Concrete is an extremely versatile material for yards, patios, driveways, and many other surfaces. Concrete can have many different forms and does not all resemble the flat grayish-white surface that many of us think of. Concrete can also be used as a foundation for bricks or tile.
A mixture of cement, sand, water, and aggregate, concrete gets its hardness from the cement in it. The aggregate, which is usually gravel, and sand control shrinkage and act as filler. Concrete can be made from scratch or bought in wet or dry form. For large projects, ready-mixed concrete can be delivered right to the site.
Before concrete paving, the base must be stable and well-drained. If the ground shifts after the concrete is finished, it may end up cracking the concrete slab. The site should be graded, with any soft soil being moistened and tamped. In addition to a 4 inch (10 cm) cement slab, you should prepare for a 2 to 8 inch (5 to 20 cm) gravel base, depending upon drainage needs.
Prior to pouring the concrete, a wood form must be built. The form should be strong, fastened to stakes every four feet (1.2 m) at minimum. If the forms are temporary, they should be oiled to assist in removal. If the concrete paving area is larger than eight square feet, it should be reinforced with steel mesh to prevent cracking.
Concrete for concrete paving may be mixed by hand in a wheelbarrow, or in a cement mixer, following the concrete's specific directions. Concrete should slide off a trowel but not run off of it, and should be easy to smooth. Stiff or crumbly concrete should have water added to it, while soupy and wet concrete should have cement and sand added.
The concrete should be poured at one end of the form while being spread — ideally by a second person — with a shovel or a hoe. Tamp the concrete into all corners and level it by using a screed, a piece of wood for leveling. After leveling, use a bull float to smooth down any high spots or small dents.
Because concrete paving should be completed before the concrete is dry, edging and joining should be performed immediately after floating. Edging is done with a trowel and edger, smoothing the area right on the edges of the forms. Jointing is performed with a jointer, and creates divides in the concrete for expansion and contraction due to temperature.
After the concrete has dried somewhat but has not yet become completely stiff, a final floating and trowing should be performed for a smooth surface. If a nonskid surface is desired, a broom can be dragged along the surface of the concrete, instead of a trowel. To "cure" the concrete and make it hard, it should be kept wet for at least a few days. The concrete can be covered with plastic sheeting or you can wet it down each day.
Written by Bronwyn Harris