Technical Note: Soil-Based Controlled Low-Strength Materials

Abstract

The U.S. Army Corps of Engineers (USACE) is investigating innovative construction techniques for future civil works construction. One of these investigations concerns the use of controlled low-strength materials (CLSM) as a backfill material. CLSM was defined by the American Concrete Institute's (ACI) Committee 116R as “… materials that result in a compressive strength of 1,200 psi (8.3 MPa) or less” (ACI, 1990, p. 19). CLSM is described in ACI 229R (ACI, 1994) as “… self-compacting, cementitious material used primarily as a backfill in lieu of compacted fill.” Unlike compacted backfill, CLSM mixtures do not require compaction after placement. This allows for a more economical approach to backfilling in that the equipment and labor required to place and compact conventional fill are eliminated. The purpose of this research is to investigate the feasibility of producing and measuring the performance of soil-based CLSM mixtures and to compare these soil-based mixture results to those of a standard CLSM mixture. Adaska (1997) reported that the use of soil-based CLSM was first reported by the U.S. Bureau of Reclamation in 1964. Howard (1994) described this material as ‘soil-cement slurry.’ It was used for pipe bedding on 515 km (320 mi) of the Canadian River Aqueduct Project, which runs from north of Amarillo to south of Lubbock, Texas. Following the successful evaluation of some test sections, soil-cement slurry that incorporated ‘local blow sand’ deposits was used (Howard, 1994). CLSM has evolved into a deliverable product by ready-mix concrete producers, with the materials used to produce it readily available to the producer. These materials are usually some combination of portland cement, fly ash, fine aggregate, and water. The producer is able to maintain a quality-controlled mixture with known properties by using constituent materials normally used to produce mortar. CLSM mixtures normally do not use soil …