Cleaning Concrete: the Sol
Did a long hard winter turn your driveway black? Those pesky rust spots just keep coming back? Today you’ll learn that choosing cleaners is just part of the answer. How you mix them provides the solution.
Black streaks and patches are fungus and mildew. And rust is either iron oxide from lawn fertilizer and sprinklers or iron particles in the concrete. To remove mildew, add 1 ounce of laundry detergent powder and 3 ounces of Trisodium Phosphate (TSP) to 1 quart of bleach and 3 quarts of water. Apply with a soft brush.
Let it stand for awhile and then hose it off. For rust stains, put 1 pound of oxalic acid (wood bleach) in 1 gallon of water, and scrub with a stiff bristle broom or brush. You might have tried some or all of these in the past — possibly without success. While the cleaners may well have been the right ones, the key is having the correct proportions.
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