Effects of clinker contents of different C₃A and C₄AF on the performance of PSC cement

Abstract

Phosphogypsum-slag-clink (PSC) cement were prepared by original phosphogypsum(PG), which was grinded after dried at 60 °C combined with different contents of phosphogypsum (15%, 20%, 30%), and a small amount of different C₃A, C₄AF contents of finely ground cement clinker, and ground granulated blast furnace slag (GGBFS). Physical mechanical and sugaring properties were studied. The results show that compressive strength of PSC cement with 20% phosphogypsum at 3 d ages would be higher than 17 MPa and even 50 MPa at 28 days. Compressive strength at longer curing stage and sugaring properties of PSC with lower content of C₃A higher C₄AF clinker were improved. pH value of PSC cement system at early stage was relatively low, and pH gradually increased with the addition of clinker. pH increased firstly and then decreased with the hydration stage. SEM analyses showed that the amount of ettringite, which was influenced by pH and content of Al, must be controlled in PSC cement system, which may cause damage to microstructure or even expansive cracks if large amount of ettringite formed in hardened paste.

Keywords

phosphogypsum / clinker / ettringite / surface sugaring

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