Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers

The understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The por...

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Main Authors: Dongming Yan, Lingjun Xie, Xiaoqian Qian, Shaoqin Ruan, Qiang Zeng
Format: Article
Language:English
Published: MDPI AG 2020-07-01
Series:Materials
Subjects:
Online Access:https://www.mdpi.com/1996-1944/13/13/2973
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spelling doaj-95bd30384ccd49dab56ceb28231fad8d2020-11-25T03:51:25ZengMDPI AGMaterials1996-19442020-07-01132973297310.3390/ma13132973Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based GeopolymersDongming Yan0Lingjun Xie1Xiaoqian Qian2Shaoqin Ruan3Qiang Zeng4College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, ChinaCollege of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, ChinaCollege of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, ChinaCollege of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, ChinaCollege of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, ChinaThe understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The pore structure and strength were measured by mercury intrusion porosimetry and compression tests, respectively, which both showed obvious correlations with the material composition. Mass loss, strength loss, visual rate, and microscopic observation were adopted to assess the changes of the material properties and microstructure caused by F-T loads. The results showed that the strength-porosity relationship roughly followed a linear plot. Increases of the Si/Al ratio increased the capillary pore volume, but decreased the gel pore volume and the F-T resistance. Increases of the Na/Al ratio decreased the gel pore, but roughly enhanced the F-T resistance. The MKG mortar at the Na/Al ratio of 1.26 showed the lowest total pore volume and the best F-T resistance. The mechanisms of our experimental observations were that the abundantly distributed air voids connected by the capillary pores facilitated the relaxation of hydraulic pressures induced by the freezing of the pore liquid. The findings of this work help better clarify the compositional dependence of the pore structure, strength, and freezing-thawing resistance of MKG materials and provide fundamental bases for their engineering applications in cold regions.https://www.mdpi.com/1996-1944/13/13/2973geopolymeralkaline activator materialpore structurefreezing-thawing
collection DOAJ
language English
format Article
sources DOAJ
author Dongming Yan
Lingjun Xie
Xiaoqian Qian
Shaoqin Ruan
Qiang Zeng
spellingShingle Dongming Yan
Lingjun Xie
Xiaoqian Qian
Shaoqin Ruan
Qiang Zeng
Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
Materials
geopolymer
alkaline activator material
pore structure
freezing-thawing
author_facet Dongming Yan
Lingjun Xie
Xiaoqian Qian
Shaoqin Ruan
Qiang Zeng
author_sort Dongming Yan
title Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
title_short Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
title_full Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
title_fullStr Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
title_full_unstemmed Compositional Dependence of Pore Structure, Strengthand Freezing-Thawing Resistance of Metakaolin-Based Geopolymers
title_sort compositional dependence of pore structure, strengthand freezing-thawing resistance of metakaolin-based geopolymers
publisher MDPI AG
series Materials
issn 1996-1944
publishDate 2020-07-01
description The understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The pore structure and strength were measured by mercury intrusion porosimetry and compression tests, respectively, which both showed obvious correlations with the material composition. Mass loss, strength loss, visual rate, and microscopic observation were adopted to assess the changes of the material properties and microstructure caused by F-T loads. The results showed that the strength-porosity relationship roughly followed a linear plot. Increases of the Si/Al ratio increased the capillary pore volume, but decreased the gel pore volume and the F-T resistance. Increases of the Na/Al ratio decreased the gel pore, but roughly enhanced the F-T resistance. The MKG mortar at the Na/Al ratio of 1.26 showed the lowest total pore volume and the best F-T resistance. The mechanisms of our experimental observations were that the abundantly distributed air voids connected by the capillary pores facilitated the relaxation of hydraulic pressures induced by the freezing of the pore liquid. The findings of this work help better clarify the compositional dependence of the pore structure, strength, and freezing-thawing resistance of MKG materials and provide fundamental bases for their engineering applications in cold regions.
topic geopolymer
alkaline activator material
pore structure
freezing-thawing
url https://www.mdpi.com/1996-1944/13/13/2973
work_keys_str_mv AT dongmingyan compositionaldependenceofporestructurestrengthandfreezingthawingresistanceofmetakaolinbasedgeopolymers
AT lingjunxie compositionaldependenceofporestructurestrengthandfreezingthawingresistanceofmetakaolinbasedgeopolymers
AT xiaoqianqian compositionaldependenceofporestructurestrengthandfreezingthawingresistanceofmetakaolinbasedgeopolymers
AT shaoqinruan compositionaldependenceofporestructurestrengthandfreezingthawingresistanceofmetakaolinbasedgeopolymers
AT qiangzeng compositionaldependenceofporestructurestrengthandfreezingthawingresistanceofmetakaolinbasedgeopolymers
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