Removing any oil stain from porous concrete typically takes time, soap, something to absorb the oil and chemicals that break oil down. According to "Wired Magazine," WD-40 contains mineral oil, so any surfactant that breaks the bonds in mineral oil can remove most of the stain. Mineral oil is a broad term that describes oils made from plant-based products or hydrocarbons. Both types of mineral oil respond to cleanup using detergents and absorbent materials such as kitty litter or sawdust saturated with solvents.
Wipe up as much of the WD-40 spill as you can as soon as you can with old rags or paper towels. If the oil sits on the concrete too long, it will penetrate deeply into the concrete; over time, the stain may keep rising to the surface. WD-40 is both lubricating and penetrating oil, so acting quickly minimizes the work and time involved in removing the stain.
Use a strong detergent to remove as much oil from the stain as you can. Either use it straight from the container or mix it with some water. Pour it on the stain and scrub it in with a bristle brush. Do not use a wire brush since the wires can damage the concrete surface. Hose the surface off and let it dry.
Place enough kitty litter or sawdust to cover the stain in a glass or metal container if the detergent didn't remove the entire stain. Slowly add a strong solvent such as acetone, kerosene or lacquer thinner to make a paste. These solvents evaporate quickly, so you'll have to work fairly fast. Stir with an old stick or spoon until the litter or sawdust forms a poultice.
Put on protective gloves, either rubber, leather shop or gardening gloves. Spread the mixture over the stain and cover it with a small piece of plastic from a tarp or old shower curtain. The mineral oil in the WD-40 will start to soak into the sawdust or kitty litter.
Sweep the absorbent material into a dust pan after a few hours to see how much of the stain has lifted. Reapply treated litter or sawdust until the stain is gone. Let the treated absorbent material dry thoroughly before throwing it in the trash or bringing it to your hazardous waste center.