For use in the Denver Water Service Area

Materials Specification – 19
for
Controlled Low Strength Backfill Material (CLSM)

1. CLSM Mix Submittal:

A minimum of 2 days prior to starting CLSM work, CLSM mix designs shall be submitted for Denver Water approval. No changes shall be made in the amounts or sources of the approved mix ingredients without written approval of Denver Water. Production inspection and field testing of the approved mix may be made by Denver Water.

2. CLSM Products:

A. Cementitious Materials:

1) Cement

All cement used shall be Type II portland cement which shall conform to the requirements of ASTM C 150.

2) Fly Ash

The fly ash shall conform to ASTM C 618. Fly ash may be either Class C or Class F.

B. Aggregates:

1) Fine Aggregates

All fine aggregate shall conform to the grading and quality requirements of ASTM C 33.

2) Coarse Aggregates

Coarse aggregate shall conform to the grading and quality requirements of ASTM C 33 for Size No. 467, No. 57, or No. 67.

C. Water:

The batch mixing water and mixer washout water shall conform to the requirements ASTM C 94.

D. Admixtures:

Chemical admixtures which do not contain calcium chloride and which conform to ASTM C 494 for concrete may be used in the CLSM mix. All chemical admixtures shall be compatible with the cement and all other admixtures in the batch.

3. CLSM Proportions:

CLSM shall have a minimum 28 day compressive strength of 100 psi and a maximum 28 day compressive strength of 200 psi when molded and cured as in compliance with ASTM D 4832.

All CLSM shall be air entrained to a total air content of approximately 5%. The minimum slump shall be 6 inches and the maximum slump shall be 8 inches as when tested in accordance with ASTM C 143.

Fine aggregates shall be between 50% and 60% by volume of the total aggregates in the CLSM mix.