Patches of cement are often uneven and stand out from the rest of foundational walls, especially if cracks in the original walls necessitated the repair. Usually the patched areas are visibly noticeable, even if the area gets painted. Even adding siding or some other wall covering to the patched area can cause problems because of the uneven surface. It is possible to sand the patched areas of the walls so that they sit on an even level with the use of an angle grinder.
Things You'll Need
Angle grinder with diamond grinding wheel
Make sure the patched area is dry before attempting the grinding process. The grinder will only work on fully cured cement and concrete. If the concrete is still somewhat wet, the grinder could ruin the entire patch.
Put on all safety gear. The angle grinder is loud, and it will produce a lot of dust. To prevent the inhalation of dust or damage to the ear drums, safety gear is a must.
Attach the grinding wheel to the angle grinder. Make sure the casing holding the grinder in place is secure. Tighten all bolts and screws so that the blade cannot escape while the grinder is on.
Plug the grinder into a power source. Place the grinding blade against the patch before turning it on. Always hold the grinder with both hands as you use it.
Turn on the grinder and carefully and slowly grind down the cement. The use of the grinder may generate sparks, so take care when handling the machine. You may want to wear work gloves and long sleeves when operating the tool.
Grind the patch down until it sits on the same level with the rest of the foundation wall and until it is smooth to the touch. You may have to grind some of the surrounding area of the original wall to even out the wall.
Brush away the dust with a soft brush, then vacuum it with a shop vacuum.