Concrete stone is a tough material; however, it is not resistant to dirt. As a flooring material, concrete stone accumulates dirt, grime, mildew and stain, especially when used outdoors and in high-traffic areas. Fortunately, you can clean concrete stone to bring back its beauty.
Sweep the surface to remove most of the dirt, grime and any foreign materials. Work your way in from one edge toward the opposite end. Sweep the concrete stone twice, using a deck broom for the first sweep and a regular kitchen broom for the last sweep.
Remove grease using kitchen detergent and scrub brush. Mix one part detergent with two parts hot water. Apply the detergent with the scrub brush in circular motion and then rinse with a warm stream of water. For stubborn grease, you may need to leave the detergent for 30 minutes before rinsing.
Wash the surface twice using pressure washer. Test the spray of the pressure washer before using it by spraying away from the concrete. Then, point the wand toward the concrete from 4 feet away. Wash starting from the edge going to the opposite side. Make slow passes over the concrete’s surface and stop to inspect if the surface is clean. Continue if it is still dirty. The pressure coming from water increases cleaning density. A power washer with at least 3,000 psi and with a flow rate of at least four gallons per minute should be sufficient.
Remove stubborn stains using muriatic acid. Muriatic is highly intense and potentially dangerous chemical, so wear gloves and a face mask during the stripping process. If the concrete surface has efflorescence — concrete stain caused by excessive moisture — dampen the surface first with water. Blend one part muriatic acid with 10 parts water. Spray the mixture on the affected area. Let the mixture sit for 15 minutes, then scrub off using water and a stiff brush. If you do not see stains coming off, leave the muriatic acid mixture longer before scrubbing again.