Effects of phosphogypsum on hydration properties and strength of calcium aluminate cement

Abstract

• Phosphogypsum reduces setting time and flowability of calcium aluminate cement and increases compressive strength. • Phosphogypsum changes the hydration products of calcium aluminate cement. • Phosphogypsum improves pore structure of aluminate cement pastes. Phosphogypsum (PG) is a solid waste discharged from the industrial wet production of phosphoric acid. In order to improve the utilization rate of PG and understand the performance of PG mixed with calcium aluminate cement (CAC), it is necessary to determine the effect of different dosages of PG on the performance of CAC. therefore, this study investigated the hydration properties and compressive strength of PG and CAC mixtures. PG was added into CAC in an equal proportion, and the hydrated products were studied by XRD, TG-DTG, SEM and MIP methods. The research demonstrate that with the increase of PG content, the setting time and flowability of CAC pastes gradually decreased, and the compressive strength increased gradually. However, when the content of PG is greater than 15%, the growth rate of compressive strength of CAC becomes slower. The presence of PG resulted in the complete disappearance of the hydration products CAH 10 and C 2 AH 8 of CAC. With the increase of PG content, the pore size distribution of CAC paste was changed, and its main hydration products were transformed into ettringite, AFm and AH 3 , which became the main source of affecting the compressive strength of CAC.