The correlation between Al incorporation and alkali fixation by calcium aluminosilicate hydrate: Observations from hydrated C₃S blended with and without metakaolin

TY - JOUR

T1 - The correlation between Al incorporation and alkali fixation by calcium aluminosilicate hydrate

T2 - Observations from hydrated C3S blended with and without metakaolin

AU - Wei, Shihua

AU - Zheng, Keren

AU - Chen, Wei

AU - Chen, Lou

AU - Zhou, Jin

AU - Mi, Tangwei

N1 - Copyright: © 2023 Elsevier Ltd. All rights reserved.

PY - 2023/10

Y1 - 2023/10

N2 - This study aims to investigate the correlation between Al incorporation and Na fixation by C-(A)-S-H, which was derived from hydrated C3S blended with and without 10 wt% metakaolin at 1, 2, and 3 wt% Na2O content. C-(A)-S-H compositions were calculated based on mass balance method. NMR was used to calculate the fraction of different coordinations of Si and Al in C-(A)-S-H. Results show that the incorporation of Al into C-S-H enhances the polymerization of silicate chains, it also increases the Ca/Si of the formed C-A-S-H because more Ca ions are required to stabilize the incorporated Al(VI). The increased Ca/Si subsequently decreases the alkali fixation capacity of C-A-S-H compared to that of C-S-H. Increasing alkali concentration favors the polymerization of C-A-S-H by incorporating more Al(IV) in bridging sites and shows less effect on Al(VI)/Si and Ca/Si due to the different negative charges and calcium coordination environment regarding Al(VI) and Al(IV).

AB - This study aims to investigate the correlation between Al incorporation and Na fixation by C-(A)-S-H, which was derived from hydrated C3S blended with and without 10 wt% metakaolin at 1, 2, and 3 wt% Na2O content. C-(A)-S-H compositions were calculated based on mass balance method. NMR was used to calculate the fraction of different coordinations of Si and Al in C-(A)-S-H. Results show that the incorporation of Al into C-S-H enhances the polymerization of silicate chains, it also increases the Ca/Si of the formed C-A-S-H because more Ca ions are required to stabilize the incorporated Al(VI). The increased Ca/Si subsequently decreases the alkali fixation capacity of C-A-S-H compared to that of C-S-H. Increasing alkali concentration favors the polymerization of C-A-S-H by incorporating more Al(IV) in bridging sites and shows less effect on Al(VI)/Si and Ca/Si due to the different negative charges and calcium coordination environment regarding Al(VI) and Al(IV).

KW - Al incorporation

KW - C-(A)-S-H

KW - Hydrated pastes

KW - Mass balance method

KW - Na fixation

UR - https://www.scopus.com/pages/publications/85163876517

U2 - 10.1016/j.cemconres.2023.107249

DO - 10.1016/j.cemconres.2023.107249

M3 - Article

AN - SCOPUS:85163876517

SN - 0008-8846

VL - 172

JO - Cement and Concrete Research

JF - Cement and Concrete Research

M1 - 107249

ER -