The only efficient method is to use a High Pressure Cleaner at least 35 psi   
   and a minimum of 75 degrees Celsius and persistence and patience. I do this   
   for a living and the fastest way is to place the high pressure gun   
   approximately an 8th of an inch    
   from the gum and move the gun in a small circular motion each piece of gum   
   takes approximately 20 to 30 seconds to remove. The gum however does not break   
   down the heat and pressure simply melts the gums hold on the concrete I   
   suggest collecting the    
   removed gum and disposing of it in an environmentally friendly manner as it is   
   essentially Synthetic Rubber which will rather rapidly cause damage to the   
   local sewerage system and plant not to mention it really is not something that   
   we want in our    
   waterways.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)