Efflorescence in crawl space
Effervescence of concrete of your type is a reaction of the added concrete.  It is generally found in acidic compounds.  I recommend using some ammonia over the entire concrete surface with no added water.  Use a mask please!  The ammonia will neutralize the acid and in many cases solve the issues.  I see this on my acid stain projects and that Is how we mitigate it.  Now if the ammonia comes in contact with any metal surface it will cause rust so avoid electrical and metal surface...AND WEAR A MASK!