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Internal Curing Effect of Pre-Soaked Zeolite Sand on the Performance of Alkali-Activated Slag.

Authors
  • Zhang, Guang-Zhu1
  • Lee, Han-Seung2
  • Wang, Xiao-Yong3, 4
  • Han, Yi4
  • 1 Songsim Global Campus, Catholic College, The Catholic University of Korea, Bucheon-si 14662, Korea. , (North Korea)
  • 2 Department of Architectural Engineering, Hanyang University, Ansan-si 15588, Korea. , (North Korea)
  • 3 Department of Architectural Engineering, Kangwon National University, Chuncheon-si 24341, Korea. , (North Korea)
  • 4 Department of Integrated Energy and Infra System, Kangwon National University, Chuncheon-si 24341, Korea. , (North Korea)
Type
Published Article
Journal
Materials
Publisher
MDPI AG
Publication Date
Feb 03, 2021
Volume
14
Issue
4
Identifiers
DOI: 10.3390/ma14040718
PMID: 33546508
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

This study clarifies the effects of pre-soaked zeolite sand as an internal curing material on the hydration, strength, autogenous shrinkage, and durability of alkali-activated slag (AAS) mortars. The liquid-to-binder ratio (L/b) of all of the AAS mortars was 0.55. Sodium hydroxide solution was used as an alkali activator and an internal curing liquid. Calcined zeolite and natural zeolite sand replaced the standard sand at 15% and 30%, respectively. The setting time, autogenous shrinkage, compressive strength, ultrasonic pulse velocity, and surface electrical resistivity were tested. The following conclusions were drawn: (1) The addition of zeolite significantly reduces the autogenous shrinkage of AAS mortar. Compared with the control group, 30% calcined zeolite reduced the autogenous shrinkage by 96.4%. Moreover, the autogenous shrinkage of the AAS mortars was noticed in two stages (a variable temperature stage and an ambient temperature stage), and the two stages split at one day of age. (2) The compressive strength of all of the specimens increased as the zeolite sand content increased, and the highest compressive strength was obtained for AAS combined with 30% natural zeolite sand. (3) Internal curing accelerated the formation of the second peak of heat flow and reduced the accumulated heat release. (4) Calcined zeolite sand delayed the setting time of the AAS mortars. (5) The addition of zeolite significantly reduced the surface electrical resistivity of the AAS mortars. In summary, zeolite sand is extremely useful as an internal curing agent to reduce autogenous shrinkage and to increase the compressive strength of AAS mortars.

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