You're sick of looking at a boring, gray concrete slab and want to cover it up. Paint is the most inexpensive option, but not always the best. If you're putting it on vertical surfaces such as walls, it has a much better chance of lasting than if you're applying it to horizontal slabs such as patios or floors.
While you can use typical acrylic paints on your concrete slabs, you'll need to keep in mind that most acrylic paints aren't made to take the abuse that a horizontal surface takes. Typical acrylic paint will not last for a long period of time due to this abuse. When you do use typical acrylic paints on your concrete, you'll also need to purchase a sealer to help preserve the life of your paint. Like with most painting jobs, you'll brush the corners and near the walls and roll the rest.
Preparation is pivotal in painting concrete, much like in other painting jobs. When preparing your slab for paint, your first step is determining if you have a moisture problem on your slab. To do this, tape a section of plastic--approximately 2-by-2-feet--to your concrete and wait for 24 hours. Check for condensation under the plastic; if there is some, you'll need to forget the paint and use a different product. If the moisture is fine, you'll also need to clean your slab with a mild detergent. If you have oil spots or other stains, use the appropriate cleaners for each. Acid etching will allow the paint to better adhere to your concrete surface; a muriatic acid solution followed by diluted ammonia will do the trick. You'll also need to patch any holes or defects in your slab with a vinyl concrete patch prior to painting.
Instead of dealing with the hassles of a typical acrylic paint on your slab, consider instead using an acrylic stain. Acrylic stains penetrate deeply into the concrete surface and create a semi-transparent finish. Acrylic stains won't peel and flake like paint will on a concrete surface. Acrylic stains are made to withstand the traffic and other abuse concrete slabs typically get; this includes ultraviolet rays, foot traffic, moisture and others. Like paint, you can also find acrylic concrete stains in a variety of colors to suit your taste.
Acrylic stain isn't your only other choice when choosing to alter your concrete slab. Acid-based stains are a transparent stain that lets you keep the character of your slab. Epoxy floor coatings are extremely durable and resistant to oils, greases and other things that can quickly ruin a painted concrete floor. Both of these products are available in a wide variety of colors and possible effects.