Keeping concrete clean is a concern of many homeowners, since stained driveways and other areas can make the outside of the home look less than attractive. It's important to note that concrete and cement are not the same thing although many people tend to confuse the two. Cement is a gray powder that is part of concrete, along with rock, sand, water and other materials. While you may want to occasionally use a high-pressure concrete cleaning service or do the work yourself, it's also a good idea to clean concrete on a regular basis.
For light to medium dirt build-up, try a detergent and water mixture or a mixture of phosphoric acid and water for cleaning concrete. Phosphoric acid is made up of the elements phosphorous, hydrogen and oxygen. It's used in some detergents because of its ability to remove mineral deposits and rust from surfaces. For heavy dirt build-up on concrete, a hydrochloric acid-based cleaner may be used, but hydrochloric acid should be used carefully. Not only is this acid strong, it may, ironically, create rust-colored stains when you clean concrete, even though it's also used to remove rust.
Always test any cleaner you use to clean concrete by first trying it in an unnoticeable place on the concrete. Alkaline-based cleaners are commonly used for removing greasy dirt on concrete. For example, large expanses of greasy concrete floors could be cleansed with an alkaline-based floor cleaner.
Trisodium phosphate (TSP) is a solvent that may also remove greasy stains from concrete. Solvents are used as cleaners because they are liquid substances that have the property of dissolving other substances. Mineral spirits are refined naptha solvents that can be applied in a paste form to clean concrete. The paste is rubbed into the stain on the concrete and then left to dry before rinsing with water. It may take several applications of mineral spirits to remove the entire stain.
Sealing can reduce the amount of time needed to clean concrete. Acrylic or methacrylate clear sealers help to protect against dirt build-up. To remove moss, which tends to grow on damp concrete, try a product containing ammonium sulfamate. Ammonium sulfamate is a fairly low toxicity weed killer with a white crystalline appearance.