Be ready for placing, finishing, and curing when the ready mix truck arrives. The concrete must be placed in the forms and struck off level within 1½ hours after the water is added to the mix at the plant. In very hot weather, the work should be done in shorter time.

Placing
Spray or brush release oil on all forms and moisten the subgrade just before placing concrete. However, there should be no free water or muddy or soft spots on the subgrade when concrete is placed.

Avoid having the heavy truck back over any existing sidewalks or driveways to deliver the concrete. If the site of your project is especially difficult to reach, ask your dispatcher or the driver for suggestions on how to transport the concrete from the truck to the job.

Placing concrete is strenuous work and it pays to have several strong men on hand for the job. A good wheelbarrow is needed to transport the concrete from the truck chute to the jobsite. You will also need the proper tools for placing and finishing. Most local equipment rental stores have construction wheelbarrows and concrete tools to rent.

Starting at the far end of the project, place the concrete in the forms to the full depth. Place the concrete into previously placed concrete and work toward the near end. If you are pouring on an incline or steps, use stiffer concrete and start at the bottom and move to the top. To consolidate the concrete by hand, spade along the sides with a short-handled square-ended shovel to ensure complete filling. Do not use a rake because it can cause aggregate separation.

Strike off the concrete with a stiff board (screed) that rides on the edge forms. Tilt the screed slightly, and use a sawlike motion across the slab to smooth the surface of the concrete while cutting it off to proper elevation. For larger slabs, this is more easily done with two people, one at each end of the screed. Go over the concrete a second time in the same way to take out any bumps that remain after the first pass. This will make finishing easier. Any low spots should be filled before the second pass to provide a uniform surface for the finishing operations.

To consolidate and strike off concrete mechanically, use a vibrator attached to twin strikeoff boards.

Finishing
Immediately after striking off, work a bullfloat back and forth across the slab to smooth it and remove irregularities. Work a slight amount of cement paste to the surface. Do not overwork concrete; overworking will result in a less durable surface. For cramped areas, use a darby or hand float to accomplish this smoothing operation.

Immediately after bullfloating or darbying, the concrete should be cut away from the forms to a depth of 1 in. using a margin trowel.

The remaining finishing operations of edging, jointing, floating, and brooming must wait until all bleed water has left the surface and the concrete stiffens slightly. When the water sheen is gone and the concrete will sustain foot pressure with only slight indentation (¼in.), finishing should begin.

First, do the preliminary edging with a ½-in. or smaller-radius edger along all forms, including any wood strips left in the concrete to serve as joints. If joints are formed with a hand groover, do this operation at the same time or after edging. Final edging and jointing are done near the end of finishing and before brooming.

Control joints should be spaced at intervals in each direction as required by the type of project. You can mark the joint locations on the forms with a string line or straight board before the concrete is delivered.

Control joints are made by cutting into the partially set concrete with a groover, or by using a concrete saw after the concrete hardens.

Floating is done after the concrete has begun to stiffen. Get out on the slab by walking and kneeling on 10x24-in. kneeboards. Work the hand float in wide, sweeping arcs across the slab, backing off as you work.

If you desire, the relatively even (but not smooth) texture produced by the hand float can be the final finish. Using the hand float in a swirl pattern will improve the appearance. If you prefer a roughened texture without float marks, draw a damp broom across the surface. The concrete should be hard enough to retain the grooves or marks made by the broom. The roughness of the texture can be varied by using a stiff-or soft-bristled broom.

For a very smooth surface, you can do the final finishing with a steel trowel. However, a very smooth surface is rarely necessary or desirable on outdoor walks, driveways, patios, and steps, and it is recommended that such a finish be avoided in these areas whenever possible.

Caution: The tendency in most cases is to float and trowel the surface while the concrete is too soft and plastic. All outdoor construction is subject to severe punishment from temperature extremes. Premature floating and troweling of outdoor flatwork may cause scaling, crazing, or dusting and result in a less durable and less wear-resistant surface. Clean your tools with water.

As soon as the concrete is hard, moisten it and cover it with waterproof paper or polyethylene film, weighted down around the edges to prevent evaporation. The slab can also be kept continuously wet with a sprinkler or by ponding. The concrete can be covered with burlap that is kept moist by occasionally spraying it with water. Liquid membrane-forming curing compounds sprayed onto the surface can be used before the middle of September.

Preparation for First Winter
In addition to proper mix ingredients and sufficient moist curing, at least 30 days of air drying are essential to develop resistance to deicer chemicals. If time does not permit this air drying, the concrete surface should be sealed with a breathable surface treatment. Such treatments often consist of a penetrating sealer made with boiled linseed oil, silane, siloxane, meth-acrylate, or other materials.