Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Article


Ouyang, Xiaowei, Ma, Yuwei, Liu, Ziyang, Liang, Jianjun and Ye, Guang. 2019. "Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag." Minerals. 10 (1), pp. 1-17. https://doi.org/10.3390/min10010015
Article Title

Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

ERA Journal ID201274
Article CategoryArticle
AuthorsOuyang, Xiaowei (Author), Ma, Yuwei (Author), Liu, Ziyang (Author), Liang, Jianjun (Author) and Ye, Guang (Author)
Journal TitleMinerals
Journal Citation10 (1), pp. 1-17
Article Number15
Number of Pages17
Year2019
Place of PublicationSwitzerland
ISSN2075-163X
Digital Object Identifier (DOI)https://doi.org/10.3390/min10010015
Web Address (URL)https://www.mdpi.com/2075-163X/10/1/15
Abstract

This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N-A-S-H gel and C-A-S-H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C-A-S-H gel had a higher space-filling ability than N-A-S-H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5.

KeywordsActivator modulus; Alkali-activated fly ash/slag; Fresh and hardened properties; Slag content
ANZSRC Field of Research 2020400505. Construction materials
Byline AffiliationsGuangzhou University, China
Centre for Future Materials
Delft University of Technology, Netherlands
Open access urlhttps://www.mdpi.com/2075-163X/10/1/15
Institution of OriginUniversity of Southern Queensland
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