Carbonation and Mechanical Properties of Reactive Magnesium Oxide Cements

Reactive magnesium oxide (MgO) cements offer a low-carbon alternative to ordinary Portland cement by capturing CO₂ through carbonation reactions that yield stable magnesium carbonate phases. In an initial hydration stage, MgO transforms into brucite (Mg(OH)₂), which subsequently reacts with CO₂ to form hydrated carbonates such as nesquehonite and hydromagnesite. The extent and nature of these phases govern pore refinement, matrix densification and compressive strength development. Key factors influencing performance include the reactivity and specific surface area of MgO, its purity and particle agglomeration, and the conditions of CO₂ exposure during curing. Enhanced carbonation curing not only accelerates strength gain—often matching or exceeding conventional cement classes—but also contributes to durable microstructures with reduced porosity. As a result, reactive MgO cements hold promise for sustainable construction and carbon-sequestration applications, leveraging renewable-energy-driven calcination processes or industrial brine feedstocks to produce highly reactive binders.

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Carbonation and Mechanical Properties of Reactive Magnesium Oxide Cements publication trend

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Technical terms

Reactive MgO: Magnesium oxide engineered with high surface area and porosity to accelerate hydration and carbonation reactions.

Hydration: Chemical reaction of MgO with water to form brucite (Mg(OH)₂).

Carbonation: Reaction of CO₂ with brucite or MgO to produce magnesium carbonate phases that densify the cement matrix.

Brucite: Magnesium hydroxide, the primary hydrate phase that precedes carbonation in MgO cements.

Nesquehonite: A hydrated magnesium carbonate (MgCO₃·3H₂O) often formed under accelerated carbonation curing.

Hydromagnesite: A more stable hydrous carbonate (4MgCO₃·Mg(OH)₂·4H₂O) that contributes to long-term strength and durability.

Specific surface area (SSA): Total surface area of MgO particles per unit mass, directly influencing reactivity and strength development.

Agglomeration ratio: Measure of particle clustering in MgO powders, affecting water access, hydration kinetics and mechanical performance.

References

1. Evaluation of the technical properties of reactive-MgO cements produced by solar calcination of magnesite in a fluidized bed reactor. Renewable Energy (2024).
2. Production of reactive magnesia from desalination reject brine and its use as a binder. Journal of CO2 Utilization (2021).
3. Exploring Mechanisms of Hydration and Carbonation of MgO and Mg(OH)2 in Reactive Magnesium Oxide-Based Cements. The Journal of Physical Chemistry C (2022).
4. Investigation of the properties of reactive MgO-based cements and their effect on performance. Cement and Concrete Composites (2023).