Grain bins come in several shapes and sizes, and are used to store grains, such as corn, wheat or barley, until the grains can be shipped or used. These buildings often consist of metal siding over steel supports on top of a concrete floor. Concrete slabs that are significantly larger than the bin help prevent weathering and leaking and provide support for decades.
Measure the area where the grain bin will sit and add 4 feet around each side. Dig into the ground and remove the dirt inside the area where the bin will sit. Place temporary wooden stakes around the perimeter of the area. Place 2-inch by 4-inch studs (2x4s) inside the stakes along the perimeter of the future grain bin floor. Use a leveler to determine if the grade and slope are correct. If the center float is steady and between the lines on the level, the grade and slope are level. Make any necessary adjustments. Nail the 2x4s to the stakes -- nails going through the boards and into the stakes. Stack the boards on top of each other, narrow sides touching to form a wall, repeating until the mold is the size and shape of the grain bin floor.
Wet the inside of the concrete mold thoroughly. Add the wet concrete and spread it around. While wearing rubber boots, walk inside the form and ensure that the concrete touches the edges of the wood. This will prevent air from being trapped inside the floor. Lay a board across the form and trace the line to form a straight guide in the concrete every 4 feet or so. This will give a layout for placement of contraction joints. Concrete can shift in different temperatures and adding joints gives the concrete someplace to go when shifting, preventing cracks.
Coat several 2x4s with oil and set them on their sides in the concrete, until they are the height of the mold. Allow the concrete to dry slightly. Once the mix is thickened, remove the top board in each contraction joint. Once the concrete is almost completely dry, run a broom over the surface to give it a finished, textured look.