Citation

Farrag K. Transp. Res. Rec. 2011; 2251: 157-164.

Copyright

(Copyright © 2011, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2251-16

PMID

unavailable

Abstract

Controlled low-strength material (CLSM) is commonly used as an alternative to traditional soil backfill materials around buried pipes. Laboratory and field tests were performed on various CLSM mixtures to evaluate their performance for the following: short- and long-term compressive strength, bearing resistance, and resilient modulus; setting time; settlement under repeated traffic loads in comparison with other backfills and adjacent pavement; susceptibility to freeze-thaw cycles; and freeze depth in the backfill. Several mix ratios based on the standard specifications of various state highway agencies were evaluated in the testing program. The strength properties of CLSM and its susceptibility to freeze-thaw were highly dependent on the amount and type of fly ash, cement content, and the amount of water added to the mix. Test results of samples obtained from the field did not compare well with those of laboratory-mixed samples of similar mix ratios. This difference was mainly due to the addition of water in the field to achieve flowability and lack of field quality control procedures to ensure proper mix ratios. The results demonstrated the need for well-defined quality control procedures to prevent variability in the mix ratios in the field. Tests of pavement sections under repeated traffic loads showed that CLSM backfill had lower settlement under repeated traffic loads than did other compacted soil backfills. However, CLSM with high fly ash had lower frost heave and thawing resistance than soils had. The frost heave susceptibility was negligible in mixes with an air-entraining mix without fly ash.