Advances in Chemical Beneficiation of Fly Ashes Containing Natural Carbon or Powdered Activated Carbon

摘要

Due to increased air pollution control regulations throughout North America and other parts of the world, contamination of fly ash with natural carbon or powdered activated carbon (PAC) is becoming a growing threat to the continued use of fly ash in air- entrained concrete applications. This work will provide information on the collaborative efforts between FlyAshDirect and BASF on the development of advanced chemical methods for treating fly ashes affected by various forms of natural carbon or PAC. Results from testing of treated fly ashes in air-entrained concrete evaluations are included, showing that entrained air can be generated and remain stable during concrete agitation. Such stability of entrained air in the presence of chemically-treated fly ash is demonstrated with a mortar screening method and also with laboratory concrete studies. This presentation will further describe a unique method to measure the adsorptive potential of carbon-containing fly ashes in relation to air-entraining admixture performance in concrete. FlyAshDirect’s patented CarbonBlocker~(TM) (CB) technology, utilizing BASF chemistry, is shown to provide a commercially-viable method to treat fly ash that is contaminated with even the most aggressive types of PAC, so that the fly ash can be used with predictable performance in air-entrained concrete.