One rule to remember in finishing concrete: work the surface as little as possible to get the finish you desire. Sounds simple and it is. But the temptation to overwork concrete is tough to put down. Don’t let it hang you up. Your choice of finish should depend on your skill with a trowel. The very hardest finish to make is the steel-troweled smooth surface you see on most concrete. This finish is fine indoors for concrete basement floors, concrete garage floors and such. It is hard, takes lots of wear and cleans easily. But it’s too slippery for use outdoors.
For patios, concrete sidewalks and concrete driveways use a non slip finish. One of the easiest non-slip surfaces to make is the metal float finish. That’s METAL float, not steel trowel. Use an aluminum or magnesium float. A broomed finish is easy to make, to, You can use a non slip finish inside and avoid the hard-to-make steel-troweled finish completely. The surface will be harder to sweep and wash down and not as comfortable for roller skating. Otherwise it will be serviceable. If you must have a smooth-floor look, it might pay to hire a skilled cement finisher by the hour to produce it for you.
You can do it yourself or hire a professional concrete contractor, but don’t try to do too much in one day. An area of more than 100 square feet can get away from you on a hot, windy day. The part you gave a first-troweling may get past the stage for its second troweling before you finish the first-troweling elsewhere. This can happen to concrete contractor pros too. Watch it. If you plan a float or broom finish, you can handle much more without danger of “losing it.” Cool, damp weather helps too.
Most concrete projects you’ll build will be slab work. Every slab should be cast on a firm, dry subgrade (in-place soil) or subbase (special material). If your soil is sandy and well drained, you can cast a slab right on the ground. First remove all sod and vegetation. You can also cast on the ground if you live in a nonfreezing climate. Clay and other poorly drained soils call for a compacted 2-inch layer of crushed stones, gravel or sand to keep water away from the bot- tom of the slab. Sand is easier to shovel and grade but it should not be very wet when concrete-placing begins. Just damp.
“Mucky” soil should be dug out and replaced with gravel or crushed stones in 4-inch lifts. Tamp each one well. Build forms for 4-inch-thick slabs out of 2×4’s. For 6-inch slabs use 2×6’s. These give slightly less thickness than the full 4 or 6 inches, of course, but that’s the name of the game. Don’t worry about it.
Brace forms by driving 1×2 or 2×2 wood stakes into the ground every 4 feet. In nailing through the stakes into the form it helps to back up the form with the head of a sledge hammer or other heavy object. Forms will strip easier later if you use double-headed form nails. Oil the forms with old crankcase oil so they’ll strip from the concrete without sticking. Gently curving forms can be made of doubled-up 1-inch lumber in place of the 2-inch. For sharper curves use 4-or 6-inch plywood or hardboard bent and staked to the desired radius. Build up two or more layers until you have enough thickness to take the pressure of fresh concrete. The sharper your curve the less thickness is needed. Forms for slabs may be level or sloped for drainage. In order to drain well. you’ll need a slope of 1/8 to 1/4 inch per foot.
If you use ready mix, try to have it dumped directly into the forms. This saves work. Otherwise you’ll have to wheel it in and dump from the wheelbarrow. In a pinch you can use a bucket brigade, if you have enough helpers. It’s hard on backs and buckets. Mix-your-own concrete will probably have to be transported by wheelbarrow. Or leave the hard work to the professionals by calling Concrete Salt Lake City.
Concrete should not be dumped in separate piles and raked together. Nor should it be placed in one pile and pushed or allowed to run into place. This practice makes weak slabs. The less pushing, shoving and raking you do, the better for both you and the concrete. Dump concrete against the forms as near to grade as possible. Start so that each succeeding load can be dumped against the previous one. This tends to compact the mix into place.
After placing concrete, strike off the surface to the correct elevation. Form tops should be at this elevation so they can be used for supports for the straight- edge. Place the strike board across the forms and begin see-sawing along them. Advance an inch or so with each stroke. You’ll soon see a roll of excess concrete form ahead of the screed. With air-entrained concrete this roll is round and plump, telling you there’s air in the mix. The roll of extra concrete fills in any low spots. If the roll gets too big, shovel some of it away.
Right after strike-off, get going with your bull float or darby. It works mortar to the surface while putting down ridges left by the strike board. The leading edge of the bull float should always be raised. This is done by raising or lowering the handle as it is pulled or pushed. The secret to handling a derby without messing up your newly struck surface is to use a light touch. Hold up some of the weight of the darby if the mix is wet. Bear down a bit if it’s stiff. Don’t disturb the elevation, just smooth off the ridges. You’ll soon get the hang of it.