TY - JOUR
T1 - Sulfuric acid degradation of alkali-activated metakaolin cements supplemented with brucite
AU - Gevaudan, Juan Pablo
AU - Craun, Zoey
AU - Srubar, Wil V.
N1 - Funding Information:
This research was made possible by the Department of Civil, Environmental, and Architectural Engineering, the College of Engineering and Applied Sciences, and the Living Materials Laboratory at the University of Colorado Boulder. This work was supported by the United States National Science Foundation (Award No. CBET-1604457 ). Dr. J.P. Gevaudan's participation in completing this study was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 839436 .
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/8
Y1 - 2021/8
N2 - This study investigated the effect of alkali content (Na:Al = 0.86 and 1.39) and brucite (i.e., Mg(OH)2) mineral addition on the sulfuric acid resistance of alkali-activated metakaolin (i.e., geopolymers). Geopolymers consist primarily of a sodium-stabilized aluminosilicate hydrate (N-A-S-H) framework. Results demonstrate that higher alkali contents and brucite addition improve the acid resistance of N-A-S-H, as evidenced by reduced dealumination and Si and Na leaching upon exposure to acid. These results are mechanistically explained by increased retention of Mg+2 within the microstructure and increased Mg–Al interaction upon acid exposure. Higher Mg+2 retention and increased Mg–Al coupling together provide empirical evidence of polyvalent cationic stabilization—a mechanism involving polyvalent cations (e.g., Mg+2) that stabilize the N-A-S-H binder by arresting acid-induced electrophilic attack. Results further illustrate that brucite addition, especially at high-alkali content formulations, reduces micro-scale porosity while increasing the proportion of gel pores (<5 nm), which suggests that increased tortuosity of gel pores may aid in Mg+2 retention and promote the increased Mg–Al coupling observed herein.
AB - This study investigated the effect of alkali content (Na:Al = 0.86 and 1.39) and brucite (i.e., Mg(OH)2) mineral addition on the sulfuric acid resistance of alkali-activated metakaolin (i.e., geopolymers). Geopolymers consist primarily of a sodium-stabilized aluminosilicate hydrate (N-A-S-H) framework. Results demonstrate that higher alkali contents and brucite addition improve the acid resistance of N-A-S-H, as evidenced by reduced dealumination and Si and Na leaching upon exposure to acid. These results are mechanistically explained by increased retention of Mg+2 within the microstructure and increased Mg–Al interaction upon acid exposure. Higher Mg+2 retention and increased Mg–Al coupling together provide empirical evidence of polyvalent cationic stabilization—a mechanism involving polyvalent cations (e.g., Mg+2) that stabilize the N-A-S-H binder by arresting acid-induced electrophilic attack. Results further illustrate that brucite addition, especially at high-alkali content formulations, reduces micro-scale porosity while increasing the proportion of gel pores (<5 nm), which suggests that increased tortuosity of gel pores may aid in Mg+2 retention and promote the increased Mg–Al coupling observed herein.
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U2 - 10.1016/j.cemconcomp.2021.104063
DO - 10.1016/j.cemconcomp.2021.104063
M3 - Article
AN - SCOPUS:85105291789
VL - 121
JO - Cement and Concrete Composites
JF - Cement and Concrete Composites
SN - 0958-9465
M1 - 104063
ER -