The bug

Red sand cannot be used as a replacement for sand in the recipes for concrete powder.

Quote from a "Block of the week article" from 2017:

In Mesa biomes, you'll find a variant of sand that's red and acts exactly like regular sand except that you can't use it to make concrete. Actually, that sounds like a bug. Maybe we should fix that.

- Duncan Geere (https://www.minecraft.net/en-us/article/block-week-sand)

To reproduce

1. Place four red sand, four gravel, and one dye in a crafting table

Observed behavior

No item is present in the output slot of the crafting table.

Expected behavior

Concrete powder would be present in the output slot of the crafting table; red sand would be able to be used in the recipes for concrete powder.