TECHNICAL NOTE/A PLANT INVESTIGATION INTO THE USE OF TREATED PHOSPHOGYPSUM AS A SET-RETARDER IN OPC AND AN OPC/FLY ASH BLEND

摘要

This investigation describes the successful substitution of phosphogypsum for natural gypsum as a set-retarder for cement as proved in two separate plant trials.Large amounts of phosphogypsum are produced by especially the fertiliser industry. This material has significant potential to be used as a set-retarder by the cement industry, provided that it does not contain too much phosphate-type impurities. These have a large detrimental effect on the setting behaviour of cement and could greatly retard the setting times of cement (Lea, 1970; Taylor, 1997). Too high concentrations of P_2O_5 can even influence the strength development of cement or concrete made from it (Zhang and Odler, 1996).