Laying asphalt for an apartment parking lot must be done in stages. It takes several months for fresh asphalt to cure before the protective topcoat can be applied. During that time your asphalt is susceptible to certain conditions and hazards that can cause damage before the asphalt is protected. One of the most common menaces to freshly poured asphalt is an oil spot.
Oil spots come from cars parked in your parking lot. When a car drips oil from the undercarriage, it pools on the pavement and creates an oil stain. There are enough leaky cars in any population that this kind of damage happens quite often. The problem is that oil, in particular, is bad for unprotected concrete. This is true for both new asphalt before the topcoat and old asphalt that needs a fresh topcoat.
Oil is a problem for unsealed asphalt because of how asphalt is made. The binding agent for asphalt is softened by oil. In fact, the reason that asphalt needs a few vulnerable months to cure is so that the oil in the asphalt binding agent evaporates and the asphalt hardens. So when oil forms a puddle on unsealed asphalt, it loosens the binding agent. This creates an initial pit and then an entire softened area of asphalt. The sooner you catch an oil stain, the easier repairs will be.
When an oil stain is visible on the pavement but no other damage has occurred, this is the first stage of oil damage. It isn't pretty, and the reason for that is that it is already beginning to eat away at the asphalt. However, oil is slow-acting and you have a few weeks before any irreversible damage is done. If you catch an oil spot at this phase, repair only requires cleaning the oil off the pavement and keeping it safe until it's time for the topcoat.
In the earliest stage of an asphalt oil stain, detergent and water should be all you need to enact a repair. Simply clean the oil off your pavement and give it a thorough washing. Make sure no oil remains on the surface of your asphalt. A proactive property manager who does this every time a new oil stain appears will never have to deal with long-term oil spot damage.
If an oil stain is allowed to stay and puddle, it will slowly start to eat away at the asphalt and soften the area just under the puddle. This will cause a depression to form, a pit where other oil, water, and parking lot chemicals will pool and do further damage. The second phase of asphalt damage is more difficult to repair, as the area has to be cleared, dried, and cured before repairs can occur.
Once the oil has caused a pit or depression in your parking lot, it will be necessary to completely clear and dry the area, then fill it with new asphalt. Start by washing out the pit of oil and other outdoor chemicals. Local heaters can then be used to dry the penetrating oil out of the softened area. From there, new hot asphalt mix can be used to fill the depression and repair the parking lot.
However, once the damage starts resulting in crumbling aggregate, you have a real problem. The oil spot eventually eats away at the asphalt binding agent and makes the whole area soft. Rocks and gravel from the asphalt itself start to wear away with use. This results in loose gravel in and around the pit. Worse, the surrounding asphalt starts to soften and feel spongy underfoot. When your asphalt reaches this point, the damage is irreparable without completely removing the damaged asphalt.
There are two ways to repair the worst stage of an oil spot on asphalt. The first is to cut away the damaged asphalt. Cut it all the way down through the asphalt layers and remove the damaged square. Then pour new hot asphalt mix to fill the cut-out and bind it to the rest of your asphalt parking lot.
The second method is less intensive if the damage is not too deep. You may be able to grind away the top layer of damaged asphalt. Once all of the softened asphalt is removed, no matter how deep, new hot asphalt can be poured in to patch the area. In this case, you will want to clean the area and then apply a tack coat before filling with a hot asphalt mix. The new asphalt can then bind with the old asphalt and your parking lot will be repaired.
As you can see, the best way to repair oil stains is to catch them early. The earliest stage of an oil stain merely needs to be washed away with detergent. But as the oil spot gets worse and the asphalt takes damage, you will need to worry about new hot asphalt mix and then cutting away any extensively damaged asphalt.
Early detection is the key to avoiding costly and unnecessary repairs. Once it's safe for you to sealcoat your asphalt, put it on your calendar. Timely sealcoating is what keeps your asphalt safe from oil spots over the long-term. And when your old sealcoat starts wearing off, scheduling a new sealcoating will continue to keep your asphalt safe.