Influence of substitution of natural gypsum by phosphogypsum on the properties of Portland cement

Phosphogypsum is an important industrial by-product of phosphoric acid manufacturing by dihydrate process in Egypt. It consists of CaSO4.2H(2)O and some impurities such as P2O5, F- and organic substances. It can be successfully used in the manufacture of ordinary portland cement. The effect of substitution of natural gypsum by phosphogypsum on the physico-mechanical properties as well as the kinetics of hydration of the portland cement pastes up to 90-days was studied. The data in hand show that the partially up to fully substitution of natural gypsum by phosphogypsum does not adversely affect the setting time of the cement pastes, but improves the rate of hydration as well as the mechanical properties up to 90 days.