UCLA researchers have developed a process to manufacture stable vaterite, a calcium carbonate polymorph, by carbonating portlandite under mild conditions and using stabilizers to prevent its conversion to more stable forms. The resulting material can be used as a cement replacement to help reduce embodied carbon in concrete systems.
Ordinary Portland Cement (OPC) production is a major contributor to CO₂ emissions globally. Alternative cementitious materials and calcium carbonate polymorphs like vaterite are promising because they can bind CO₂ and substitute for OPC. However, vaterite is metastable—it naturally tends to convert to calcite or aragonite, which reduces its utility. Existing methods for making vaterite often require expensive or highly soluble precursors, strong alkalis, or harsh conditions. There’s a need for scalable, mild, and stable production of vaterite using more ambient feedstocks and CO₂ sources.
This work demonstrates that portlandite (or calcium hydroxide) can be carbonated under relatively mild conditions (moderate temperature, CO₂ partial pressure, humidity) in the presence of additives or stabilizers to form a high vaterite fraction. They explore how different stabilizing agents (e.g. magnesium species, magnesium salts or hydroxides, or other additives) and reaction parameters (e.g. CO₂ concentration, temperature, Ca:Mg ratio) affect the kinetics and thermodynamic evolution of the phases. By optimizing these, they obtain vaterite-rich products with stability over time. The process also suggests that industrially available portlandite or alkaline calcium sources (including potentially OPC or waste materials) can be used rather than pure lab precursors.
Produces a high-vaterite fraction under mild, near-ambient conditions.
Uses abundant, low-cost calcium sources (portlandite) rather than high-purity salts.
Stabilizes vaterite against transformation to calcite/aragonite, improving durability and usefulness.
Possible incorporation of CO₂ in the process, offering carbon sequestration benefits.
Likely lower energy, chemical, and capital cost compared to more extreme or lab-scale vaterite synthesis methods.
Use in low-carbon cementitious binders or OPC replacement materials in concrete, precast, or masonry products.
Materials where carbonate morphology (e.g. particle shape, porosity) influences performance, such as in repair mortars or overlays.
Building materials or construction systems aiming for GHG reductions or carbon neutral targets.
Carbon capture and utilization frameworks where CO₂ is used to produce useful building materials.
Additive fillers or functional materials in composites where controlled carbonate phases are beneficial.
Sant, G. N.; Prentice, D. P.; Simonetti, D.; et al. (2023). Vaterite synthesis via portlandite carbonation. ACS Sustainable Chemistry & Engineering, Vol. 11, Issue 18, Pages approximate; DOI: 10.1021/acssuschemeng.5c01554