Influence of Alkalis on Natural Carbonation of Limestone Calcined Clay Cement Pastes

Ruoying Li and Hailong Ye
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Ruoying Li: Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
Hailong Ye: Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China

Sustainability, 2021, vol. 13, issue 22, 1-18

Abstract: Vulnerability to atmospheric carbonation is one of the major durability concerns for limestone calcined clay cement (LC 3 ) 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 4 , Na 2 SO 4 , and K 2 SO 4 ) are studied, with the aim of revealing the influence of alkali cations (Na + , K + ). Detailed analyses on the hydrated phase assemblage, composition, microstructure, and pore structure of LC 3 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 3 pastes, likely through enhancement of ettringite formation, but undermines its later age strength achievement due to the deleterious effect of alkali cations (Na + , K + ) on late age OPC hydration. The carbonation resistance of LC 3 systems is considerably undermined, particularly with the incorporation of Na 2 SO 4 or K 2 SO 4 salts, due to the simultaneous pore coarsening effect and reduced CO 2 -binding capacity. The carbonation-induced phase and microstructural alterations of LC 3 pastes are discussed and compared with those of reference OPC pastes.

Keywords: limestone calcined clay cement; low-carbon binder; natural carbonation; durability of concrete (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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