Controlled Low Strength Material (CLSM), commonly referred to as flowable fill, has been used for years as a trench backfill for utility repairs in Kentucky, and is now being used by the Kentucky Department of Highways (KDOH) on a limited basis. Flowable fill, when used as trench backfill, typically consists of natural sand, fly ash, cement, and water with a design compressive strength of 50 to 100 psi at 28 days. Flowable fill was used on two KDOH projects in 1991. One project was new construction in the widening and realignment of Breckinridge Lane in Louisville and the other was a maintenance project involving the replacement of cross drains on US 25 in Fayette County. These two uses of flowable fill were monitored for material engineering performance and characteristics, construction procedures, and cost effectiveness. Field observation and testing, laboratory testing, and determination of remedial costs from sites not using flowable fill were all components of the study.

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The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky nor the Kentucky Transportation Cabinet. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and trade names are for identification purposes and are not to be considered as endorsements.