At times, all the concrete in the driveways looks the same. There is no color differentiation, streaks or shade variations. Other driveways may have various shades and colors of gray.
Why is this?
Generally it happens because of how the finishers trowel the concrete after it is first placed, or there could have been different loads of concrete or there was a moisture difference in various areas of the concrete.
Concrete curing compounds and the “Green” environmental friendly components used to make the concrete can also affect the color.
The majority of the time the color differences have little affect on the structural strength of the concrete. Most of the time, it is just a cosmetic issue.
Oil dripping from a car engine is probably the most common cause of stains on a driveway or garage floor. Other stains can be from things being accidentally cast on the drive such as yard fertilizer that contains iron. Eucalypts tree leaves or trees that drop berries on the drive will also leave stains.
High-pressure washing or store purchased concrete cleaning compounds can be used to remove or reduce many of the oil type stains.
Who to consult? Oil type stains are usually cleaned by the homeowner, or a company that does high pressure washing.
Driveways and garage floors with oil type stains often are cleaned by the home owner or a company that does high pressure cleaning of concrete. Re-staining of concrete is generally done by a concrete contractor.