Laying concrete at home can seem like a daunting task, made more challenging when trying to form a specific geometric shape. The two main concerns for this task are to lay the concrete smoothly and pouring it in a perfect circle. Both of these concerns can be overcome by being prepared, organized and methodical when preparing the area and laying the concrete itself.
Preparing the Ground
Measure out how large the circle is to be, find the center of it and place a stake in the ground.
Attach a length of rope half the desired diameter of the circle to the stake, stretch out the rope to where the edge of the circle will be and walk around the circle, holding the end of the rope. Apply a circle of paint in a perfect circle as you go to mark a boundary for the concrete.
Dig out the ground within the circle to a depth of 8 inches with a shovel to lay a foundation.
Lay a hardwood dam around the edge of the circle. Take lengths of flexible hardwood 8 inches wide and 12 inches long and place them all the way around the perimeter.
Drive wooden stakes into the ground every 3 feet and attach to the outside of the hardwood dam with screws. These are to keep the dam secure.
Pour gravel into the foundations so it is 4 inches deep. This helps with drainage, smoothing the concrete and reduces the amount of concrete required.
Laying the Cement
Make sure there is enough concrete. To work out the area of a circle multiply the diameter of the circle by pi -- 3.14. Multiply this figure by depth of the circle and add about 5 percent extra to ensure there is enough concrete.
Make the concrete by hand by mixing 1 part cement with 4 parts sand and adding water. For larger jobs it is worth ordering a cement mixer.
Pour a layer of concrete over the gravel foundation and smooth over with a rake. Do not pour all the concrete in at once, as this leads to an uneven finish.
Apply the rest of the concrete in layers, raking it over the entire surface every time.
Place a screed board across the diameter of the circle and work across the concreted area in a sawing motion.
Go over the top of the concrete with a bull float. Push away from the body with the front edge raised and pull towards the body with the back edge raised to smooth the concrete.
Smooth the concrete surface by sweeping it with a magnesium float.
Use the edger around the inside of the hardwood dams to remove any lumps and air pockets.