Lifting weights made from concrete have certain advantages. One is the cost of concrete compared to metal alloy and cast iron. Another is that concrete doesn’t rust. Making your own concrete weights is not complicated. A sand casting mold is easy to put together and you can form the casting to any size. Concrete topping mix creates a smooth finish and concrete with pea gravel creates a textured finish. A release agent is needed so the wet concrete doesn’t bond to the casting. A concrete admix is included to strengthen the mix and reduce chipping when the weights are used with a barbell.
Cut four pieces of 2-inch-by-6-inch lumber 24 inches long using a circular saw. Stand the pieces on edge in the form of a box. Log cabin the corners by butting the end of the pieces to the edge of the next at the corners similar to a pinwheel. Nail the corners together with 16-penny framing nails.
Spread a 36 inch square piece of thick mil plastic on the floor or a workbench. Set the square mold in the center of the plastic.
Mix a dry batch of clean washed sand and water. Add just enough water to stabilize the sand so it holds its shape. Fill the wood mold with the sand mix.
Level the surface of the sand using a random piece of straight wood as a rod. Work the rod in a sawing motion across the top of the mold from one side to the other. Brush away any residual sand from the top of the mold and rod the sand one more time.
Place a can or other round object on the center of the sand as a pattern for the weight. Push down to create an outline in the casting sand. Scoop out the sand from inside the outline with a large kitchen spoon to create the casting.
Push a short length of 1 1/4-inch diameter steel pipe into the center of the casting to create the hole for a barbell. Push the piece all the way through the casting so it is stable.
Refer to the admix mixture table and mix the appropriate portions of concrete, water and admix in a 5-gallon bucket. The consistency should be fluid, but not washy.
Stir the mix thoroughly.
Apply a liberal amount of the release agent to the bottom and sides of the sand casting and the steel pipe using a utility paintbrush. Slowly pour the concrete mix into the mold until it tops off with the surface of the sand casting.
Allow the concrete to dry completely. Twist the steel pipe by hand and pull it out of the casting. Reach into the hole in the weight and lift the concrete weight out of the casting. Clean the surfaces of the weight with a wet sponge.