Two companies have recently introduced admixtures designed to increase air content and reduce water content of flowable fill, also called controlled low-strength materials (CLSM). Benefits of CLSM made with admixtures include:
- more homogenous mix. A lower water content can lead to material segregation and settling of cement and aggregate. Admixtures are said to produce more consistent density and lighter weight fill.
- Better control of ultimate strength. Backfill may need to be re-excavated later, and the admixtures allow CLSM to be made with less cementitious material and less water, thus limiting the strength CLSM can attain.
- Easy handling and economical transport and delivery. Supplied in premeasured packages, the admixtures require no special dispensing equipment or technical supervision for correct use. They can be added to the mixer drum at the jobsite.
The admixtures add about $2.50 to $3.50 to the cost of a cubic yard of CLSM. In some cases, this extra cost may be offset by the need for less cement or fly ash to produce a mix with comparable properties.
KEYWORDS: air entrainment, CLSM, flowable fill