Preliminary Reactivity Test for Precursors of Alkali-Activated Materials
Alkali-activated materials (AAMs) result from the dissolution process and polycondensation of precursors in high pH solutions. This material is considered alternative cement with similar properties and lower environmental impact than Portland cement. However, AAMs are subjected to the same standardi...
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| Format: | Article |
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MDPI AG
2023-03-01
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| Series: | Buildings |
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| Online Access: | https://www.mdpi.com/2075-5309/13/3/693 |
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| author | Sâmara França Leila Nóbrega Sousa Marcos Vinicio de Moura Solar Silva Paulo Henrique Ribeiro Borges Augusto Cesar da Silva Bezerra |
| author_facet | Sâmara França Leila Nóbrega Sousa Marcos Vinicio de Moura Solar Silva Paulo Henrique Ribeiro Borges Augusto Cesar da Silva Bezerra |
| author_sort | Sâmara França |
| collection | DOAJ |
| description | Alkali-activated materials (AAMs) result from the dissolution process and polycondensation of precursors in high pH solutions. This material is considered alternative cement with similar properties and lower environmental impact than Portland cement. However, AAMs are subjected to the same standardization applied to cement-based materials since no formal methods exist to characterize this material and/or the precursor reactivity. Therefore, this work aims to develop a method to characterize the reactivity of the main precursors used to produce AAMs. Hence, the precursors were assessed in two steps after chemical, physical, and mineralogical characterization. The first step evaluated the crystallinity change of the material after the acid attack by mixing 1 g of each material in 100 mL of 1% HF solution for 6 h at ambient temperature. The crystallinity change was evaluated by comparing the X-ray diffraction of the materials before and after the acid attack. The second step involved evaluating the formation of geopolymerization products in the pastes of studied precursors through FTIR test. The pastes were produced with Na<sub>2</sub>SiO<sub>3</sub> and NaOH as activators. After 28 days of curing, the pastes were submitted to a FTIR test for structural analysis. This method was tested evaluating the reactivity of traditional precursors for alkali activation (i.e., silica fume (SF), blast furnace slag (BFS), and metakaolin (MK)), in addition sugarcane bagasse ash mechanically treated (SCBAM) and sugarcane bagasse ash mechanically and heat treated (SCBAMH) since SCBA is a promising precursor for alkali activation. Considering the crystallinity change of precursors (step 01), the formation of geopolymerization products (step 02), and the chemical composition of precursors (preliminary characterization), it could be concluded that: (i) surface area is not relevant to materials with small particle size (<23 µm); (ii) amorphous area is only relevant if the material exhibits the optimal chemical composition; and (iii) the chemical composition is a crucial parameter for alkali activation. In addition, the potential precursors for alkali activation should have a significant amorphous halo and a SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratio of 2 to 5. Also, it could be concluded that SF and SCBAMH do not exhibit adequate reactivity while BFS, MK, and SCBAM can be classified as reactive precursors. |
| first_indexed | 2024-03-11T06:49:25Z |
| format | Article |
| id | doaj.art-39d625557ffb484789032d9db1ff3796 |
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| issn | 2075-5309 |
| language | English |
| last_indexed | 2024-03-11T06:49:25Z |
| publishDate | 2023-03-01 |
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| spelling | doaj.art-39d625557ffb484789032d9db1ff37962023-11-17T10:02:50ZengMDPI AGBuildings2075-53092023-03-0113369310.3390/buildings13030693Preliminary Reactivity Test for Precursors of Alkali-Activated MaterialsSâmara França0Leila Nóbrega Sousa1Marcos Vinicio de Moura Solar Silva2Paulo Henrique Ribeiro Borges3Augusto Cesar da Silva Bezerra4Department of Civil Engineering, Federal Center for Technological Education of Minas Gerais, Belo Horizonte 30421-169, BrazilDepartment of Materials Engineering, Federal Center for Technological Education of Minas Gerais, Belo Horizonte 30421-169, BrazilEnergy Company of Minas Gerais, Belo Horizonte 30190-131, BrazilDepartment of Civil Engineering, Federal Center for Technological Education of Minas Gerais, Belo Horizonte 30421-169, BrazilDepartment of Transport Engineering, Federal Center for Technological Education of Minas Gerais, Belo Horizonte 30421-169, BrazilAlkali-activated materials (AAMs) result from the dissolution process and polycondensation of precursors in high pH solutions. This material is considered alternative cement with similar properties and lower environmental impact than Portland cement. However, AAMs are subjected to the same standardization applied to cement-based materials since no formal methods exist to characterize this material and/or the precursor reactivity. Therefore, this work aims to develop a method to characterize the reactivity of the main precursors used to produce AAMs. Hence, the precursors were assessed in two steps after chemical, physical, and mineralogical characterization. The first step evaluated the crystallinity change of the material after the acid attack by mixing 1 g of each material in 100 mL of 1% HF solution for 6 h at ambient temperature. The crystallinity change was evaluated by comparing the X-ray diffraction of the materials before and after the acid attack. The second step involved evaluating the formation of geopolymerization products in the pastes of studied precursors through FTIR test. The pastes were produced with Na<sub>2</sub>SiO<sub>3</sub> and NaOH as activators. After 28 days of curing, the pastes were submitted to a FTIR test for structural analysis. This method was tested evaluating the reactivity of traditional precursors for alkali activation (i.e., silica fume (SF), blast furnace slag (BFS), and metakaolin (MK)), in addition sugarcane bagasse ash mechanically treated (SCBAM) and sugarcane bagasse ash mechanically and heat treated (SCBAMH) since SCBA is a promising precursor for alkali activation. Considering the crystallinity change of precursors (step 01), the formation of geopolymerization products (step 02), and the chemical composition of precursors (preliminary characterization), it could be concluded that: (i) surface area is not relevant to materials with small particle size (<23 µm); (ii) amorphous area is only relevant if the material exhibits the optimal chemical composition; and (iii) the chemical composition is a crucial parameter for alkali activation. In addition, the potential precursors for alkali activation should have a significant amorphous halo and a SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratio of 2 to 5. Also, it could be concluded that SF and SCBAMH do not exhibit adequate reactivity while BFS, MK, and SCBAM can be classified as reactive precursors.https://www.mdpi.com/2075-5309/13/3/693reactivityprecursorsalkali-activated materialssugarcane bagasse ashchemical compositionsurface area |
| spellingShingle | Sâmara França Leila Nóbrega Sousa Marcos Vinicio de Moura Solar Silva Paulo Henrique Ribeiro Borges Augusto Cesar da Silva Bezerra Preliminary Reactivity Test for Precursors of Alkali-Activated Materials Buildings reactivity precursors alkali-activated materials sugarcane bagasse ash chemical composition surface area |
| title | Preliminary Reactivity Test for Precursors of Alkali-Activated Materials |
| title_full | Preliminary Reactivity Test for Precursors of Alkali-Activated Materials |
| title_fullStr | Preliminary Reactivity Test for Precursors of Alkali-Activated Materials |
| title_full_unstemmed | Preliminary Reactivity Test for Precursors of Alkali-Activated Materials |
| title_short | Preliminary Reactivity Test for Precursors of Alkali-Activated Materials |
| title_sort | preliminary reactivity test for precursors of alkali activated materials |
| topic | reactivity precursors alkali-activated materials sugarcane bagasse ash chemical composition surface area |
| url | https://www.mdpi.com/2075-5309/13/3/693 |
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