What Is The Black Stuff On My Concrete Driveway?

What Is The Black Stuff On My Concrete Driveway?

The black stuff on your concrete driveway is most likely green or black algae. This type of algae is the most common type and is usually a light green or blue color. It thrives in moist environments and can grow quickly, making it a nuisance on concrete driveways, sidewalks, and other surfaces.

Black algae is most likely to blame if your concrete has unsightly charcoal-gray or black streaks or splotches. Black algae may develop on a variety of exterior surfaces, including concrete and roof shingles, and will thrive in the presence of moisture and sunshine.

Fungi reproduce by spores, as do many algae species, including Gloeocapsa magma, the most likely cause of the black patches on your driveway.

When tiny spores settle on an appropriate surface, such as your driveway, they send out roots that feed on tar, limestone, and gravel, and they develop into a colony that may sustain other creatures, including mold.

Although black algae may not pose a health risk, some of the mold development it promotes may, and in any event, algae are slippery and unattractive and should be removed.

To remove mold safely from your driveway, use a pressure of 2,500 psi or less, which many electric models can deliver.

You want a nozzle that disperses the spray broadly enough to minimize harm but not so widely that the pressure’s benefits are lost. Pressure washer nozzles are color-coded, with yellow (15 degrees) and green (25 degrees) being the best for driveway cleaning.

It’s a good idea to soak the algae in detergent before pressure washing to lessen its hold and make it simpler to wash away.

Use a regular mold-killing pressure washer detergent that does not contain bleach, which will damage the washer pump and is harmful to the environment.

Apply it using a pressure washer and a black nozzle (65 degrees) for about an hour before blasting away at full pressure with a green or yellow nozzle. To avoid streaking, keep the nozzle at least 6 inches away from the surface.

How Do You Fix A Pitted Concrete Driveway?

Over time, stress, exposure to the outdoors, and salt all wreak havoc on concrete. Pitting is one of the first noticeable signs that a pathway or driveway needs to be repaired since concrete is not indestructible.

You may repair pitted concrete on your home without employing pricey professionals to rebuild the entire section. The key to preserving your concrete is to begin repairs as soon as you discover pitting. Here is how you can fix a pitted concrete driveway;

Step 1

Prepare the pits for filling. This involves removing any debris, loose pebbles, or dust. Loose debris in the holes will make adhering the new epoxies and concrete to the old cement more difficult.

To clear out the pits, use a wire brush. Sweep up any leftover dust with a brush and water off the area to flush out any lingering material before allowing it to dry.

Step 2

Fill minor holes and pits 12 inches or less in diameter with pre-mixed epoxy or latex repair materials designed exclusively for concrete. These items are available at your local home improvement store as kits or in tubes with a caulking gun application.

Step 3

Using a tiny trowel, smooth the mended area. If the epoxy has settled and the patch is lower than the surrounding concrete, continue the operation until the repair is flush with the rest of the area. Allow the patch to be set for at least a day before removing it.

Step 4

Prepare bigger holes and fractures by chipping away at the bottom of the pits with a chisel. The bottom of the perforations should be somewhat broader than the top. This ensures a long-lasting repair since concrete shrinks and expands as it dries and ages. Clean the area as specified for smaller pits after chiseling.

Step 5

Prepare your concrete according per the directions on the cement bag. Mix only as much concrete as you need since it dries quickly in tiny batches and you don’t want it to solidify before you’ve completed mending your pits.

Step 6

Pour the concrete mixture into the holes slowly. Pouring the concrete should be done in tiny increments. Smooth the fresh concrete using a trowel after each pour.

Build the concrete slowly until it is flush with the surrounding cement, then trowel the area one more time.

Step 7

Mark the patched area with a stake for at least three days. Maintain a moist but not wet environment. While the concrete hardens, saturate the area with water and cover it with a plastic sheet.