Selected Answers

From Brian Trimble of IMI on February 14, 2018:
I would agree with Zenith Czora's recommendations ...read more I would agree with Zenith Czora's recommendations except when cleaning "insoluble efflorescence" (which I would call lime run or calcium carbonate deposits). I have seen too many walls damaged with inappropriate high-pressure cleaning. It can be done right, but there are specific proprietary cleaners for calcium carbonate stains that should be considered first.

From Zenith Czora of Durotech Industries, Inc. on February 12, 2018:
First of all, the efflorescence that is existing o ...read more First of all, the efflorescence that is existing on the CMU surface needs to be assessed. Efflorescence does cause discoloration of the affected surface. Determine whether it is a primary efflorescence (whitish bloom or color fade), which develops during setting and curing of the CMU, or a secondary efflorescence ( uniform discoloration or localized encrustations), which develops later where moisture or water exits the CMUs. Or  it may be a cryptoflorescence, which is a salt crystallized within the pore structures of the CMUs. It forms below the surface and is not visible until the crystal growth develops enough to cause surface scaling and spalling. There are two methods of removing efflorescence. Chemical removal uses diluted acid like acetic acid, citric acid or phosphoric acid, but it may alter the surface color and texture. (Bear in mind that efflorescence also causes discoloration.) and then the treated surface may be neutralized with 10% ammoniacal solution or KOH.  Mechanical removal by dry brushing can remove fresh deposits of water-soluble efflorescence using a stiff bristle brush and vacuuming the loosened materials from the substrates and surrounding surfaces..Wet brushing can be used if dry brushing is ineffective, provided there is no opportunity for salt redepositing back on the surface when water evaporates. High-pressure water jetting can be used for insoluble efflorescence. If the sources of efflorescence--soluble salts, water/moisture in contact with the salts forming salt solutions, and a passage allowing salt solution to migrate to the surface--are not minimized or at least one is eliminated, efflorescence may possibly reoccur.