Concrete is an extremely versatile material that can be made to look like many different materials, when poured or stamped in different patterns. Pouring concrete may be intimidating at first, but an amateur should be able to pour concrete, provided there are two or more people working together and that they start with a small project.
When preparing to pour concrete, plan to do it in stages that will not be overwhelming. Concrete should be poured in sections, as it is much easier to deal with in this way. The ground should be graded and prepared, with any soft soil wetted and tamped down. You will also need to make sure that you have a gravel base: 2 inches (5.1 cm) in areas without frost and drainage problems and between 4 to 8 inches (10.2 to 20.3 cm) in areas with these issues.
Concrete should generally follow the ratio of one part cement, 2.5 parts sand, 2.5 parts aggregate, and 0.5 part water. If you live in an area which has severe freezes and thaws, you will need to add an air-entraining agent, which creates tiny air bubbles, helping the concrete to expand and contract without cracking.
Since wet concrete exerts considerable pressure, the wooden form should be strong and anchored to the ground. Forms can either be removed after pouring concrete to let dry, or be left in the concrete as permanent edging. If you are planning to leave the wood in place, use pressure-treated lumber.
If a concrete area is going to be large, it should be reinforced with steel mesh. After the forms are built, but before pouring concrete, install the mesh, cutting it to the correct size with bolt cutters. The mesh should be supported on brick, pieces of broken concrete, or stones, so that it is held up in the middle of the concrete slab.
Concrete can be mixed by hand or with a power mixer. If you are not pouring much concrete, it is probably easier to do it in a wheelbarrow by hand. For larger projects, you may want to rent a power mixer. Concrete that has been mixed correctly should slide off of a trowel and be smoothed down easily.
Pouring concrete involves two or more people unless the job is very small. Begin pouring the concrete at one end of the form while another person spreads it with a hoe or a shovel. Make sure you work the concrete into all corners. Next, using a screed — a long straight board — make sure that the surface of the concrete is even. Simply move the board along the form, using a slight zigzag motion.
After pouring concrete and screeding it, you will need to float the concrete. Using a bull float, float the concrete by pushing the flat part of the bull float away from you. This will smooth down any bumps and fill in any dips in the concrete. Using an edger, work around the edges of the concrete, smoothing the part of the slab right next to the forms.
To give the concrete a way to expand and contract during temperature changes, a jointer is used. Jointing divides the concrete, and is usually done in straight lines at regular intervals. When the concrete has dried enough that the water sheen is no longer visible, either give the slab another floating to make the surface smooth, or perform brooming — dragging a broom across the slab — for a nonskid surface.
Finally, you will need to cure the concrete. Cover the concrete slab with a material such as straw or burlap that can be wetted down or with plastic sheeting that will trap the water evaporating from the concrete. The concrete should be cured over a period of time that varies from a few days to a week.
Written by Bronwyn Harris