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March 26, 2023
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Controlled Low Strength Materials Specification

Specification For:
Controlled Low-Strength Materials (CLSM)

Furnish and place CLSM in accordance with contract documents, County permit requirements, or as directed by the engineer. This specification will replace the County’s current slurry specification on August 13, 2001. Prior to that date, both the old slurry specification and approved products from this specification will be allowed. Effective that date, all products shall be pre-approved in accordance with this specification.

CLSM - A highly flowable lean concrete mix consisting of a mixture of cement, fly ash, densely graded mineral aggregates, water, and admixtures. CLSM shall be capable of freely flowing to fill all voids in trenches or other areas without compaction or other additional effort, shall be of uniform density, shall be of low permeability to prevent migration of adjacent fines into the set mix, and shall excavate easily at any later time with minimal risk of damage to buried services.

Fine Aggregate CLSM - A CLSM containing a maximum size aggregate of 3/8-inch.

Materials shall meet the requirements of the following sections of the 1996 ODOT Standard Specifications for Highway Construction, or as modified by this specification.

• Fly Ash - 02030
• Portland Cement - 02010
• Water - 02020
• Admixtures - 02040
• Aggregates - shall be a densely graded virgin rock or appropriate recycle material which produces a mix meeting all requirements within this specification. A minimum of 50% of the total aggregate by weight shall pass a #8 sieve and no more that 5% of the total aggregate by weight may pass a #200 sieve. The maximum size aggregate for standard CLSM shall pass a 1-inch sieve. The maximum size aggregate for fine aggregate CLSM shall pass a 3/8-inch sieve.

Performance Specification:
CLSM shall meet the following requirements:
• Flowability - The mix shall have a slump of between 6 and 8 inches as per AASHTO Designation T 119-82 or ASTM Designation C 143
• Compressive strength - The mix shall have a 28-day compressive strength of between 50 and 150 psi, per AASHTO Designation T 22-90 or ASTM Designation C 39

Mix Design and Testing:
Vendors who purpose to supply CLSM for work within Jackson County right-of-way shall submit a mix design and test results to Jackson County Roads for approval. Jackson County will maintain an approved products list on the Jackson County Roads website. The mix submittal shall include the following information:

• Company Name and Address
• Company Contact Information
• Identifying name and/or number for the mix design
• Mix Design (including aggregate type and gradation)
• Certified test results for flowability, and compressive strength

Submittals which do not contain all required information shall not be considered.

Products that are rejected in the field may be removed from the approved list at the discretion of the County.

Mixing and Placement:
CLSM shall be mixed in accordance with 1996 ODOT Standard Specifications for Highway Construction, section 00540.21; delivered in a truck mixer conforming to 00540.21(c); and conveyed in accordance with 00540.22. Contractor shall provide and maintain steel jump plates as required for traffic and safety. In paved areas open to the public, the top of the trench shall be patched with hot-mix asphalt cement not sooner than the CLSM is adequately set (generally 48 hours), nor later than 10 calendar days following placement of the CLSM.

When CLSM is delivered to the job site, delivery tags shall be collected from the delivery driver and provided to the County inspector or engineer. The delivery tag shall contain the supplier's name and the mix identifying name and/or number as identified in the supplier’s submitted mix design.

The county inspector or engineer may reject any mix that does not appear to meet the requirements of this specification (for example, segregation, insufficient slump, or open graded aggregates). The county inspector or engineer may require removal of any mix that has been placed but does not perform as specified.

Only fine aggregate CLSM will be allowed in pipe zones or trenches of less than 1-foot width.

In the event of extremely cold or wet conditions, and with the approval of the county inspector or engineer prior to use, an approved fine aggregate CLSM may have up to 94 additional pounds of cement per cubic yard added to the design mix to facilitate setting.

CLSM Approved Products List

Standard CLSM

Southern Oregon Ready Mix
Vance McGonagle
Approved Product: CLSM 

LTM, Inc., dba Knife River Materials
Mike Milhoan
Approved Product: 16LJACOSTD

Crater Sand and Gravel
Allen Savage
Approved Product: 1" Standard CLSM

Fine Aggregate CLSM

Crater Sand and Gravel/Savage Redi-Mix
Approved Product: Sand Slurry

LTM, Inc, dba Knife River Materials
Mike Milhoan
Approved Product: 16LJACOFINE & 16LCLSM2

Johnny Cat Inc.
Mark Biencourt
Approved Product: 1-Sack CLSM
Approved Product: 2-Sack CLSM