[Publication] Iron-rich slag addition in ternary binders of Portland cement, aluminate cement and calcium sulfate

Monday, May 16, 2022 - 10:37
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Cements mixture has made it possible to modify the reactivity of a metallurgical residue and the manufacture of mortars with particular mechanical and physical properties. Transmission electron microscopy was used to describe the morphology of the hydrates formed during the slag reaction, their chemical composition and their diffraction pattern. This article, made with the University of KU Leuven and the company Imerys, paves the way for the formulation of innovative binders with a lower environmental impact.

The growing demand for sustainability in the recent decades has driven the exploration for new supplementary cementitious materials such as the non-ferrous metallurgy slags.

In this study, the hydration of an iron-rich slag incorporated in Calcium Aluminate Cement - Portland Cement ‑ calcium sulfate ternary binders was investigated. The dimensional stability of mortars demonstrated the contribution of the slag addition in mitigating excessive expansion while maintaining an acceptable mechanical strength over 180 days.

The degree of slag hydration estimated with X-ray Computed Tomography supports the activating effect of the Portland cement while isothermal calorimetry, X-ray diffraction, thermogravimetric analysis and infrared spectroscopy were used to delineate the evolution of the phase assemblage. Finally, transmission electron microscopy revealed the incorporation of iron in hydrate gels grouped into two clusters according to a Ca-Al-Si ternary diagram:

  • Al-rich gels in the formulation with no Portland cement
  • intermixed hydrate gels associated with Ca, Al and Si in the formulations with Portland cement.

Transmission Electron Microscopy images focused on different hydrate of paste sample containing 30% of iron-rich slags after 28 days of hydration Transmission Electron Microscopy images focused on different hydrate of paste sample containing 30% of iron-rich slags after 28 days of hydration
 

Title: Iron-rich slag addition in ternary binders of Portland cement, aluminate cement and calcium sulfate

Authors: Jennifer Astoveza, Romain Trauchessec, Sylvie Migot-Choux, Ratana Soth, Yiannis Pontikes.

Journal: Cement and Concrete Research

Date of publication (online): December 2021

Link: https://doi.org/10.1016/j.cemconres.2021.106689

Image caption:
Transmission Electron Microscopy images focused on different hydrate of paste sample containing 30% of iron-rich slags after 28 days of hydration : a) diffraction pattern (lower right corner) of the gel B1,  b-d)  hydrated gels  (B1, B2, C3) containing 0,9 to 3,2% of iron and e) ettringite particles (C6-C7) incorporating only 0,2% of iron.

Image
Transmission Electron Microscopy images focused on different hydrate of paste sample containing 30% of iron-rich slags after 28 days of hydration