What can you do with harden clay on minecraft?

"Hardened Clay is a block with a blast resistance comparable to that of stone-based blocks. It serves no purpose except as a building material, but in that role it is decorative and moderately blast-resistant. Hardened clay can be obtained by smelting clay blocks or harvested from Mesa Biomes. (Minecraft Wiki)"

It is a decorative block. It's color can easily be changed by surrounding a dye with 8 pieces of hardened clay, getting you 8 pieces of clay in the new color. It is used in no other crafting recipe.

They take explosions as well as ordinary stone, which is much better than basic clay, but they still don't resist well enough to be used for serious blast resistance.