Organic, tannin-based stains commonly occur on concrete driveways when dry leaves, nuts or acorns fall and are left to sit on the surface. The brownish discoloration left when these natural items are finally removed are formed as a result of the tannin in the organic matter. Acorn stains needn't leave a permanent mark on your driveway. When proper supplies and techniques are used, the stains can be fully removed from the concrete surface.
Pour 2 cups of hydrogen peroxide into a bucket. Add 2 tbsp. of ammonia. Stir in enough sawdust to make a thick paste.
Spread the paste over the acorn stains on the concrete surface. Allow the paste to dry so it can lift the stains. Remove the dried paste and discard.
Wet the concrete with the garden hose. Add a squirt of dishwashing detergent to the surface and work into a lather by scrubbing the concrete with a scrub brush.
Cover the soapy lather with sawdust to absorb the soap and water, rather than having to rinse it into the grass or garden. Sweep up the sawdust to remove the soap solution.
Rinse the concrete with the garden hose to remove remaining sawdust. Allow the driveway to air dry.