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Cement-based materials are the most used construction and building materials in the world. This paper reviews the state-of-the-art of fractal geometry on cement-based materials. The porous structure of cement-based materials is extremely complicated and irregular, which is difficult to be described in terms of geometry. The fractal geometry is widely applied to investigate the pore structure of cement-based materials. In this work, the fractal characteristics of porous cement-based materials combined with the mathematical methods are discussed. Some direct and indirect methods for the evaluation of fractal dimensions are introduced, such as mercury intrusion porosimetry (MIP), nitrogen adsorption/desorption (NAD) and nuclear magnetic resonance (NMR). Some experimental results from different methods are compared to illustrate the advantages and disadvantages of these methods. Finally, correlations among fractal dimensions and properties of cement-based materials, such as permeability, diffusivity, strength and fluidity, are summarized.
Shengwen Tang; Jiasheng Huang; Lian Duan; Peng Yu; E. Chen. A review on fractal footprint of cement-based materials. Powder Technology 2020, 370, 237 -250.
AMA StyleShengwen Tang, Jiasheng Huang, Lian Duan, Peng Yu, E. Chen. A review on fractal footprint of cement-based materials. Powder Technology. 2020; 370 ():237-250.
Chicago/Turabian StyleShengwen Tang; Jiasheng Huang; Lian Duan; Peng Yu; E. Chen. 2020. "A review on fractal footprint of cement-based materials." Powder Technology 370, no. : 237-250.
This work systematically investigated the early hydration process of magnesium oxysulfate (MOS) cement pastes by non-contact impedance measurement (NCIM) and other microstructural tests. According to the evolution of impedance response, the hydration process of MOS cement pastes can be divided into three stages (dissolution, acceleration and hardened stages). The identification of hydration is strongly related to the transformation of solid phases and alkalinity of pastes. The presence and crystalline degrees of 517 phase and 318 phase are evaluated by DTG and XRD tests, respectively. It seems that MgO/MgSO4 ratio does not affect crystalline degree of hydrated products much. MH crystals and cracks are considered to result in the low mechanical strength of MOS cement paste. It can be inferred from experimental results that NCIM is a good method to analyze the hydration evolution of MOS cement pastes in-situ.
Shengwen Tang; Junhui Yuan; Rongjin Cai; Changrong Wei; Jingtao Chen; E. Chen. In situ monitoring of hydration of magnesium oxysulfate cement paste: Effect of MgO/MgSO4 ratio. Construction and Building Materials 2020, 251, 119003 .
AMA StyleShengwen Tang, Junhui Yuan, Rongjin Cai, Changrong Wei, Jingtao Chen, E. Chen. In situ monitoring of hydration of magnesium oxysulfate cement paste: Effect of MgO/MgSO4 ratio. Construction and Building Materials. 2020; 251 ():119003.
Chicago/Turabian StyleShengwen Tang; Junhui Yuan; Rongjin Cai; Changrong Wei; Jingtao Chen; E. Chen. 2020. "In situ monitoring of hydration of magnesium oxysulfate cement paste: Effect of MgO/MgSO4 ratio." Construction and Building Materials 251, no. : 119003.
This work systematically presented the pore structure evolution of different magnesium oxysulfate (MOS) cement pastes by non-contact impedance measurement (NCIM), fractal theory and other microstructural experiments. According to the evolution of electrical impedance response, three hydration stages (dissolution, acceleration and hardened stages) can be identified in the pastes. Furthermore, based on the results obtained from NCIM and fractal theory, the porosity, incremental pore volume, pore tortuosity, average pore diameter and maximal pore diameter of MOS cement pastes are investigated. The influence of MgSO4/H2O ratio on pore structure of MOS cement paste is primarily explained. It can be inferred from predicted and experimental results that NCIM is a good method to analyze the microstructure evolution of MOS cement pastes in-situ.
Shengwen Tang; Changrong Wei; Rongjin Cai; Jiasheng Huang; E. Chen; Junhui Yuan. In situ monitoring of pore structure of magnesium oxysulfate cement paste: Effect of MgSO4/H2O ratio. Journal of Industrial and Engineering Chemistry 2019, 83, 387 -400.
AMA StyleShengwen Tang, Changrong Wei, Rongjin Cai, Jiasheng Huang, E. Chen, Junhui Yuan. In situ monitoring of pore structure of magnesium oxysulfate cement paste: Effect of MgSO4/H2O ratio. Journal of Industrial and Engineering Chemistry. 2019; 83 ():387-400.
Chicago/Turabian StyleShengwen Tang; Changrong Wei; Rongjin Cai; Jiasheng Huang; E. Chen; Junhui Yuan. 2019. "In situ monitoring of pore structure of magnesium oxysulfate cement paste: Effect of MgSO4/H2O ratio." Journal of Industrial and Engineering Chemistry 83, no. : 387-400.
Molecular dynamics simulations are used to investigate the interactions between water molecules and C-S-H surfaces and transport properties of water confined in the nanopore. Firstly, a C-S-H model based on experimental results is constructed, then a nanopore induced by tensile loading is taken into account for the first time. Structural and dynamical properties of confined water and interactions between water solution and C-S-H surface are further investigated at the molecular level. Water molecules gathering in the vicinity of C-S-H surfaces perpendicular to Z direction present peculiar structural and dynamic characteristic: layer structure, high density, obvious orientation preference, and low diffusion coefficient. The silicate chains are connected with water molecules by the high-strength hydrogen bonds formed among water and non-bridge oxygen atoms (ONB), bridge oxygen atoms (OB) in silicate chains, while surface calcium ions sheets are prone to attract oxygen atoms in water molecules. The special structural and dynamic features are mainly determined by the interactions among water, silicate chains, and surface calcium ions sheets. Due to the lack of strong constraint from the C-S-H substrates and driven by water molecules in the nanopore, the surface calcium ions diffuse more rapidly than those constrained inside of the C-S-H gel and could diffuse into the nanopore full of water molecules.
Shengwen Tang; Hubao A.; Jingtao Chen; Wenzhi Yu; Peng Yu; E Chen; Hongyang Deng; Zhen He. The interactions between water molecules and C-S-H surfaces in loads-induced nanopores: A molecular dynamics study. Applied Surface Science 2019, 496, 143744 .
AMA StyleShengwen Tang, Hubao A., Jingtao Chen, Wenzhi Yu, Peng Yu, E Chen, Hongyang Deng, Zhen He. The interactions between water molecules and C-S-H surfaces in loads-induced nanopores: A molecular dynamics study. Applied Surface Science. 2019; 496 ():143744.
Chicago/Turabian StyleShengwen Tang; Hubao A.; Jingtao Chen; Wenzhi Yu; Peng Yu; E Chen; Hongyang Deng; Zhen He. 2019. "The interactions between water molecules and C-S-H surfaces in loads-induced nanopores: A molecular dynamics study." Applied Surface Science 496, no. : 143744.
This work discusses the development of hydropower in four Southeast Asia countries. With rapid economic development and insufficient energy supply, hydropower, as an important clean energy, plays a bigger role than before. It is shown that hydropower has immense potential and is the best choice to cater for the energy demand in Southeast Asia. In this work, Malaysia, Indonesia, Thailand and Myanmar are selected to analyze their hydropower development. This work introduces the status of hydropower resources, the current situation of hydropower development and the main distribution of hydropower stations in the four countries. In addition, the paper also introduces some energy policies, the development advantages and obstacles of the four countries, and puts forward suggestions for the future hydropower development of these four countries.
Shengwen Tang; Jingtao Chen; Peigui Sun; Yang Li; Peng Yu; E. Chen. Current and future hydropower development in Southeast Asia countries (Malaysia, Indonesia, Thailand and Myanmar). Energy Policy 2019, 129, 239 -249.
AMA StyleShengwen Tang, Jingtao Chen, Peigui Sun, Yang Li, Peng Yu, E. Chen. Current and future hydropower development in Southeast Asia countries (Malaysia, Indonesia, Thailand and Myanmar). Energy Policy. 2019; 129 ():239-249.
Chicago/Turabian StyleShengwen Tang; Jingtao Chen; Peigui Sun; Yang Li; Peng Yu; E. Chen. 2019. "Current and future hydropower development in Southeast Asia countries (Malaysia, Indonesia, Thailand and Myanmar)." Energy Policy 129, no. : 239-249.
Magnesium oxychloride cement (MOC) has been considered as a kind of eco-friendly cement in view of its significantly low calcination temperature and large capacity of carbon dioxide sequestration, compared with ordinary Portland cement (OPC). In this work, a computer model is established to simulate the hydration and leaching of MOC paste at the micro-scale. The composition of MOC paste in the ultimate hydration is investigated based on the thermodynamic method, and pore structure obtained from the computer simulation is compared with the one from experiments and literature, respectively. The simulated leaching results show that the original solid phase skeleton of MOC paste decomposes into magnesium hydroxide crystals. It is demonstrated that the simulation results are in good agreement with experimental data from literature and the proposed simulation can provide an effective method to reveal the hydration and leaching mechanism of MOC paste.
Shengwen Tang; Yang Hu; Wang Ren; Peng Yu; Qing Huang; Xiaoying Qi; Ying Li; E. Chen. Modeling on the hydration and leaching of eco-friendly magnesium oxychloride cement paste at the micro-scale. Construction and Building Materials 2019, 204, 684 -690.
AMA StyleShengwen Tang, Yang Hu, Wang Ren, Peng Yu, Qing Huang, Xiaoying Qi, Ying Li, E. Chen. Modeling on the hydration and leaching of eco-friendly magnesium oxychloride cement paste at the micro-scale. Construction and Building Materials. 2019; 204 ():684-690.
Chicago/Turabian StyleShengwen Tang; Yang Hu; Wang Ren; Peng Yu; Qing Huang; Xiaoying Qi; Ying Li; E. Chen. 2019. "Modeling on the hydration and leaching of eco-friendly magnesium oxychloride cement paste at the micro-scale." Construction and Building Materials 204, no. : 684-690.
The effects of silica fume, PVA fiber and their combinations on the mechanical properties, microstructure, abrasion resistance and volume stability of cement pastes and/or fly ash concrete were studied experimentally in this work. The results indicated that the compressive strength and tensile strength of concrete containing both silica fume and PVA fiber were obviously improved compared with the control concrete. The addition of PVA fiber in concrete considerably reduced the drying shrinkage and improved the anti-cracking resistance of cement pastes and concrete, and the abrasion resistance of concrete significantly increased with the addition of silica fume and PVA fiber. These findings have been successfully adopted to guide the design and construction of hydraulic structures in the southwest of China.
L. Wang; S.H. Zhou; Y. Shi; S.W. Tang; E. Chen. Effect of silica fume and PVA fiber on the abrasion resistance and volume stability of concrete. Composites Part B: Engineering 2017, 130, 28 -37.
AMA StyleL. Wang, S.H. Zhou, Y. Shi, S.W. Tang, E. Chen. Effect of silica fume and PVA fiber on the abrasion resistance and volume stability of concrete. Composites Part B: Engineering. 2017; 130 ():28-37.
Chicago/Turabian StyleL. Wang; S.H. Zhou; Y. Shi; S.W. Tang; E. Chen. 2017. "Effect of silica fume and PVA fiber on the abrasion resistance and volume stability of concrete." Composites Part B: Engineering 130, no. : 28-37.
This paper reviews the evaluation of hydration of cement-based materials by means of electrical methods from the view point of direct and alternative current methods. The merits, demerits and application scenarios of electrical methods for hydration characterization are described. Influencing factors (pore solution conductivity, porosity, pore size distribution and pore connectivity) of electrical methods are briefly commented. Besides, the predictions of setting time and shrinkage, and the determination of hydration stages by electrical methods are presented. The combinations of some mainstream computer simulations and electrical methods are reviewed.
Shengwen Tang; X.H. Cai; Z. He; W. Zhou; H.Y. Shao; Z.J. Li; Tao Wu; E. Chen. The review of early hydration of cement-based materials by electrical methods. Construction and Building Materials 2017, 146, 15 -29.
AMA StyleShengwen Tang, X.H. Cai, Z. He, W. Zhou, H.Y. Shao, Z.J. Li, Tao Wu, E. Chen. The review of early hydration of cement-based materials by electrical methods. Construction and Building Materials. 2017; 146 ():15-29.
Chicago/Turabian StyleShengwen Tang; X.H. Cai; Z. He; W. Zhou; H.Y. Shao; Z.J. Li; Tao Wu; E. Chen. 2017. "The review of early hydration of cement-based materials by electrical methods." Construction and Building Materials 146, no. : 15-29.
This paper presents a preliminary work to evaluate influences of water to cement ratio, hydration age and content of superplasticizer on porosity, volume and surface fractal dimensions of pore structure in 56 groups of calcium sulfoaluminate cement pastes by nitrogen adsorption/desorption (NAD) tests and low temperature differential scanning calorimetry (LT-DSC). Additionally, a fractal sponge model is developed to analyze intrinsic relations among porosity, volume and surface fractal dimensions by changing the removed number of cells, iterate steps and number of fractal cells.
S.W. Tang; Z. He; X.H. Cai; R.J. Cai; W. Zhou; Z.J. Li; H.Y. Shao; T. Wu; E. Chen. Volume and surface fractal dimensions of pore structure by NAD and LT-DSC in calcium sulfoaluminate cement pastes. Construction and Building Materials 2017, 143, 395 -418.
AMA StyleS.W. Tang, Z. He, X.H. Cai, R.J. Cai, W. Zhou, Z.J. Li, H.Y. Shao, T. Wu, E. Chen. Volume and surface fractal dimensions of pore structure by NAD and LT-DSC in calcium sulfoaluminate cement pastes. Construction and Building Materials. 2017; 143 ():395-418.
Chicago/Turabian StyleS.W. Tang; Z. He; X.H. Cai; R.J. Cai; W. Zhou; Z.J. Li; H.Y. Shao; T. Wu; E. Chen. 2017. "Volume and surface fractal dimensions of pore structure by NAD and LT-DSC in calcium sulfoaluminate cement pastes." Construction and Building Materials 143, no. : 395-418.
This paper reviews the evaluation of pore structure in cementitious materials by means of electrical impedance methods from the view point of direct and alternative current tests with or without electrodes. Some main equivalent circuit models in the literatures, which are employed to evaluate the pore structure from experimental results of alternating current impedance spectroscopy (ACIS), are discussed. The latest utilization of non-contact resistivity/impedance measurement for the hydration monitoring, pore structure and transportation investigation is presented in this review. The related merits and demerits of ACIS with electrodes and non-contact methods and their application scenarios are also discussed.
Shengwen Tang; X.H. Cai; Z. He; W. Zhou; H.Y. Shao; Zongjin Li; Tao Wu; E. Chen. The review of pore structure evaluation in cementitious materials by electrical methods. Construction and Building Materials 2016, 117, 273 -284.
AMA StyleShengwen Tang, X.H. Cai, Z. He, W. Zhou, H.Y. Shao, Zongjin Li, Tao Wu, E. Chen. The review of pore structure evaluation in cementitious materials by electrical methods. Construction and Building Materials. 2016; 117 ():273-284.
Chicago/Turabian StyleShengwen Tang; X.H. Cai; Z. He; W. Zhou; H.Y. Shao; Zongjin Li; Tao Wu; E. Chen. 2016. "The review of pore structure evaluation in cementitious materials by electrical methods." Construction and Building Materials 117, no. : 273-284.
This paper investigates the microstructure evolution of CSA cement pastes with different water to cement ratios in various hydration stages. Microstructure information, such as porosity, cumulative and incremental pore volume of cement pastes, is revealed by the innovative non-contact electrical impedance measurement (NCEIM), low temperature differential scanning calorimetry (LT-DSC), nitrogen adsorption test and mercury intrusion porosimetry (MIP). The hydration features associated with microstructure evolution are identified by NCEIM, Micro-Raman spectra and heat evolution test. Through the overall analysis of experimental results, initial formation and evolution of microstructure of CSA cement pastes are identified.
S.W. Tang; X.H. Cai; W. Zhou; H.Y. Shao; Z. He; Z.J. Li; W.M. Ji; E. Chen. In-situ and continuous monitoring of pore evolution of calcium sulfoaluminate cement at early age by electrical impedance measurement. Construction and Building Materials 2016, 117, 8 -19.
AMA StyleS.W. Tang, X.H. Cai, W. Zhou, H.Y. Shao, Z. He, Z.J. Li, W.M. Ji, E. Chen. In-situ and continuous monitoring of pore evolution of calcium sulfoaluminate cement at early age by electrical impedance measurement. Construction and Building Materials. 2016; 117 ():8-19.
Chicago/Turabian StyleS.W. Tang; X.H. Cai; W. Zhou; H.Y. Shao; Z. He; Z.J. Li; W.M. Ji; E. Chen. 2016. "In-situ and continuous monitoring of pore evolution of calcium sulfoaluminate cement at early age by electrical impedance measurement." Construction and Building Materials 117, no. : 8-19.
This study focuses on the early-age hydration development in fly ash blended cement pastes. The characteristic features in different hydration stages and the evolution of zeolites phase, viz., gismondine, are identified in high-dosage fly ash blended cement-based materials using the innovative non-contact impedance measurement (NCIM), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), heat evolution test and pore solution analysis. It is found that the zeolite formation stage is comparatively distinct at the late hydration period. Besides, the influence of fly ash dosages in cement pastes on setting time and compressive strength are further examined.
S.W. Tang; X.H. Cai; Z. He; H.Y. Shao; Zongjin Li; E. Chen. Hydration process of fly ash blended cement pastes by impedance measurement. Construction and Building Materials 2016, 113, 939 -950.
AMA StyleS.W. Tang, X.H. Cai, Z. He, H.Y. Shao, Zongjin Li, E. Chen. Hydration process of fly ash blended cement pastes by impedance measurement. Construction and Building Materials. 2016; 113 ():939-950.
Chicago/Turabian StyleS.W. Tang; X.H. Cai; Z. He; H.Y. Shao; Zongjin Li; E. Chen. 2016. "Hydration process of fly ash blended cement pastes by impedance measurement." Construction and Building Materials 113, no. : 939-950.
This paper presents a preliminary work to evaluate the thermal conductivity performance in pure and blended cement pastes with fly ash, slag and silica fume. The thermal conductivity of cement pastes cured in saturated and dry status with different hydration ages are also measured and predicted by quick thermal conductivity meter (QTM) and innovative non-contact impedance measurement (NCIM) based on a newly proposed fractal model. Besides, a corresponding simulation of fractal-like network is developed to evaluate the influences of pore structure parameters, intrinsic thermal conductivity coefficients of solid and water or gas phase on thermal conductivity performance of cement pastes.
S.W. Tang; E. Chen; H.Y. Shao; Z.J. Li. A fractal approach to determine thermal conductivity in cement pastes. Construction and Building Materials 2014, 74, 73 -82.
AMA StyleS.W. Tang, E. Chen, H.Y. Shao, Z.J. Li. A fractal approach to determine thermal conductivity in cement pastes. Construction and Building Materials. 2014; 74 ():73-82.
Chicago/Turabian StyleS.W. Tang; E. Chen; H.Y. Shao; Z.J. Li. 2014. "A fractal approach to determine thermal conductivity in cement pastes." Construction and Building Materials 74, no. : 73-82.