Washed Concrete Sand is a coarse sand with the fine particles washed out of it. It is used to mix concrete with. Other uses include as a sand for zen gardens and under pavers. This sand comes in various colors, it may be shades of tan, or shades of grey at different times. The key with a washed concrete sand is that the material has all the fine particles washed out of it and all that remains is the coarser sand particles. Removing the fine particles is necessary for use in concrete or curbing mixtures.