Effect of hydrated magnesium carbonate grown in situ on the property of MgO-activated reactive SiO₂ mortars

Abstract

The effects of carbonation on the strength and microstructural evolution of MgO-activated reactive SiO₂ (M-A-R-S) mortars under different conditions have been investigated. M-A-R-S mortars with a binder-to-silica sand ratio of 50% were prepared by light-calcined MgO and silica fume (SF) under accelerated carbonation at 20% CO₂ condition for different periods. Carbonation significantly increases the compressive strength of M-A-R-S mortars. The specimens cured for 28 days in air and placed to accelerated carbonation for ∼14 days achieved the highest strength of ∼83 MPa and the lowest porosity of 13.5%. The increased strength and density resulted from the formation of the hydrated magnesium carbonate (i.e. nesquehonite (MgCO₃·3H₂O) with a needle/column-like morphology. However, it was also found that continuous carbonation for longer periods (e.g. 28 days), associated with excessive carbonated phase(s) formed, caused micro-cracking and a reduction in compressive strength.

Keywords:

• MgO-activated reactive SiO₂
• accelerated carbonation
• hydrated magnesium carbonate
• compressive strength
• microstructure

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors wish to express their gratitude and sincere appreciation for the financial support by the national natural science foundation of China [51808217, 51778101], natural science foundation of Liaoning province of China [2020-MS-115], foundation for high-level talent innovation support program of Dalian [2019RD05], natural science foundation of Hebei province [E2019209403], and “XingLiaoYingCai” project of Liaoning province of China [XLYC2007126].