Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Evaluation of the pore structure of concrete using single-sided 1H nuclear magnetic resonance Relaxometry
https://orcid.org/0000-0002-2846-1445
In recent years, there has been growing interest in the use of proton nuclear magnetic resonance (1H NMR) relaxometry to obtain information on porosity and pore structure of cementitious materials. Investigations were mostly limited to white cement pastes and the use of closed magnet setups. In this thesis including the appended five papers, a comprehensive approach is followed to expand the existing knowledge for quantitative measurements of porosity and pore structure of concrete using single-sided 1H NMR. Differences in measurement and results due to the single-sided measurement setup, the influence of paramagnetic iron as well as aggregates are investigated and discussed. Single-sided 1H NMR allows the quantification of all liquid pore water in cement stone, mortar, and concrete without the need for sample preparation, destruction or a material-dependent calibration. Results from cement paste samples show that paramagnetic iron concentration increases surface relaxation rate linearly. This allows a transfer of the existing relaxation time to pore size conversions from white cement to ordinary Portland cement and thus, a quantified measurement of pore sizes. The influence of crystalline compounds, such as Portlandite and Ettringite, on the received signal is evaluated using T1-T2 experiments. Based on the results, partially new interpretations for off-diagonal signals in T1-T2 distributions have been developed. Aggregates in mortars and concrete reduce the amount of porous cement stone and alter the overall pore size distribution due to the development of the interfacial transition zone. This effect, though, is not as pronounced as expected based on past investigations. The immense influence of moisture on the pore structure of dried and rewetted mortars might explain this and other discrepancies found in the past for pore sizes and its influence on material properties. Single-sided 1H NMR is used to investigate the influence of fresh concrete pressure as well as an extreme superficially applied temperature exposure on concrete cover porosity. Prospective future usage of singlesided 1H NMR in research, material testing, and on-site investigations is outlined.
Evaluation of the pore structure of concrete using single-sided 1H nuclear magnetic resonance Relaxometry
https://orcid.org/0000-0002-2846-1445
In recent years, there has been growing interest in the use of proton nuclear magnetic resonance (1H NMR) relaxometry to obtain information on porosity and pore structure of cementitious materials. Investigations were mostly limited to white cement pastes and the use of closed magnet setups. In this thesis including the appended five papers, a comprehensive approach is followed to expand the existing knowledge for quantitative measurements of porosity and pore structure of concrete using single-sided 1H NMR. Differences in measurement and results due to the single-sided measurement setup, the influence of paramagnetic iron as well as aggregates are investigated and discussed. Single-sided 1H NMR allows the quantification of all liquid pore water in cement stone, mortar, and concrete without the need for sample preparation, destruction or a material-dependent calibration. Results from cement paste samples show that paramagnetic iron concentration increases surface relaxation rate linearly. This allows a transfer of the existing relaxation time to pore size conversions from white cement to ordinary Portland cement and thus, a quantified measurement of pore sizes. The influence of crystalline compounds, such as Portlandite and Ettringite, on the received signal is evaluated using T1-T2 experiments. Based on the results, partially new interpretations for off-diagonal signals in T1-T2 distributions have been developed. Aggregates in mortars and concrete reduce the amount of porous cement stone and alter the overall pore size distribution due to the development of the interfacial transition zone. This effect, though, is not as pronounced as expected based on past investigations. The immense influence of moisture on the pore structure of dried and rewetted mortars might explain this and other discrepancies found in the past for pore sizes and its influence on material properties. Single-sided 1H NMR is used to investigate the influence of fresh concrete pressure as well as an extreme superficially applied temperature exposure on concrete cover porosity. Prospective future usage of singlesided 1H NMR in research, material testing, and on-site investigations is outlined.
Evaluation of the pore structure of concrete using single-sided 1H nuclear magnetic resonance Relaxometry
https://orcid.org/0000-0002-2846-1445
In recent years, there has been growing interest in the use of proton nuclear magnetic resonance (1H NMR) relaxometry to obtain information on porosity and pore structure of cementitious materials. Investigations were mostly limited to white cement pastes and the use of closed magnet setups. In this thesis including the appended five papers, a comprehensive approach is followed to expand the existing knowledge for quantitative measurements of porosity and pore structure of concrete using single-sided 1H NMR. Differences in measurement and results due to the single-sided measurement setup, the influence of paramagnetic iron as well as aggregates are investigated and discussed. Single-sided 1H NMR allows the quantification of all liquid pore water in cement stone, mortar, and concrete without the need for sample preparation, destruction or a material-dependent calibration. Results from cement paste samples show that paramagnetic iron concentration increases surface relaxation rate linearly. This allows a transfer of the existing relaxation time to pore size conversions from white cement to ordinary Portland cement and thus, a quantified measurement of pore sizes. The influence of crystalline compounds, such as Portlandite and Ettringite, on the received signal is evaluated using T1-T2 experiments. Based on the results, partially new interpretations for off-diagonal signals in T1-T2 distributions have been developed. Aggregates in mortars and concrete reduce the amount of porous cement stone and alter the overall pore size distribution due to the development of the interfacial transition zone. This effect, though, is not as pronounced as expected based on past investigations. The immense influence of moisture on the pore structure of dried and rewetted mortars might explain this and other discrepancies found in the past for pore sizes and its influence on material properties. Single-sided 1H NMR is used to investigate the influence of fresh concrete pressure as well as an extreme superficially applied temperature exposure on concrete cover porosity. Prospective future usage of singlesided 1H NMR in research, material testing, and on-site investigations is outlined.
Evaluation of the pore structure of concrete using single-sided 1H nuclear magnetic resonance Relaxometry
Bestimmung der Porenstruktur von Beton mittels einseitiger Wasserstoff-Kernspinresonanz Relaxometrie
Schulte Holthausen, Robert Wilhelm (Autor:in) / Raupach, Michael (Akademische:r Betreuer:in) / Blümich, Bernhard (Akademische:r Betreuer:in) / Schüttrumpf, Holger (Akademische:r Betreuer:in)
01.01.2019
1 Online-Ressource : Illustrationen, Diagramme pages
Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019; Aachen 1 Online-Ressource : Illustrationen, Diagramme (2019). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019
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