Some concrete does not contain fly ash. Why?
There are a number of reasons fly ash isn’t used in all concrete. Prior to ProAsh beneficiation there were most often the issues of inconsistent product quality and availability. Just when the concrete producer needed it most the utility ran out of quality product. Today the biggest issues are strength gain and set times. Though ultimate strengths of a fly ash concrete are greater than a reference without it, fly ash concrete gains early strength a little slower than reference mixtures without it. Form stripping can be somewhat delayed if the slower strength gain is not balanced with admixtures. And, even though properly proportioned fly ash concrete can generally be finished more easily, If the mixture is not set balanced with accelerators in cooler weather finishers might take longer to put the final finish on the concrete.
