Whole bags of Quikrete last quite a long time. We have several culverts where we lined the approaches with Quikrete bags 10 years ago; a small % of bags have cracked, but not displaced, since then.

NOTE: You want to get the smallest size of Quikrete bags you can, unless you enjoy schlepping 80 lbs around.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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