Eighty-two years after fly ash was first used in the concrete mix of the Hoover Dam, its use in concrete still has no consensus with regard to opinions on environmental harm and human safety. Simply stated: there is no clear conclusion. We prepared this report to assist building owners and design professionals in their decision-making processes about the safety and ecological implications of using this building material. For the fly ash that is diverted into concrete, there is the unanswered question. Is fly ash chemically changed when it is mixed into concrete? This is an important question because fly ash carries the same toxic burden as the coal from which it was derived. If the harmful substances in fly ash were rendered harmless when bonded into concrete, this would be one of the most significant benefits to the use of fly ash, even exceeding the value of recycled content.
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