Supercritical CO2-Induced Evolution of Alkali-Activated Slag Cements

Kamasani Chiranjeevi Reddy; Joonho Seo; H N Yoon; Seonhyeok Kim; G M Kim; H M Son; Seunghee Park; Solmoi Park

doi:10.3390/ma15175873

Supercritical CO₂-Induced Evolution of Alkali-Activated Slag Cements

Materials (Basel). 2022 Aug 25;15(17):5873. doi: 10.3390/ma15175873.

Authors

Kamasani Chiranjeevi Reddy¹, Joonho Seo², H N Yoon², Seonhyeok Kim², G M Kim³, H M Son⁴, Seunghee Park⁵, Solmoi Park¹

Affiliations

¹ Department of Civil Engineering, Pukyong National University, 45 Yongso-ro, Nam-gu, Busan 48513, Korea.
² Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea.
³ Mineral Processing & Metallurgy Research Center, Resources Utilization Division, Korea Institute of Geoscience and Mineral Resources, 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, Korea.
⁴ Device Solutions, Samsung Electronics, 1 Samsungjeonja-ro, Hwaseong-si 18448, Korea.
⁵ School of Civil, Architectural Engineering& Landscape Architecture, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Korea.

Abstract

The phase changes in alkali-activated slag samples when exposed to supercritical carbonation were evaluated. Ground granulated blast furnace slag was activated with five different activators. The NaOH, Na₂SiO₃, CaO, Na₂SO₄, and MgO were used as activators. C-S-H is identified as the main reaction product in all samples along with other minor reaction products. The X-ray diffractograms showed the complete decalcification of C-S-H and the formation of CaCO₃ polymorphs such as calcite, aragonite, and vaterite. The thermal decomposition of carbonated samples indicates a broader range of CO₂ decomposition. Formation of highly cross-linked aluminosilicate gel and a reduction in unreacted slag content upon carbonation is observed through ²⁹Si and ²⁷Al NMR spectroscopy. The observations indicate complete decalcification of C-S-H with formation of highly cross-linked aluminosilicates upon sCO₂ carbonation. A 20-30% CO₂ consumption per reacted slag under supercritical conditions is observed.

Keywords: X-ray diffraction; alkali-activated slag; carbonation; solid-state NMR; supercritical CO2.

Grants and funding

This work was supported by Samsung Electronics Co., Ltd. (IO211203-09223-01), the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2021R1A4A3033128), and Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government (MOTIE) (No. 20212010200080, in situ carbonation technology development using CO₂ emissions from cement industry).