Is this your home? Business? First off, if there is enough cement dust floating around to solidify in your AC - you have a potentially serious health hazard. Cement is caustic and can irritate the nose and airways. Long term exposure to cement containing silica (sand) can lead to silicosis - an irreversible scarring of the lungs that can ultimately be
fatal. You and our family (if applicable) need to be out of this environment ASAP. See this link:
http://www.osha.gov/SLTC/constructio...te/index.html..
Secondly, good luck in getting
solidified cement out of your coil - nothing short of dynamite will remove it.