Learning how to color your concrete opens up a world of decorating and landscaping possibilities. Black may well be one of the more challenging colors to obtain, but with a little preparation, you can achieve a dark black concrete. Talk to your local hardware or home improvement stores to obtain the pigment needed for black concrete. Store the pigment in an air-tight container. You'll be able to turn that dull, gray concrete into a black masterpiece whenever the desire strikes.
Mix up your concrete in a 5 gallon bucket according to the manufacturer's directions. Add the recommended amount of water to your powdered concrete and mix, using mixing paddles and a drill.
Open a bag of black iron oxide pigment.
Read the labels on your concrete to find out how much cement is in the concrete mix. You need to know the amount of cement in the bag of concrete in order to figure how much black iron oxide to add for effective coloration. For common ready-to-set concrete, that amount is usually about 15 percent. If you can't find that information, call the manufacturer and ask for the amount.
Add the black iron oxide, making sure you don't put more than 7 percent of the amount of cement. In most ready-to-use concrete mixes, this means you should use not more than 1/2 lb. of black iron oxide.
Mix your black iron oxide into your concrete with mixing paddles attached to a drill. Mix thoroughly so the black iron oxide is evenly distributed throughout the concrete.