Remove mold from concrete using a bleach solution to scrub the surface. If you prefer to use something other than bleach, commercially prepared mold killing detergents and solutions are also available. Regardless of the method you choose, the process is the same.
Put on rubber gloves and eye protection before using mold-killing products such as bleach. Mix the cleaning solution by adding one part bleach to four parts water. If you are using a commercial product, mix the solution according to the label directions.
Scrub the surface with the solution to kill the mold. Give the solution some time to soak into the porous concrete to kill any spores that are beneath the surface. Rinse the solution from the concrete, being careful to protect any nearby landscaping. If a pressure washer is available and the concrete is in good condition, use the machine to force any organic materials from the concrete.
Give the concrete time to dry. To prevent future mold growth, apply a coat of clear acrylic concrete sealer for outdoor use. The sealer prevents moisture and mold spores from penetrating the surface.
Mold grows where surfaces remain wet. If the concrete is growing mold inside the house, locate the source of the moisture, and eliminate the water leak or condensation to keep the mold from returning.