How To Remove The Black Stuff Between Concrete Slabs In Chula Vista?

7 Tips To Remove The Black Stuff Between Concrete Slabs Chula VistaConcrete slabs are one of the most popular choices for outdoor walkways, patios and driveways. Unfortunately, the black stuff (also referred to as “efflorescence”) that can build up between slabs is unsightly and can cause discoloration. Fortunately, there are several tried-and-true methods you can use to remove this black stuff from your concrete slabs:

  1. Sweep away any loose debris before attempting to clean your concrete surfaces.
  2. Use a pressure washer with a 15-degree nozzle on high power setting to blast away surface dirt and grime. Be sure to keep the pressure washer moving so it doesn’t damage the surface of your concrete slabs. Avoid using a pressure washer on joints smaller than 1/4 inch to prevent any damage.
  3. Use a mild solution of detergent and water to clean the surface of your concrete slabs. Be sure to use an environmentally-friendly detergent that won’t harm plants or wildlife near your outdoor space.
  4. Scrub away stubborn spots using a stiff brush and the cleaning solution you prepared earlier. Once you have finished scrubbing, rinse away all residue with fresh water from a hose or power washer.
  5. Treat tough stains with oxalic acid by diluting it in water according to manufacturer’s instructions before applying it to the stain with a brush and rinsing away after 10 minutes.
  6. Cover areas affected by the black stuff with muriatic acid and allow it to sit for 1 hour before rinsing off with a hose or pressure washer. This method is not recommended for smaller joints as it can cause damage to concrete surfaces if left on too long.
  7. If all else fails, use a commercial floor stripper to remove the black stuff from your concrete slabs. Follow the manufacturer’s instructions to ensure you don’t damage your surfaces in the process.


What Is The Black Stuff On Concrete?

The black stuff found on concrete is a form of efflorescence, which is a salt deposit that forms when water evaporates from the concrete surface.

How Do I Prevent Efflorescence?

To help prevent efflorescence, you can seal your concrete surfaces and ensure they are adequately drainage. Additionally, avoiding wetting the concrete during warm weather conditions and using less sodium chloride when winterizing outdoor spaces can help reduce the risk of efflorescence.

What Kills Black Mold On Concrete?

To kill black mold on concrete, you should use a cleaner specifically designed for killing and removing mold. Be sure to follow the manufacturer’s instructions carefully to ensure safety as some cleaners can be hazardous if not used properly.


It is not uncommon to find black stuff between concrete slabs. While it can be unsightly, there are several methods you can use to remove it safely and effectively. For more information, contact Concrete Contractor Chula Vista at (619) 304-9911.