Development of Soil-Based Controlled Low-Strength Materials

This study reports research on the use of soil-based controlled low-strength material CLSM as an economical approach to conventional backfilling at new navigation lock chambers and other large construction activities. This research comprises one element of the U.S. Army Corps of Engineers Innovations for Navigation research program, which is investigating innovative construction techniques for future Corps navigation structures. As defined by the American Concrete institute, CLSM includes those materials that result in a compressive strength of 1,200 psi 8,274 KPa or less. CLSM is self-compacting, cement-based material that, unlike conventional backfill, does not require mechanical compaction after placement. This allows for a more economical approach to backfilling since the equipment and labor required to place and compact conventional fill are eliminated. The case study was a proposed lock chamber at the Marmet Locks and Dam on the Kanawha River in West Virginia. A large void between the existing lock chambers and the proposed new lock chamber will result. Plans are to backfill this area to meet the structural requirements of the lock walls and to satisfy other project operational needs. Use of an economical soil-based CLSM in this area, incorporating otherwise undesirable material excavated during project construction, represents an attractive option. More than 30 CLSM mixtures were proportioned, mixed in the laboratory, and tested for unhardened properties and uncompressive strength. The flow consistency of all the CLSM mixtures tested was equal to or higher than the control mixture, and all of the mixtures exhibited a gain in unconfined compressive strength. These results indicate that a soil-based CLSM is feasible.