The Experts below are selected from a list of 9411 Experts worldwide ranked by ideXlab platform
Ravi Ajitbhai Patel - One of the best experts on this subject based on the ideXlab platform.
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a three dimensional lattice boltzmann method based reactive transport model to simulate changes in cement paste microstructure due to calcium leaching
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BreugelAbstract:Abstract In this paper, a newly developed lattice Boltzmann method based reactive transport model to simulate changes in microstructure of ordinary Portland cement paste due to calcium leaching is presented. The model takes three-dimensional digitized cement paste microstructure as input and is capable to capture an evolution of microstructure due to leaching, accounting for the dissolution of portlandite and corresponding increase in Capillary Porosity and the decalcification of C-S-H resulting in increase in gel Porosity. The developed model has been applied to microstructures generated using two cement hydration models, CEMHYD3D and HYMSOTRUC, for three water-to-cement ratios. It was observed that the rate of leaching is directly proportional to ability of microstructure to transport calcium ions and higher fraction of percolated Capillary pores result in higher rate of leaching. The model qualitatively reproduces experimentally observed changes in cement paste Porosity and pore size distribution due to leaching. The quantitative validation of model at this scale is not possible by comparison of leaching obtained experiments and simulations which can be attributed to several factors including the differences in the scales of experiment and modelling study presented in this paper.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Guang Ye, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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diffusivity of saturated ordinary portland cement based materials a critical review of experimental and analytical modelling approaches
Cement and Concrete Research, 2016Co-Authors: Ravi Ajitbhai Patel, Quoc Tri Phung, Suresh Seetharam, Janez Perko, Diederik Jacques, Norbert Maes, Geert De Schutter, Klaas Van BreugelAbstract:Abstract This paper provides a comprehensive overview of existing experimental and modelling approaches to determine effective diffusion coefficients of water saturated ordinary Portland cement-based materials. A dataset for diffusivity obtained from different experimental techniques have been presented for cement paste, mortar and concrete. For cement paste at low porosities, diffusivity reported by different authors varies up to a factor of five and electrical resistivity measurements for low Capillary Porosity are up to one order of magnitude higher compared to other techniques. Experimental data of mortar and concrete reveals predominant influence of increasing tortuosity due to aggregates and limited influence of interface transition zone. Hence, a particular emphasis has been placed on assessing predictability of diffusivity models for cement paste on a larger dataset collected in this paper. It has been observed that all predictive models have similar level of accuracy and fail to predict electrical resistivity data at low Capillary Porosity as these models are not calibrated using electrical resistivity data.
N F Fang - One of the best experts on this subject based on the ideXlab platform.
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mixed artificial grasslands with more roots improved mine soil infiltration capacity
Journal of Hydrology, 2016Co-Authors: Gaolin Wu, N F Fang, Zheng YangAbstract:Summary Soil water is one of the critical limiting factors in achieving sustainable revegetation. Soil infiltration capacity plays a vital role in determining the inputs from precipitation and enhancing water storage, which are important for the maintenance and survival of vegetation patches in arid and semi-arid areas. Our study investigated the effects of different artificial grasslands on soil physical properties and soil infiltration capacity. The artificial grasslands were Medicago sativa , Astragalus adsurgens , Agropyron mongolicum , Lespedeza davurica , Bromus inermis , Hedysarum scoparium, A. mongolicum + Artemisia desertorum, A. adsurgens + A. desertorum and M. sativa + B. inermis . The soil infiltration capacity index (SICI), which was based on the average infiltration rate of stage I (AIRSI) and the average infiltration rate of stage III (AIRS III), was higher (indicating that the infiltration capacity was greater) under the artificial grasslands than that of the bare soil. The SICI of the A. adsurgens + A. desertorum grassland had the highest value (1.48) and bare soil (−0.59) had the lowest value. It was evident that artificial grassland could improve soil infiltration capacity. We also used principal component analysis (PCA) to determine that the main factors that affected SICI were the soil water content at a depth of 20 cm (SWC20), the below-ground root biomasses at depths of 10 and 30 cm (BGB10, BGB30), the Capillary Porosity at a depth of 10 cm (CP10) and the non-Capillary Porosity at a depth of 20 cm (NCP20). Our study suggests that the use of Legume-poaceae mixtures and Legume-shrub mixtures to create grasslands provided an effective ecological restoration approach to improve soil infiltration properties due to their greater root biomasses. Furthermore, soil water content, below-ground root biomass, soil Capillary Porosity and soil non-Capillary Porosity were the main factors that affect the soil infiltration capacity.
Janez Perko - One of the best experts on this subject based on the ideXlab platform.
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a three dimensional lattice boltzmann method based reactive transport model to simulate changes in cement paste microstructure due to calcium leaching
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BreugelAbstract:Abstract In this paper, a newly developed lattice Boltzmann method based reactive transport model to simulate changes in microstructure of ordinary Portland cement paste due to calcium leaching is presented. The model takes three-dimensional digitized cement paste microstructure as input and is capable to capture an evolution of microstructure due to leaching, accounting for the dissolution of portlandite and corresponding increase in Capillary Porosity and the decalcification of C-S-H resulting in increase in gel Porosity. The developed model has been applied to microstructures generated using two cement hydration models, CEMHYD3D and HYMSOTRUC, for three water-to-cement ratios. It was observed that the rate of leaching is directly proportional to ability of microstructure to transport calcium ions and higher fraction of percolated Capillary pores result in higher rate of leaching. The model qualitatively reproduces experimentally observed changes in cement paste Porosity and pore size distribution due to leaching. The quantitative validation of model at this scale is not possible by comparison of leaching obtained experiments and simulations which can be attributed to several factors including the differences in the scales of experiment and modelling study presented in this paper.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Guang Ye, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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diffusivity of saturated ordinary portland cement based materials a critical review of experimental and analytical modelling approaches
Cement and Concrete Research, 2016Co-Authors: Ravi Ajitbhai Patel, Quoc Tri Phung, Suresh Seetharam, Janez Perko, Diederik Jacques, Norbert Maes, Geert De Schutter, Klaas Van BreugelAbstract:Abstract This paper provides a comprehensive overview of existing experimental and modelling approaches to determine effective diffusion coefficients of water saturated ordinary Portland cement-based materials. A dataset for diffusivity obtained from different experimental techniques have been presented for cement paste, mortar and concrete. For cement paste at low porosities, diffusivity reported by different authors varies up to a factor of five and electrical resistivity measurements for low Capillary Porosity are up to one order of magnitude higher compared to other techniques. Experimental data of mortar and concrete reveals predominant influence of increasing tortuosity due to aggregates and limited influence of interface transition zone. Hence, a particular emphasis has been placed on assessing predictability of diffusivity models for cement paste on a larger dataset collected in this paper. It has been observed that all predictive models have similar level of accuracy and fail to predict electrical resistivity data at low Capillary Porosity as these models are not calibrated using electrical resistivity data.
Geert De Schutter - One of the best experts on this subject based on the ideXlab platform.
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a three dimensional lattice boltzmann method based reactive transport model to simulate changes in cement paste microstructure due to calcium leaching
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BreugelAbstract:Abstract In this paper, a newly developed lattice Boltzmann method based reactive transport model to simulate changes in microstructure of ordinary Portland cement paste due to calcium leaching is presented. The model takes three-dimensional digitized cement paste microstructure as input and is capable to capture an evolution of microstructure due to leaching, accounting for the dissolution of portlandite and corresponding increase in Capillary Porosity and the decalcification of C-S-H resulting in increase in gel Porosity. The developed model has been applied to microstructures generated using two cement hydration models, CEMHYD3D and HYMSOTRUC, for three water-to-cement ratios. It was observed that the rate of leaching is directly proportional to ability of microstructure to transport calcium ions and higher fraction of percolated Capillary pores result in higher rate of leaching. The model qualitatively reproduces experimentally observed changes in cement paste Porosity and pore size distribution due to leaching. The quantitative validation of model at this scale is not possible by comparison of leaching obtained experiments and simulations which can be attributed to several factors including the differences in the scales of experiment and modelling study presented in this paper.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Guang Ye, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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diffusivity of saturated ordinary portland cement based materials a critical review of experimental and analytical modelling approaches
Cement and Concrete Research, 2016Co-Authors: Ravi Ajitbhai Patel, Quoc Tri Phung, Suresh Seetharam, Janez Perko, Diederik Jacques, Norbert Maes, Geert De Schutter, Klaas Van BreugelAbstract:Abstract This paper provides a comprehensive overview of existing experimental and modelling approaches to determine effective diffusion coefficients of water saturated ordinary Portland cement-based materials. A dataset for diffusivity obtained from different experimental techniques have been presented for cement paste, mortar and concrete. For cement paste at low porosities, diffusivity reported by different authors varies up to a factor of five and electrical resistivity measurements for low Capillary Porosity are up to one order of magnitude higher compared to other techniques. Experimental data of mortar and concrete reveals predominant influence of increasing tortuosity due to aggregates and limited influence of interface transition zone. Hence, a particular emphasis has been placed on assessing predictability of diffusivity models for cement paste on a larger dataset collected in this paper. It has been observed that all predictive models have similar level of accuracy and fail to predict electrical resistivity data at low Capillary Porosity as these models are not calibrated using electrical resistivity data.
Diederik Jacques - One of the best experts on this subject based on the ideXlab platform.
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a three dimensional lattice boltzmann method based reactive transport model to simulate changes in cement paste microstructure due to calcium leaching
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BreugelAbstract:Abstract In this paper, a newly developed lattice Boltzmann method based reactive transport model to simulate changes in microstructure of ordinary Portland cement paste due to calcium leaching is presented. The model takes three-dimensional digitized cement paste microstructure as input and is capable to capture an evolution of microstructure due to leaching, accounting for the dissolution of portlandite and corresponding increase in Capillary Porosity and the decalcification of C-S-H resulting in increase in gel Porosity. The developed model has been applied to microstructures generated using two cement hydration models, CEMHYD3D and HYMSOTRUC, for three water-to-cement ratios. It was observed that the rate of leaching is directly proportional to ability of microstructure to transport calcium ions and higher fraction of percolated Capillary pores result in higher rate of leaching. The model qualitatively reproduces experimentally observed changes in cement paste Porosity and pore size distribution due to leaching. The quantitative validation of model at this scale is not possible by comparison of leaching obtained experiments and simulations which can be attributed to several factors including the differences in the scales of experiment and modelling study presented in this paper.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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effective diffusivity of cement pastes from virtual microstructures role of gel Porosity and Capillary pore percolation
Construction and Building Materials, 2018Co-Authors: Ravi Ajitbhai Patel, Janez Perko, Diederik Jacques, Geert De Schutter, Guang Ye, Klaas Van BruegelAbstract:Abstract The role of Capillary pores percolation and gel pores are investigated to explain the underlying differences between relative diffusivity obtained from different experimental techniques using microstructures generated from two different types of hydration model viz., CEMHYD3D (a voxel based approach) and HYMOSTRUC (a vector based approach). These models provide microstructures with different Capillary pore connectivity for the same degree of hydration and the same Porosity due to the underlying assumptions. In order to account for a C-S-H diffusivity at the micro-scale, a continuum micro-mechanics based model has been proposed. These simulations show that deperolation of Capillary pores at around 20% of Capillary Porosity is essential in order to correctly predict diffusivity of cement paste with water-cement ratio by mass (w/c) in between 0.4 and 0.5. Furthermore from our analysis we present a viable postulate that the higher diffusivity measured by electric resistivity compared to other methods is due to differences in contribution from gel pores. For electrical resistivity measurement it is proposed that all gel pores are diffusive whereas for ion and tracer transport it is proposed that only nitrogen accessible gel pores are diffusive.
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diffusivity of saturated ordinary portland cement based materials a critical review of experimental and analytical modelling approaches
Cement and Concrete Research, 2016Co-Authors: Ravi Ajitbhai Patel, Quoc Tri Phung, Suresh Seetharam, Janez Perko, Diederik Jacques, Norbert Maes, Geert De Schutter, Klaas Van BreugelAbstract:Abstract This paper provides a comprehensive overview of existing experimental and modelling approaches to determine effective diffusion coefficients of water saturated ordinary Portland cement-based materials. A dataset for diffusivity obtained from different experimental techniques have been presented for cement paste, mortar and concrete. For cement paste at low porosities, diffusivity reported by different authors varies up to a factor of five and electrical resistivity measurements for low Capillary Porosity are up to one order of magnitude higher compared to other techniques. Experimental data of mortar and concrete reveals predominant influence of increasing tortuosity due to aggregates and limited influence of interface transition zone. Hence, a particular emphasis has been placed on assessing predictability of diffusivity models for cement paste on a larger dataset collected in this paper. It has been observed that all predictive models have similar level of accuracy and fail to predict electrical resistivity data at low Capillary Porosity as these models are not calibrated using electrical resistivity data.
