This page has only limited features, please log in for full access.
The hydraulic concrete structures commonly suffer from severe dissolution. Dissolution has a great influence on the mechanical properties and durability of concrete, which would be detrimental to the normal operation and even cause structure failure. In this study, the effects of an accelerated dissolution method, namely NH4NO3 dissolution, on the microstructure and micro-mechanics of hardened cement pastes have been investigated via X ray fluorescence (XRF), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance (29Si MAS NMR) and microhardness techniques. Besides, an attempt was made to reveal the relationship between the C-S-H microstructure and micro-mechanics of cement paste during the NH4NO3 dissolution process. The results demonstrated that the decalcification process of the cement pastes under NH4NO3 erosion can be classified into two stages. The first stage was the dissolution of Ca(OH)2 in cement pastes. The Ca(OH)2 was almost completely removed, and C-S-H was partly decalcified in this stage. In the second stage, as the C/S of cement pastes decreased to a constant value about 1.83, C-S-H was further decalcified. It was also observed that the continuous dissolution would significantly weaken the microhardness of cement pastes. The long-term hydrated cement paste decalcified for 500 min exhibited nearly no microhardness. In addition, the results indicated that the microhardness of the cement pastes was related to the paste C/S, the proportion of Q1 and the polymerization of C-S-H. Finally, it was concluded that the Ca(OH)2 dissolution and degradation of C-S-H structure are the main causes for the degradation of cement pastes under NH4NO3 dissolution.
Lei Wang; Minmin Jin; Shihua Zhou; Shengwen Tang; Xiao Lu. Investigation of microstructure of C-S-H and micro-mechanics of cement pastes under NH4NO3 dissolution by 29Si MAS NMR and microhardness. Measurement 2021, 185, 110019 .
AMA StyleLei Wang, Minmin Jin, Shihua Zhou, Shengwen Tang, Xiao Lu. Investigation of microstructure of C-S-H and micro-mechanics of cement pastes under NH4NO3 dissolution by 29Si MAS NMR and microhardness. Measurement. 2021; 185 ():110019.
Chicago/Turabian StyleLei Wang; Minmin Jin; Shihua Zhou; Shengwen Tang; Xiao Lu. 2021. "Investigation of microstructure of C-S-H and micro-mechanics of cement pastes under NH4NO3 dissolution by 29Si MAS NMR and microhardness." Measurement 185, no. : 110019.
This paper focuses on inspecting the influences of anti-foaming agent (AFA) on the performance of 3D printing cementitious materials (3DPC). The mini-slump, spreading diameter, yield stress, and strength of 3DPC were evaluated. Additionally, the air-void content, air-void morphology, and air-void size distribution of mortar with and without 0.05% AFA were assessed through image analysis. The mechanical performance and air-void structure of 3D printed samples were also investigated and compared to that of conventionally mould cast samples. Test results show that an optimal AFA content enables 3DPC to achieve favorable workability and mechanical performance. The addition of AFA exhibits lower air-void content in 3DPC than that of the sample without the AFA addition. This reduction in air-void content is further strengthened by the results of strength analysis. Electron microscope analysis shows that the use of AFA results in the suppressed formation of large air-voids during the process of fresh 3DPC. Moreover, the air-void morphology substantially influenced the mechanical performance of hardened 3DPC.
Yujun Che; Shengwen Tang; Huashan Yang; Weiwei Li; Mengyuan Shi. Influences of Air-Voids on the Performance of 3D Printing Cementitious Materials. Materials 2021, 14, 4438 .
AMA StyleYujun Che, Shengwen Tang, Huashan Yang, Weiwei Li, Mengyuan Shi. Influences of Air-Voids on the Performance of 3D Printing Cementitious Materials. Materials. 2021; 14 (16):4438.
Chicago/Turabian StyleYujun Che; Shengwen Tang; Huashan Yang; Weiwei Li; Mengyuan Shi. 2021. "Influences of Air-Voids on the Performance of 3D Printing Cementitious Materials." Materials 14, no. 16: 4438.
In cement-based materials, alkalis mainly exist in the form of different alkali sulfates. In this study, the impacts of different alkali sulfates on the shrinkage, hydration, pore structure, fractal dimension and microstructure of low-heat Portland cement (LHPC), medium-heat Portland cement (MHPC) and ordinary Portland cement (OPC) are investigated. The results indicate that alkali sulfates magnify the autogenous shrinkage and drying shrinkage of cement-based materials with different mineral compositions, which are mainly related to different pore structures and hydration processes. LHPC has the lowest shrinkage. Otherwise, the effect of alkali sulfates on the autogenous shrinkage is more profound than that of drying shrinkage. Compared with the pore size distribution, the fractal dimension can better characterize the shrinkage properties of cement-based materials. It is noted that the contribution of K2SO4 (K alkali) to the promotion effect of shrinkage on cement-based materials is more significant than that of Na2SO4 (Na alkali), which cannot be ignored. The microstructure investigation of different cement-based materials by means of nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) shows that this effect may be related to the different pore structures, crystal forms and morphologies of hydration products of cement-based materials.
Yang Li; Hui Zhang; Minghui Huang; Haibo Yin; Ke Jiang; Kaitao Xiao; Shengwen Tang. Influence of Different Alkali Sulfates on the Shrinkage, Hydration, Pore Structure, Fractal Dimension and Microstructure of Low-Heat Portland Cement, Medium-Heat Portland Cement and Ordinary Portland Cement. Fractal and Fractional 2021, 5, 79 .
AMA StyleYang Li, Hui Zhang, Minghui Huang, Haibo Yin, Ke Jiang, Kaitao Xiao, Shengwen Tang. Influence of Different Alkali Sulfates on the Shrinkage, Hydration, Pore Structure, Fractal Dimension and Microstructure of Low-Heat Portland Cement, Medium-Heat Portland Cement and Ordinary Portland Cement. Fractal and Fractional. 2021; 5 (3):79.
Chicago/Turabian StyleYang Li; Hui Zhang; Minghui Huang; Haibo Yin; Ke Jiang; Kaitao Xiao; Shengwen Tang. 2021. "Influence of Different Alkali Sulfates on the Shrinkage, Hydration, Pore Structure, Fractal Dimension and Microstructure of Low-Heat Portland Cement, Medium-Heat Portland Cement and Ordinary Portland Cement." Fractal and Fractional 5, no. 3: 79.
Cement-based materials are widely utilized in infrastructure. The main product of hydrated products of cement-based materials is calcium silicate hydrate (C-S-H) gels that are considered as the binding phase of cement paste. C-S-H gels in Portland cement paste account for 60–70% of hydrated products by volume, which has profound influence on the mechanical properties and durability of cement-based materials. The preparation method of C-S-H gels has been well documented, but the quality of the prepared C-S-H affects experimental results; therefore, this review studies the preparation method of C-S-H under different conditions and materials. The progress related to C-S-H microstructure is explored from the theoretical and computational point of view. The fractality of C-S-H is discussed. An evaluation of the mechanical properties of C-S-H has also been included in this review. Finally, there is a discussion of the durability of C-S-H, with special reference to the carbonization and chloride/sulfate attacks.
Shengwen Tang; Yang Wang; Zhicheng Geng; Xiaofei Xu; Wenzhi Yu; Hubao A; Jingtao Chen. Structure, Fractality, Mechanics and Durability of Calcium Silicate Hydrates. Fractal and Fractional 2021, 5, 47 .
AMA StyleShengwen Tang, Yang Wang, Zhicheng Geng, Xiaofei Xu, Wenzhi Yu, Hubao A, Jingtao Chen. Structure, Fractality, Mechanics and Durability of Calcium Silicate Hydrates. Fractal and Fractional. 2021; 5 (2):47.
Chicago/Turabian StyleShengwen Tang; Yang Wang; Zhicheng Geng; Xiaofei Xu; Wenzhi Yu; Hubao A; Jingtao Chen. 2021. "Structure, Fractality, Mechanics and Durability of Calcium Silicate Hydrates." Fractal and Fractional 5, no. 2: 47.
The non-contact alternating current (AC) impedance method is widely used in the study of electrochemical properties of cement-based materials,the instrument of this paper provide a new way for the study of pore structure of cement-based materials. Due to the loss of magnetic materials and the parasitic capacitance of measuring circuit, the ratio difference and phase difference of current sensor inevitably exit. Traditionally the standard resistor calibration method is used to determine the ratio error and phase error under different frequencies based on polynomial fitting (FT). In this paper, a machine-learning support vector machine (SVM) model is used to predict the calibration data with a small test sample. For the accuracy assessment, SVM model has the best comprehensive performance among FT, artificial neural network (ANN). The actual impedance test of typical cement-based materials under different frequencies is given and the results verify the excellent performance of SVM.
Tao Wu; Chao Li; Yifei Wang; Yongbo Li; Shengwen Tang; Ruben Paul Borg. Improved non-contact variable-frequency AC impedance instrument for cement hydration and pore structure based on SVM calibration method. Measurement 2021, 179, 109402 .
AMA StyleTao Wu, Chao Li, Yifei Wang, Yongbo Li, Shengwen Tang, Ruben Paul Borg. Improved non-contact variable-frequency AC impedance instrument for cement hydration and pore structure based on SVM calibration method. Measurement. 2021; 179 ():109402.
Chicago/Turabian StyleTao Wu; Chao Li; Yifei Wang; Yongbo Li; Shengwen Tang; Ruben Paul Borg. 2021. "Improved non-contact variable-frequency AC impedance instrument for cement hydration and pore structure based on SVM calibration method." Measurement 179, no. : 109402.
The crack resistance and durability of face slab concrete are two important factors determining the normal operation and safety of concrete face rockfill dams (CFRDs). This paper investigates the influence of polypropylene (PP), polyvinyl alcohol (PVA) and polyacrylonitrile (PAN) fiber with two lengths (10 mm and 20 mm) on workability, strength, shrinkage behavior, cracking resistance and durability performance of face slab concrete. Besides, the parameters of the pores at multi-scales were investigated by a linear traverse method and the mercury intrusion porosimetry (MIP), respectively. The results in this study demonstrate that: (1) the efficiency in reducing the shrinkage and in enhancing the cracking resistance of face slab concrete follows the order of PVA > PAN > PP. In addition, both the impermeability and frost resistance of concrete can be improved by adding fibers, the efficiency is in the sequence: PAN > PVA > PP and PVA > PAN > PP, respectively. (2) increasing fiber length from 10 mm to 20 mm reduces the shrinkage by about 5.1%−7.0%, enhances the tensile strength (σ) by about 7.9%−9.2% and declines the cracking temperature (Tc) by about 5.6–6.5℃, all of which could significantly improve the cracking resistance. Moreover, the increase in fiber length improves the frost resistance, but increases the relative permeability coefficient (Kr) by about 28%−47%. (3) The correlation analyses reveal that, the addition of PAN fibers produces a lower porosity, a lower fraction of large capillary pores as well as a lower hardened air content than the PVA and PP fibers at 28 days, thereby resulting in better impermeability of concrete. PVA fiber enhanced concrete gives the smallest spacing factor and the largest total number of air voids among all the fiber enhanced concretes, thus exhibiting the best frost resistance.
Lei Wang; Tingshu He; Yongxiang Zhou; Shengwen Tang; Jianjun Tan; Zhentao Liu; Jianwen Su. The influence of fiber type and length on the cracking resistance, durability and pore structure of face slab concrete. Construction and Building Materials 2021, 282, 122706 .
AMA StyleLei Wang, Tingshu He, Yongxiang Zhou, Shengwen Tang, Jianjun Tan, Zhentao Liu, Jianwen Su. The influence of fiber type and length on the cracking resistance, durability and pore structure of face slab concrete. Construction and Building Materials. 2021; 282 ():122706.
Chicago/Turabian StyleLei Wang; Tingshu He; Yongxiang Zhou; Shengwen Tang; Jianjun Tan; Zhentao Liu; Jianwen Su. 2021. "The influence of fiber type and length on the cracking resistance, durability and pore structure of face slab concrete." Construction and Building Materials 282, no. : 122706.
Low heat Portland (LHP) cement has been widely used in hydraulic projects in China, while the relatively low early strength limits its further application in engineering. In this study, the effect of silica fume (SF) content, varying between 0 and 12%, by mass of binder, on hydration heat, hydration products and pore structure of LHP cement-based materials were investigated by isothermal calorimetry, thermal analysis, and mercury intrusion porosimetry (MIP), respectively. Besides, the mechanical strength, shrinkage behavior and fractal characteristics of SF modified LHP cement-based materials were studied and compared with those of ordinary Portland cement (OPC)-based ones. The results indicate that the addition of SF effectively accelerates the hydration of LHP cement and obviously consumes the Ca(OH)2 in LHP cement paste. In addition, concrete based on LHP cement with 8 wt% SF exhibits excellent performance such as high early strength, low hydration heat and low shrinkage. It is also found that the pore structure of SF-modified LHP cement concrete becomes finer and more complex as the SF dosage increases, resulting in higher fractal dimension (Ds) values. Moreover, there exists a linear relationship between Ds and shrinkage of concrete, thus Ds may serve as a new parameter to evaluate the shrinkage behavior of concrete.
Lei Wang; Minmin Jin; Yonghua Wu; Yongxiang Zhou; Shengwen Tang. Hydration, shrinkage, pore structure and fractal dimension of silica fume modified low heat Portland cement-based materials. Construction and Building Materials 2020, 272, 121952 .
AMA StyleLei Wang, Minmin Jin, Yonghua Wu, Yongxiang Zhou, Shengwen Tang. Hydration, shrinkage, pore structure and fractal dimension of silica fume modified low heat Portland cement-based materials. Construction and Building Materials. 2020; 272 ():121952.
Chicago/Turabian StyleLei Wang; Minmin Jin; Yonghua Wu; Yongxiang Zhou; Shengwen Tang. 2020. "Hydration, shrinkage, pore structure and fractal dimension of silica fume modified low heat Portland cement-based materials." Construction and Building Materials 272, no. : 121952.
For cementitious materials, electrical resistivity is often used in the study of the cement hydration process at early age, as one of the few indicators that can be continuously and non-destructively monitored. Variation characteristics of resistivity are widely reported to interact with the early-age performance of cement paste, such as hydration kinetics parameters and setting time. However, there is no reasonable mathematical model to predict the resistivity at early ages, especially within the first 24 h, due to significant changes in the porosity and degree of saturation. In this work, a mathematical model was developed by considering the partially saturated state and density change of C-S-H (calcium silicate hydrate). To verify the model, two experimental methods were chosen, including the non-contact electrical resistivity test and isothermal calorimetry test. The hydration heat and resistivity of cement paste with a water–cement ratio of 0.35 and 0.45 were continuously monitored for 3 days. In the resistivity test, embedded temperature sensors were used to monitor the internal temperature and temperature correction was treated carefully in order to obtain accurate data. The test results prove that the mathematical model can accurately predict electrical resistivity and describe the saturation state of early-age cement pastes under sealed curing.
Ye Tian; Xin Xu; Haodong Ji; Zushi Tian; Xianyu Jin; Nanguo Jin; Dongming Yan; Shengwen Tang. A Mathematical Model for the Electrical Resistivity of Cement Paste at Early Ages Considering the Partially Saturated State. Materials 2020, 13, 3306 .
AMA StyleYe Tian, Xin Xu, Haodong Ji, Zushi Tian, Xianyu Jin, Nanguo Jin, Dongming Yan, Shengwen Tang. A Mathematical Model for the Electrical Resistivity of Cement Paste at Early Ages Considering the Partially Saturated State. Materials. 2020; 13 (15):3306.
Chicago/Turabian StyleYe Tian; Xin Xu; Haodong Ji; Zushi Tian; Xianyu Jin; Nanguo Jin; Dongming Yan; Shengwen Tang. 2020. "A Mathematical Model for the Electrical Resistivity of Cement Paste at Early Ages Considering the Partially Saturated State." Materials 13, no. 15: 3306.
Fly ash (FA) has been widely used in hydraulic projects. The utilization of phosphorous slag (PS) to partially or completely replace FA in hydraulic concrete has gained much attention in China in recent years. In this study, the effects of PS and FA on C-S-H structure, long-term hydration heat, hydration products, mechanical properties and volume deformation of cement paste/concrete were investigated and compared via 29Si NMR nuclear magnetic resonance (29Si NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis and the dissolution method. The retarding effect of PS at early age hinders the generation of C-S-H, whereas the pozzolanic reaction of PS largely occurs at middle and late age. More than half of the Ca(OH)2 content in cement paste is consumed and lots of C-S-H gels with high polymerization degree are produced at middle and late age, leading to a dense microstructure of cement paste. FA has a more noticeable effect on the enhancement of the polymerization degree and Al content of C-S-H than PS. There is a reduction of 25.3% and 18.6% in the cement hydration heat within 3 days and 180 days when 30 wt% FA is blended. By contrast, PS is more helpful for lowering the hydration heat at early age, the incorporation of 30 wt% PS reduces the 180-day hydration heat by about 9.2%. Additionally, after the first few days, PS concretes possess stronger mechanical properties in comparison with FA ones, confirming PS has a higher pozzolanic activity than FA. The adiabatic temperature rising of plain cement concrete at 28 days was reduced by 4–5 ℃ due to 30 wt% PS incorporation. The addition of 30 wt% PS reduces the early autogenous shrinkage significantly and declines the 180-day drying shrinkage and autogenous shrinkage by about 7.2%-9.0% and 8–11%, respectively. However, FA is more effective in reducing the adiabatic temperature rising, long-term autogenous shrinkage and drying shrinkage of concrete than PS. The results in this study could provide useful experience for the utilization of PS in hydraulic projects.
Lei Wang; Fanxing Guo; Yuqiang Lin; Huamei Yang; S.W. Tang. Comparison between the effects of phosphorous slag and fly ash on the C-S-H structure, long-term hydration heat and volume deformation of cement-based materials. Construction and Building Materials 2020, 250, 118807 .
AMA StyleLei Wang, Fanxing Guo, Yuqiang Lin, Huamei Yang, S.W. Tang. Comparison between the effects of phosphorous slag and fly ash on the C-S-H structure, long-term hydration heat and volume deformation of cement-based materials. Construction and Building Materials. 2020; 250 ():118807.
Chicago/Turabian StyleLei Wang; Fanxing Guo; Yuqiang Lin; Huamei Yang; S.W. Tang. 2020. "Comparison between the effects of phosphorous slag and fly ash on the C-S-H structure, long-term hydration heat and volume deformation of cement-based materials." Construction and Building Materials 250, no. : 118807.
The creep of concrete is significantly affected by ambient temperature and humidity. In design codes, the influence of ambient temperature and humidity on concrete creep is approximately considered by correction coefficient terms. However, this method is not suitable for creep analysis of specific structure under complex temperature and humidity environments. At present, the Microprestress-Solidification (MPS) theory is widely adopted to analyze the complex influence of temperature and humidity on concrete creep. However, the MPS theory still has some shortcomings (The MPS theory fails to reflect the size effect in drying creep. Besides, the humidity dependence of transient thermal creep cannot be correctly modeled.). On the basis of MPS theory, this paper makes some appropriate corrections and modifications: firstly, the evolution equation of micro-prestress S is reasonably updated by redefining the relationship between the long-term creep viscosity and micro-prestress S. Meanwhile, based on the thermodynamics, the influence of temperature and humidity variation on the evolution of micro-prestress S is reformulated and the transient thermal creep effect is modified to be humidity-dependent. In order to verify the improved MPS model, experiment data in literatures are adopted to make verifications. Results prove the correctness of the modifications and the practicability of the improved model.
P. Yu; Y.H. Duan; Q.X. Fan; S.W. Tang. Improved MPS model for concrete creep under variable humidity and temperature. Construction and Building Materials 2020, 243, 118183 .
AMA StyleP. Yu, Y.H. Duan, Q.X. Fan, S.W. Tang. Improved MPS model for concrete creep under variable humidity and temperature. Construction and Building Materials. 2020; 243 ():118183.
Chicago/Turabian StyleP. Yu; Y.H. Duan; Q.X. Fan; S.W. Tang. 2020. "Improved MPS model for concrete creep under variable humidity and temperature." Construction and Building Materials 243, no. : 118183.
This work systematically investigates the early hydration process and pore structure evolution of high limestone powder wastes content blended cement pastes by non-contact impedance measurement and microstructural tests. According to the evolution of impedance response, the early hydration process of blende cement pastes can be divided into four stages, denominated as dissolution, acceleration, dynamic balance and hardened stages, respectively. Dynamic balance stage not present in hydration process of pure cement, is a characteristic hydration stage for blended cement pastes. Furthermore, fractal approach for predicting the evolution of pore structure is proposed originally, based on the impedance results.
Zhen He; Rongjin Cai; E. Chen; Shengwen Tang. The investigation of early hydration and pore structure for limestone powder wastes blended cement pastes. Construction and Building Materials 2019, 229, 116923 .
AMA StyleZhen He, Rongjin Cai, E. Chen, Shengwen Tang. The investigation of early hydration and pore structure for limestone powder wastes blended cement pastes. Construction and Building Materials. 2019; 229 ():116923.
Chicago/Turabian StyleZhen He; Rongjin Cai; E. Chen; Shengwen Tang. 2019. "The investigation of early hydration and pore structure for limestone powder wastes blended cement pastes." Construction and Building Materials 229, no. : 116923.
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.
The lack of systematic evaluation on the feasibility of fabricating solderable coatings through a hot-dipped tinning process restricts the increasing applications of this process in the electronics industry. In this paper, the temperature-dependence, wettability, thermal stability, and microstructure of solderable Sn coatings produced by hot-dipped tinning are evaluated synthetically, which aims at developing a cost-efficient and environment-friendly way to fabricate solderable Sn coatings. Experimental results show that a dipping temperature of 280–320°C and dipping time of 4–6 s are appropriate process conditions for C1100 foils. The solderability of C1100 foils is superior to C194 foils. After long-term service (up to 500 h) at elevated temperature, sharp spines caused by SnO2 whiskers appear on the surface of coated C194 foils, which increase the risk of short circuit in use and lower their reliability. The addition of microalloying elements may be a possible solution to restrain SnO2 whiskers.
Nan Xiang; Ting Yin; Bao-Hong Tian; Shengwen Tang; E. Chen. Evaluation on the Manufacturability of Solderable Sn Coatings Obtained by Employing Hot-Dipped Tinning Process. JOM 2019, 71, 4284 -4295.
AMA StyleNan Xiang, Ting Yin, Bao-Hong Tian, Shengwen Tang, E. Chen. Evaluation on the Manufacturability of Solderable Sn Coatings Obtained by Employing Hot-Dipped Tinning Process. JOM. 2019; 71 (12):4284-4295.
Chicago/Turabian StyleNan Xiang; Ting Yin; Bao-Hong Tian; Shengwen Tang; E. Chen. 2019. "Evaluation on the Manufacturability of Solderable Sn Coatings Obtained by Employing Hot-Dipped Tinning Process." JOM 71, no. 12: 4284-4295.
Benzene compounds generates a series of reducing substances under high temperature conditions and is capable of converting insulating polycrystalline C12A7 into a conductive material. Conductive C12A7:e- is prepared by placing the C12A7 insulation and benzene compounds together and calcining at 1100°C for a period of time. At present, the conductivity of C12A7:e- prepared by this method can be as high as 8.71 S·cm-1, and the electron concentration can reach 1.68 × 1020 cm-3. Studies on the conductive mechanism of C12A7 show that all benzene ring-containing compounds enable to significantly improve its conductivity. Moreover, the process is similar to the industrial preparation methods of cement and ceramics, and does not need to be performed in a vacuum environment, which is considerably suitable for the large-scale industrial manufacture in the future.
Wei Zhou; Wenzhi Yu; Yang Li; Shengwen Tang. Versatile options for preparing conductive 12CaO·7Al2O3 by benzene compounds. Materials Letters 2019, 251, 106 -109.
AMA StyleWei Zhou, Wenzhi Yu, Yang Li, Shengwen Tang. Versatile options for preparing conductive 12CaO·7Al2O3 by benzene compounds. Materials Letters. 2019; 251 ():106-109.
Chicago/Turabian StyleWei Zhou; Wenzhi Yu; Yang Li; Shengwen Tang. 2019. "Versatile options for preparing conductive 12CaO·7Al2O3 by benzene compounds." Materials Letters 251, no. : 106-109.
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.
Ionic zinc is considered as an environmental pollutant. This work systematically investigated leaching mechanisms of calcium sulfoaluminate cement (CSA) pastes incorporated with/without ZnCl2 under the attacks of chloride and/or sulfate. The leaching behaviors of CSA pastes in the leaching solution are in-situ and continuously monitored by innovative non-contact electrical impedance measurement (NCEIM) and pH meter. The dissolution and diffusion during the leaching process are experimentally identified. Other techniques are also performed to verify the finding of NCEIM: the ion chromatograph and inductively coupled plasma optical emission spectrometer reveal the leaching or decomposition sequence of CSA pastes during the leaching process. Besides, results from XRD and SEM techniques demonstrate that main solid products in CSA pastes are ettringite and calcium monosulfoaluminate hydrates. The incorporation of Zn in the pastes has great impact on the decomposition of CSA pastes in the temperature elevation. External chloride and/or sulfate attacks significantly alter the pore structure of CSA pastes during the leaching process.
Shengwen Tang; Junhui Yuan; Rongjin Cai; Xuanchun Wei; Cheng Zhao; Xinhua Cai; Zhen He; E. Chen. Continuous monitoring for leaching of calcium sulfoaluminate cement pastes incorporated with ZnCl2 under the attacks of chloride and sulfate. Chemosphere 2019, 223, 91 -98.
AMA StyleShengwen Tang, Junhui Yuan, Rongjin Cai, Xuanchun Wei, Cheng Zhao, Xinhua Cai, Zhen He, E. Chen. Continuous monitoring for leaching of calcium sulfoaluminate cement pastes incorporated with ZnCl2 under the attacks of chloride and sulfate. Chemosphere. 2019; 223 ():91-98.
Chicago/Turabian StyleShengwen Tang; Junhui Yuan; Rongjin Cai; Xuanchun Wei; Cheng Zhao; Xinhua Cai; Zhen He; E. Chen. 2019. "Continuous monitoring for leaching of calcium sulfoaluminate cement pastes incorporated with ZnCl2 under the attacks of chloride and sulfate." Chemosphere 223, no. : 91-98.
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.
A microstructure model combined with diffusion-based mechanism is reconstructed. The objective is to propose a model that could describe the long-term microstructure evolution driven by certain physical mechanisms. With modifications in parametric control, the introduced kinetics is extended to directly consider the particle size distribution (PSD) of cement (alite). The particle impingement is analyzed for the effects of PSD and water-to-cement ratio (w/c ratio). The variations of C–S–H bulk density and hydrates distribution under different temperature are explored in the microstructural modeling. Numerical results for effects of PSD, w/c ratio, temperature, as well as the ambient humidity are obtained and compared with experimental results. Validations especially for early hydration prove that the current model could capture characteristics regarding hydration and evolved microstructure from hours to years.
W. Zhou; L. Duan; S. W. Tang; E. Chen; A. Hanif. Modeling the evolved microstructure of cement pastes governed by diffusion through barrier shells of C–S–H. Journal of Materials Science 2018, 54, 4680 -4700.
AMA StyleW. Zhou, L. Duan, S. W. Tang, E. Chen, A. Hanif. Modeling the evolved microstructure of cement pastes governed by diffusion through barrier shells of C–S–H. Journal of Materials Science. 2018; 54 (6):4680-4700.
Chicago/Turabian StyleW. Zhou; L. Duan; S. W. Tang; E. Chen; A. Hanif. 2018. "Modeling the evolved microstructure of cement pastes governed by diffusion through barrier shells of C–S–H." Journal of Materials Science 54, no. 6: 4680-4700.
In some special oscillatory applications, especially those operated at high speeds, the eddy current loss of linear permanent magnet (PM) synchronous machine (LPMSM) should be fully considered because the loss might be large and concentrated in PMs during the oscillation period. This paper presents a loss analysis method based on computationally efficient finite element analysis (CE-FEA) for a 20 Hz oscillatory tubular LPMSM. Since the mover speed varies with time, an equally-divided model in 1/4 period is introduced to calculate the average PM eddy current loss. The flux density curves in PMs are calculated at 18 intervals by the CE-FEA, through which the change rate of magnetic flux density is analyzed, considering both the entering and leaving effects and coil end effects. The calculation results show that the eddy current loss is obviously concentrated in PMs near the two ends of coils. The calculation results at a speed of 3.6 m/s obtained by the CE-FEA and 2D&3D time-stepping FEAs are compared to validate the accuracy. Finally, the proposed method is validated by the experimental test results on a prototype LPMSM.
Tao Wu; Kang Lu; Jianguo Zhu; Gang Lei; Youguang Guo; Shengwen Tang. Calculation of Eddy Current Loss in a Tubular Oscillatory LPMSM Using Computationally Efficient FEA. IEEE Transactions on Industrial Electronics 2018, 66, 6200 -6209.
AMA StyleTao Wu, Kang Lu, Jianguo Zhu, Gang Lei, Youguang Guo, Shengwen Tang. Calculation of Eddy Current Loss in a Tubular Oscillatory LPMSM Using Computationally Efficient FEA. IEEE Transactions on Industrial Electronics. 2018; 66 (8):6200-6209.
Chicago/Turabian StyleTao Wu; Kang Lu; Jianguo Zhu; Gang Lei; Youguang Guo; Shengwen Tang. 2018. "Calculation of Eddy Current Loss in a Tubular Oscillatory LPMSM Using Computationally Efficient FEA." IEEE Transactions on Industrial Electronics 66, no. 8: 6200-6209.
In this study, a microstructure-based homogenization method is proposed for the creep behavior of cement paste at early age. With the aid of hydration model, the evolution of microstructure in hydrating cement paste is represented as a function of time. The inherent creep of C-S-H is characterized by the B3 creep model proposed by Bazant, whereas other chemical phases are assumed to behave elastically. A two-step homogenization method combining the analytical and numerical homogenization is proposed. Analytic homogenization method is applied for the effective mechanic properties of composites in the hydration model. Then the numerical homogenization is conducted based on the obtained microstructures. The numerical homogenization is implemented with the aid of FEM software Comsol Multiphysics. The reliability and precision of homogenization method are validated by experimental data in literature. The creep and creep recovery behavior of cement paste at early age is comprehensively studied. The main novelty of this study is the quantification of the contribution of each mechanisms to the creep and creep recovery behavior of cement paste at early age, which provides insights to better understand the creep mechanisms.
P. Yu; Y.H. Duan; E. Chen; S.W. Tang; Asad Hanif; Y.L. Fan. Microstructure-based homogenization method for early-age creep of cement paste. Construction and Building Materials 2018, 188, 1193 -1206.
AMA StyleP. Yu, Y.H. Duan, E. Chen, S.W. Tang, Asad Hanif, Y.L. Fan. Microstructure-based homogenization method for early-age creep of cement paste. Construction and Building Materials. 2018; 188 ():1193-1206.
Chicago/Turabian StyleP. Yu; Y.H. Duan; E. Chen; S.W. Tang; Asad Hanif; Y.L. Fan. 2018. "Microstructure-based homogenization method for early-age creep of cement paste." Construction and Building Materials 188, no. : 1193-1206.