University of Oulu

Juho Rasmus, Katja Ohenoja, Paivo Kinnunen, Mirja Illikainen, Effect of green liquor dregs as an alkali source for alkali-activated blast furnace slag mortar, Case Studies in Construction Materials, Volume 18, 2023, e01950, ISSN 2214-5095,

Effect of green liquor dregs as an alkali source for alkali-activated blast furnace slag mortar

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Author: Rasmus, Juho1; Ohenoja, Katja1; Kinnunen, Päivö1;
Organizations: 1Fibre and Particle Engineering Research Unit, University of Oulu, Erkki Koiso-Kanttilan katu 5, 90570 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 5.2 MB)
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Language: English
Published: Elsevier, 2023
Publish Date: 2023-09-25


Sodium-rich green liquor dregs (GLD) are one of the main landfilled residues generated in pulp mills, and to date, no economically profitable ways to utilise GLD has been identified. In this study, GLD have been studied to be used as an alternative alkali source together with alkali-activator, sodium metasilicate (Na₂SiO₃), for blast furnace slag (BFS) mortar. Microsilica was used as an additional silica source to ensure steady Na₂O:SiO₂-ratio (0.16). In purpose to remove the remaining organic carbon and increase the suitability of GLD to be used in alkali-activated materials, it has been first thermally treated in 525 °C. The amount of GLD in the recipes varied from 0 to 45 wt%. Calorimetry measurements showed that increasing the amount of GLD reduced the hydration heat and postponed the reaction. With thermogravimetric analysis, X-ray diffractometry and scanning electron microscopy it was found that hydrated samples with more GLD contained more carbonate phases, which indicated that the reactivity of GLD was lower in comparison with that of other raw materials. Compressive and flexural strength measurements showed that increasing the amount of GLD affected the early strength gain (2 and 7 days) of the samples, but at the age of 29 days, the difference was not as high. The compressive strength of the reference sample at 29 days was 59 MPa, while the compressive strength of four sample recipes containing GLD (up to 36 wt%) was higher than 49 MPa. According to the results, green liquor dregs have potential to be used as a secondary alkali source in alkali-activated materials, but more detailed study should be conducted for the recipe in the future.

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Series: Case studies in construction materials
ISSN: 2214-5095
ISSN-E: 2214-5095
ISSN-L: 2214-5095
Volume: 18
Article number: e01950
DOI: 10.1016/j.cscm.2023.e01950
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
215 Chemical engineering
Funding: This research was part of the MIMEPRO-project (7935/35/2019), which is a Business Finland funded Co-Innovation Project, together with the following companies: Metsä Fibre Oy, Stora Enso Oyj, Valmet Oy, Fortum Waste Solutions Oy, Matnur Oy, Betoniteollisuus ry, and Parma-Consolis Oy. Päivö Kinnunen is grateful for financial support from the University of Oulu and the Academy of Finland (Profi5 326291).
Copyright information: © 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (