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Surendra P Shah - One of the best experts on this subject based on the ideXlab platform.

  • nanoscratch study of the modification effects of nanosio2 on c s h gel Cement Grain interfaces
    2017
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    AbstractThe modification effects of nanoSiO2 on properties of the interface region between Cement Grain and C─ S─ H gel in Cement-based composites are investigated by means of the nanoscratch techn...

  • nanomechanical properties of c s h gel Cement Grain interface by using nanoindentation and modulus mapping
    2015
    Co-Authors: Jing Xu, David J Corr, Surendra P Shah
    Abstract:

    Investigation on the mechanical properties of Cement-based materials at micron and sub-micron scales is important for understanding its overall performance. Recent progress in experimental nanomechanics opens new access to nano-engineering of Cement-based composites. In this study, nanoindentation and viscoelastic modulus mapping were employed to study the interfacial properties. The interface width measured by modulus mapping was around 250 nm as compared to a rough estimation of less than 5 µm by nanoindentation, due to the fact that 2 orders of magnitude increase in spatial resolution could be achieved by modulus mapping. Both the nanoindetation and modulus mapping results indicated that the modulus of the interface falls between 60–70 GPa. The packing density in the interface was non-uniform as two peaks of value were observed for the storage modulus distribution. This interface could be regarded as a dense hydration coating around Cement Grains, which was less permeable and hindered the further hydration of Cement.

  • nanomechanical investigation of the effects of nanosio2 on c s h gel Cement Grain interfaces
    2015
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    Abstract In this paper, nanoindentation and viscoelastic modulus mapping were employed to study the influence of nanoSiO2 on the properties of the interface between C–S–H gel and Cement Grains. The interface width measured by modulus mapping was around 200 nm as compared to a rough estimation of less than 5 μm by nanoindentation, due to the fact that 2 orders of magnitude increase in spatial resolution can be achieved with modulus mapping. Although the influence of nanoSiO2 on the interface width was not significant, its impact on nanomechanical properties of the interface was marked. The data suggest an improvement of modulus and hardness of the interface by nanoSiO2 in early age. This interface, which could be regarded as a layer surrounding Cement Grains, become denser by the addition of nanoSiO2.

  • application of nanomechanical methods in investigation of c s h gel Cement Grain interface
    2014
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    Investigation on the mechanical properties of Cement-based materials at micron and submicron scales is important for understanding the overall performance, particularly of high-performance concrete (HPC). Due to low water-toCement ratio of HPC, a large amount of unhydrated Cement Grains remain in matrix, and a significant impact of the interface between C–S–H gel and Cement Grains on concrete behavior could be expected. Recent progress in experimental nanomechanics opens new access to nanoengineering of Cement-based composites. In this paper, nanoindentation and viscoelastic modulus mapping were used to study the interfacial properties. The interface width measured by modulus mapping was around 200 nm as compared to a rough estimation of less than 5 μm by nanoindentation, due to the fact that two orders of magnitude increase in spatial resolution could be achieved with modulus mapping.

David J Corr - One of the best experts on this subject based on the ideXlab platform.

  • nanoscratch study of the modification effects of nanosio2 on c s h gel Cement Grain interfaces
    2017
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    AbstractThe modification effects of nanoSiO2 on properties of the interface region between Cement Grain and C─ S─ H gel in Cement-based composites are investigated by means of the nanoscratch techn...

  • nanomechanical properties of c s h gel Cement Grain interface by using nanoindentation and modulus mapping
    2015
    Co-Authors: Jing Xu, David J Corr, Surendra P Shah
    Abstract:

    Investigation on the mechanical properties of Cement-based materials at micron and sub-micron scales is important for understanding its overall performance. Recent progress in experimental nanomechanics opens new access to nano-engineering of Cement-based composites. In this study, nanoindentation and viscoelastic modulus mapping were employed to study the interfacial properties. The interface width measured by modulus mapping was around 250 nm as compared to a rough estimation of less than 5 µm by nanoindentation, due to the fact that 2 orders of magnitude increase in spatial resolution could be achieved by modulus mapping. Both the nanoindetation and modulus mapping results indicated that the modulus of the interface falls between 60–70 GPa. The packing density in the interface was non-uniform as two peaks of value were observed for the storage modulus distribution. This interface could be regarded as a dense hydration coating around Cement Grains, which was less permeable and hindered the further hydration of Cement.

  • nanomechanical investigation of the effects of nanosio2 on c s h gel Cement Grain interfaces
    2015
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    Abstract In this paper, nanoindentation and viscoelastic modulus mapping were employed to study the influence of nanoSiO2 on the properties of the interface between C–S–H gel and Cement Grains. The interface width measured by modulus mapping was around 200 nm as compared to a rough estimation of less than 5 μm by nanoindentation, due to the fact that 2 orders of magnitude increase in spatial resolution can be achieved with modulus mapping. Although the influence of nanoSiO2 on the interface width was not significant, its impact on nanomechanical properties of the interface was marked. The data suggest an improvement of modulus and hardness of the interface by nanoSiO2 in early age. This interface, which could be regarded as a layer surrounding Cement Grains, become denser by the addition of nanoSiO2.

  • application of nanomechanical methods in investigation of c s h gel Cement Grain interface
    2014
    Co-Authors: David J Corr, Surendra P Shah
    Abstract:

    Investigation on the mechanical properties of Cement-based materials at micron and submicron scales is important for understanding the overall performance, particularly of high-performance concrete (HPC). Due to low water-toCement ratio of HPC, a large amount of unhydrated Cement Grains remain in matrix, and a significant impact of the interface between C–S–H gel and Cement Grains on concrete behavior could be expected. Recent progress in experimental nanomechanics opens new access to nanoengineering of Cement-based composites. In this paper, nanoindentation and viscoelastic modulus mapping were used to study the interfacial properties. The interface width measured by modulus mapping was around 200 nm as compared to a rough estimation of less than 5 μm by nanoindentation, due to the fact that two orders of magnitude increase in spatial resolution could be achieved with modulus mapping.

Zhigang Zhu - One of the best experts on this subject based on the ideXlab platform.

  • diffusivity of Cement paste via a continuum based microstructure and hydration model influence of Cement Grain shape
    2021
    Co-Authors: Zhigang Zhu, Huisu Chen, Yuan Wang, Xiaofan Gou, Lin Liu
    Abstract:

    Abstract A microstructure-guided diffusivity model of Cement paste is devised to explore the dependence of the relative diffusivity on the microstructure evolutions of Cement paste from fresh state via non-spherical Cement particles hydration to hardened state. The microstructure-guided diffusivity model contains three main components: (1) the microstructure of fresh Cement paste is generated to simulate the initial state of non-spherical Cement particles in water; (2) a continuum-based hydration model of non-spherical Cement particles (HYD-NSP) is proposed to describe the evolutions of various phases (hydration products and pores) from fresh state to hardened state; (3) a random walk model is implemented to the microstructures of hydrated Cement paste digitalized at the resolution of 0.1 μm/voxel for the determination of relative diffusivity of Cement paste. Although this study takes five kinds of Platonic particles and sphere as an introductory example, this microstructure-guided model is readily applicable to other complex microstructures induced by the hydration of non-spherical Cement particles. Finally, we utilize the framework to evaluate the influence of the geometrical shape of Cement particles on the hydrated microstructure and relative diffusivity of Cement paste. Results shed light on that the relative diffusivity increases with the increase of sphericity as a shape descriptor of Cement particle. This is due to the specific surface area decreasing with the increase of sphericity, resulting in less hydration products and more porosity, which ultimately increases the relative diffusivity.

Christian Hirsch - One of the best experts on this subject based on the ideXlab platform.

  • impact of zeta potential of early Cement hydration phases on superplasticizer adsorption
    2007
    Co-Authors: Johann Plank, Christian Hirsch
    Abstract:

    The zeta potential of early hydration products of Cement was found to be a key factor for superplasticizer adsorption. A highly positive zeta potential results in a strong superplasticizer adsorption whereas a negative zeta potential does not allow adsorption. Synthetic ettringite precipitated from solution shows a highly positive zeta potential, hence it adsorbs great amounts of negatively charged superplasticizer. Monosulfate (AFm) has a less positive zeta potential. Therefore, it adsorbs smaller amounts of superplasticizers. For syngenite, portlandite and gypsum, the zeta potential is around zero or negative. These phases do not adsorb superplasticizers. Consequently, a hydrating Cement Grain is best represented by a mosaic structure, with superplasticizer molecules mainly adsorbed on ettringite and some on monosulfate and C–S–H nucleated at surface.

  • new model describing distribution of adsorbed superplasticizer on the surface of hydrating Cement Grain
    2007
    Co-Authors: Johann Plank, Panagiotis Chatziagorastou, Christian Hirsch
    Abstract:

    The adsorption behaviour of chemically different superplasticizers, such as melamine formaldehyde sulphite polycondensate(PMS), β-naphthalene sulfonate formaldehyde polycondensate(BNS) and polycarboxylate(PC), on early hydrating Cement phases was studied. For this purpose, pure ettringite(AFt), monosulfate (AFm) and syngenite were prepared. The adsorbed amount and zeta potential of early hydration products were measured. It is found that zeta potential is the key factor determining the amount of superplasticizer absorbed. Synthetic ettringite precipitated from solution shows a highly positive zeta potential, hence it adsorbs great amount of negatively charged superplasticizer. Monosulfate has only a slightly positive zeta potential and adsorbs smaller amounts of superplasticizer. For syngenite, portlandite and gypsum, the zeta potential is around zero or negative. These phases do not adsorb superplasticizers.Consquently, a hydrating Cement Grain is best represented by a mosaic structure, with superplasticizer molecules mainly adsorbed on ettringite spots.

Lin Liu - One of the best experts on this subject based on the ideXlab platform.

  • diffusivity of Cement paste via a continuum based microstructure and hydration model influence of Cement Grain shape
    2021
    Co-Authors: Zhigang Zhu, Huisu Chen, Yuan Wang, Xiaofan Gou, Lin Liu
    Abstract:

    Abstract A microstructure-guided diffusivity model of Cement paste is devised to explore the dependence of the relative diffusivity on the microstructure evolutions of Cement paste from fresh state via non-spherical Cement particles hydration to hardened state. The microstructure-guided diffusivity model contains three main components: (1) the microstructure of fresh Cement paste is generated to simulate the initial state of non-spherical Cement particles in water; (2) a continuum-based hydration model of non-spherical Cement particles (HYD-NSP) is proposed to describe the evolutions of various phases (hydration products and pores) from fresh state to hardened state; (3) a random walk model is implemented to the microstructures of hydrated Cement paste digitalized at the resolution of 0.1 μm/voxel for the determination of relative diffusivity of Cement paste. Although this study takes five kinds of Platonic particles and sphere as an introductory example, this microstructure-guided model is readily applicable to other complex microstructures induced by the hydration of non-spherical Cement particles. Finally, we utilize the framework to evaluate the influence of the geometrical shape of Cement particles on the hydrated microstructure and relative diffusivity of Cement paste. Results shed light on that the relative diffusivity increases with the increase of sphericity as a shape descriptor of Cement particle. This is due to the specific surface area decreasing with the increase of sphericity, resulting in less hydration products and more porosity, which ultimately increases the relative diffusivity.