Ceramics-Silikáty 51 (3) 153-159 (2007)

INFLUENCE OF PHOSPHATIC IMPURITIES ON THE ANHYDRITE BINDING MATERIAL OF PHOSPHOGYPSUM

J. Cesniene

A possibility to use an unwashed, lime neutralized waste phosphogypsum - dihydrate calcium sulphate was analyzed in order to obtain an anhydrite binding material. Influence of calcination temperature on the properties of the obtained material was analyzed. It was determined that phosphoanhydrite calcined at 800°C temperature is characterized by optimal physical and mechanical properties. Temperature influence on the phosphatic impurities (hydroxyapatite) of neutralized phosphogypsum, which out of partially amorphous state transforms into the crystalline state, was analyzed. These impurities impede hydration and hardening processes. Waste phosphogypsum, in which P₂O₅ does not exceed 1.7 %, is needed to produce the binding material. In order to activate phosphoanhydrite binding properties, the influence of hardening activators was analyzed and their optimal amount was determined.

Keywords: Anhydrite, Phosphogypsum, Impurities, Hydration, Activators