How to Create a Rock Salt Finish on Concrete. Creating an interesting finish on concrete can immediately improve the look of the typical old gray standard patio. Apply rock salt to the newly laid and wet concrete to produce speckles or craters. The process is time consuming but will create an interesting outdoor area.
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Purchase water softener salt crystals that are about 1/8 to 3/8 inches or those labeled as coarse or extra coarse. Rent or purchase a concrete roller.
Choose the best time to begin the process. For the best results, the salt should be spread when the concrete is just starting to set. This time can be determined when there is about a ¼-inch give in the wet concrete when gently pressed with a fingertip.
Spread the salt crystals onto the concrete in even patterns. This process should be done until you create the finish you think you want, and it's distributed very evenly. You can always add more crystals so start with less than you think you'll need.
Allow it to dry for at least 24 hours. Rinse the surface with a power washer or with water while scrubbing with a brush.
Let the surface and any pockets dry for another 24 hours. Apply a curing compound.