Performance and hydration mechanisms of ultrafine iron ore tailings enhanced supersulfated cement with high phosphogypsum content.

Abstract

This study systematically investigates the influence of ultrafine iron ore tailings (UIOT) on the performance and hydration process of supersulfated cement (SSC) with high phosphogypsum (PG) content. UIOT incorporation retards early-age strength but enhances later-age strength, with a 20% replacement ratio of granulated blast furnace slag (GBFS) leading to a 52% increase in 28-day compressive strength. The performance improvement can be primarily attributed to the following aspects: in the first instance, UIOT regulates the formation rate of ettringite (AFt) by promoting the formation of Fe-Al-bearing AFt ((Fe, Al)-AFt), thereby reducing the excessive formation of AFt typically observed in high-gypsum blended systems. Furthermore, UIOT promotes the formation of calcium-alumino-silicate hydrate (C-(A)-S-H) gel and optimizes the Si/Ca ratio of the gel. The unreacted UIOT particles also play a physical filling role, contributing to the performance enhancement.