Baking soda is an amazing household cleaner, and it can work really well on your pavers too.
SOAK WITH BAKING SODA
Pour baking soda on the stained spot, then add a bit of warm water. You can add some detergent or white vinegar for a stronger vinegar solution. Let the mixture sit for at least 1 hour. Scrub the top of the pavers, with extra attention to the gaps between the stones or bricks.
Mild detergent and water.
Mix some mild dish soap with water in a bucket to create suds, then use a brush or a sponge to scrub the surface of the pavers. If your pavers are textured or have intricate designs, this cleaning method can be gentler than a power washer.
Use Vinegar or Bleach
If you are going to try this approach to remove mold or algae, first try a mixture of white vinegar and water to spray down the area and kill the mold.
On the other hand, baking soda is useful because it is slightly abrasive, which is excellent for the rough surfaces of paving slabs. When it is mixed with water, it can dissolve dirt and grease, and like vinegar, you'll only need a brush or broom when cleaning.
Study Shows Adding Baking Soda to Concrete Slurry Reduces Embodied Carbon by 15% The additive also quickens the curing time, say the researchers.
To clean paver slabs, you can use a detergent, such as Dawn, or a vinegar-water solution that is gentle enough to effectively clean without causing damage to your concrete pavers.
Often, mould works its way into the porous surface of the pavers, and a pressure washer is not enough on its own to remove all the traces. I'd suggest you use a product specifically designed to remove lichen, moss, algae and mould like Step Spray And Walk Away.
OxiClean is a powerful concrete cleaner that works well on various materials, including pavement and grout. This concentrated solution provides excellent cleaning without leaving residue.
Use a specialist cleaner
Try a specialist cleaner like Wet & Forget, at Walmart, which you spray onto the surface of the paving and leave. It can also be used on steps, fountains, patio umbrellas and other smaller outdoor areas. It's bleach-free and non-acidic but will remove mold, moss and grime without any scrubbing.
The pressure washer in combination with a dirt cutter is an excellent option. This removes not only weeds and moss from the surface, but also from indentations. Keeping up with this type of cleaning means that there is less time for weeds to grow. It also helps to maintain the beauty of the paving stones' surface.
White vinegar is good for cleaning pavers, though it's also acidic enough to erode the stones' surface. Diluted vinegar can be used safely to clean paving stones, though it should be used sparingly and infrequently to protect your paving from damage.
Similar to cleaning pavers with muriatic acid, avoid an intense concentration of bleach, as it can damage the pavers.
Although bleach is great at the whitening effect, you can use peroxide to achieve this. Hydrogen peroxide is an oxygenated bleach. It is safe for plants, so when you rinse this solution, it won't harm anything. It works together with the dish soap and baking soda to remove dirt and whiten dirty concrete.
Simply put, black stains on flagstones are caused by certain types of mold and mildew. These fungi find their way onto the stones either from their spores landing on the stones or from simply extending onto the stones from patches of mold or mildew right beside them—a pretty common occurrence for garden pavers.
If you have greenish-black stuff on your concrete patio, it's probably mold, mildew, or moss. Damp or moist conditions from rain or humidity can encourage mold and mildew to grow in those nooks and cracks of concrete pavers or bricks.
Vinegar Solution
Spraying a vinegar solution (1 cup of vinegar per gallon of water) onto the surface, saturating it fully, should kill most strains of mold. Vinegar spray can be followed by power washing or manual hand scrubbing to remove the dead mold.
Regular Soap and Water
A solution of regular dishwashing soap or hand soap is simple to create, and it will remove mild to moderate dirt, stains, and grease. Just mix your soap and some warm water in a large bucket and you're ready to start cleaning.
Depending on the material of the paver (non-coloured concrete is safe), CLR may be suitable. Always spot test in an inconspicuous area first. Make sure the pavers are not coloured, stamped, sealed or coated.
Can you power wash pavers? Power washing (also known as pressure washing) is also a very effective method by which you can remove dust deposits and various stains from your pavers. Just make sure that the water jet is not directed directly at the joints between the paving stones.
NOTE: Don't use baking soda for cleaning glass surfaces, silverware, stone countertops, and wooden floors or furniture. Also, dermatologists warn against using baking soda routinely as a dry shampoo or underarm deodorant, because its alkalinity will disrupt the natural acidity of skin and scalp.
Pour out the soda and let it sit on the concrete for 15-30 minutes. Depending on the size of the stain, you may use scrub brushes, towels or a mop to take care of the rest with cleaner and water.
“In technical terms, sugar (coke) acts as a retarder and delays the setting time of concrete.” This is the reason why transit mixer drivers are sometimes advised to add some soft drink to the concrete mix if the vehicle gets stuck up in the traffic for too long.