COMPARISON OF CLASS C AND CLASS F FLY-ASHES AS FOUNDARY SAND BINDERS AND THE EFFECTIVENESS OF ACCELERATORS IN REDUCING CURING TIME

摘要

Fly-ashes are a potential alternative to conventional bentonite to be used as binders for the production of foundry sand molds. The performance of two different fly-ashes in this application was evaluated. These fly-ashes were classified as a Class F (pozzolanic) ash and a Class C (pozzolanic and cementitious) ash according to American Society for Testing and Materials (ASTM) specifications. It was determined that both types of fly-ash could reach bonding strengths in the test specimens that were higher than that achieved with bentonite. However, the Class C ash required less than one-tenth as much curing time as the Class F ash to reach strengths comparable to those of bentonite-bonded specimens. It was also determined that the use of accelerators allowed the necessary curing time of Class C ash to be reduced to less than an hour.