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Qingjun Ding
School of Materials Science and Engineering, Wuhan University of Technology, No. 122, Luoshi Road, Hongshan District, Postcode: 430070 Wuhan, China

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Journal article
Published: 08 May 2021 in Construction and Building Materials
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The dehydration and dehydroxylation of C-S-H gel ubiquitously occurs in the thermal destruction or recycle of the concrete materials, and the latter is closely related to the sustainability in the construction industry. Utilizing reactive molecular dynamics simulation, this paper presents an investigation on the structure, dynamics and mechanical properties evolution of the C-S-H with decreasing water content, at the molecular level. Dynamically, it is found that the dehydration and dehydroxylation are successively occurred as the hydration degree of C-S-H decreases. At the dehydration stage, water molecules are dissociated to maintain the number of hydroxyls. The C-S-H structure does not change much at this stage. At the dehydroxylation stage, the number of hydroxyl groups sharply decreases, along with large structural transformation in the C-S-H, including fast decreasing interlayer spacing, merging of interlayer calcium layers and disordering of the primary calcium silicate layers. With respect to the mechanical properties, the interlayer spacing collapse significantly increases the stiffness and toughness of the C-S-H structure. On the other hand, drastic volume shrinkage of the C-S-H structure due to dehydroxylation can lead to decreasing contact points between C-S-H nano-globules. This means an increase in the mechanical properties of C-S-H matrix but a decrease in the packing density of C-S-H gel. Eventually, the indentation modulus of C-S-H gel monotonously decreases during dehydration and dehydroxylation.

ACS Style

Jun Yang; Wei Zhang; Dongshuai Hou; Gaozhan Zhang; Qingjun Ding. Structure, dynamics and mechanical properties evolution of calcium silicate hydrate induced by dehydration and dehydroxylation. Construction and Building Materials 2021, 291, 123327 .

AMA Style

Jun Yang, Wei Zhang, Dongshuai Hou, Gaozhan Zhang, Qingjun Ding. Structure, dynamics and mechanical properties evolution of calcium silicate hydrate induced by dehydration and dehydroxylation. Construction and Building Materials. 2021; 291 ():123327.

Chicago/Turabian Style

Jun Yang; Wei Zhang; Dongshuai Hou; Gaozhan Zhang; Qingjun Ding. 2021. "Structure, dynamics and mechanical properties evolution of calcium silicate hydrate induced by dehydration and dehydroxylation." Construction and Building Materials 291, no. : 123327.

Letter
Published: 01 February 2021 in Sensors
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A new optical fiber sensor based on the fluorescence lifetime was prepared for specific detection of sulfate ion concentration, where 1,1′-(anthracene-9,10-diylbis(methylene))bis(3-(dodecylcarbamoyl)pyridin-1-ium) acted as the sulfate fluorescent probe. The probe was immobilized in a porous cellulose acetate membrane to form the sensitive membrane by the immersion precipitation method, and polyethylene glycol 400 acted as a porogen. The sensing principle was proven, as a sulfate ion could form a complex with the probe through a hydrogen bond, which led to structural changes and fluorescence for the probe. The signals of the fluorescence lifetime data were collected by the lock-in amplifier and converted into the phase delay to realize the detection of sulfate ions. Based on the phase-modulated fluorometry, the relationship between the phase delay of the probe and the sulfate ion concentration was described in the range from 2 to 10 mM. The specificity and response time of this optical fiber sensor were also researched.

ACS Style

Liyun Ding; Panfeng Gong; Bing Xu; Qingjun Ding. An Optical Fiber Sensor Based on Fluorescence Lifetime for the Determination of Sulfate Ions. Sensors 2021, 21, 954 .

AMA Style

Liyun Ding, Panfeng Gong, Bing Xu, Qingjun Ding. An Optical Fiber Sensor Based on Fluorescence Lifetime for the Determination of Sulfate Ions. Sensors. 2021; 21 (3):954.

Chicago/Turabian Style

Liyun Ding; Panfeng Gong; Bing Xu; Qingjun Ding. 2021. "An Optical Fiber Sensor Based on Fluorescence Lifetime for the Determination of Sulfate Ions." Sensors 21, no. 3: 954.

Journal article
Published: 10 July 2020 in Construction and Building Materials
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In this research, molecular dynamics simulations were employed to unravel the transmission mechanisms of chloride ions and sodium ions throughout ettringite nanopores as exposed to an external electric field 0–0.04 V/Å. The current was generated by the directional migration of cations and anions, proportional to the intensity of electric field, among which chlorides account for 80% while sodium contributes little. The migration of sodium ions was limited as a result of the attraction from the oxygen atoms in the sulfate ions on the ettringite surface. This effect weakened due to the increase in the electric field intensity. Furthermore, the relocation rate of ions may obey in the following ranking: Cl− > Ow > Na+. The development of this work can reveal the mechanism of ion migration and diffusion inside the pores of concrete during the application of the electrochemical desalination method, which has a guiding significance for the durability design of concrete structures.

ACS Style

Jinhui Li; Lanjuan Gao; Dongshuai Hou; Pan Wang; Yang Zhou; Qingjun Ding; Chenchen Xiong. Insights on the ion migration throughout the nano-channel of ettringite under an external electric field: Structure, dynamics, and mechanisms. Construction and Building Materials 2020, 262, 120074 .

AMA Style

Jinhui Li, Lanjuan Gao, Dongshuai Hou, Pan Wang, Yang Zhou, Qingjun Ding, Chenchen Xiong. Insights on the ion migration throughout the nano-channel of ettringite under an external electric field: Structure, dynamics, and mechanisms. Construction and Building Materials. 2020; 262 ():120074.

Chicago/Turabian Style

Jinhui Li; Lanjuan Gao; Dongshuai Hou; Pan Wang; Yang Zhou; Qingjun Ding; Chenchen Xiong. 2020. "Insights on the ion migration throughout the nano-channel of ettringite under an external electric field: Structure, dynamics, and mechanisms." Construction and Building Materials 262, no. : 120074.

Journal article
Published: 25 December 2019 in Construction and Building Materials
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The MgCl2 induced material degradation is the major durability issue facing the cement-based system. In this study, the degradation mechanism induced by MgCl2 attack at nanoscale is investigated for cement paste exposed to MgCl2 solution with different concentrations for 28 and 180 days by combing X-ray diffraction (XRD), 29Si and 27Al Nuclear Magnetic Resonance Spectroscopy (NMR), Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and thermodynamic modeling. The XRD, SEM-EDS and NMR results show that the cement paste exposed to 5 ~ 15 wt% MgCl2 cause disintegration of the main hydration product, calcium aluminosilicate hydrate (C–A–S–H) gel, portlandite, along with the formation of extensive Friedel’s salt, brucite precipitation and the small amount of ettringite. The phase transformation is closely related with the polymerization of the C–A–S–H gel and the de-aluminization characterized by the increasing mean silicate chain length and reduction of the Al[4]/Si ratio in the low calcium environment induced by MgCl2 attacking. Additionally, the predicted phase diagram from thermodynamic modeling matches well with the experimental analysis and gives a supplement support to the phase transformation. By correlating the phase composition change and the local structure of aluminate species and polymerization evolution, this study provides molecular insight on the fundamental MgCl2 induced degradation reactions happening in cement paste.

ACS Style

Jun Yang; Dongshuai Hou; Qingjun Ding; Gaozhan Zhang; Yang Zhang; Hao Hu. Insight on the nanoscale chemical degradation mechanism of MgCl2 attack in cement paste. Construction and Building Materials 2019, 238, 117777 .

AMA Style

Jun Yang, Dongshuai Hou, Qingjun Ding, Gaozhan Zhang, Yang Zhang, Hao Hu. Insight on the nanoscale chemical degradation mechanism of MgCl2 attack in cement paste. Construction and Building Materials. 2019; 238 ():117777.

Chicago/Turabian Style

Jun Yang; Dongshuai Hou; Qingjun Ding; Gaozhan Zhang; Yang Zhang; Hao Hu. 2019. "Insight on the nanoscale chemical degradation mechanism of MgCl2 attack in cement paste." Construction and Building Materials 238, no. : 117777.

Journal article
Published: 16 May 2019 in Materials Chemistry and Physics
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In order to gain a molecular-level insight on the structure and performance of cement-based materials in high temperature environment, this paper investigates the structure, dynamics and mechanical properties of their main hydration product, calcium aluminosilicate hydrate (C-A-S-H), at elevated temperatures by using reactive molecular dynamics simulation. The results show that rising temperature can destroy the H-bond network of interlayer water molecules in C-A-S-H, leading to pronounced expansion of the interlayer regions. Meanwhile, interlayer water molecules lose its glassy water dynamics and exhibit dramatically high diffusivity with rising temperature. In addition, the calcium atoms show inhomogeneous dynamics at high temperature. At 1500K, the interlayer calcium atoms can escape from their coordination “cages” and diffuse, while the motion of those located in the principal layer are restricted by the Si–O and Al–O bonds throughout the simulation. Furthermore, reactive force field couples the mechanical response and chemical reaction during the uniaxial tensile test for C-A-S-H gel. The de-polymerization and hydrolytic reaction happens frequently in the deformed C-A-S-H gel at high temperature, resulting in degradation of stiffness and strength. On the other hand, the atomic rearrangement at elevated temperature contributes to the re-connection of broken chemical bonds, enhancing ductility of C-A-S-H.

ACS Style

Jianhua Zhang; Jun Yang; Dongshuai Hou; Qingjun Ding. Molecular dynamics study on calcium aluminosilicate hydrate at elevated temperatures: Structure, dynamics and mechanical properties. Materials Chemistry and Physics 2019, 233, 276 -287.

AMA Style

Jianhua Zhang, Jun Yang, Dongshuai Hou, Qingjun Ding. Molecular dynamics study on calcium aluminosilicate hydrate at elevated temperatures: Structure, dynamics and mechanical properties. Materials Chemistry and Physics. 2019; 233 ():276-287.

Chicago/Turabian Style

Jianhua Zhang; Jun Yang; Dongshuai Hou; Qingjun Ding. 2019. "Molecular dynamics study on calcium aluminosilicate hydrate at elevated temperatures: Structure, dynamics and mechanical properties." Materials Chemistry and Physics 233, no. : 276-287.

Article
Published: 18 June 2018 in Journal of Wuhan University of Technology-Mater. Sci. Ed.
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The microstructural evolution of C-(A)-S-H gel in Portland cement pastes immersed in pure water and 5.0 wt% Na2SO4 solution for different ages was comparatively investigated, by means of 29Si NMR spectroscopy, and SEM-EDS analysis. Additionally, molecular dynamics simulation was performed to study the aluminum coordination status and interaction of sulfate ions in C-(A)-S-H gel. The results showed significant changes in the microstructural evolution of C-(A)-S-H gel in Portland cement paste. Sulfate attack has decalcifying and dealuminizing effect on C-(A)-S-H gel which is evident from increase in mean chain length (MCL) and decrease in Ca/Si & Al[4]/Si ratios of C-(A)-S-H gel. Additionally, Molecular dynamics simulation proves that Al[4] substituted in silicate chains of C-(A)-S-H gel is thermodynamically metastable, which may explain its migration from the silicate chains and transformation to Al[6], thus lowering the Al[4]/Si ratio of C-(A)-S-H gel. SO42- ions can carry the interfacial Ca2+ ions into the pore solution by the diffusion-absorption-desorption process, which unravels the mechanism of sulfate attack on C-(A)-S-H gel.

ACS Style

Gaozhan Zhang; Xiaojia Zhang; Qingjun Ding; Dongshuai Hou; Kaiwei Liu. Microstructural Evolution Mechanism of C-(A)-S-H Gel in Portland Cement Pastes Affected by Sulfate Ions. Journal of Wuhan University of Technology-Mater. Sci. Ed. 2018, 33, 639 -647.

AMA Style

Gaozhan Zhang, Xiaojia Zhang, Qingjun Ding, Dongshuai Hou, Kaiwei Liu. Microstructural Evolution Mechanism of C-(A)-S-H Gel in Portland Cement Pastes Affected by Sulfate Ions. Journal of Wuhan University of Technology-Mater. Sci. Ed.. 2018; 33 (3):639-647.

Chicago/Turabian Style

Gaozhan Zhang; Xiaojia Zhang; Qingjun Ding; Dongshuai Hou; Kaiwei Liu. 2018. "Microstructural Evolution Mechanism of C-(A)-S-H Gel in Portland Cement Pastes Affected by Sulfate Ions." Journal of Wuhan University of Technology-Mater. Sci. Ed. 33, no. 3: 639-647.

Article
Published: 15 October 2015 in Journal of Wuhan University of Technology-Mater. Sci. Ed.
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The mechanical behavior and failure mechanism of recycled semi-flexible pavement material were investigated by different scales method. The macroscopic mechanical behavior of samples was studied by static and dynamic splitting tensile tests on mechanics testing system (MTS). The mechanical analysis in micro scale was carried out by material image analysis method and finite element analysis system. The strains of recycled semi-flexible pavement material on samples surface and in each phase materials were obtained. The test results reveal that the performance of recovered asphalt binder was the major determinant on the structural stability of recycled semi-flexible pavement material. The asphalt binder with high viscoelasticity could delay the initial cracking time and reduce the residual strain under cyclic loading conditions. The failure possibility order of each phase in recycled semi-flexible pavement material was asphalt binder, reclaimed aggregate, cement paste and virgin aggregate.

ACS Style

Qingjun Ding; Mingyu Zhao; Fan Shen; Xiaoqiang Zhang. Mechanical behavior and failure mechanism of recycled semi-flexible pavement material. Journal of Wuhan University of Technology-Mater. Sci. Ed. 2015, 30, 981 -988.

AMA Style

Qingjun Ding, Mingyu Zhao, Fan Shen, Xiaoqiang Zhang. Mechanical behavior and failure mechanism of recycled semi-flexible pavement material. Journal of Wuhan University of Technology-Mater. Sci. Ed.. 2015; 30 (5):981-988.

Chicago/Turabian Style

Qingjun Ding; Mingyu Zhao; Fan Shen; Xiaoqiang Zhang. 2015. "Mechanical behavior and failure mechanism of recycled semi-flexible pavement material." Journal of Wuhan University of Technology-Mater. Sci. Ed. 30, no. 5: 981-988.

Journal article
Published: 30 September 2015 in Microfluidics and Nanofluidics
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Water molecules confined in the interlayer region of calcium silicate hydrate (C–S–H) are closely related to the cohesion in the cementitious materials. In this research, molecular dynamics is employed to investigate the structure, dynamics and mechanical properties of water molecules in the nanopore of C–S–H gels at ambient temperature. In order to consider the confinement effect of calcium silicate sheets, the pore size expressed as interlayer distance changes from 13 to 22 Å. The water molecules near the C–S–H surface are strongly influenced by the ONB atoms in the silicate chains and Caw atoms in the interlayer region. They demonstrate following structural features: layering in the water density profile, the orientation preference in the dipolar angle distribution and long special correlation in the radial distribution function. Dynamically, while the interlayer distance increases by 10 Å, the diffusion coefficient transfers through two orders of magnitude from 3.42 × 10−12 to 5.3 × 10−10 m2/s2. In the mean square displacement curves, the cage stage, a characteristic of the dynamics in the glasses, gradually disappears with increasing interlayer distance. The dynamic evolution of water molecules is primarily induced by the changes in the strength of H-bonds and Ca–Ow connections, which is consistent with lowering of the frequency in the simulated vibration spectrum. The strongly attractive interaction between water molecules and calcium silicate layer is weakened and the motion of water molecules is less restricted at large interlayer distance. Furthermore, the interlayer fluid pressure study shows that the cohesion in the C–S–H gel, contributed by the interlayer calcium atoms, progressively diminishes from 1.5 to 0 GPa, due to the enhancing disjoining effect of water molecules connected with calcium atoms with increasing interlayer distance.

ACS Style

Dongshuai Hou; Cong Lu; Tiejun Zhao; Peng Zhang; Qingjun Ding. Structural, dynamic and mechanical evolution of water confined in the nanopores of disordered calcium silicate sheets. Microfluidics and Nanofluidics 2015, 19, 1309 -1323.

AMA Style

Dongshuai Hou, Cong Lu, Tiejun Zhao, Peng Zhang, Qingjun Ding. Structural, dynamic and mechanical evolution of water confined in the nanopores of disordered calcium silicate sheets. Microfluidics and Nanofluidics. 2015; 19 (6):1309-1323.

Chicago/Turabian Style

Dongshuai Hou; Cong Lu; Tiejun Zhao; Peng Zhang; Qingjun Ding. 2015. "Structural, dynamic and mechanical evolution of water confined in the nanopores of disordered calcium silicate sheets." Microfluidics and Nanofluidics 19, no. 6: 1309-1323.

Cementitious material
Published: 05 October 2013 in Journal of Wuhan University of Technology-Mater. Sci. Ed.
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The effect of curing regime on the distribution of Al3+ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance(NMR) with deconvolution technique. The results indicate that the tetrahedral coordination Al3+ incorporated in C-S-H structure mainly originate from the Al3+ incorporated in the alite and belite phases in the Portland cement. The curing regime of constant temperature of 20 °C is beneficial to the octahedral coordination Al3+ transforming to tetrahedral coordination Al3+ incorporated in C-S-H structure. However, at curing regime of variable temperature, the temperature rising process is more advantageous to the transformation from ettringite to monosulphate, substitution of Al3+ for Si4+ in the C-S-H structure and the formation of the third aluminate hydrate (TAH) than that at constant temperature of 20 °C. The high temperature of 60 °C in the holding temperature process promotes the decomposition of ettringite, and enhances the consumption of the Al3+ incorporated in C-S-H phases and the Al3+ in TAH for the monosulphate forming. The temperature decreasing promotes the transformation from monosulphate to ettringite, and increases the consumption of the Al3+ incorporated in C-S-H phases, and then increases the quantity of the TAH.

ACS Style

Qingjun Ding; Chenguang Hu; Xiaoxin Feng; Xiulin Huang. Effect of curing regime on the distribution of Al3+ coordination in hardened cement pastes. Journal of Wuhan University of Technology-Mater. Sci. Ed. 2013, 28, 927 -933.

AMA Style

Qingjun Ding, Chenguang Hu, Xiaoxin Feng, Xiulin Huang. Effect of curing regime on the distribution of Al3+ coordination in hardened cement pastes. Journal of Wuhan University of Technology-Mater. Sci. Ed.. 2013; 28 (5):927-933.

Chicago/Turabian Style

Qingjun Ding; Chenguang Hu; Xiaoxin Feng; Xiulin Huang. 2013. "Effect of curing regime on the distribution of Al3+ coordination in hardened cement pastes." Journal of Wuhan University of Technology-Mater. Sci. Ed. 28, no. 5: 927-933.