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Bo Diao - One of the best experts on this subject based on the ideXlab platform.

  • Impact of Cyclic Loading on Chloride Diffusivity and Mechanical Performance of RC Beams under Seawater Corrosion
    Advances in Materials Science and Engineering, 2020
    Co-Authors: Sen Pang, Bo Diao, Yinghua Ye, Shuxin Chen, Xin Wang
    Abstract:

    An experimental study was conducted to investigate the impact of cyclic loading on the mechanical performance and Chloride Diffusivity of RC beams exposed to seawater wet-dry cycles. To induce initial damage to RC beam specimen, cyclic loading controlled by max load and cycles was applied. Then beam specimens underwent 240 wet-dry cycles of seawater. Results show that the Chloride content increased as max load and cycle increased. The Chloride content at steel surface increased approximatively linearly as average crack width increased. Moreover, the max load had more influence on Chloride content at steel surface than cycle. The difference of average Chloride diffusion coefficient between tension and compression concrete was little at uncracked position. Average Chloride diffusion coefficient increased as crack width increased when crack width was less than 0.11 mm whereas the increasing tendency was weak when crack width exceeded 0.11 mm. The residual yield load and ultimate load of RC beams decreased as max load and cycle increased. Based on univariate analysis of variance, the max load had more adverse effect on yield load and ultimate load than cycle.

  • Chloride Diffusivity and service life prediction of fatigue damaged rc beams under seawater wet dry environment
    Construction and Building Materials, 2018
    Co-Authors: Jieqiong Wu, Wuman Zhang, Bo Diao, Yinghua Ye, Dan Wang
    Abstract:

    Abstract The effects of low fatigue load level with lower limit of 0.1 Pu and upper limit of 0.2 Pu or 0.3 Pu on Chloride Diffusivity of RC beams were experimentally studied after 100 times of seawater wet-dry cycles, where Pu is the static ultimate strength of the RC beams and the cycles of fatigue loading was 200,000. Based on the test results, residual service life was also discussed here. Results show that, Chloride Diffusivity was accelerated as fatigue load level increased. When the load level was 0.2, based on Fick’s 2nd law, Chloride diffusion coefficient of tensile concrete was higher than that of compressive concrete, but the result was reverse for the load level of 0.3. Furthermore, based on the Monte-Carlo Method, the predicted residual service life in one-dimensional state of Chloride diffusion would be shortened by 85 percent when the fatigue load level was 0.2, and by 95 percent when fatigue load level was 0.3, compared with that of no fatigue damaged RC beam. The predicted service life in two-dimensional state was about half of that in one-dimensional state. It was concluded that fatigue damage has a more considerable effect on shortening service life of RC structures in Chloride environment.

  • Chloride Diffusivity and service life prediction of rc columns with sustained load under Chloride environment
    Construction and Building Materials, 2018
    Co-Authors: Jieqiong Wu, Papa Niane Faye, Wuman Zhang, Bo Diao
    Abstract:

    Abstract The synthetic effects of crack width and environment actions on Chloride Diffusivity of reinforced concrete (RC) columns were experimentally studied after the alternative action of 300 cycles of freeze-thaw and 75 times of seawater immersion. Cracks and tension strain of concrete were induced by eccentric compression load which was sustained till the alternative action finished. The experimental results show that, when the crack width was less than 0.07 mm, the effect of cracks on Chloride Diffusivity was slight and it could be neglected. When the crack width was more than 0.07 mm, cracks accelerated the Chloride Diffusivity and the synthetic effects of crack and environment on Chloride Diffusivity was bigger than tension strain. Furthermore, Chloride diffusion in one-dimensional and two-dimensional state was respectively considered. And the corresponding service life of RC columns were predicted by Monte-Carlo Method. It was concluded that crack width significantly expedited Chloride Diffusivity and shortened the service life of RC structures in cold coastal regions or deicing condition.

Jianjun Zheng - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation and analytical modeling of Chloride Diffusivity of fly ash concrete
    Materials, 2020
    Co-Authors: Jian Zhang, Xin-zhu Zhou, Jianjun Zheng, Hailong Ye, Jin Yang
    Abstract:

    Owing to its importance in the assessment of reinforced concrete structures, it is essential to determine the Chloride Diffusivity of fly ash concrete. This paper presents an investigation into the diffusion characteristics of Chloride ions in fly ash concrete. Through experiment, the relationship between Chloride Diffusivity and curing age up to 1800 days is measured and the effects of curing age, water/binder ratio, aggregate volume fraction, and fly ash content (i.e., percentage of total cementitious material by mass) on Chloride Diffusivity are evaluated. It is found that the Chloride Diffusivity decreases with the increase of curing age, aggregate volume fraction, and fly ash content, but increases with the increase of water/binder ratio. In analytical modeling, an equivalent aggregate model is constructed and the equivalent interfacial transition zone (ITZ) thickness is derived analytically. With the equivalent aggregate model, three-phase fly ash concrete reduces to a two-phase composite material. By extending the Maxwell method, the Chloride Diffusivity of fly ash concrete is formulated. Finally, the validity of the analytical method is verified by experimental results.

  • numerical method for predicting Chloride Diffusivity of mature cement paste
    Journal of Materials in Civil Engineering, 2019
    Co-Authors: Jianjun Zheng, Xin-zhu Zhou, Jian Zhang, Xiaoru Wang
    Abstract:

    AbstractThis paper develops a highly efficient numerical method for estimating the Chloride Diffusivity of mature cement paste. In the method, the two-dimensional microstructure of cement paste is ...

  • A Brownian motion simulation for the Chloride Diffusivity of concrete
    Construction and Building Materials, 2016
    Co-Authors: Jianjun Zheng, Cong-yan Zhang, Xin-zhu Zhou
    Abstract:

    Abstract The purpose of this paper is to present a Brownian motion simulation for the Chloride Diffusivity of concrete. According to stereological theory, the probability density function and cumulative distribution function for the circular aggregates in terms of the number of aggregates are derived. By coating each aggregate with an interfacial transition zone (ITZ) layer of equal thickness, concrete is then reduced to a two-phase composite material, composed of a bulk cement paste and equivalent aggregates. The equivalent ITZ thickness and the Chloride Diffusivity of each equivalent aggregate are formulated in an analytical manner. The Brownian motion simulation is used to compute the Chloride Diffusivity of concrete. Finally, the validity of the numerical simulation is verified with two sets of experimental results and the effects of the aggregate area fraction, the Chloride Diffusivity of ITZ, and the ITZ thickness on the Chloride Diffusivity of concrete are evaluated in a quantitative manner. The paper concludes that the numerical simulation can predict the Chloride Diffusivity of concrete with an average relative error smaller than 6% for the two selected verification examples.

  • random walk algorithm for Chloride Diffusivity of concrete with aggregate shape effect
    Journal of Materials in Civil Engineering, 2016
    Co-Authors: Jianjun Zheng, Cong-yan Zhang, Yufei Wu
    Abstract:

    AbstractOwing to its importance to the assessment and design of reinforced concrete structures, it is essential to determine the Chloride Diffusivity of concrete. This paper develops a random walk algorithm for the Chloride Diffusivity of concrete with the aggregate shape effect. In this algorithm, an equivalent aggregate model is established by coating each aggregate particle with an interfacial transition zone (ITZ) layer and the equivalent ITZ thickness is estimated through stereological analysis. The Chloride Diffusivity of each equivalent aggregate is then formulated by an effective medium approximation. Finally, the random walk algorithm is adopted to compute the Chloride Diffusivity of concrete. After the validity of the simulation algorithm is verified with two sets of experimental data, the effects of the aggregate content, the aggregate aspect ratio, and the ITZ thickness on the Chloride Diffusivity of concrete are evaluated in a quantitative manner. The paper concludes that the random walk algo...

  • experiment and modeling of the effect of aggregate shape on the Chloride Diffusivity of concrete
    Journal of Materials in Civil Engineering, 2014
    Co-Authors: Jianjun Zheng, Xin-zhu Zhou, Xiaofeng Huang, Chuanqing Fu
    Abstract:

    The purpose of this paper is to evaluate the effect of aggregate shape on the Chloride Diffusivity of concrete through laboratory experiments and theoretical analysis. In the experiment, three types of crystal glass spheroids with aspect ratios of 1, 2, and 3 are used as coarse aggregate. The experimental results show that the Chloride Diffusivity of concrete decreases with an increase in aggregate aspect ratio. When the coarse aggregate volume fraction is equal to 0.1, 0.2, and 0.3, the Chloride Diffusivity of concrete at an aggregate aspect ratio of 3 is, on average, smaller than that at an aggregate aspect ratio of 1 by 5.29%, 11.4%, and 19.6%, respectively. An analytical approximate is derived for the Chloride Diffusivity of concrete with spheroidal aggregates and verified with the experimental results. The analytical approximate can predict the Chloride Diffusivity with an average relative error of less than 8%.

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

  • experimental investigation and analytical modeling of Chloride Diffusivity of fly ash concrete
    Materials, 2020
    Co-Authors: Jian Zhang, Xin-zhu Zhou, Jianjun Zheng, Hailong Ye, Jin Yang
    Abstract:

    Owing to its importance in the assessment of reinforced concrete structures, it is essential to determine the Chloride Diffusivity of fly ash concrete. This paper presents an investigation into the diffusion characteristics of Chloride ions in fly ash concrete. Through experiment, the relationship between Chloride Diffusivity and curing age up to 1800 days is measured and the effects of curing age, water/binder ratio, aggregate volume fraction, and fly ash content (i.e., percentage of total cementitious material by mass) on Chloride Diffusivity are evaluated. It is found that the Chloride Diffusivity decreases with the increase of curing age, aggregate volume fraction, and fly ash content, but increases with the increase of water/binder ratio. In analytical modeling, an equivalent aggregate model is constructed and the equivalent interfacial transition zone (ITZ) thickness is derived analytically. With the equivalent aggregate model, three-phase fly ash concrete reduces to a two-phase composite material. By extending the Maxwell method, the Chloride Diffusivity of fly ash concrete is formulated. Finally, the validity of the analytical method is verified by experimental results.

  • numerical method for predicting Chloride Diffusivity of mature cement paste
    Journal of Materials in Civil Engineering, 2019
    Co-Authors: Jianjun Zheng, Xin-zhu Zhou, Jian Zhang, Xiaoru Wang
    Abstract:

    AbstractThis paper develops a highly efficient numerical method for estimating the Chloride Diffusivity of mature cement paste. In the method, the two-dimensional microstructure of cement paste is ...

  • A Brownian motion simulation for the Chloride Diffusivity of concrete
    Construction and Building Materials, 2016
    Co-Authors: Jianjun Zheng, Cong-yan Zhang, Xin-zhu Zhou
    Abstract:

    Abstract The purpose of this paper is to present a Brownian motion simulation for the Chloride Diffusivity of concrete. According to stereological theory, the probability density function and cumulative distribution function for the circular aggregates in terms of the number of aggregates are derived. By coating each aggregate with an interfacial transition zone (ITZ) layer of equal thickness, concrete is then reduced to a two-phase composite material, composed of a bulk cement paste and equivalent aggregates. The equivalent ITZ thickness and the Chloride Diffusivity of each equivalent aggregate are formulated in an analytical manner. The Brownian motion simulation is used to compute the Chloride Diffusivity of concrete. Finally, the validity of the numerical simulation is verified with two sets of experimental results and the effects of the aggregate area fraction, the Chloride Diffusivity of ITZ, and the ITZ thickness on the Chloride Diffusivity of concrete are evaluated in a quantitative manner. The paper concludes that the numerical simulation can predict the Chloride Diffusivity of concrete with an average relative error smaller than 6% for the two selected verification examples.

  • experiment and modeling of the effect of aggregate shape on the Chloride Diffusivity of concrete
    Journal of Materials in Civil Engineering, 2014
    Co-Authors: Jianjun Zheng, Xin-zhu Zhou, Xiaofeng Huang, Chuanqing Fu
    Abstract:

    The purpose of this paper is to evaluate the effect of aggregate shape on the Chloride Diffusivity of concrete through laboratory experiments and theoretical analysis. In the experiment, three types of crystal glass spheroids with aspect ratios of 1, 2, and 3 are used as coarse aggregate. The experimental results show that the Chloride Diffusivity of concrete decreases with an increase in aggregate aspect ratio. When the coarse aggregate volume fraction is equal to 0.1, 0.2, and 0.3, the Chloride Diffusivity of concrete at an aggregate aspect ratio of 3 is, on average, smaller than that at an aggregate aspect ratio of 1 by 5.29%, 11.4%, and 19.6%, respectively. An analytical approximate is derived for the Chloride Diffusivity of concrete with spheroidal aggregates and verified with the experimental results. The analytical approximate can predict the Chloride Diffusivity with an average relative error of less than 8%.

  • differential effective medium theory for the Chloride Diffusivity of concrete
    Aci Materials Journal, 2014
    Co-Authors: Jianjun Zheng, Xin-zhu Zhou, Hongyan Xing
    Abstract:

    A differential effective medium scheme for the Chloride Diffusivity of concrete with spheroidal aggregate particles is presented. By taking the interfacial transition zone (ITZ)-coated aggregate particle as an "equivalent aggregate particle," the three-phase concrete is reduced to a two-phase composite material. The differential effective medium theory is then adopted to derive an analytical approximation for the Chloride Diffusivity of concrete. After the validity of the analytical approximation is verified with two sets of experimental results, the effects of various key factors on the Chloride Diffusivity of concrete are evaluated quantitatively. Numerical results indicate that the Chloride Diffusivity of concrete increases with an increase in Chloride Diffusivity and thickness of ITZ, but decreases by increasing the aggregate aspect ratio and maximum aggregate diameter. It is also found that the aggregate gradation has a significant influence on the Chloride Diffusivity of concrete.

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

  • Origin of Chloride Diffusivity of cement pastes - a scale transition analysis
    2020
    Co-Authors: Peter Pivonka, David Smith, Christian Hellmich
    Abstract:

    For estimation of the durability of structures, it is highly desirable to quantify and simulate the Chloride diffusion process in concrete. To this end, diffusion-cell experiments delivering the Chloride Diffusivity of cement pastes with different water-cement ratios (related to different microporosities) are evaluated in a scale-transition analysis. For prediction of the apparent Chloride Diffusivity, cement paste can be modelled by means of a differential scheme involving non-diffusive spherical inclusions in a diffusive matrix. As a result, Chloride Diffusivity of cement paste is obtained as a function of the microporosity and the Chloride Diffusivity in the micropore solution. Remarkably, the latter turns out to be one order of magnitude smaller than the Chloride Diffusivity in a pure salt solution system. The smaller Diffusivity is probably caused by structuring of water molecu les along the pore surface of cement paste.

  • microscopic effects on Chloride Diffusivity of cement pastes a scale transition analysis
    Cement and Concrete Research, 2004
    Co-Authors: Peter Pivonka, Christian Hellmich, David Smith
    Abstract:

    For estimation of the durability of structures, it is highly desirable to quantify and simulate the Chloride diffusion process in concrete. To this end, diffusion-cell experiments delivering the Chloride Diffusivity of cement pastes with different water-cement ratios (related to different microporosities) are evaluated in a scale-transition analysis. For prediction of the apparent Chloride Diffusivity, cement paste can be modelled by means of a differential homogenization scheme involving nondiffusive spherical inclusions in a diffusive matrix. As a result, Chloride Diffusivity of cement paste is obtained as a function of the microporosity and the Chloride Diffusivity in the micropore solution. Remarkably, the latter turns out to be one order of magnitude smaller than the Chloride Diffusivity in a pure salt solution system. The smaller Diffusivity is probably caused by structuring of water molecules along the pore surface of cement paste.

Odd E Gjorv - One of the best experts on this subject based on the ideXlab platform.

  • effect of Chloride source concentration on Chloride Diffusivity in concrete
    Aci Materials Journal, 2005
    Co-Authors: Tiewei Zhang, Odd E Gjorv
    Abstract:

    In this paper, the results of an experimental investigation on migration testing of Chloride Diffusivity in concrete are presented. The results confirm that the effective Chloride Diffusivity is not a constant but a function of the Chloride source concentration. This concentration dependence reflects an important property of the transport behavior of Chloride ions in concrete, which is due to various interactions in the concrete system such as ionic interaction, ion-solvent interaction, Chloride binding, as well as dielectric properties of the concrete. For the various types of concrete tested, the effective Chloride Diffusivity at 0.01 M was 10 to 20 times higher than that at 1.0 M Chloride source concentration (NaCl). This concentration dependence of the Chloride Diffusivity is much stronger than what can be predicted by use of the Debye-Huckel theory. For a proper characterization of Chloride penetration into concrete, therefore, a complete relationship between Chloride Diffusivity and Chloride source concentration should be established. Also, for the purpose of characterizing the resistance of the concrete against Chloride penetration, the intrinsic Chloride Diffusivity at infinite dilution may be considered as a mote basic material parameter.

  • Chloride Diffusivity based on migration testing
    Cement and Concrete Research, 2001
    Co-Authors: L Tong, Odd E Gjorv
    Abstract:

    The present article presents the results of an experimental investigation, where the Chloride diffusivities from steady-state migration, non-steady-state migration, and electrical conductivity measurements were compared. A very good correlation between all these diffusivities were obtained, but the non-steady-state migration testing gave a Chloride Diffusivity that was about 10 times higher than from the steady-state migration and up to several times higher than that from the conductivity method. A good correlation was also observed between the initial electrical conductivity, the conductivity of NaCl saturated concrete, and the charge passed through the concrete. The correlation was further good between the electrical conductivity and the Diffusivity obtained from both the steady-state and the non-steady-state migration method. For a given binder system and type of concrete, measurements of initial electrical conductivity appear to provide a good basis both for estimation of Chloride Diffusivity and for routine control of concrete quality.

  • Diffusivity OF ChlorideS FROM SEAWATER INTO HIGH-STRENGTH LIGHTWEIGHT CONCRETE
    Aci Materials Journal, 1994
    Co-Authors: Odd E Gjorv, Minhong Zhang
    Abstract:

    As part of a more comprehensive research program on high-strength lightweight concrete, test results on the Diffusivity of Chlorides from natural seawater are presented. The Chloride Diffusivity of the various concrete mixes was very low. Of the various material parameters included in the test program, it was the presence of silica fume that had the most dominating effect on the Diffusivity. Nine percent replacement of the cement by silica fume reduced the Chloride Diffusivity by a factor of about 5, while an increasing content of the total amount of cementitious materials decreased the Diffusivity by a factor of about 2. Five different types of lightweight aggregate with increasing particle densities were used. The difference of the concretes with the least dense aggregate was about two times higher than those obtained with the most dense aggregate. Type of fine aggregate and maximum aggregate size had only a minor effect on the Chloride Diffusivity. The impact of the obtained Chloride Diffusivity on service life is also discussed.

  • an electrochemical method for accelerated testing of Chloride Diffusivity in concrete
    Cement and Concrete Research, 1994
    Co-Authors: Tiewei Zhang, Odd E Gjorv
    Abstract:

    Abstract In the present paper an electrochemical method for accelerated testing of Chloride Diffusivity in concrete is presented. The method is based on a theoretical relationship between Chloride Diffusivity and observed steady-state rate of Chloride migration through the concrete. The concrentration of the Chloride source solution has a significant influence on the rate of Chloride migration and, therefore, a correction factor for ionic interaction in the relationship is introduced. It is shown that the relationship can be used for calculation of Chloride Diffusivity under various testing conditions. Some experimental results are also presented.

  • effect of silica fume on pore structure and Chloride Diffusivity of low parosity cement pastes
    Cement and Concrete Research, 1991
    Co-Authors: Minhong Zhang, Odd E Gjorv
    Abstract:

    Abstract This paper presents the results of an experimental investigation on the effect of silica fume on pore structure and Diffusivity of low porosity cement pastes. For cement pastes with w/c ratios in the range of 0.20 to 0.30, a 10% replacement of the cement with silica fume only reduced the total porosity to a small extent. However, a refinement of the pore size distribution took place in such a way that the content of larger pores was reduced for decreasing w/c ratio. For pure portland cement pastes the effect of a certain constant change of w/c ratio on the Chloride Diffusivity was substantially higher at high w/c ratios than at low w/c ratios. A 10% replacement with silica fume reduced the Chloride Diffusivity for all w/c ratios so much that the effect of w/c ratio became less important.