State Key Laboratory of High Performance Civil Engineering Materials

Nanjing, China

State Key Laboratory of High Performance Civil Engineering Materials

Nanjing, China
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Tang J.,Nanjing Southeast University | Tang J.,State Key Laboratory of High Performance Civil Engineering Materials | Liu J.,Nanjing Southeast University | Liu J.,Jiangsu Subote New Material Co. | And 5 more authors.
Construction and Building Materials | Year: 2017

The cation polyurethane (PUC) was used to improve the mechanical property of cement-based materials. Meanwhile, hydration kinetics, mineral phase compositions and microstructure characterization of hydration products were also investigated by isothermal calorimetry, quantitative X-ray diffraction and scanning electron microscope. The results show that the addition of PUC accelerated the cement hydration, altered the mineralogical compositions and morphology of hydration products, and correspondingly the microstructure of cement based materials. It is found that the addition of PUC decrease the brittleness of cement-based materials, especially for the early age. When the dosage of PUC is 0.5%, as the optimal mixing amounts, the tensile strengths of hardened cement pastes at 1 day, 3 day and 7 day separately increase by 49.92%, 93.63% and 88.44%, simultaneously the flexural strengths also exert corresponding increases by 8.38%, 26.61% and 36.40%, comparing with the plain cement-based materials. While, the addition of sand, will migitigate or even eliminate this toughness improving benefit due to the introduction of interfacial zone. © 2016


Chen Q.,Tongji University | Chen Q.,Chang'an University | Chen Q.,State Key Laboratory of High Performance Civil Engineering Materials | Jiang Z.,Tongji University | And 3 more authors.
International Journal of Damage Mechanics | Year: 2017

An improved micromechanical framework with interfacial transition zone (ITZ) effects is proposed for saturated concrete repaired by electrochemical deposition method (EDM) based on our recent studies. A multiphase micromechanical model with ITZs is proposed based on the material microstructure and a new multilevel homogenization scheme with inter-particle interactions is employed to predict the effective properties of repaired concrete considering the ITZ effects. The equivalent particle, composed by the water, deposition product and ITZ, is obtained by modifying the generalized self-consistent model. The mechanical properties of the healed concrete are calculated by micromechanical homogenization considering the inter-particle interactions. Moreover, modification procedures considering the ITZ effects are presented to attain the properties of repaired concrete in the dry state. To demonstrate the feasibility of the proposed micromechanical model, predictions in this study are compared with those of the existing models and the experimental data. Finally, the influences of ITZ on the equivalent particle and repaired concrete are discussed based on the proposed micromechanical framework. © The Author(s) 2017.


Wei T.,Jiangsu Sobute New Materials Co. | Wei T.,State Key Laboratory of High Performance Civil Engineering Materials | Hong J.,Jiangsu Sobute New Materials Co. | Hong J.,State Key Laboratory of High Performance Civil Engineering Materials | Lin J.,Jiangsu Research Institute of Building Science
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2017

The strength development of cold regeneration with asphalt emulsion(CRAE) under the constant environment condition was revealed by indoor simulation test, and then the strength contribution in different periods under the conditions of different content of cement and asphalt emulsion was studied. The cement hydration process in cement emulsified asphalt mortar, and asphalt emulsion demulsification process were analyzed by micro analysis method such as ESEM et al. The results indicate that the development of strength of CRAE shows the long-term mode that not only the rapid growth in the early stage and the slow growth in the late stage, but also the early and late strength can be promoted significantly by cement. It has also shown that the larger the content, the higher the amplitude; cement contributes to the rapid improvement of early strength. Demulsification asphalt provides the main source of strength. At the best asphalt emulsion content maximum early or late strength can be achieved. The early cement hydration reaction can be inhibited by asphalt emulsion and the effect of cement on asphalt emulsion demulsification is mainly reflected by the attraction of cement particles and the particles agglomeration due to the hydration product. The reinforced structure formed by cement hydration products and asphalt can promote the strength further. © 2017, Editorial Department of Journal of Building Materials. All right reserved.


Zhou H.,State Key Laboratory of High Performance Civil Engineering Materials | Zhou H.,Jiangsu Academy of Building Science Co | Liu J.,State Key Laboratory of High Performance Civil Engineering Materials | Liu J.,Jiangsu Academy of Building Science Co | And 2 more authors.
Procedia Engineering | Year: 2012

In this paper, based on the kinetic process and mechanism of cement hydration, three basic processes of low alkalinity sulphoaluminate cement hydration are characterized, including nucleation and growth interaction (NG), phase-boundary interaction (I), and diffusion interaction (D). It also studies the influence of water-cement ratio on the hydration exothermic chemical characteristics and kinetic process of low alkalinity sulphoaluminate cement. The results show that the hydration reaction of low alkalinity sulphoaluminate cement is very rapid. The lower the water cement ratio is, the longer the thermal effect will last. The hydration kinetic process of low alkalinity sulphoaluminate cement is NG-I-D. With a higher water-cement ratio, the hydration kinetic process will transfer from the NG process into I process with a lower hydration degree. And with the water-cement ratio increasing gradually, the hydration reaction from I process to D process is also reduced. © 2011 Published by Elsevier Ltd.


Lv J.,State Key Laboratory of High Performance Civil Engineering Materials | Lv J.,Jiangsu Subote New Materials Co. | Liu J.Z.,Jiangsu Subote New Materials Co.
Applied Mechanics and Materials | Year: 2014

In order to investigate the bond strength between deformed steel fiber and concrete, various deformed steel fibers, like hooked end fiber, spiral type fiber, bundle fiber, hooked fiber and so on, are produced. Straight type fiber and deformed fiber were embedded in mortar to do the bond strength experiment. A comparison with each other was carried out. It has been found that the change of the fiber cross section increases the bond strength between steel fiber and concrete matrix, growth range outweighs 100%. When modified both ends of anchorages, the bond strength raises 400% in contrast with straight type steel fiber. Besides, the deformed fiber, which went through two modified methods, enhances the bond strength over 700% in comparison with straight type fiber. © (2014) Trans Tech Publications, Switzerland.


Gao Y.,Nanjing Southeast University | Gao Y.,Jiangsu Key Laboratory of Construction Materials | Mu S.,State Key Laboratory of High Performance Civil Engineering Materials | Jiang J.,Nanjing Southeast University | Jiang J.,Jiangsu Key Laboratory of Construction Materials
Key Engineering Materials | Year: 2016

Though discussed a lot, it remains a practical challenge to modeling pore structure in cement paste. The fractal approach shows a great advantage since it allows to generate complex pore structure via simple geometric iterations and to incorporate the wide scope of pores in a self-similar manner. In this paper, the solid mass fractal model is proposed for pore structure in cement paste. The parametric analysis is performed in conjunction with the porosimetric test. It is shown that the proposed solid mass fractal well describes pore structure in cement paste. © 2016 Trans Tech Publications, Switzerland.


Liu J.,Jiangsu Research Institute of Building Science | Liu J.,Jiangsu Bote New Material Ltd. | Yang Y.,Jiangsu Research Institute of Building Science | Zhou D.,Jiangsu Research Institute of Building Science | Ran Q.,State Key Laboratory of High Performance Civil Engineering Materials
American Concrete Institute, ACI Special Publication | Year: 2015

Slump loss of fresh concrete was a common issue in engineering construction, especially under high temperature and long distance transportation conditions. Therefore, slow-release polycarboxylate superplasticizers (PCEs) have been widely used to reduce the slump loss in various engineering projects. In this study, three kinds of PCEs with different proportions of hydroxyl ester groups (HEG) were synthesized and characterized by 1H-NMR and Gel Permeation Chromatography (GPC). The effects of the HEG content on dispersion retention, adsorption kinetics and zeta potential of fresh cement suspensions were systematically investigated to figure out the mechanism. For PCEs with the same molar ratio of carboxyl group and reactive polyether, the dispersion retention ability of PCEs is improved with the increasing of HEG ratio. HEG in PCEs can be slowly converted to carboxyl groups in the alkaline environment of cement suspension, which could enhance the adsorption of PCE molecules onto the surface of cement particles. Despite major of the initially adsorbed-PCE molecules might have been embedded in hydration products, free PCE molecules with released carboxyl groups in the solution can continuously adsorb onto the surface of cement particles and play a role in dispersion. This explains why slow-release PCEs have a dispersion retention effect on cement particles within a certain time.


Song Z.,Hohai University | Jiang L.,Hohai University | Li W.,State Key Laboratory of High Performance Civil Engineering Materials | Xiong C.,Hohai University | Chu H.,Hohai University
Construction and Building Materials | Year: 2016

Fatigue damage is one of the most important factors impacting the chloride diffusion coefficient in concrete. In this paper, the electrical impedance spectra (EIS) method is used to analyze the damage level of the fatigue concrete. An electrical equivalent circuit is established to extract the electrochemical parameters from the impedance spectra. It is shown that the fitting results of the equivalent circuit match well with the experimental spectra. By analyzing the physical meanings of the parameters, the reciprocal of the overall resistance (1/RCDP + 1/RCCP) is finally adopted as an indicator of the fatigue damage level. Chloride diffusion coefficients of concrete undergoing fatigue damage were determined by a modified RCM method. It is found that the chloride diffusion coefficients decrease linearly with the overall resistances. The reduction in DRCM is found to be rapid for the high w/c ratio (w/c 0.5) concrete and gradual for the low w/c ratio (w/c 0.36) concrete. It is also found that DRCM increases nonlinearly with the indicator IDF. The increasing rates get smaller when IDF grows, and DRCM has a maximum value when IDF trends to infinity. © 2016 Elsevier Ltd. All rights reserved.


Shi L.,Jiangsu Research Institute of Building Science | Wu Y.,State Key Laboratory of High Performance Civil Engineering Materials | Liu J.Z.,State Key Laboratory of High Performance Civil Engineering Materials
Applied Mechanics and Materials | Year: 2013

In order to achieve a scientific selection of fly ash used in concrete, the influences of fly ash level on cementitious system rheological parameters, hydration degree and capillary adsorption properties were quantitative analyzed. The results show that Class I fly ash reduces the yield stress and plastic viscosity of cementitious system. The yield stress of system increases dramatically and the plastic viscosity of system reduces when Class III fly ash added. Rheological parameters of cementitious system change little when Class II fly ash added. The higher level fly ash uses the more CSH gel generates and the less Ca(OH)2 crystals generates in cementitious system at early age (3d to 7d). High level fly ash increases the cement paste initial capillary adsorption amount but reduces the capillary absorption rate. © (2013) Trans Tech Publications, Switzerland.


Shi L.,Jiangsu Research Institute of Building Science | Liu J.,State Key Laboratory of High Performance Civil Engineering Materials
Procedia Engineering | Year: 2012

Polymer coating is progressively being used in fields of concrete curing and concrete surface strengthening. However, only very few researches have been reported to investigate the effect of polymer coating on the properties of surface layer concrete. The effects of polymer coating on shrinkage, mechanical property, carbonation, capillary absorption and chloride ion diffusion of surface layer concrete were studied in the present investigation. The experimental results showed that polymer coating could obviously reduce the mortar shrinkage of the concrete surface, and the thicker the polymer coating, the greater shrinkage reducing ratio at early ages. It has been found that the polymer coating enhanced the mortar early age strength of the concrete surface. Meanwhile, the carbonation resistance of surface layer concrete, as well as the mortar infiltration resistance on the surface of concrete was improved by polymer coating. The results also demonstrated that the capillary absorption ratio of mortar in the surface layer of concrete cured under the polymer coating condition could be reduced by 87% and 78%, respectively compared with dry and standard curing conditions. In the same way, polymer coating had an improvement effect on chloride ion diffusion resistance of surface layer concrete. © 2011 Published by Elsevier Ltd.

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