Black concrete is one of the craftable blocks in the game and they are used for decoration. You will need Sand, Gravel Blocks, Squid for Ink Sac and Black Concrete Powder to make a Black Concrete. Please follow the following steps to make Black Concrete .
In order to make Black concrete, the basic item you will need is sand block. You will have to find and get at least four sand blocks. Use your iron shovel to get them.
The next required item that you will need to find is gravel block. Get at least four of them using your iron shovel.
Squid for Ink Sac
After that you will have to find and kill squid to get ink sac. You will find them under water. Use your iron sword to kill a squid.
Black Concrete Powder
Now you can craft Black concrete powder because you have ink sac, sand blocks and gravel blocks in your inventory. Add these things on the 3*3 crafting grid in the same way as shown in the image below.
Add 4 gravel blocks at the four corner cells of the crafting grid, ink sac in the center cell of the crafting grid and 4 sand blocks in the remaining 4 cells of the crafting grid. You will get Black concrete powder in the right-side box to the crafting table. Add this item into your “ready to use” stock.
Now you can make Black concrete by placing Black concrete powder in the water. After placing it into water you can obtain this Black concrete by using your iron pickaxe. Black concrete blocks can be used for decoration.