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Characterizing the Effects of Al(OH)3 and Mg(OH)2 on Reaction Products and Drying Shrinkage Characteristics of Alkali-activated Slag

Journal Article (2022)
Author(s)

Jing Li (South China University of Technology, Guangxi University)

Suhong Yin (South China University of Technology)

Haoliang Huang (South China University of Technology)

Jie Hu (South China University of Technology)

Chaofan Yi (Guangxi University)

Zheng Chen (Guangxi University)

Yuwei Ma (Guangzhou University)

Guang Ye (TU Delft - Civil Engineering & Geosciences)

Research Group
Materials and Environment
DOI related publication
https://doi.org/10.1016/j.cscm.2022.e01309 Final published version
More Info
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Publication Year
2022
Language
English
Research Group
Materials and Environment
Volume number
17
Article number
e01309
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Abstract

This study is undertaken to explore the relationship between the reaction products and the drying shrinkage of alkali-activated slag (AAS) with the varying hydroxide dosage. AAS pastes were firstly produced with either Al(OH)3 or Mg(OH)2 to investigate the effects of hydroxide on the composition of reaction products and the drying shrinkage of AAS. Secondly, the main reaction products formed in AAS pastes, viz. C4AH13, M4AH10, C-S-H, C-A-S-H and C-M-S-H, were synthesized individually. Synthetic products were then taken to cast the respective paste sample to examine the performance against the drying exposure. The results show that adding Mg(OH)2 indeed improved the shrinkage resistance of AAS. This is primarily connected to the increased crystalline phases, namely the hydrotalcite-like phases and the unreacted Mg(OH)2. Whereas adding Al(OH)3 did not relieve the drying shrinkage of AAS as the interlayer spacing of C-A-S-H was enlarged, which in turn allowed for more shrinkage. Further, the investigation of individual synthetic products illustrates that their drying shrinkage scales satisfied the following order: C4AH13 < M4AH10 < C-M-S-H < C-S-H < C-A-S-H. Moreover, the shrinkage scale of C-S-H was found to evolve as the Ca/Si ratio decreased.