Let's pour some concrete! Could you use some paving stones for a backyard path? Maybe you'd like to add a concrete pad at the bottom of your deck stairs. What about that one area of your driveway or sidewalk that's cracked and broken?
For these and other small concrete projects, you don't need to have a truck deliver pre-mixed concrete. Mixing a small batch of concrete, though somewhat heavy work, is not complicated, nor does it require expensive equipment. Start by preparing the area where you want the concrete. Dig deep enough so that you can put down a layer of gravel that's several inches deep. Tamp the gravel thoroughly. If you're repairing shallow holes or narrow cracks in concrete, clean the area as thoroughly as possible (a special concrete repair mix might work better in these situations than normal concrete). Build strong forms to contain the wet concrete - 2-by-4 or 2-by-6 lumber makes good forms for small projects. Use old motor oil to coat the side of the forms that will touch the concrete so that the forms will be easier to remove after the concrete is dry. To hold the forms in place use 2-by-2 stakes every 24 inches (trim the stakes off level with the top of your forms so that you can level the concrete after you pour it). Take measurements so that you know the volume of cement you'll need. Set some wire mesh or rebar in the space you're going to pour the concrete. This will make the final product stronger and less likely to crack. If you use mesh, pull it up into the wet concrete with a rake as you're filling the forms so it's really in the concrete, not just under it. If you use rebar, wire it together into a grid shape, then drive a few short pieces of rebar into the ground and wire the "grid" to the rebar stakes so that the rebar grid is about in the middle of the concrete pad. You might want to buy the sand, gravel and "concrete" parts in separate bags and mix them yourself, but you can buy pre-mixed concrete (just add water), too. Directions on the bag will tell you how much you'll need for your project. To mix a small batch of concrete, you won't need a cement mixer. Use a plastic cement mixing pan (like a huge cake pan about 6 inches deep and 3 feet by 4 feet). A wheelbarrow works well, too. To mix the concrete, you might want to use a concrete hoe, which looks like a garden hoe, but has two holes in the blade. Check if you have a tool library or can rent tools in your area before buying these tools. Adding too much water is the most common mistake when mixing concrete. Using less water makes the concrete stronger, so add water very gradually. The finished mix should be thick enough so that it forms a small mound and doesn't immediately flow into a level puddle. After you've filled the forms, tap the outside of the forms with a hammer to drive air bubbles out of the concrete and cause it to settle. Level the concrete by dragging a straight 2-by-4 across the top of the form. You can use a trowel to give the concrete a more finished look. The more slowly the concrete dries (cures), the stronger it will be, so it's better to pour concrete on a cool day. If it's hot, spray the concrete with water throughout the day to slow the drying process. On the other hand, you don't want the concrete to freeze as it's drying either. When it's partially dry you can cover it with a tarp and spread a layer of loose straw on it to protect it from a frost. After a few days, remove the forms and fill in the area around the concrete with gravel or topsoil as necessary. Let the Pour Begin! If you're mixing your own concrete using the 1-2-4 cement, sand and crushed stone recipe, make sure to keep it on the dry side. Adding too much water makes concrete easier to work with, but also ultimately weaker. The ideal mix should have the stiff texture of chocolate chip cookie dough. Pouring is the fun part. Start by dumping wheelbarrow loads of concrete into the form, starting at one side and working across. Use a garden rake to work the concrete into every corner, half way up the sides of the form. Now lay metal reinforcing mesh onto the concrete, before covering it up with more concrete to a level slightly higher than the form sides. Concrete mesh is available at any building supply store. It'll increase pad strength and resistance to cracking. If your form is narrower than 3 or 4 feet, use a hammer to tap the sides to introduce vibration that'll compact and strengthen the concrete before it hardens. Pads wider than 36 inches should be compacted with an electric concrete vibrator. Some ready-mix companies offer the use of these as a customer courtesy, otherwise get one for the day at a rent-all. You'll also need some help dragging a straight 2-by-6 across the top of the forms on edge (an operation called screeding), to level the concrete. The surface will start drying out in an hour or so, and that's when you should screed the surface again, giving it the final finish. Hardware stores everywhere sell something called an edger - the hand tool you'll need if you want the kind of rounded edges you can see on sidewalks. A few weeks after the pour, rent a gas-powered masonry saw and cut 2-inch-deep, crack-control grooves in the top of the pad, every 10 or 12 feet. If the pad does fall victim to frost heaving, it'll crack along these lines in a controlled and harmless way. Making Concrete Look Like Stone Textured concrete is one outdoor surface option that deserves more attention than it gets. It goes down quickly, is reasonably priced and offers more visual choices than interlocking brick. There are trades people who specialize in textured concrete installations that look like cobblestone, bricks and random flagstone, but the process is practical for any ambitious do-it-yourselfer. In fact, it's one of the best outdoor-surface options around. Besides concrete and wooden forms, you'll need three things to get going: a textured rubber mat, something to pound the mat down into the concrete with (you can make your own pounder out of a 12-by-12-inch piece of 3/4-inch plywood with a 2-by-2 handle) and a powdered release agent to prevent the concrete from sticking to the mat. You may not find any of these at your local building center, but that's OK. L.M. Scofield Co. is one company that supplies textured concrete products continentwide. Look in the phone book or do an Internet search for more options. The time to use the texturing mat is when the concrete has lost some surface sheen from drying, yet is still soft. Use the mat too soon and water will rise to the surface, weakening the top layer. Use the mat too late and you won't get crisp details. Sprinkle an even coat of powdered release agent on the concrete, lay the mat down, then drive it into the concrete with multiple blows from your pounding tool. Lift the mat slowly, reapply some release agent and repeat in the next spot over. If you live in an area that gets freezing weather, seal the surface with a water repellent after the concrete has cured for month. Preventing water absorption stops the surface chipping and flaking, or spalling, which eventually ruins so much concrete.
