During repair work, hydraulic oil from a forklift leaked onto an exposed aggregate driveway that was only 2 months old. The driveway wasn't sealed and is now stained by the oil. The stain occurred about a week ago. The driveway has a steep slope so any liquid used for cleaning will run down the slope. Also, we're in California and aren't permitted to use petroleum-based products or turpentine. Is there any way to remove the stain?
Try using a poultice. Dissolve 1 pound, 6 ounces of sodium orthophosphate (also called trisodium phosphate or TSP) in a gallon of water. You can buy TSP at most hardware stores. Add enough finely ground calcium carbonate (also called whiting or agricultural lime) to make a thick paste. Agricultural lime is available at garden supply stores. Spread the poultice over the stain and allow it to dry for a day if possible. Then brush off the dry paste with a stiff natural bristle brush and scrub the concrete with clear water. A second possible solution is to sprinkle dry cement on the stain when the driveway is dry and the weather is sunny. Cover the cement with a glass plate. The sun's heat reportedly draws oil into the dry cement which can then be swept away. As with any stain removal method, it's safest to try these two approaches on a small area first and observe the results.