Which of the following can be used as backfill outside a foundation without being compacted?

Controlled low strength material (CLSM) is specifically designed to be used as backfill around foundations without the need for extensive compaction. This material has properties that provide adequate support while being easy to work with. Its flowable nature allows it to fill spaces and conform to the shape of the area being backfilled, thereby reducing the likelihood of voids that could compromise the integrity of the foundation. Additionally, CLSM reaches a strength characteristic that is sufficient for most backfill applications, making it an ideal choice when compaction efforts are impractical or undesirable.

In contrast, granular fill, while effective for many backfill applications, typically requires compaction to achieve the desired density and stability. Embedded soil tends to vary widely in consistency and may not provide uniform support without some form of compaction. Concrete rubble, while potentially useful in certain contexts, often leads to uneven settling and requires careful placement to ensure structural integrity, which generally necessitates some compaction. Consequently, CLSM stands out as the optimal solution for backfilling around foundations without compaction.