PHOSPHOGYPSUM-FLY ASH CEMENTITIOUS BINDER - ITS HYDRATION AND STRENGTH DEVELOPMENT

The paper deals with the formulation of a cementitious binder based on calcined phosphogypsum, flyash, hydrated lime and portland cement. Strength properties and hydration of the cementitious binder studied at room temperature and at 50 degrees C in over 90% R.H are presented. It was found that the compressive strength of the cementitious binder was remarkably enhanced at 50 degrees C than at 27 degrees C. The hydration of the cementitious binder as studied by differential thermal analysis and scanning electron microscopy showed that the early age strength in the cementitious binder was due to the hardening of calcined gypsum and the hydration of portland cement while later age strength development was ascribed to the formation of ettringite and CSH.