Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution
In this study, the sulfate attack on uncarbonated cement paste partially exposed to Na<sub>2</sub>SO<sub>4</sub> solution was experimentally investigated and compared with that on carbonated specimens with the same exposure regime and uncarbonated specimens without exposure....
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doaj-f5667729f09247ca948583840a6c54282020-11-25T04:05:33ZengMDPI AGMaterials1996-19442020-11-01134920492010.3390/ma13214920Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> SolutionZanqun Liu0Min Pei1Yuelin Li2Qian Yuan3School of Civil Engineering, National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, ChinaSchool of Civil Engineering, National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, ChinaDepartment of Civil Engineering, KU Leuven, Campus Bruges, 8200 Bruges, BelgiumSchool of Civil Engineering, National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, ChinaIn this study, the sulfate attack on uncarbonated cement paste partially exposed to Na<sub>2</sub>SO<sub>4</sub> solution was experimentally investigated and compared with that on carbonated specimens with the same exposure regime and uncarbonated specimens without exposure. N<sub>2</sub> was used to protect specimens from carbonation throughout the sulfate exposure period. The effects of the water-to-cement (w/c) ratio and the fly ash as cement replacement on the sulfate attack were evaluated. Portland cement paste specimens with different w/c ratios of 0.35, 0.45, and 0.55 or fly ash replacement rates of 10%, 20%, and 30% were prepared. These specimens were partially immersed in 5% Na<sub>2</sub>SO<sub>4</sub> solution for 50 d and 100 d exposure periods. The micro-analysis was conducted to evaluate the effect of the partial sulfate attack on the uncarbonated cement paste using X-ray diffraction (XRD) and thermo-gravimetric (TG) techniques. The results confirmed that, for uncarbonated cement paste, the chemical attack rather than the physical attack is the deterioration mechanism and is responsible for more severe damage in the evaporation zone (dry part) compared with the immersed zone (immersed part). When the effect of carbonation is well excluded, there is an optimal w/c ratio of 0.45 for minimizing the sulfate attack, while incorporating fly ash tends to reduce the sulfate attack resistance.https://www.mdpi.com/1996-1944/13/21/4920chemical sulfate attackphysical sulfate attackcarbonationcement |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Zanqun Liu Min Pei Yuelin Li Qian Yuan |
spellingShingle |
Zanqun Liu Min Pei Yuelin Li Qian Yuan Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution Materials chemical sulfate attack physical sulfate attack carbonation cement |
author_facet |
Zanqun Liu Min Pei Yuelin Li Qian Yuan |
author_sort |
Zanqun Liu |
title |
Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution |
title_short |
Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution |
title_full |
Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution |
title_fullStr |
Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution |
title_full_unstemmed |
Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na<sub>2</sub>SO<sub>4</sub> Solution |
title_sort |
sulfate attacks on uncarbonated fly ash + cement pastes partially immersed in na<sub>2</sub>so<sub>4</sub> solution |
publisher |
MDPI AG |
series |
Materials |
issn |
1996-1944 |
publishDate |
2020-11-01 |
description |
In this study, the sulfate attack on uncarbonated cement paste partially exposed to Na<sub>2</sub>SO<sub>4</sub> solution was experimentally investigated and compared with that on carbonated specimens with the same exposure regime and uncarbonated specimens without exposure. N<sub>2</sub> was used to protect specimens from carbonation throughout the sulfate exposure period. The effects of the water-to-cement (w/c) ratio and the fly ash as cement replacement on the sulfate attack were evaluated. Portland cement paste specimens with different w/c ratios of 0.35, 0.45, and 0.55 or fly ash replacement rates of 10%, 20%, and 30% were prepared. These specimens were partially immersed in 5% Na<sub>2</sub>SO<sub>4</sub> solution for 50 d and 100 d exposure periods. The micro-analysis was conducted to evaluate the effect of the partial sulfate attack on the uncarbonated cement paste using X-ray diffraction (XRD) and thermo-gravimetric (TG) techniques. The results confirmed that, for uncarbonated cement paste, the chemical attack rather than the physical attack is the deterioration mechanism and is responsible for more severe damage in the evaporation zone (dry part) compared with the immersed zone (immersed part). When the effect of carbonation is well excluded, there is an optimal w/c ratio of 0.45 for minimizing the sulfate attack, while incorporating fly ash tends to reduce the sulfate attack resistance. |
topic |
chemical sulfate attack physical sulfate attack carbonation cement |
url |
https://www.mdpi.com/1996-1944/13/21/4920 |
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