Grout is a mixture of cement, sand and water that you apply to tiles, bricks and pavers to secure them. When the grout dries, it forms a hard layer that seals crevices between the bricks and pavers and prevents them from moving. Workers apply grout using trowels and other tools, which sometimes leaves grout on top of the pavers. This excess grout creates a unattractive stain on the surface of the paver that requires a heavy-duty solvent to remove.
Turn on a garden hose and place it next to the paver so that water flows over the top of it.
Place a chisel against the bottom edge of the grout and lower the handle so that it is almost perpendicular to the surface of the paver. Tap the top of the chisel gently with a hammer to remove the majority of the grout from the paver. Be careful not to drive the chisel into the brick, as this will damage it. Turn off the garden hose.
Pour 295ml. of water into a plastic bucket and add 29.6ml. muriatic acid.
Wet the paver again with water so that it is damp. Insert a sponge or cloth into the acid and wipe it onto the grout stains on the paver.
Allow the acid solution to sit on the paver for five to 10 minutes to begin dissolving the grout. You will see tiny bubbles form in the area of the grout stain.
Scrub the grout-stained area with a scrub brush to dislodge the grout particles.
Rinse the paver with water thoroughly to remove all traces of the acid. Examine the paver to see if any trace of the grout remains. If grout remains, repeat the application of acid to dissolve the remaining grout.
Do not use muriatic acid on fresh grout. Allow the grout to cure for at least two weeks before treating it with acid.
Put on eye protection and gloves to protect yourself from the muriatic acid. Do not breathe muriatic acid fumes; they are toxic.