Commercial property owners, facilities managers and home-owners often struggle to remove oil and grease stains from concrete areas such as parking areas and driveways.
Bryan Perrie, managing director of The Concrete Institute, says although most common, oil stains can indeed be extremely difficult to remove because of the stains’ rapid ingress into the concrete.
However, there is a solution and he provides some guidelines on how to deal with this problem:
First of all, before attempting to remove any stain from concrete, a small trial area in an inconspicuous place should be treated first to assess the effect the cleaning method will have on the concrete.
It is important to stop the stain from spreading so it should be encircled by a fine, dry material such as sand, cement, sawdust or even cat litter.
Mop up as much of the stain as possible with paper towels or cloths by blotting rather than wiping, and sprinkle the entire stain generously with the fine material. This can then be broomed back and forth and then swept up and disposed of.
The Concrete Institute has found the following cleaning materials to be effective for removing oil stains:
•Automotive engine degreasers
•High-foam washing powder
•Concentrated liquid detergent
These products are more effective when mixed and applied with boiling water.
A stiff bristle brush, although useful for removing thick surface oil deposits, is inadequate for reaching deposits that have already penetrated into the pores of the concrete.
A high-pressure water jet cleaner (100 Bar) can be extremely effective in removing ingrained stains and will also remove chewing gum deposits.
The high-pressure water jet cleaner should be applied some time after the cleaning agent was applied but before it has evaporated. Consequently, application of the cleaning agent in strong, direct sunlight is not recommended.
As soon as the oil or grease deposit has been dislodged, the entire area should be flushed with copious amounts of clean water to prevent soiled water re-depositing the oil on adjacent concrete.
When using high-pressure water jets, protective clothing and goggles should be worn to protect against the rebounding of grit when the jet displaces material from the concrete or between block paving.
Once most of the surface stain has been removed as described above, cover the residue with a poultice made up of one part agricultural lime to two parts mineral turpentine.
Spread a layer of about 5 mm of the paste over the stained area, ensuring that there is a margin of approximately 50 to 100 mm around the edges.
Cover the plastic sheeting and leave for 24 hours. Builders’ lime should not be used as it could cause skin burns.
It may be necessary to repeat this process within a day or so to remove any deeply ingrained oil or grease that sometimes continues to rise to the surface.
Finally, scrub the stained area with warm water and laundry detergent, then rinse well with clean water to end the treatment.
A clean and neat concrete driveway creates a good impression at both commercial and domestic buildings.
More information from Bryan Perrie, Tel: +27(0)11 315 0300/ www.theconcreteinstitute.org.za
