Carbonation of MgO‐Nesquehonite Cements

ABSTRACT MgO‐based binders containing hydrated magnesium carbonates are promising low‐carbon materials due to their ability to store CO 2 during hardening and carbonation. This study investigates MgO‐nesquehonite (MgCO 3 ˑ3H 2 O) binders containing 0, 20 and 40 mass‐% of nesquehonite hydrated in N 2 ‐filled desiccators or at 4 vol‐% CO 2 , as well as hydration and long‐term storage experiments on blends with up to 50 mass‐% of nesquehonite under different relative humidity conditions. Phase evolution, CO 2 absorption and mechanical properties were evaluated using phase analyses and strength measurements. Exposure to 4 vol‐% CO 2 significantly increased carbonation and mechanical performance, with the blend with 20 mass‐% nesquehonite achieving the highest compressive (77 MPa) and flexural strengths (10 MPa) after 91 days. Carbonation promoted the formation of hydrous carbonate‐containing brucite (HCB) and amorphous magnesium carbonate, which progressively transformed into dypingite and hydromagnesite. The partial transformation of HCB and of amorphous magnesium carbonate was more distinct under high relative humidity, which accelerated carbonation and increased CO 2 uptake.