Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations
Geopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopoly...
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MDPI AG
2021-11-01
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| Online Access: | https://www.mdpi.com/1996-1944/14/23/7109 |
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| author | Wei Yang Pinghua Zhu Hui Liu Xinjie Wang Wei Ge Minqi Hua |
| author_facet | Wei Yang Pinghua Zhu Hui Liu Xinjie Wang Wei Ge Minqi Hua |
| author_sort | Wei Yang |
| collection | DOAJ |
| description | Geopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopolymer concrete (GPC) with different binding materials and concentrations of sodium hydroxide solution (NaOH), metakaolin, high-calcium fly ash, and low-calcium fly ash were chosen as binding materials of GPC for the geopolymerization process. A mixture of sodium silicate solution (Na<sub>2</sub>SiO<sub>3</sub>) and NaOH solution with different concentrations (8 M and 12 M) was selected as the alkaline activator with a ratio (Na<sub>2</sub>SiO<sub>3</sub>/NaOH) of 1.5. GPC specimens were immersed in the sulfuric acid solution with the pH value of 1 for 6 days and then naturally dried for 1 day until 98 days. The macroscopic properties of GPC were characterized by visual appearance, compressive strength, mass loss, and neutralization depth. The materials were characterized by SEM, XRD, and FTIR. The results indicated that at the immersion time of 28 d, the compressive strength of two types of fly ash-based GPC increased to some extent due to the presence of gypsum, but this phenomenon was not observed in metakaolin-based GPC. After 98 d of immersion, the residual strength of fly ash based GPC was still higher, which reached more than 25 MPa, while the metakaolin-based GPC failed. Furthermore, due to the rigid 3D networks of aluminosilicate in fly ash-based GPC, the mass of all GPC decreased slightly during the immersion period, and then tended to be stable in the later period. On the contrary, in metakaolin-based GPC, the incomplete geopolymerization led to the compressive strength being too low to meet the application of practical engineering. In addition, the compressive strength of GPC activated by 12 M NaOH was higher than the GPC activated by 8 M NaOH, which is owing to the formation of gel depended on the concentration of alkali OH ion, low NaOH concentration weakened chemical reaction, and reduced compressive strength. Additionally, according to the testing results of neutralization depth, the neutralization depth of high-calcium fly ash-based GPC activated by 12 M NaOH suffered acid attack for 98 d was only 6.9 mm, which is the minimum value. Therefore, the best performance was observed in GPC prepared with high-calcium fly ash and 12 M NaOH solution, which is attributed to gypsum crystals that block the pores of the specimen and improve the microstructure of GPC, inhibiting further corrosion of sulfuric acid. |
| first_indexed | 2024-03-10T04:50:12Z |
| format | Article |
| id | doaj.art-49b9cf1b464748dab109199577f743b9 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-10T04:50:12Z |
| publishDate | 2021-11-01 |
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| spelling | doaj.art-49b9cf1b464748dab109199577f743b92023-11-23T02:38:24ZengMDPI AGMaterials1996-19442021-11-011423710910.3390/ma14237109Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali ConcentrationsWei Yang0Pinghua Zhu1Hui Liu2Xinjie Wang3Wei Ge4Minqi Hua5Department of Civil Engineering, Changzhou University, Changzhou 213164, ChinaDepartment of Civil Engineering, Changzhou University, Changzhou 213164, ChinaDepartment of Civil Engineering, Changzhou University, Changzhou 213164, ChinaDepartment of Civil Engineering, Changzhou University, Changzhou 213164, ChinaDepartment of Materials Science and Engineering, Anhui University of Science and Technology, Huainan 232001, ChinaSchool of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, ChinaGeopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopolymer concrete (GPC) with different binding materials and concentrations of sodium hydroxide solution (NaOH), metakaolin, high-calcium fly ash, and low-calcium fly ash were chosen as binding materials of GPC for the geopolymerization process. A mixture of sodium silicate solution (Na<sub>2</sub>SiO<sub>3</sub>) and NaOH solution with different concentrations (8 M and 12 M) was selected as the alkaline activator with a ratio (Na<sub>2</sub>SiO<sub>3</sub>/NaOH) of 1.5. GPC specimens were immersed in the sulfuric acid solution with the pH value of 1 for 6 days and then naturally dried for 1 day until 98 days. The macroscopic properties of GPC were characterized by visual appearance, compressive strength, mass loss, and neutralization depth. The materials were characterized by SEM, XRD, and FTIR. The results indicated that at the immersion time of 28 d, the compressive strength of two types of fly ash-based GPC increased to some extent due to the presence of gypsum, but this phenomenon was not observed in metakaolin-based GPC. After 98 d of immersion, the residual strength of fly ash based GPC was still higher, which reached more than 25 MPa, while the metakaolin-based GPC failed. Furthermore, due to the rigid 3D networks of aluminosilicate in fly ash-based GPC, the mass of all GPC decreased slightly during the immersion period, and then tended to be stable in the later period. On the contrary, in metakaolin-based GPC, the incomplete geopolymerization led to the compressive strength being too low to meet the application of practical engineering. In addition, the compressive strength of GPC activated by 12 M NaOH was higher than the GPC activated by 8 M NaOH, which is owing to the formation of gel depended on the concentration of alkali OH ion, low NaOH concentration weakened chemical reaction, and reduced compressive strength. Additionally, according to the testing results of neutralization depth, the neutralization depth of high-calcium fly ash-based GPC activated by 12 M NaOH suffered acid attack for 98 d was only 6.9 mm, which is the minimum value. Therefore, the best performance was observed in GPC prepared with high-calcium fly ash and 12 M NaOH solution, which is attributed to gypsum crystals that block the pores of the specimen and improve the microstructure of GPC, inhibiting further corrosion of sulfuric acid.https://www.mdpi.com/1996-1944/14/23/7109geopolymer concretefly ashmetakaolinalkali concentrationsulfuric acid corrosion |
| spellingShingle | Wei Yang Pinghua Zhu Hui Liu Xinjie Wang Wei Ge Minqi Hua Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations Materials geopolymer concrete fly ash metakaolin alkali concentration sulfuric acid corrosion |
| title | Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations |
| title_full | Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations |
| title_fullStr | Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations |
| title_full_unstemmed | Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations |
| title_short | Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations |
| title_sort | resistance to sulfuric acid corrosion of geopolymer concrete based on different binding materials and alkali concentrations |
| topic | geopolymer concrete fly ash metakaolin alkali concentration sulfuric acid corrosion |
| url | https://www.mdpi.com/1996-1944/14/23/7109 |
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