does anybody know what concrete cancer is
 

does anybody know what concrete cancer is?
i am in the tropics and i would like to know a little about concrete cancer? how to fix? how to prevent?
i see many unfinnished building where i am with rebar exposed to the elements, sun rain tropic heat and humidity.
thanks in advance
david

many forms of concrete deterioration. no real definity on "concrete cancer". what you are describing is likely deterioration resulting from chloride intrusion, which causes corrosion of the rebar and consequential spalling of the concrete, thus exposing the rebar to the elements.
"concrete cancer" is alkali-silica reaction, you can look it up on the internet. prevention is by correct selection of aggregates. from what you describe it seems as likely that poor workmanship or low cement content is the cause.
if you are refering to rebar left exposed while awaiting completion of the structure then the rebar can be temporarily protected by coating with a cement grout wash.
zambo