Diluted salts that are carried to the surface of a concrete subfloor by water coming up from the ground below. These salts may cause installation failure of resilient flooring by destroying the adhesive bond. They can work their way up through tile joints and sheet goods' seams. In dry concrete, normal surface alkalinity on a pH scale is 9 or less. When alkali readings on a slab are above 9, alkali can cause problems with a flooring installation. There is no guarantee any treatment will keep the surface free of alkali, but washing the surface with clear water or soda water will lower the alkalinity. Traditionally, muriatic acid has been used, but it too may leave behind residue, which can adversely affect the flooring installation.