Is there any danger of alkali-aggregate reaction with concrete when fiberglass forms are used?
Forms that are often referred to as fiberglass are actually plastic forms that have been reinforced with fiberglass. Glass fibers can react with alkalies in the concrete to cause discoloration. For this reason it is necessary to be sure that the resin cover over the fibers is maintained, but this is no great problem. Fiberglass-reinforced plastics are widely and successfully used for producing architectural concrete finishes.