Determination of a Suitable Formulation of Fluorogypsum, Class C Fly Ash, and Portland Type II Cement as an Oyster Cultch Material Based on Leaching Characteristics

Lofton, C.D., Barbato, M., Rusch, K.A., and Gutierrez-Wing, M.T.

Due to the high cost of limestone as an oyster cultch material in the State of Louisiana, an economical, locally available material is needed to provide a binding substrate for the oysters. Fluorogypsum (CaSO₄·H₂O), a by-product of the hydrofluoric acid production process, is a low cost, locally available material that is currently being utilized as road bed material. The high solubility of fluorogypsum (FG) has limited its usage to dry applications. Previous research has demonstrated that stabilizing phosphogypsum, a material with similar properties to FG, with class C fly ash and Portland type II cement a viable underwater material can be produced. The current study focuses on determining a viable composition of FG, class C fly ash, and Portland type II cement that is suitable as an oyster cultch material. Results indicate that a composition of 60% FG, 2% cement, and 38% fly ash has the highest potential as an oyster cultch material.