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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.


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.


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..


Zhou W.,Nanjing Southeast University | Zhou W.,Jiangsu Academy of Building Science Co | Sun W.,Nanjing Southeast University | Chen C.,Jiangsu Academy of Building Science Co | Miao C.,Jiangsu Academy of Building Science Co
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2011

Micro-mechanical properties of cement paste and paste with ground slag were examined by a nanoindentation technique. The elastic modulus and hardness of indentated places were calculated and mapped in two dimension surface. A multi-peak regressive fitting was carried out in the frequency plots of the tested parameters based on the Gaussian function. The statistical distribution of the micro-mechanical properties (such as the capillary pores, low density C-S-H, high density C-S-H and portlandite) was summarized for the hydrates in cementitious paste. The results show that the hardness, elastic modulus, and the volume fraction of high density C-S-H in cement paste increase with the curing age. The hardness and elastic modulus of C-S-H in late age paste might increase when ground slag was added. Little calcium hydroxide peak appeared in the fitting curves of frequency plots at the mixing amount of slag of 50%, indicating that the secondary hydration of slag consumed the most of portlandite in the paste.


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.


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-).


Liu J.P.,Jiangsu Academy of Building Science Co | Li L.,Jiangsu Academy of Building Science Co | Miao C.W.,Jiangsu Academy of Building Science Co | Tian Q.,Jiangsu Academy of Building Science Co | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2010

This paper is concerned about the possibility to prepare compact monolayers from octadecanol (OA) emulsion on the plastic concrete surface in order to restrain water evaporation. The concrete was prepared with ordinary Portland cement with typical water to cement ratio=0.5. The results showed that the monolayers prepared from the emulsion could effectively reduce the water evaporation on the concrete surface, especially for the emulsion containing 0.12g sodium dodecyl sulfate (SDS) and 0.48g sorbitan monododecanoate (Span20) which could reduce the water evaporation to 41%. The microstructure of the monolayers was characterized by surface pressure-area (π-A) isotherms, dynamic elasticity (π-Ed) curves and atomic force microscopy (AFM). It is revealed that the emulsifier concentration has great influence on the monolayer structure. High emulsifier concentration would lead to the monolayers with incompact, unstable structure and low water evaporation resistance due to the good solubility of the emulsifier. © 2010 Elsevier B.V.


Liu J.P.,Jiangsu Academy of Building Science Co | Li L.,Jiangsu Academy of Building Science Co | Miao C.W.,Jiangsu Academy of Building Science Co | Tian Q.,Jiangsu Academy of Building Science Co | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

This paper is concerned about the reduction of water evaporation and cracks on plastic concrete surface by monolayers which prepared from poly(lauryl methacrylate) emulsions. The results showed that the monolayers could effectively reduce water evaporation and improve concrete surface properties, such as inhibiting the formation of plastic-shrinkage cracking and crust. After characterizing the monolayer microstructure in detail, it was pointed out that the emulsifier concentration had great impaction on monolayer structure though the relationship was complicated. Finally, the technique was successfully used in a practical engineering to further testify its effect on plastic concrete surface. © 2011 Elsevier B.V.


Liu J.,Jiangsu Academy of Building Science Co | Liu J.,Nanjing Southeast University | Li H.,Jiangsu Academy of Building Science Co | Tian Q.,Jiangsu Academy of Building Science Co | Wang Y.,Jiangsu Academy of Building Science Co
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2013

To test the wettabilities of cement and mineral admixtures with water, the dynamic contact angles between water and cement paste powders, fly ash, slag, silica fume and other mineral admixtures with different hydration times were characterized by using thin-layer wicking technique. The results show that by using ethanol as the reference liquid, the relative dynamic contact angle of water and cement particles is initially about 56°; as the hydration proceeds, the contact angle gradually decreases and eventually stabilizes at (22±1)°. The relative dynamic contact angle of water and fly ash powder and that of water and slag powder are 56° to 60° and 53° to 63°, respectively. The relative dynamic contact angle of water and silica fume powder and that of water and CaCO3 powder are about 43° and 70°, respectively. The order of the hydrophilicities of these powder materials, from strong to weak, is silica fume, cement, fly ash, slag and CaCO3 powder. As the hydration proceeds, the contact angle between cement paste and water decreases gradually and finally tends to be constant.


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.

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