Rust

• 1). Fill a bucket with oxalic acid and water. Combine 1 pound of oxalic acid for every gallon of water. Oxalic acid can be purchased at most home improvement centers.
  
  
• 2). Dip a mop into the solution. Wring it out well.
  
  
• 3). Mop the oxalic acid solution onto the concrete floor. Allow it to sit on the stained area of the floor for three hours.
  
  
• 4). Rinse the floor using clean water and a stiff scrub brush. Soak up excess moisture with dry rags. Repeat the process if necessary.
  
  

Oil

• 1). Sprinkle kitty litter onto fresh oil stains. Allow it to set for a day or so, then sweep up the kitty litter (and oil) with a broom.
  
  
• 2). Sprinkle powdered dishwashing detergent onto the oil stain. Scrub the stained area with a stiff brush and hot water.
  
  
• 3). Rinse the area with plain water. Repeat this process a few times to remove the stain.
  
  
• 4). Use trisodium phosphate if the stain persists. Mix 1 cup trisodium phosphate with 1 gallon of hot water. Pour it onto the stained area, allow it to sit for about 20 minutes and then scrub with a stiff scrub brush. Rinse with plain water.
  
  

Mold and Mildew

• 1). Scrape away loose mold and mildew from the surface using a dry wire brush.
  
  
• 2). Combine 3 oz. of oxygen bleach (sodium percarbonate) and 1 gallon of hot water into a bucket. Allow the oxygen bleach to completely dissolve in the water.
  
  
• 3). Dip a stiff scrub brush into the cleaning solution. Scrub the mold and mildew from the concrete.
  
  
• 4). Rinse the area well with plain water. Soak up excess water with rags.
  
  

Paint

• 1). Scrape away as much paint from the concrete as possible using a putty knife. Brush away paint flakes with a broom.
  
  
• 2). Dampen a rag with a commercial paint remover. Place the rag directly on top of the paint-stained area of the concrete.
  
  
• 3). Allow it to set on the concrete for about 20 minutes. In the meantime, mix a solution of water and dish soap into a bucket.
  
  
• 4). Remove the rag and wipe down the area with a sponge and the soapy water. Remove excess moisture with rags or paper towels.
  
  
• 5). Wipe down the concrete with a sponge and plain water.