Concrete is a porous material used for sidewalks and patios. According to the U.S. Army Corps of Engineers, concrete is easily stained but most stains can be removed as long as the stain is worked on immediately. To remove dry raw egg from concrete, try using an acid, such as cola or vinegar. These liquids are readily available and are less toxic than regular commercial cleaners. Dried raw egg should be handled as an oil or grease stain.
Attach a spray nozzle to your hose and spray a fine mist over the dry egg. Excessive water pressure can force the stain further into the concrete, so use a gentle mist only.
Brush the area to remove some of the dried egg. If it is very hard, scrape the egg with a metal scrapper, such as a spackling knife. Try to remove as much of the egg as you can.
Soak 10-inch square flannel in cola or vinegar. Both are acids and can break down the dried raw egg on the concrete. Place the saturated flannel over the entire area. If the area is larger than 10-by-10-inches, soak and use more flannel.
Place a piece of concrete slab over the flannel to give pressure to the stained area. Wait for 15 minutes. Remove the concrete slab and flannel. Spray the area with the hose again.
Scrub the area with the brush to remove the dried raw egg. If the stain persists, mix salt with the cola or vinegar to create a scrub. Use the mixture with the brush in circular motions to remove the egg. Hose the mixture away.