Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

Abstract

This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis.

Recent development in magnesium oxychloride cement

“…In the production of MgO, lower temperature is required, and as a result, energy can be saved . Furthermore, MgO can absorb CO 2 from the atmosphere to form a range of carbonates and hydroxycarbonates, so the MOC is a proved ecofriendly and “carbon‐neutral” cement …”

CO2 Absorption and Magnesium Carbonate Precipitation in MgCl2–NH3–NH4Cl Solutions: Implications for Carbon Capture and Storage

“…Dypingite-like Mg-carbonates can serve as a flame-retardant or fire-retardant additive for polymers [81][82][83] or simply as backfill [84]. Hydromagnesite is also a promising material to replace CaO in calcium-based cement, which usually has a net release of CO 2 , as opposed to Mg-based cement, which could potentially absorb nearly as much CO 2 during its service life as was emitted during its manufacture (carbon-neutral) [85].…”

Microstructural evolution and texture analysis of magnesium phosphate cement

“…Cement performance has been shown to depend upon the magnesia‐to‐phosphate molar ratio, water‐to‐solid weight ratio, grain‐size distribution, and reactivity of MgO . Comparison between results of the numerous studies on MPCs has been severely hampered by the wide variations in the use of retarders, amount of water, and typology of MgO . In a series of papers, we have studied the role of MgO reactivity in affecting the cement properties to gain insights into the mechanisms of the reaction, as key to product design .…”