Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources
The possibility of the formation of an alkali–silicate reaction (ASR) is a crucial issue for the service life of concrete. The coexistence of key parameters such as the presence of alkalis, reactive SiO<sub>2</sub>, humidity, and temperature predetermine the possibility of its formation...
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| Format: | Article |
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MDPI AG
2022-07-01
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| Online Access: | https://www.mdpi.com/1996-1944/15/14/4730 |
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| author | Michal Marko Petr Hrubý Martin Janča Jakub Kříkala Jan Hajzler František Šoukal Jan Vojtíšek Martin Doležal |
| author_facet | Michal Marko Petr Hrubý Martin Janča Jakub Kříkala Jan Hajzler František Šoukal Jan Vojtíšek Martin Doležal |
| author_sort | Michal Marko |
| collection | DOAJ |
| description | The possibility of the formation of an alkali–silicate reaction (ASR) is a crucial issue for the service life of concrete. The coexistence of key parameters such as the presence of alkalis, reactive SiO<sub>2</sub>, humidity, and temperature predetermine the possibility of its formation and application. When an ASR gel forms, it results in the concreting cracking and spalling as well as in the deterioration of its overall properties. The risk of ASR depends on the concentration of alkalis and their mobility, which influence their ability to penetrate the concrete. The objective of this study was to determine the ionic mobility of not only Na<sup>+</sup> and K<sup>+</sup>, but Ca<sup>2+</sup> as well, from external sources (0.5 and 1.0 mol/L solutions of Na/K carbonate, nitrate, and hydroxide) to a cementitious matrix as the precursor for ASR. The concentrations of ions in both the immersion solutions (ICP) and the cementitious matrix itself (SEM-EDX) were studied as a function of time, from 0 to 120 days, for leaching, and according to temperature (25 and 40 °C). The reaction products were characterized using SEM-EDX. Different diffusion rates and behavior were observed depending on the anion type of the external alkali source. Both sodium and potassium ions in all the three environments studied, namely carbonate, hydroxide, and nitrate, penetrated into the composite and further into its structure by different mechanisms. The action of hydroxides, in particular, transformed the original hydration products into calcium-silicate-hydrate (CASH) or ASR gel, while nitrates crystallized in pores and did not cause any changes in the hydration product. The driving force was the increased temperature of the experiment as well as the increased concentration of the solution to which the test specimen was exposed. |
| first_indexed | 2024-03-09T10:16:03Z |
| format | Article |
| id | doaj.art-1353514d854e44c08b8d6667848a687b |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T10:16:03Z |
| publishDate | 2022-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Materials |
| spelling | doaj.art-1353514d854e44c08b8d6667848a687b2023-12-01T22:22:23ZengMDPI AGMaterials1996-19442022-07-011514473010.3390/ma15144730Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External SourcesMichal Marko0Petr Hrubý1Martin Janča2Jakub Kříkala3Jan Hajzler4František Šoukal5Jan Vojtíšek6Martin Doležal7Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicFaculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech RepublicThe possibility of the formation of an alkali–silicate reaction (ASR) is a crucial issue for the service life of concrete. The coexistence of key parameters such as the presence of alkalis, reactive SiO<sub>2</sub>, humidity, and temperature predetermine the possibility of its formation and application. When an ASR gel forms, it results in the concreting cracking and spalling as well as in the deterioration of its overall properties. The risk of ASR depends on the concentration of alkalis and their mobility, which influence their ability to penetrate the concrete. The objective of this study was to determine the ionic mobility of not only Na<sup>+</sup> and K<sup>+</sup>, but Ca<sup>2+</sup> as well, from external sources (0.5 and 1.0 mol/L solutions of Na/K carbonate, nitrate, and hydroxide) to a cementitious matrix as the precursor for ASR. The concentrations of ions in both the immersion solutions (ICP) and the cementitious matrix itself (SEM-EDX) were studied as a function of time, from 0 to 120 days, for leaching, and according to temperature (25 and 40 °C). The reaction products were characterized using SEM-EDX. Different diffusion rates and behavior were observed depending on the anion type of the external alkali source. Both sodium and potassium ions in all the three environments studied, namely carbonate, hydroxide, and nitrate, penetrated into the composite and further into its structure by different mechanisms. The action of hydroxides, in particular, transformed the original hydration products into calcium-silicate-hydrate (CASH) or ASR gel, while nitrates crystallized in pores and did not cause any changes in the hydration product. The driving force was the increased temperature of the experiment as well as the increased concentration of the solution to which the test specimen was exposed.https://www.mdpi.com/1996-1944/15/14/4730alkali–silicate reactiondiffusionionic mobilitycementdegradation |
| spellingShingle | Michal Marko Petr Hrubý Martin Janča Jakub Kříkala Jan Hajzler František Šoukal Jan Vojtíšek Martin Doležal Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources Materials alkali–silicate reaction diffusion ionic mobility cement degradation |
| title | Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources |
| title_full | Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources |
| title_fullStr | Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources |
| title_full_unstemmed | Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources |
| title_short | Monitoring of Ion Mobility in the Cement Matrix to Establish Sensitivity to the ASR Caused by External Sources |
| title_sort | monitoring of ion mobility in the cement matrix to establish sensitivity to the asr caused by external sources |
| topic | alkali–silicate reaction diffusion ionic mobility cement degradation |
| url | https://www.mdpi.com/1996-1944/15/14/4730 |
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