The Experts below are selected from a list of 1771020 Experts worldwide ranked by ideXlab platform

Feng Xing - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of carbon fiber reinforced cementitious matrix as a recyclable strengthening Material
    Journal of Cleaner Production, 2019
    Co-Authors: Wan-qian Li, Feng Xing, Ji-hua Zhu, Pi-yu Chen, Dawang Li, Mei-ni Su
    Abstract:

    Abstract The use of fiber-reinforced polymer (FRP)-epoxy resin is a common retrofitting technique usually employed by engineers. In the research presented in this paper, a new Cement-Based Material was developed introducing chopped carbon fiber. The carbon-fiber-reinforced cementitious matrix (C-FRCM) containing a Cement-Based matrix and embedded carbon-fiber mesh is an alternative solution to FRP-epoxy resin, addressing cost, durability, and reversibility issues. The flexural performance of carbon-fiber-reinforced cementitious matrix plates with chopped carbon fibers was explored in this study. A series of three-point bending tests were conducted to investigate the effects of chopped carbon fiber content. The measured mechanical properties of the proposed C-FRCM mix were compared with those made of commercial formulations. The flexural strengths and failure modes of the carbon-fiber-reinforced cementitious matrix plates were obtained and recorded during tests, and then the interlaminar shear strengths were calculated. Upon the completion of three-point bending tests, scanning electron microscopy was used to observe the microscopic appearance of tested specimens. The optimum content of chopped carbon fibers in the Cement-Based Materials was determined based on the structural behavior and microstructural analysis. The results also show that the carbon fiber mesh is effective in strengthening the carbon-fiber-reinforced cementitious matrix.

  • damping property of a cement based Material containing carbon nanotube
    Journal of Nanomaterials, 2015
    Co-Authors: Yi Liu, Feng Xing, Y F Liu
    Abstract:

    This study aimed to explore the damping property of a Cement-Based Material with carbon nanotube (CNT). In the study, the cement composites with different contents of CNT (0 wt%, 0.033 wt%, 0.066 wt%, and 0.1 wt%) were investigated. Logarithmic Decrement method and Dynamic Mechanical Analysis (DMA) method were utilized to study the damping property of CNT/cement composite. The influences of CNT on pore size distribution and microstructure of composite were analyzed by Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscopy (SEM), respectively. The experimental results showed that CNT/cement composite presented higher flexural strength index than that of a pure cement paste. Additional CNT could improve the vibration-reduction capacity of cement paste. Furthermore, the experiments proved that CNT could bridge adjacent hydration products and support load transfer within cement matrix, which contributed to the energy dissipation during the loading process.

  • Investigation on the mechanical properties of a Cement-Based Material containing carbon nanotube under drying and freeze-thaw conditions
    Materials, 2015
    Co-Authors: Wei Wen Li, Yi Liu, Wei Ming Ji, Yao Cheng Wang, Ruo Xu Shen, Feng Xing
    Abstract:

    © 2015 by the authors. This paper aimed to explore the mechanical properties of a Cement-Based Material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT) could improve to different degrees the mechanical properties (compressive and flexural strengths) and physical performances (shrinkage and water loss) of Cement-Based Materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for Cement-Based Materials, as well as the density of Materials due to CNT's filling action.

  • cement based piezoelectric ceramic composite and its sensor applications in civil engineering
    Aci Materials Journal, 2011
    Co-Authors: Biqin Dong, Feng Xing
    Abstract:

    In this study, a new kind of mechanical sensor for application in civil engineering is achieved by introducing piezoelectric ceramic into cement Material, which can be used to monitor real-time structural health and provide instantaneous information on a condition of a specified structure. It is especially ideal for situ-dynamic measurement for a concrete structure, as it combines the high piezoelectric activity of piezoelectric ceramic and high mechanical properties of Cement-Based Material. From the experimental results, a linear mechanic-electrical relationship is obtained. It is believed that Cement-Based piezoelectric ceramic composites hold a great application potential in civil engineering.

  • Cement-Based piezoelectric ceramic composite and its sensor applications in civil engineering
    ACI Materials Journal, 2011
    Co-Authors: Biqin Dong, Feng Xing, Zongjin Li
    Abstract:

    In this study, a new kind of mechanical sensor for application in civil engineering is achieved by introducing piezoelectric ceramic into cement Material, which can be used to monitor real-time structural health and provide instantaneous information on a condition of a specified structure. It is especially ideal for situ-dynamic measurement for a concrete structure, as it combines the high piezoelectric activity of piezoelectric ceramic and high mechanical properties of Cement-Based Material. From the experimental results, a linear mechanic-electrical relationship is obtained. It is believed that Cement-Based piezoelectric ceramic composites hold a great application potential in civil engineering. Copyright © 2011, American Concrete Institute. All rights reserved.

Chunsheng Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Indirect assessment of hydraulic diffusivity and permeability for unsaturated Cement-Based Material from sorptivity
    Cement and Concrete Research, 2016
    Co-Authors: Chunsheng Zhou, Wei Chen, Wei Wang, Frédéric Skoczylas
    Abstract:

    The hydraulic diffusivity, water permeability and relative gas permeability for Cement-Based Materials are indirectly evaluated from measured sorptivity and water vapor sorption isotherms (WVSIs). The dependence of sorptivity on initial saturation degree is first established to help calculate hydraulic diffusivity and other transport properties. An experimental program with a self-scaled preconditioning strategy is also carefully designed and conducted on three concretes to measure their sorptivity, WVSIs as well as permeability to various fluids. It's found that hydraulic diffusivity of ambiguous physical significance may be not a good durability indicator. The predicted water permeability is larger than measured value but at the same order of magnitude. This overestimation is attributed to the required drying preconditioning. The predicted relative water permeability agrees well with reported data. However, the predicted relative gas permeability agrees with the measured data from classical CEMBUREAU method better than that from tri-axial permeameter with higher inlet gas pressure.

  • Unified determination of relative molecular diffusivity and fluid permeability for partially saturated Cement-Based Materials
    Cement and Concrete Research, 2015
    Co-Authors: Chunsheng Zhou, Wei Chen, Wei Wang, Frédéric Skoczylas
    Abstract:

    From conductivity theory, general models for relative molecular diffusivity and fluid permeability are first derived with unknown tortuosity function and modification coefficient, which can be respectively deduced from hydraulic diffusivity and water retention curve (WRC). Based on empirical laws for hydraulic diffusivity and WRC of Cement-Based Material, unified models for relative molecular diffusivity and fluid permeability are further formulated with only two measurable parameters. Because of practical difficulty for measuring water permeability and pure gaseous molecular diffusivity, only relative gas permeability and relative chloride diffusivity models are verified by the reported data. It is found that the predicted relative gas permeability agrees with measured values and exponential law is a little more preferable than power law for quantifying hydraulic diffusivity. Moreover, relative chloride diffusivity from the unified model also agrees well with experimental data derived via Nernst–Einstein Equation. However, the unified model doesn't capture the possibly overestimated relative chloride diffusivity from Fick's law.

  • predicting water permeability and relative gas permeability of unsaturated cement based Material from hydraulic diffusivity
    Cement and Concrete Research, 2014
    Co-Authors: Chunsheng Zhou
    Abstract:

    In this paper, unsaturated water permeability and relative gas permeability of Cement-Based Materials are predicted indirectly. First, the theoretical relationship between water permeability and hydraulic diffusivity is thoroughly analyzed, which leads to a new restriction on capacity function, the first derivative of water retention curve (WRC) model. To comply with this restriction, a new WRC model is then proposed, based on which unsaturated water permeability can be easily estimated from hydraulic diffusivity. Furthermore, the relative gas permeability is evaluated from relative water permeability through their relationship. The proposed WRC model is validated with measured water retention data of various Cement-Based Materials. Moreover, predicted relative gas permeability agrees with reported testing results very well. Additionally, the influence of fitting parameters of the WRC model and shape parameter, which determines the shape of hydraulic diffusivity, is investigated. It is found that they have rather limited effects on relative water and gas permeability.

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

  • in situ ca oh 2 consumption of teos on the surface of hardened cement based Materials and its improving effects on the ca leaching and sulfate attack resistivity
    Construction and Building Materials, 2016
    Co-Authors: Pengkun Hou, Xin Cheng, Rui Zhang, Yamei Cai, Surendra P Shah
    Abstract:

    Abstract Ca(OH)2 (CH) is a critical constituent that influences the durability of Cement-Based Materials. By taking the advantages of the in situ hydrolysis of tetraethoxysilane, TEOS, and the in situ consumption of CH at the surface of hardened Cement-Based Material, this work studied the effects of TEOS-treatment on the CH-related durability, i.e., the calcium-leaching and sulfate-attack resistivity. Results suggested that TEOS can penetrate into hardened Cement-Based Material more easily than water. Thermogravimetric analysis showed that TEOS consumed CH on the surface of hardened Cement-Based Material, resulting in a gradient distribution of CH, and benefited the CH-related durability. The loss of compressive strength of mortar samples suffering decalcification was reduced by TEOS-treatment, and the lower Ca-leaching of the TEOS-treated sample introduced by the reduction of CH content and the polymerization of C-S-H gel (shown by NMR results) could be two of the critical reasons. XRD results showed that the formation of the gypsum on the surface of Cement-Based Material that cured in Na2SO4 solution could be reduced by the in situ consumption of CH of TEOS, which benefited the reduction of the loss of the compressive strength in the corrosive environment. It can be deduced from this study that the in situ consumption of CH of TEOS on the surface of hardened Cement-Based Material would favor the improvement of the durability, showing its potential for surface-treatment of hardened Cement-Based Material.

  • effects and mechanisms of surface treatment of hardened cement based Materials with colloidal nanosio2 and its precursor
    Construction and Building Materials, 2014
    Co-Authors: Xin Cheng, Jueshi Qian, Surendra P Shah
    Abstract:

    Abstract A dense surface structure of Cement-Based Material is important for its resistance to the impacts of environment. Effectiveness and mechanisms of colloidal nanoSiO2 (CNS) and its precursor, tetraethoxysilane (TEOS), on surface-treatment of the one-month-old cement mortar by brushing technique were studied in this work. It revealed that CNS decreases the water absorption ratio of mortar when cured at 50 °C and/or in sealed condition, but its effect is negligible when samples are cured at 20 °C. A greater reduction of water absorption ratio is found in TEOS-treated mortar at 20 °C or 50 °C and under sealed or unsealed condition. Pozzolanic reaction between CNS/TEOS and Ca(OH)2 was observed by XRD, IR and EDS techniques. In addition, filler effects as revealed by SEM/EDS techniques were ascribed to for the densification of the exposed hardened mortar. Pore size distribution analysis conducted on mercury intrusion porosimeter showed that TEOS is more effective than CNS in filling pores finer than 50 nm, while CNS is found effective in filling capillary pores coarser than 50 nm.

Tulio Honorio - One of the best experts on this subject based on the ideXlab platform.

  • monte carlo molecular modeling of temperature and pressure effects on the interactions between crystalline calcium silicate hydrate layers
    Langmuir, 2019
    Co-Authors: Tulio Honorio
    Abstract:

    The interactions of calcium silicate hydrates with water are at the heart of critical features of Cement-Based Material behavior such as drying and autogenous shrinkage, hysteresis, creep, and ther...

  • Monte Carlo Molecular Modeling of Temperature and Pressure Effects on the Interactions between Crystalline Calcium Silicate Hydrate Layers
    2019
    Co-Authors: Tulio Honorio
    Abstract:

    The interactions of calcium silicate hydrates with water are at the heart of critical features of Cement-Based Material behavior such as drying and autogenous shrinkage, hysteresis, creep, and thermal expansion. In this article, the interactions between nanocrystalline layers of calcium silicate hydrates are computed from grand canonical Monte Carlo molecular simulations. The effects of temperature, chemical potential, and pressure on these interactions are studied. The results are compared with simulation and experimental data found in the literature concerning surface energy, cohesive pressure, and out-of-plane elastic properties. The disjoining pressure isotherms of calcium silicate hydrates are negligibly affected by changes in water pressure under saturated conditions. The surface energy decreases with the temperature, the chemical potential of water, and the water pressure. Coarse-grained simulations are performed using the potential of mean force obtained at the molecular level. The mesostructure presents hysteresis with respect to mechanical and thermal loads. The anharmonicity of the interactions identified at the molecular scale translates to an asymmetry tension/compression and thermal expansion that are also observed at the mesoscale. These results leave room for a better understanding of the multiscale origin of physical properties of calcium silicate hydrates

Frédéric Skoczylas - One of the best experts on this subject based on the ideXlab platform.

  • Indirect assessment of hydraulic diffusivity and permeability for unsaturated Cement-Based Material from sorptivity
    Cement and Concrete Research, 2016
    Co-Authors: Chunsheng Zhou, Wei Chen, Wei Wang, Frédéric Skoczylas
    Abstract:

    The hydraulic diffusivity, water permeability and relative gas permeability for Cement-Based Materials are indirectly evaluated from measured sorptivity and water vapor sorption isotherms (WVSIs). The dependence of sorptivity on initial saturation degree is first established to help calculate hydraulic diffusivity and other transport properties. An experimental program with a self-scaled preconditioning strategy is also carefully designed and conducted on three concretes to measure their sorptivity, WVSIs as well as permeability to various fluids. It's found that hydraulic diffusivity of ambiguous physical significance may be not a good durability indicator. The predicted water permeability is larger than measured value but at the same order of magnitude. This overestimation is attributed to the required drying preconditioning. The predicted relative water permeability agrees well with reported data. However, the predicted relative gas permeability agrees with the measured data from classical CEMBUREAU method better than that from tri-axial permeameter with higher inlet gas pressure.

  • Unified determination of relative molecular diffusivity and fluid permeability for partially saturated Cement-Based Materials
    Cement and Concrete Research, 2015
    Co-Authors: Chunsheng Zhou, Wei Chen, Wei Wang, Frédéric Skoczylas
    Abstract:

    From conductivity theory, general models for relative molecular diffusivity and fluid permeability are first derived with unknown tortuosity function and modification coefficient, which can be respectively deduced from hydraulic diffusivity and water retention curve (WRC). Based on empirical laws for hydraulic diffusivity and WRC of Cement-Based Material, unified models for relative molecular diffusivity and fluid permeability are further formulated with only two measurable parameters. Because of practical difficulty for measuring water permeability and pure gaseous molecular diffusivity, only relative gas permeability and relative chloride diffusivity models are verified by the reported data. It is found that the predicted relative gas permeability agrees with measured values and exponential law is a little more preferable than power law for quantifying hydraulic diffusivity. Moreover, relative chloride diffusivity from the unified model also agrees well with experimental data derived via Nernst–Einstein Equation. However, the unified model doesn't capture the possibly overestimated relative chloride diffusivity from Fick's law.