Fabrication of Iron-Magnesite under Mild Conditions through Indirect Carbonation of Peridotite and Its Utilization as a Partial Substitute for Cement in Concrete

The precipitation of magnesite and dolomite from aqueous media is challenging kinetically because several hydrated or hydroxylated Mg-carbonate phases can retard or inhibit the formation of these “enigmatic” minerals under so-called mild conditions (T ≤ 90 °C and atmospheric pressure). Here, we demonstrate that Fe-magnesite can be synthesized at 60 °C in only 2 days via indirect carbonation of peridotite, following an amorphous-to-nesquehonite-to-magnesite transformation route. In this reactive configuration, the magnesite production time is significantly reduced from 2 days to only 6 h when the temperature is increased to 90 °C. The discovery of these mild conditions for magnesite production is a promising result because currently these temperatures can be reached by free-carbon energies. We also assess the incorporation of a fabricated magnesite-rich material at 90 °C as a partial cement substitute in concrete manufacturing. Preliminary results show that substituting 15 wt % of cement with magnesite-rich material could significantly reduce the CO2 footprint with minimal impact on the concrete’s mechanical-textural properties, including Young’s modulus, strength, and macro-porosity. In practice, this circular carbon approach could provide a dual advantage─reduced clinker production and permanent CO2 storage─and present a significant opportunity to lower the carbon footprint of cement production.