How To Sand Concrete Walls. Let the concrete cure completely three to five days. How to sand cement or concrete walls ?
A sand wash finish requires precise timing to ensure the quality of colors are not jeopardized. As bleedwater moves upward along the form in long channels, it washes away some of the paste and exposes sand. You'll want a high shine for clear sealant and stain.
For a countertop, just sand for about 45 seconds, then clean the surface and check it out.
Go back and flatten any raised areas. Solid concrete blocks are made of a mixture of portland cement, water, sand and gravel. You can basically sand any type of concrete surfaces, regardless of whether it is a countertop, a floor, a wall , or a decorative object. The condition you describe is called sand streaking, and it's caused by excessive bleeding.