Influence of Alkalis on Natural Carbonation of Limestone Calcined Clay Cement Pastes
Vulnerability to atmospheric carbonation is one of the major durability concerns for limestone calcined clay cement (LC<sup>3</sup>) concrete due to its relatively low overall alkalinity. In this study, the natural carbonation behaviors of ternary ordinary Portland cement-metakaolin-lime...
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| Autores principales: | , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/88de367492504988bd2e2ef57db78c30 |
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| Sumario: | Vulnerability to atmospheric carbonation is one of the major durability concerns for limestone calcined clay cement (LC<sup>3</sup>) concrete due to its relatively low overall alkalinity. In this study, the natural carbonation behaviors of ternary ordinary Portland cement-metakaolin-limestone (OPC-MK-LS) blends containing various sulfate salts (i.e., anhydrous CaSO<sub>4</sub>, Na<sub>2</sub>SO<sub>4</sub>, and K<sub>2</sub>SO<sub>4</sub>) are studied, with the aim of revealing the influence of alkali cations (Na<sup>+</sup>, K<sup>+</sup>). Detailed analyses on the hydrated phase assemblage, composition, microstructure, and pore structure of LC<sup>3</sup> pastes prior to and post indoor carbonation are conducted. The results show that the incorporation of sulfate salts accelerates the setting and strength gain of LC<sup>3</sup> pastes, likely through enhancement of ettringite formation, but undermines its later age strength achievement due to the deleterious effect of alkali cations (Na<sup>+</sup>, K<sup>+</sup>) on late age OPC hydration. The carbonation resistance of LC<sup>3</sup> systems is considerably undermined, particularly with the incorporation of Na<sub>2</sub>SO<sub>4</sub> or K<sub>2</sub>SO<sub>4</sub> salts, due to the simultaneous pore coarsening effect and reduced CO<sub>2</sub>-binding capacity. The carbonation-induced phase and microstructural alterations of LC<sup>3</sup> pastes are discussed and compared with those of reference OPC pastes. |
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