The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jean-pierre Korb - One of the best experts on this subject based on the ideXlab platform.
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comparison of proton field cycling relaxometry and molecular dynamics simulations for proton water surface dynamics in Cement based materials
Cement and Concrete Research, 2007Co-Authors: Jean-pierre Korb, P J Mcdonald, L Monteilhet, Andrey G Kalinichev, R J KirkpatrickAbstract:Diffusion coefficients of water in Hydrated Cement pastes and mortars obtained from proton field cycling NMR spin lattice relaxation over three orders of magnitude in magnetic field strength are in good agreement with values from molecular dynamics simulations of water on the surface of tobermorite. The level of agreement from these two independent approaches provides mutual support for their validity.
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Microstructure evolution of Hydrated Cement pastes.
Physical Review E, 2005Co-Authors: A Plassais, Mariepierre Pomies, F. Barberon, Jean-pierre Korb, Dominique Petit, Nicolas Lequeux, Bruno BressonAbstract:We propose an original method based on both proton nuclear magnetic relaxation dispersion and highresolution NMR spectra to investigate the microstructure of synthesized Ca3SiO5-Hydrated Cement paste. This method allows a clear assessment of the local proton chemical sites as well as the determination of dynamical information of moving proton species in pores. We show also how the microstructure evolves during and after completion of hydration in a range of length scales between 2 and 500 nm. In particular, we show how the pore size distribution of the Cement paste reaches progressively a power-law characteristic of a surface-fractal distribution with a dimension Df = 2.6, which takes into account the hierarchical order in the material. Last, we study how this pore size distribution is modified during setting by varying either the water-to-Cement ratio or addition of ultrafine particles. This shows that our method could be relevant to relate the mechanical properties to the microstructure of the material. This proposed NMR method is general enough for the characterization of microstructure of any porous media with reactive surface involving water confinement.
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micropore size analysis in Hydrated Cement paste by nmr
Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule C-chimie, 2001Co-Authors: A Plassais, Mariepierre Pomies, Jean-pierre Korb, Philippe Boch, Nicolas Lequeux, Dominique PetitAbstract:Abstract We present a time evolution of 1 H spin-lattice relaxation rates in the laboratory (1/ T 1 ) and in the rotating (1/ T 1ρ ) frame of a synthetic Cement paste. The typical results found for both rates allow us to follow the main hydration stages of the Cement paste and the refinement of its microporosity. In particular the texturation of the porosity and the structuration of the surface of the material are evidenced on two model Cement pastes. An interpretation in terms of fractal size distribution is considered as well as the effect of the curing temperature.
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micropore size analysis in Hydrated Cement paste by nmr
Magnetic Resonance Imaging, 2001Co-Authors: A Plassais, Mariepierre Pomies, Philippe Boch, Nicolas Lequeux, Jean-pierre KorbAbstract:Abstract We present a time evolution of 1H spin-lattice relaxation rates in the laboratory (1/T1) and in the rotating frame (1/T1ρ) of a synthetic Cement paste. The typical results found for both rates allows us to follow the main hydration stages of the Cement paste and the refinement of its microporosity. In particular the texturation of the porosity and the structuration of the surface of the material is evidenced.
P J Sereda - One of the best experts on this subject based on the ideXlab platform.
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mechanism of the carbonatation shrinkage of lime and Hydrated Cement
Journal of Chemical Technology & Biotechnology, 2007Co-Authors: E G Swenson, P J SeredaAbstract:Carbonatation of Hydrated lime compacts produces shrinkage and changes in mechanical properties comparable with those found in similarly treated compacts of bottle-Hydrated Cement and samples of hardened Portland Cement paste. From experimental results obtained with the simpler lime system a mechanism for carbonatation shrinkage is proposed that postulates a through-solution reaction and induced cycles of wetting and drying. Experiments on compacts of bottle-Hydrated Cement show that carbonatation of the ‘combined lime’ is at least as rapid and extensive as the carbonatation of the ‘free lime,’ and that contrary to current opinion the former reaction results in even greater carbonatation shrinkage. The mechanism for carbonatation shrinkage of this system is considered to be connected with dehydration and polymerisation of the hydrous silica product of carbonatation.
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sorption of water on compacts of bottle Hydrated Cement i the sorption and length change isotherms
Journal of Chemical Technology & Biotechnology, 2007Co-Authors: R F Feldman, P J SeredaAbstract:To obtain information with regard to the porous structure of Hydrated Cement and the extent of its interaction with water, sorption and length-change isotherms were determined for this material. Compacts of bottle-Hydrated Cement were brought to equilibrium in a high-vacuum system at various humidities, and measurements of the changes in length and weight during this process, were made to draw the isotherms. Results showed that this system is basically similar to systems composed of other porous materials, although complicated by a discontinuity in the adsorption part of the cycle and a secondary hysteresis. It is considered that these characteristics are related and are the result of water associated with the system by a process other than physical adsorption. It is also shown that menisci exist in the system on desorption to as low as 31% R.H. and cause considerable contraction. A surface-area calculation by a new method for estimating the zero adsorbed water yield a value of 80·6 m.2/g.
Hamlin M Jennings - One of the best experts on this subject based on the ideXlab platform.
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structural changes to the calcium silicate hydrate gel phase of Hydrated Cement with age drying and resaturation
Journal of the American Ceramic Society, 2008Co-Authors: Jeffrey J Thomas, Andrew J Allen, Hamlin M JenningsAbstract:The effects of drying to various relative humidity (RH) levels on the internal structure of Hydrated Cement paste were investigated using small-angle neutron scattering (SANS). Specimens of young and mature portland Cement paste were analyzed in the initial saturated state, in the dried state, and then again after resaturation, allowing reversible and irreversible effects to be separated. While the observed changes on drying are mainly physical in nature, the ability of the microstructure to resist permanent structural rearrangement increased over time as the hydration and aging reactions progressed. Permanent changes to the nanometer-to-micrometer scale microstructure induced by drying were quantified by applying a fractal model to the SANS data for resaturated pastes. At RH levels above ≈54%, capillary stresses compact the nanometer-level pore structure of the calcium–silicate–hydrate (C–S–H) gel phase, increasing the gel density by a mechanism related to that governing the classical “constant rate period” for pure gels. Owing to the restraining effects of the other solid phases in Cement paste, this decrease in the volume of the C–S–H gel also increases the intensity of surface fractal scattering that arises from the deposition of hydration product onto the surface of the reacting Cement particles. At all RH levels, but particularly below 54%, drying decreases the measured total internal surface area of the specimens. This is attributed to a loss of surface area at particle contacts as the average separation distance between adjacent C–S–H gel nanoparticles decreases on drying.
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Effect of Heat Treatment on the Pore Structure and Drying Shrinkage Behavior of Hydrated Cement Paste
Journal of the American Ceramic Society, 2002Co-Authors: Jeffrey J Thomas, Hamlin M JenningsAbstract:The effect of a short heat treatment on Hydrated Cement paste has been investigated by measuring the weight and length changes of specimens as they undergo various combinations of heating, drying, and resaturation. Heating a Cement paste to 60°C coarsens the capillary pore system, decreases the volume of mesopores, and increases the degree of polymerization of the silicates. In addition, the saturated weight of the paste is permanently decreased by a heat treatment. This weight loss can be explained by conversion of bound hydroxyl groups into liquid water during polymerization of the C-S-H gel phase. These experiments help reconcile and interpret published results describing the properties of Cement cured at various temperatures, the effects of a short heat treatment on Cement paste, and the thermal expansion behavior of saturated and dry Cement paste.
Hamid Nikraz - One of the best experts on this subject based on the ideXlab platform.
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characterisation analysis and design of Hydrated Cement treated crushed rock base as a road base material in western australia
Journal of civil engineering and architecture, 2012Co-Authors: Peerapong Jitsangiam, Hamid Nikraz, Komsun Siripun, Suphat ChummuneeratAbstract:Hydrated Cement Treated Crushed Rock Base (HCTCRB) is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests (RLT tests) were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion (c) and 42° for the internal friction angle (). The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle (ESA) of 10 million.
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performances of Hydrated Cement treated crushed rock base for western australian roads
Proceedings of the ISAP 2012 International Symposium on Heavy Duty Asphalt Pavements and Bridge Deck Pavements, 2012Co-Authors: Suphat Chummuneerat, Peerapong Jitsangiam, Hamid NikrazAbstract:Abstract: The resilient modulus (RM) of Hydrated Cement treated crushed rock base (HCTCRB) affected by amount of hydration periods, compaction and dryback processes was presented using repeated load triaxial tests. The related trends of RM corresponding to the different hydration periods still cannot be concluded. Instead, It is found that the moisture content plays more major influence on the RM performance. Higher additional water during compaction of HCTCRB, even at its optimum moisture content and induced higher dry density, led to the inferior RM performance compared to the sample without water addition. The RM of damper samples can be improved through dryback process and superior to that of the sample without water addition at the same moisture content. However, the samples without water addition during compaction deliver the comparable RM values even its dry density is lower than the other two types. These results indicate the significant influence of moisture content to the performances of HCTCRB with regardless of the dry density. Finally, the experimental results of HCTCRB and parent material are evaluated with the K - θ model and the model recommended by Austroads. These two models provide the excellent fit of the tested results with high degree of determination.
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characterization of Hydrated Cement treated crushed rock base as a road base material in western australia using disturbed state concept
2nd International Conference on Transportation Geotechnics (ICTG)International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE), 2012Co-Authors: Pakdee Khobklang, Vanissorn Vimonsatit, Peerapong Jitsangiam, Hamid NikrazAbstract:Hydrated Cement Treated Crushed Rock Base (HCTCRB) is normally used as base course material to design road pavement in Western Australia. HCTCRB has been used and designed based on practical experience and empirical approach but these cannot explain the behavior of HCTCRB base course. Currently, analysis and design and behavior of structural pavement can be more reliable and more understood by the use of a mechanistic approach, one of which is the Disturbed State Concept (DSC). The purpose of this study is to assess the mechanical characteristics of HCTCRB by modeling the results of laboratory tests using DSC. Conventional triaxial tests and Repeated Load Triaxial (RLT) tests, following the Austroads—APRG 00/33 test standard, were performed and the experimental results were used to construct the DSC equation for HCTCRB. Also, the effect of moisture content on the behavior of HCTCRB was investigated. The results reveal that the resilient modulus characteristics of HCTCRB can be modeled by the use of the proposed DSC equation.
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performance of Hydrated Cement treated crushed rock base as a road base material in western australia
Proceedings of the 11th Australia - New Zealand Conference on Geomechanics (ANZ 2012), 2012Co-Authors: Suphat Chummuneerat, Peerapong Jitsangiam, Hamid NikrazAbstract:Hydrated Cement Treated Crushed Rock Base (HCTCRB) is produced by adding 2%-Portland Cement with standard crushed rock base. The mixture is disturbed after the specific hydration period to prevent setting up and retain its unbound property. HCTCRB has been commonly adopted for Western Australian roads, however based on empirical method and experiences. Thus, the characterisation of HCTCRB following the pavement mechanistic approach is needed. This paper aims to presents the performances of HCTCRB in terms of permanent deformation and resilient modulus. The repeated load triaxial tests were performed to study the performances of HCTCRB that affected by manufacturing (hydration period) and construction procedures (amount of water added during compaction and dry back). This study has found that HCTCRB exhibited the stress dependent behaviour. All these studied factors significantly affect the resilient performances of HCTCRB in dissimilar trends. The certain impact on the material performances related to the hydration periods still could not be concluded. The higher water addition even at the optimum moisture content of HCTCRB resulted in the poorer performances, although it induced the higher dry density, which indicated that the HCTCRB is still susceptibility to moisture content. The dryback process has potential to improve the material performances of the material in different level which depends on amount of additional water. All the tested results indicated the significant influence of moisture content to the performances of HCTCRB with regardless of the dry density.
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resilient modulus of Hydrated Cement treated crushed rock base hctcrb for road base material in western australia
Proceedings of the International Conference on HighwayEngineering 2012, 2012Co-Authors: Suphat Chummuneerat, Peerapong Jitsangiam, Hamid NikrazAbstract:Hydrated Cement Treated Crushed Rock Base (HCTCRB) is a modified base course material, with anadditional of 2% Portland Cement (by mass) to a standard crushed rock base. Based on the HCTCRB application protocol, the mix is retreated after hydration to avoid producing the base course material as a bound material. HCTCRB has been usually implemented to the Western Australian road networks based on empirical design and application with experiences. Accordingly, the material characterisation of HCTCRB in accordance with the pavement mechanistic approach is strongly required to understand its behaviours and performances under the service stage. This paper aims to present the mechanical behaviour of HCTCRB resulting from the repeated load triaxial tests. Testing results of HCTCRB in terms of resilient modulus (MR) were investigated and compared to that of standard crushed rock. It wasfound that HCTCRB technique greatly improved the performance of the parent materials about triple. The results also indicated that the hydration periods significantly affected the performances of HCTCRB. CRB and HCTCRB samples exhibited the stress dependences. Generally, the deviator and confining stresses considerable affected the resilient responses of the materials as the increase of the applied stresses resulted in the higher MR values but lower incremental rates of MR. At constant confining pressure, the MR increased with increasing deviator stresses. However, the incremental rates decreased at higher levels of confinements. Similarly, at constant deviator stress, the MR climbed upwith higher confining stresses and the rates of increase were less pronounced at higher deviator stress levels. Several constitutive models for determining the MR were examined based on the laboratory results. These evaluations suggest that the K-model is still useful for modelling of these materials due to its simplicity and high degree of determination.
A Plassais - One of the best experts on this subject based on the ideXlab platform.
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Microstructure evolution of Hydrated Cement pastes.
Physical Review E, 2005Co-Authors: A Plassais, Mariepierre Pomies, F. Barberon, Jean-pierre Korb, Dominique Petit, Nicolas Lequeux, Bruno BressonAbstract:We propose an original method based on both proton nuclear magnetic relaxation dispersion and highresolution NMR spectra to investigate the microstructure of synthesized Ca3SiO5-Hydrated Cement paste. This method allows a clear assessment of the local proton chemical sites as well as the determination of dynamical information of moving proton species in pores. We show also how the microstructure evolves during and after completion of hydration in a range of length scales between 2 and 500 nm. In particular, we show how the pore size distribution of the Cement paste reaches progressively a power-law characteristic of a surface-fractal distribution with a dimension Df = 2.6, which takes into account the hierarchical order in the material. Last, we study how this pore size distribution is modified during setting by varying either the water-to-Cement ratio or addition of ultrafine particles. This shows that our method could be relevant to relate the mechanical properties to the microstructure of the material. This proposed NMR method is general enough for the characterization of microstructure of any porous media with reactive surface involving water confinement.
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micropore size analysis in Hydrated Cement paste by nmr
Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule C-chimie, 2001Co-Authors: A Plassais, Mariepierre Pomies, Jean-pierre Korb, Philippe Boch, Nicolas Lequeux, Dominique PetitAbstract:Abstract We present a time evolution of 1 H spin-lattice relaxation rates in the laboratory (1/ T 1 ) and in the rotating (1/ T 1ρ ) frame of a synthetic Cement paste. The typical results found for both rates allow us to follow the main hydration stages of the Cement paste and the refinement of its microporosity. In particular the texturation of the porosity and the structuration of the surface of the material are evidenced on two model Cement pastes. An interpretation in terms of fractal size distribution is considered as well as the effect of the curing temperature.
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micropore size analysis in Hydrated Cement paste by nmr
Magnetic Resonance Imaging, 2001Co-Authors: A Plassais, Mariepierre Pomies, Philippe Boch, Nicolas Lequeux, Jean-pierre KorbAbstract:Abstract We present a time evolution of 1H spin-lattice relaxation rates in the laboratory (1/T1) and in the rotating frame (1/T1ρ) of a synthetic Cement paste. The typical results found for both rates allows us to follow the main hydration stages of the Cement paste and the refinement of its microporosity. In particular the texturation of the porosity and the structuration of the surface of the material is evidenced.
