Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack
Circulating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB boiler...
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MDPI AG
2021-12-01
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| Online Access: | https://www.mdpi.com/2073-4352/12/1/41 |
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| author | Guan-Yu Chen Wei-Hsing Huang |
| author_facet | Guan-Yu Chen Wei-Hsing Huang |
| author_sort | Guan-Yu Chen |
| collection | DOAJ |
| description | Circulating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB boiler is called CFB fly ash. This paper presents the hydration development on the application of CFB fly ash to activating blast furnace slag (BFS) as a supplementary binder material (SBM) for replacement of Portland cement in making concrete. Investigation of the hydration products of cement pastes prepared with combinations of BFS and CFB fly ash were conducted by means of X-ray diffraction, thermal gravimetric analysis, and scanning electronic microscope. Test results show that the main hydration products of the CFB fly ash-BFS blended pastes were found to be hydrated calcium silicate (C-S-H), ettringite, gypsum, and some portlandite. Considering that CFB fly ash produced from the combustion of high-sulfur coke has high SO<sub>3</sub> contents, the volume stability of mortar made from CFB fly ash-activated BFS was subjected to tests in accordance with ASTM C1012 and ASTM C1038 for evaluating the internal and external sulfate attack, respectively. The results indicate that, due to the high sulfur (SO<sub>3</sub>) content of CFB fly ash, the expansion caused by internal sulfate attack (ISA) increased with increasing proportion of CFB fly ash in the mixture. In contrast, no significant expansion was observed in the external sulfate attack (ESA) test, regardless of the proportion of CFB fly ash in the mixture. In order for the CFB fly ash to serve as a supplementary binder material and to maintain adequate volume stability, the amount of CFB fly ash used for the activation of BFS is recommended to be no more than 20% of the SBM. |
| first_indexed | 2024-03-10T01:41:05Z |
| format | Article |
| id | doaj.art-25754fdf252d48288de541888c311d5e |
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| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-10T01:41:05Z |
| publishDate | 2021-12-01 |
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| record_format | Article |
| series | Crystals |
| spelling | doaj.art-25754fdf252d48288de541888c311d5e2023-11-23T13:24:13ZengMDPI AGCrystals2073-43522021-12-011214110.3390/cryst12010041Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate AttackGuan-Yu Chen0Wei-Hsing Huang1Department of Civil Engineering, National Central University, Zhongli District, Taoyuan City 32001, TaiwanDepartment of Civil Engineering, National Central University, Zhongli District, Taoyuan City 32001, TaiwanCirculating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB boiler is called CFB fly ash. This paper presents the hydration development on the application of CFB fly ash to activating blast furnace slag (BFS) as a supplementary binder material (SBM) for replacement of Portland cement in making concrete. Investigation of the hydration products of cement pastes prepared with combinations of BFS and CFB fly ash were conducted by means of X-ray diffraction, thermal gravimetric analysis, and scanning electronic microscope. Test results show that the main hydration products of the CFB fly ash-BFS blended pastes were found to be hydrated calcium silicate (C-S-H), ettringite, gypsum, and some portlandite. Considering that CFB fly ash produced from the combustion of high-sulfur coke has high SO<sub>3</sub> contents, the volume stability of mortar made from CFB fly ash-activated BFS was subjected to tests in accordance with ASTM C1012 and ASTM C1038 for evaluating the internal and external sulfate attack, respectively. The results indicate that, due to the high sulfur (SO<sub>3</sub>) content of CFB fly ash, the expansion caused by internal sulfate attack (ISA) increased with increasing proportion of CFB fly ash in the mixture. In contrast, no significant expansion was observed in the external sulfate attack (ESA) test, regardless of the proportion of CFB fly ash in the mixture. In order for the CFB fly ash to serve as a supplementary binder material and to maintain adequate volume stability, the amount of CFB fly ash used for the activation of BFS is recommended to be no more than 20% of the SBM.https://www.mdpi.com/2073-4352/12/1/41circulating fluidized bed fly ashsupplementary binder materialsinternal sulfate attackdelayed ettringite formation |
| spellingShingle | Guan-Yu Chen Wei-Hsing Huang Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack Crystals circulating fluidized bed fly ash supplementary binder materials internal sulfate attack delayed ettringite formation |
| title | Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack |
| title_full | Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack |
| title_fullStr | Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack |
| title_full_unstemmed | Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack |
| title_short | Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack |
| title_sort | activation of blast furnace slag with cfb fly ash as a supplementary binder material hydration products and effects of sulfate attack |
| topic | circulating fluidized bed fly ash supplementary binder materials internal sulfate attack delayed ettringite formation |
| url | https://www.mdpi.com/2073-4352/12/1/41 |
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