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Miao C.,Jiangsu Academy of Building Science Co
Advanced Materials Research | Year: 2012

The demand for high performance concrete is increasing nowadays. The service life of high performance concrete has significant effect on the consumption of energy and resources. Adding good chemical and mineral admixtures to regulate and optimize the microstructure of concrete can ensure the service life of concrete structures and save great amount of cement simultaneously. It is a good way to turn waste into resource and turn the harmful into the beneficial. Source

Chen D.,Anhui University of Technology | Chen D.,Jiangsu Academy of Building Science Co
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2013

Based on the microstructure of concrete, a hygro-thermo-mechanical model is established to investigate the hygro-thermal deformation of concrete according to the coupling effect of multi-physical field and the transfer mechanism of moisture and heat in porous medium. The COMSOL software is used to solve the hygro-thermo-mechanical coupling question in an interactive environment with the help of the presented moisture expansion coefficient of concrete. The feasibility of the model and the solution method is validated by Hundt's experimental results. And the hygro-thermal deformation of a lake tunnel is also numerically simulated by COMSOL. The result of COMSOL multi-physical numerical simulation, the numerical result of hybrid analytic-finite element method (A-FEM) method and the fiber Bragg grating (FBG) monitoring data are comparatively analyzed. It is revealed that the COMSOL simulation result is more close to the field test data than that of the A-FEM method. It can be concluded that the COMSOL simulation is more adequate to reveal the physical progress of concrete deformation with better feasibility. Source

Yang Q.,East China University of Science and Technology | Ke D.,East China University of Science and Technology | Yang M.,East China University of Science and Technology | Hong J.,Jiangsu Academy of Building Science Co | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

This work has studied pronouncedly different phase separation situations for bitumen emulsions at various salt concentrations. With increasing sodium chloride concentration (CNaCl), the added salt promotes the degree of phase separation of bitumen emulsions at CNaCl lower than 5.2mM, where the separated water is the upper phase and the bitumen is the lower phase. Nevertheless, this kind of phase separation is gradually reduced as CNaCl increases from 5.2 to 250mM. At CNaCl=250-500mM, the bitumen emulsions with very low degree of phase separation are observed to transit from the aqueous phase in the upper position and the bitumen phase in the lower level into the reverse situation. Further increase of salt amount in bitumen emulsions leads to the enhanced phase separation at CNaCl=500-830mM. These results of phase separation of bitumen emulsions are explained as the combined influences of the screening effect on the electrostatic repulsion of the bitumen droplets and the density changes of the aqueous phase induced by the added salt. While the salt screening effect is responsible for the increased phase separation at CNaCl smaller than 5.2mM, other phase separation behaviors at higher salt amounts may be mainly attributed to the increasing density values of the aqueous phase due to the salt addition. © 2013 Elsevier B.V.. Source

Zhang Q.,Jiangsu Academy of Building Science Co | Sun W.,Nanjing Southeast University | Liu J.,Jiangsu Academy of Building Science Co
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2010

Ca(OH)2 solution was used as a kind of simulated concrete pore solution in this paper. The starting point of steel depassivation was determined by corrosion current density which could be calculated when B was obtained by potentiodynamic polarization curves. The effects of electrochemical methods and pH on the chloride threshold level were investigated in the simulated concrete pore solution. The results show that the chloride threshold level for the corrosion of steel reinforcement concluded by linear polarization is higher than that by electrochemical impedance spectroscopy. The chloride threshold level characterized by the chloride ion concentration decreases when pH decreases, while the critical chloride level increases with pH decreasing when characterized by C(Cl-)/C(OH-). Source

Li H.,Jiangsu Academy of Building Science Co | Liu J.P.,Jiangsu Academy of Building Science Co | Sun W.,Nanjing Southeast University
Applied Mechanics and Materials | Year: 2013

XRD-Rietveld method has been adopted for quantitative analysis of phases in cement powder, phases in mixed samples of cement and pure calcium hydroxide, and sulfate attack products in cement pastes, based on the TOPAS software. The results show that, Rietveld analysis values show good agreement with the actual levels of mixed samples, and the accuracy degree of Rietveld method is at least as well as that of TG/DSC method which is commonly used in quantitative analysis of calcium hydroxide. By adding appropriate internal standard substance, XRD-Rietveld analysis method can be effectively used in quantitative analysis of sulfate attack products in cement-based materials. This work has practical significance on the study of sulfate attack of cement-based material. © (2013) Trans Tech Publications, Switzerland. Source

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