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Liu Z.,Nanjing Southeast University | Zhang Y.,Nanjing Southeast University | Liu L.,Nanjing Southeast University | Liu L.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | Jiang Q.,Nanjing Southeast University
Construction and Building Materials | Year: 2013

With a combination of effective medium and percolation theory, an analytical model was proposed to acquire the relative resistivity of cement paste and C-S-H. The overall electrical resistivity and volume fraction of conductive phase, as main input values, are continuously determined by using non-contact electrical resistivity device and CEMHYD3D numerical model, respectively. The results show that an increase of hydration degree shows an improvement with the relative resistivity of solids and a reduction in critical exponent of capillary pores. While the relative resistivity of C-S-H and its exponent present constant values of 121 and 1.8, independent of hydration degree. Finally, the calculated results are compared to the reported values by previous literatures that have a good agreement. © 2013 Elsevier Ltd. All rights reserved. Source


Zhang W.,Nanjing Southeast University | Zhang Y.,Nanjing Southeast University | Liu L.,Nanjing Southeast University | Liu L.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | And 2 more authors.
Construction and Building Materials | Year: 2012

An ultrasonic measurement apparatus (UMA) was developed for in situ continuously monitoring the early age hydration process of cementitious material. Utilizing UMA, the influence of curing temperature and silica fume content on the setting and hardening process of the low water to binder ratio cementitious material were systematically investigated. The experimental results show that setting and hardening process of the silica fume blended cement paste at elevated temperature can be clearly identified into three stages including dormant stage, acceleration stage and deceleration stage. Besides, the increasing of curing temperature and silica fume content greatly accelerate the setting and hardening process of silica fume blended cement paste and increase the ultimate ultrasonic pulse velocity. To aid in comparing with the ultrasonic results, the isothermal calorimetric measurement, Vicat needle test and mechanical properties test were also conducted. © 2012 Elsevier Ltd. All rights reserved. Source


Laibao L.,Nanjing Southeast University | Laibao L.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | Yunsheng Z.,Nanjing Southeast University | Wenhua Z.,Nanjing Forestry University | And 3 more authors.
Construction and Building Materials | Year: 2013

Basalt powder is a by-product of basalt stone crushing plant. It is a big problem to propose utilization of these by-products from the aspects of disposal, environmental pollution and health hazards. In this paper, basalt is attempted to manufacture concrete as a new mineral admixture. Firstly, the chemical compositions and the pozzolan activity of the basalt were measured. Secondly, the cementitious paste with basalt powder was prepared and the normal consistency, setting time and the compressive strength were tested. Finally, the isothermal calorimetric measurement, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) test were conducted to investigate the hydration process and microstructure formation of the basalt blended paste. The results show that the basalt has obvious potential pozzolan activities and can be used as a new mineral admixture. The basalt has retardation effect on the setting and hydration heat evolution process of cement. Besides, early age compressive strength development of the basalt blended paste was normally less than the pure cement paste, but the strength are close at later ages. © 2013 Published by Elsevier Ltd. Source


Yi Y.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | Yi Y.,CAEP - China Academy of Engineering Physics | Ding Z.-J.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | Ding Z.-J.,CAEP - China Academy of Engineering Physics | And 3 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2011

The geometry optimization, the electronic and magnetic properties of the compound Ni4NdB are studied by using first-principles within the local spin-density approximation (LSDA) and the LSDA+U approximation. The results indicate that the system is a metallic conductor with very small band gap, and that the total magnetic moment is provided by the local Nd magnetic moment. The system has very complex bonding, where Nd atoms and the neighboring Ni atoms form metal bonding, also Nd atoms and the neighboring B atoms form the strong ionic banding, besides Ni atoms and the neighboring Ni atoms forming an indirect exchange interaction. Under coulomb interaction, the system magnetic moment is consistent with that of the local Nd atom, and the collapse of magnetic ordering in 2.75 eV happens to the local Ni magnetic moment. © 2011 Chinese Physical Society. Source


Yi Y.,CAEP - China Academy of Engineering Physics | Yi Y.,State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials | Li K.,CAEP - China Academy of Engineering Physics | Ding Z.-J.,CAEP - China Academy of Engineering Physics | And 4 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2011

Considering the Coulomb potential and the exchange action, electronic structure, band structure and magnetic properties of the compound Ni4PrB within the local spin-density approximation (LSDA) and the LSDA+U approximation are studied through numerical simulation. The simulation results show that this system is a metallic semi-conductor and has Pr-Ni ferromagnetic coupling. The added Coulomb U effect can strongly affect magnetic properties and stable structure, and the total magnetic moment is provided by the local Ni magnetic moment before adding U effect, when the U effect is added to the system, the total magnetic moment is provided by the local Pr magnetic moment, and the system has a high structure stability. So U effect affects strongly the strong correlation, then it can describe reasonably the strong correlation and the exclusion effect caused by the spin exclusion. © 2011 Chinese Physical Society. Source

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