Influences of Silica Fume on Compressive Strength and Chemical Resistances of High Calcium Fly Ash-Based Alkali-Activated Mortar

Journal article

Authors/Editors

Strategic Research Themes

Innovative Materials, Manufacturing and Construction (Strategic Research Themes)

Publication Details

Author list: Sothornchaiwit K., Dokduea W., Tangchirapat W., Keawsawasvong S., Thongchom C., Jaturapitakkul C.

Publisher: Mary Ann Liebert

Publication year: 2022

Volume number: 14

Issue number: 5

ISSN: 1937-0695

eISSN: 1937-0709

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125782136&doi=10.3390%2fsu14052652&partnerID=40&md5=82762822e3d0c3e66b535bb19d9cbc4f

Languages: English-Great Britain (EN-GB)

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Abstract

Although elevated temperature curing can increase the compressive strength of alkali-activated mortar, its field applications are still limited. In this study, alkali-activated mortars were prepared using high calcium fly ash (FA) as a precursor. Small amounts of silica fume were used to partially replace high calcium fly ash at 3–9% by weight to increase the strength of alkali-activated mortar. All mixtures had a liquid to binder ratio of 0.60 and sand to binder ratio of 2.75 by weight. A ratio of NaOH to Na2SiO3 solution was kept at 2:1 by weight. Mortar flow was also held between 105–115 using a superplasticizer. Compressive strength and durability were investigated in terms of acid and sulfate resistance. The effects of silica fume addition and curing temperature on compressive strength were found to be significant. The optimum content of silica fume was 6%, providing compressive strength as high as that of alkali-activated mortars cured at 45◦C. The weight loss of alkali-activated mortar due to sulfuric acid attack decreased with increasing silica fume content and curing temperature. All alkali-activated mortars were found to have a better performance than (ordinary) Portland cement (OPC) mortars and mortars containing 40% FA. Alkali-activated mortars immersed in magnesium sulfate solutions had compressive strength that decreased with an increase in curing temperature. The expansion of alkali-activated mortar due to sodium sulfate attack increased with increasing silica fume content, and the expansion decreased with increased curing temperature. All alkali-activated mortars performed better than OPC mortars after 98 days of sulfate attack. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

Alkali activated mortar, Magnesium sulfate, Sulfuric acid