Leftover mix from a project--keep small plastic containers handy to make pot feet or soap/candy molds to make embellishments to mortar or embed in future projects.

Hardened mix left in the bag--there is never hardened mix in the bag. Store your cement in 5 gallon plastic pails with lids. Never store your cement in the original bag on a dirt or concrete floor, it wicks the moisture from the floor.
I use badly broken pieces along my creek embankment to help hold the soil. Someone broke up a damaged piece and used it like tile mosaic. Someone else broke it in small chunks and added it to their stone driveway. Can you patch your broken piece or add another outside layer to cover the break and change the appearance? Billie