Fly ash with a constant loss on ignition (LOI) value makes it easier for ready mix producers to produce consistent concrete batches. Now there is a thermal processor that can produce fly ash with a constant LOI value. The processor works by heating the fly ash, burning off the carbon, then cooling the ash. LOI relates to the amount of carbon in the fly ash. Carbon content in fly ash used in concrete can greatly affect air content and water demand. Having a low carbon content in fly ash helps the concrete producer maintain consistent air content.