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Jianliang Z.,Jiangsu Sobute New Materials Co. | Jianliang Z.,State Key Laboratory of High Performance Civil Engineering Materials | Qian T.,Jiangsu Sobute New Materials Co. | Qian T.,State Key Laboratory of High Performance Civil Engineering Materials | And 4 more authors.
Key Engineering Materials | Year: 2017

A Negative pressure sensing set-up for capillary pressure test was designed and used for testing the capillary pressure of cement-based materials, cement pastes of water-cement ratio 0.30 was adopted, and the factors that may affect the measured values such as hardness of water tube, gas volume in the set-up, gas content in water, test depth, bleeding of cement pastes was studied. The results shows that the accuracy of the measured value is very large impacted by the air volume in the set-up and by the hardness of water tube, the capillary pressure at different depths could be affected by the external environment and the bleeding of cement pastes. According to the test results, methods for measuring the capillary pressure of cement-based materials were proposed, and some other recommendations that help to improve the test accuracy were given. © 2017 Trans Tech Publications, Switzerland.


Ran Q.,State Key Laboratory of High Performance Civil Engineering Materials | Ran Q.,Jiangsu Sobute New Materials Co. | Qiao M.,Jiangsu Sobute New Materials Co. | Liu J.,State Key Laboratory of High Performance Civil Engineering Materials | Liu J.,Jiangsu Sobute New Materials Co.
Iranian Polymer Journal (English Edition) | Year: 2014

Poly(acrylic acid)-g-poly(ethylene glycol) (PAA-g-PEG) comb-like copolymer (PCE) is one of the best kind of superplasticizers for cement suspensions. But PCE can be considered as polyelectrolyte which is easily affected by the ions in cement suspensions. In cement system, calcium ions are the most abundant cations which would have great influence on the performance of polymer superplasticizer. Here, the effects of calcium ion on the surface charge, adsorption and dispersion in cement system with PCE as dispersant are investigated in detail. And the changes in the conformation of PCE before and after adding calcium ions are studied by methods of dynamic light scattering and transmission electron microscopy. Calcium ions increase the zeta potential of cement particles and make the molecular chains of PCE curlier, which induces the changes in adsorption and dispersion behavior. The adding of calcium ions makes the ion bridging between calcium and PCE to take place and the ion bridging makes the PCE molecules shrink to smaller size. In this paper, it tells that the molecular structure of PCE polymer could be changed based on the conclusion to adapt the cement with different content of calcium. In cement suspensions, the effect of calcium ions on the performance of PCE polymer would be weakened by decreasing the content of carboxyl groups in the molecular chain. © 2014 Iran Polymer and Petrochemical Institute.


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.


Rong H.,Tianjin Chengjian University | Rong H.,State Key Laboratory of High Performance Civil Engineering Materials | Qian C.-X.,Nanjing Southeast University | Zhang L.,Tianjin Chengjian University | Yang J.-J.,Tianjin Chengjian University
Journal of Advanced Microscopy Research | Year: 2016

Microbe cement is a new generation of cement, which relies on microbial induced produced calcium carbonate precipitation consolidate loose particles to a whole body. In order to further explore the cementation process of microbe cement in loose sand particles environmental and explain the cementation mechanism of microbe cement, in this paper, the process of microbe cement binding loose sand particles in the dish are firstly analyzed by Scanning electron microscope (SEM) and Biological Microscope. Secondly, the loose quartz sand particles and loose sand particles treatment by microbe cement are analyzed by Infra-red spectra (IR) and X-ray photoelectron spectroscopy (XPS), respectively. The SEM results indicate that microbe in microbe cement are firstly absorbed on the surface of loose sand particles, and then the microbe react with mixture solution on the surface of loose sand particles to form calcite crystal. The biological microscope results show that microbe cement will form calcite crystal between the loose sand particles within 1.0 hour. The cementation process continues to about 5.0 hours, however, when the time continues to extend, the influence of microbe cement on cementation effect is little. The IR and XPS results indicate that there are organic matters in loose sand particles treatment by microbe cement and the organic matters interacts with calcite induced by microbe cement and sand particles to form hydrogen bond, which play a role in binding function between loose sand particles and calcite produced by microbe cement. Copyright © 2016 American Scientific Publishers All rights reserved.


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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