[cubic yards (cubic meters)\]** as computed
from the neatline plan and section, adjusted for the quantities for any
embedments, and as specified, completed, and accepted..

BASIS OF PAYMENT

**153-7.1 Payment.** Accepted quantities of controlled low strength
material shall be paid for at the contract unit price per **\[cubic yard
(cubic meter)\]**. Payment shall be full compensation for all materials,
equipment, labor, and incidentals required to complete the work as
specified.

TESTING REQUIREMENTS

ASTM C 31 Making and Curing Concrete Test Specimens in the Field

ASTM C 39 Compressive Strength of Cylindrical Concrete

MATERIAL REQUIREMENTS

ASTM C 33 Specification for Concrete Aggregates

ASTM C 150 Specification for Portland Cement

ASTM C 618 Specification for Coal Fly Ash and Raw or Calcined Natural
Pozzolan for Use as a Mineral Admixture in Concrete

ASTM C 595 Specification for Blended Hydraulic Cements

**END OF ITEM P-153**

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