Asphalt is durable, but it's not impervious to stains. Driveways are especially prone to staining, such as from leaking car fluids. Mulch, fertilizer salts, and moss on the paving can also lead to large discolored spots. Fortunately, you don't have to live with stains on your asphalt paving. There are ways to both prevent them and ways to fix those that have already occurred.
The main concern with any type of stain is that it doesn't look very attractive. Older, faded asphalt will show ugly stains more clearly, but oil and other stains can still be visible on newer, darker asphalt paving.
Oil and car fluids that leach into asphalt can break down the structural integrity of the paving and lead to crumbling or cracks. Fertilizer salts don't just stain, they also cause pits to form on the paving service. Issues with moss or algae stains may indicate a moisture concern with your paving, and trapped moisture can lead to further damage to the asphalt.
Stains can sometimes be removed, depending on the cause of the stain and whether it has seeped deeply into the asphalt. For greasy stains, such as from an oil leak, absorbent material is first laid down to soak as much of the staining medium out of the paving before treatment can begin.
Pressure washing is the method of choice for removing most asphalt stains, as it won't damage the paving if the pressure is properly adjusted. Deck scrubbing with special cleansers, such as those designed to kill moss or algae, may also be necessary to get rid of the stains.
If the stains are too stubborn to remove using a pressure washer or via scrubbing, then more in-depth repairs are necessary. Your paving service can seal coat the asphalt if the paving is otherwise in good condition. The seal coat contains sealers mixed with thin asphalt and it will camouflage light stains. If there are stains along with pits and cracks, then your paver may recommend repaving with a thin layer of fresh asphalt instead.
Prevention begins with keeping the driveway clean. Sweep it off regularly so that debris doesn't trap moisture and cause algae growth. Use edging around beds that border the driveway to help keep the paving clear of mulch and fertilizer. There are also absorbent pads available that can be placed under parked cars to avoid fluid stains.
Further, have your driveway sealed every few years by your paving service. If moisture is soaking into the asphalt instead of beading up on the surface, then that means stains can also be absorbed by the asphalt so it is time for a sealant application.
Contact a residential paving service if you are ready to be done with the stains on your asphalt.