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In this study, combined waste-derived alkali activators are used to prepare volcanic ash-based geopolymers and to evaluate their durability under freeze-thaw conditions. The comparable alkali activators are Na2SO4-Ca(OH)2 (N-C), Na2SO4-calcium carbide residue (N-CCR), Na2SO4-calcium carbide residue-NaOH (N-CCR-H), Na2SO4- calcium carbide residue-Na2SiO3 (N-CCR-S). Microstructure and strength of the geopolymers are characterized through XRD, SEM, FTIR, NMR and compressive strength measurements. Pore structure of the geopolymers is determined by adsorption/desorption isotherms and BET calculations. It is found that the ternary alkali acti-vators give superior activation synergy than dual alkali activators. The compressive strengths of N-CCR-S and N-CCR geopolymers are 61.0 MPa and 23.1 MPa after 7 d in air. After freeze-thaw cycles for 30 days, the compressive strength of the N-CCR-S geopolymer is three times higher than that of the N-CCR geopolymer. These significant differences originate from their N-A-S-H and C-(A)-S-H gel structures. The N-CCR-S geopolymers possess a more homogeneous and dense microstructure with low pore structure. This study proposes a method for the effective utilization of volcanic ash and alkaline solid wastes.
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CEMENT & CONCRETE COMPOSITES
ISSN: 0958-9465
Year: 2022
Volume: 136
1 0 . 5
JCR@2022
1 0 . 8 0 0
JCR@2023
ESI Discipline: MATERIALS SCIENCE;
ESI HC Threshold:91
JCR Journal Grade:1
CAS Journal Grade:1
Cited Count:
WoS CC Cited Count: 20
SCOPUS Cited Count: 16
ESI Highly Cited Papers on the List: 0 Unfold All
WanFang Cited Count:
Chinese Cited Count:
30 Days PV: 1