Study of the Hydration Behavior of Synthetic Ferropericlase with Low Iron Oxide Concentrations to Prevent Swelling in Steel Slags

Mattia De Colle, Sohei Sukenaga, Ko Mibu, Yusuke Kato, Hisahiro Matsunaga, Pär G. Jönsson, Andrey Karasev, Hiroyuki Shibata

Research output: Contribution to journalArticlepeer-review


Steel slags generally swell when subjected to water or humidity, which prevents proper recycling in the cement or asphalt industries. The MgO and CaO phases in steel slags are responsible for this phenomenon, as both minerals easily absorb water to form their respective hydroxides. MgO is often present in steel slags in a solid solution with several oxides, constituting the so-called RO phase. This study investigates the hydration rate of an RO phase consisting of FeO and MgO called ferropericlase. The material was synthesized in a laboratory furnace by sintering a FeO–MgO powder mixture with varying initial FeO contents (approximately 10, 15, and 20 wt%). Thereafter, electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) spectroscopies were used to characterize the structure of the samples, which were mainly composed of ferropericlase and an exsolution of magnesioferrite. Also, Mössbauer spectra showed that the total ferrous iron proportion (Fe2+/ΣFe) of the sintered samples was in the range of 0.55–0.72. To measure the hydration behavior, the samples in powder form were cured in an autoclave at an H2O partial pressure of 2 atm. Thereafter, thermal gravimetric analysis (TGA) was performed to measure the amount of water absorbed during the autoclave curing from the mass drop associated with the dehydration of the hydroxide. The study found a linear correlation between the initial FeO content and the weight loss after TGA, with a reduction down to 6% in the sample with an initial FeO content of 20 wt% content compared to pure MgO. Graphical Abstract: [Figure not available: see fulltext.]

Original languageEnglish
Pages (from-to)547-558
Number of pages12
JournalJournal of Sustainable Metallurgy
Issue number2
Publication statusPublished - 2021 Jun


  • Ferropericlase
  • Free MgO
  • Hydration
  • RO phase
  • Recycling
  • Slag

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)
  • Mechanics of Materials
  • Metals and Alloys


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