Because of the pressures involved, there is always the possibility of dislodging aggregate. Therefore, pressure washing is not really recommended. If you are extremely careful, you might have some luck by starting at the lowest possible pressure and power washing from directly above. Power washing at an angle is more likely to dislodge aggregate.Loosened aggregate can be repaired. Once the stains have been removed, consider sealing the driveway. See below for more details.