Replies

1. 
   Fred_ | Jan 02, 1999 01:55am | #1

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   Geoff-the correct term is efflorescence, and it is essentially salt compounds leaching from the inside of the CMU. During damp weather, the porous CMU gets saturated, mineral deposits within the CMU get saturated and the moisture gradient carries them to the surface of the block where the now concentrated minerals precipitate out. To get to your question, how does one stop the process? There are several excellent products on the market to do this. The first is Thoroseal, and the next(and by far the best and most costly) are Tnemec products. The most important step with either coating is to first fill the surface of the block with the mfr's approved, compatable block filler, then according to mfr recommendations, apply the surface sealer. Tnemec is out of KC, 1-816-483-3400. Thorosealis probably more locally available (although prob not @ Home Depot), call your block supplier-they'll know.

2. 
   Geoff_Sheldon | Jan 02, 1999 01:56am | #2

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   I am building a new home with exposed CMUs on the exterior. A fine white powder or effervescence forms on the block, particularly after a rain.

   How can I clean this off?

   How can I seal this to avoid future recurances?

   Thank You.