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Influence of Fly Ash Addition on the hydration of Portland Cement

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武汉理工大学学报 2010年第17期32卷 99-102页

作者： GENG h N shui z h School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

Influence of fly ash addition on the hydrationof Portland cement clinker,particularly at the initial stage,has been studied on the basis of measured data obtained. Fly ash,considering its active components,was added as a partial replacement of Portland cement at different water/cementitious ratios. The hydration heat was measured in a controlled environmental room of 20 ℃. Both non-evaporable water content and mineral phase were investigated. Data indicate that the amount of fly ash involved in hydration reaction is little at initial stage while it becomes more after 7 d hydration. As hydration reaction is a continuous process,chemical stress results in the disruption of stable structure on the surface of fly ash consisting of Ca,O,Si,Al,C,etc. Additionally,surface of glass beads begins to lose smooth and reacts to blend in with the paste.

关键词： hydration heat first-order and second derivative cure portland cement fly ash

Preparation and Microstructure Analysis of high Strength Cementitious Materials Containing Metakaolin

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武汉理工大学学报 2010年第17期32卷 117-122,136页

作者： YU R shui z h DONG J School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

The preparation and microstructure analysis of high strength cementitious materials containing metakaolin (MK) was studied in this paper. The MK was prepared firstly,and then was mixed with fly ash,ground blast furnace slag,quartz powder and cement with different percentage to produce high strength cementitious materials. After cured under different environment,the compressive strength of such materials was tested. Techniques of X-ray diffraction (XRD) and scanning electron microscopy (SEM) were further employed to identify the composition and microstructure. The results obtained reveal that the compressive strength of such materials mainly effected by component of raw materials,the water binder ratio (W/B) and the curing regime. When the three factors above are optimized,the compressive strength of such materials can get to 156 MPa in maximum. The X-ray diffraction analysis and the scanning electron microscopic images indicated that under optimal curing condition,more raw materials can take chemical reaction and the microstructure is dense to yield good mechanical properties.

关键词： preparation microstructure analysis high strength cementitious materials metakaolin

Effects of Mixing Volume and Initial Particle Size Distribution of Fly Ash on Pore Solution of Cement Paste

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武汉理工大学学报 2010年第17期32卷 112-116页

作者： shui z h DUAN P ShEN C h School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Center of Materials Research and Analysis Wuhan University of TechnologyWuhan 430070China

The effects of fly ash with different mixing volume and different particle sizes on pore solution of cement-based materials were studied. The pore solution was extracted by squeezing at scheduled ages. The particle size distribution of fly ash was classified as smaller than 45 μm and 45～80 μm,and the mixing volume was classified as 10% and 20%. The concentrations of K+,Na+ and Ca2+ were measured using Inductively Coupled Plasma Emission Spectrometer (ICP),and the ph was measured by acid-base titration. The results indicate that the concentrations of various ions were prompted at the initial time of the hydration. With further hydration,ion concentrations of K+ and Na+ raise again and finally stabilized,but there is a certain decline on Ca2+ later on. It also shows that fly ash exhibited great effect on the hydration of cement,it can lower the concentration of Ca2+ and ph of the pore solution,but raise the concentrations of K+ and Na+. More importantly,ion concentrations of K+,Na+ and Ca2+ reduced with smaller particle sizes of fly ash.

关键词： cement-based materials pore solution ion concentration squeeze

Freeze-thaw Resistance of Concrete in Seawater

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武汉理工大学学报 2010年第17期32卷 108-111页

作者： shui z h XU h G zhAN B J School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Transportation Bureau of Xinganmeng Inner Mongolia Ulanhot 137400China

The effect of freeze-thaw cycles in seawater on the performance of concrete was studied in this paper. Concrete samples with different water binder ratio and different component were prepared,and were then put into fresh water and synthesized seawater. After the experiments of freeze-thaw cycles,the mass loss,relative dynamic elastic modulus (RDEM) and compressive strength of each sample were tested. The results obtained reveal that with the increase of the water binder ratio,the resistance ability of freeze-thaw impact in seawater of concrete decrease dramatically. When the concrete contain 15% fly ash and 20% slag,its resistance ability to the freeze-thaw impact in seawater is the optimal. Compared to the seawater corrosion,the impact of freeze-thaw cycles to the properties of concrete is severer.

关键词： freeze-thaw damage seawater mass loss relative dynamic elastic modulus

Effects of Curing Condition on the Carbonation of Shrinkage-compensated Concrete

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武汉理工大学学报 2010年第17期32卷 103-107页

作者： MA J T TU L Q shui z h ChEN W School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Wuhan harbour Engineering Design & Research Co. Ltd Wuhan 430071China

Shrinkage-compensating concrete can enhance the permeability and strength. In addition,expansive admixture can densify concrete to advance the carbonation resistance ability. Due to special quality of ettringite,the relative humidity of curing environment has significant effect on the carbonation rate of concrete. This paper discusses the influence of environmental humidity on carbonation rate of shrinkage-compensating concrete. Four different curing conditions were set up,namely the natural environment (Rh 60%),standard environment (Rh 90%),early age water curing environment for 3 d and 7 d. After curing in these four environments for 28 d,an accelerated carbonation test was performed. Micro-hardness analysis was used to evaluate surface hardness,which depends on,to a great degree,the carbonation depth. TG-DSC analysis was used to study Ca(Oh)2 content gradient in the surface layer of concrete in different environment. The results show that natural condition lead to a relatively worse carbonation degree,curing in water for 3 d is harmful to the carbonation resistance,while curing in water for 7 d lead to an equivalent carbonation degree with standard condition,which show the most improvement to carbonation resistance ability.

关键词： shrinkage-compensating concretes curing humility ettringite reaction carbonation rate

Performance of Sacrificial Anodes in Reinforced Concrete

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武汉理工大学学报 2010年第17期32卷 165-169页

作者： TU L Q DONG C WANG C J zhANG G z LEI Y F shui z h School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Wuhan harbour Engineering Design & Research Co. Ltd Wuhan 430071China Key Lab of Large-span Bridge Construction Technology Minstry of CommunicationsWuhan 430071China zhejiang Province zhoushan Island Linking Construction Commanding Department Zhoushan 316032China

The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It was found that concrete mix proportion and the covering layer thickness had an impact on the performance of sacrificial anodes. The thermal-sprayed zinc alloy anodes had a more negative corrosion potential and larger galvanic current than metallurgy ones in the same conditions. They had similar chemical composition. But metallographic structure showed that the structure of thermal-sprayed zinc alloy anodes was a loose porous. This structure had the catalytic effect on the andes electrochemical reactions and made the anodes the electrochemical exchange current density increase and the corrosion potential move to negative direction.

关键词： sacrificial anode reinforced concrete concrete mix proportion thermal-sprayed anodes electrochemical performance

Moment Redistribution Effect of the Continuous Glass Fiber Reinforced Polymer-Concrete Composite Slabs Based on Static Loading Experiment

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Structural Durability & health Monitoring 2025年第1期19卷 105-123页

作者： zhao-Jun zhang Wen-Wei Wang Jing-shui zhen Bo-Cheng Li De-Cheng Cai Yang-Yang Du hui huang Offshore Oil Engineering Co.Ltd. Tianjin300461China Department of Bridge Engineering School of TransportationSoutheast UniversityNanjing211189China

This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment *** experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was *** composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab *** methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel *** experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal *** contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading *** the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan *** the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span *** GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span *** test specimens experienced compressive failure of concrete at the mid-span *** results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support *** proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.

关键词： Moment redistribution GFRP-concrete composite slabs bending moment experimental study analysis model

Pulse chirping effect on controlling the transverse cavity oscillations in nonlinear bubble regime

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Chinese Physics B 2017年第2期26卷 313-319页

作者： h Vosoughian z Riazi h Afarideh G Sarri Laser and Optic Institute Nuclear Science and Technology Research Institute Tehran Iran physics and Accelerator School Nuclear Science and Technology Research Institute Tehran Iran Department of Energy Engineering and Physics Amirkabir University of Technology P. O. Box 15875-4413 Tehran Iran School of Mathematics and Physics The Queen's University of Belfast BT7 INN Belfast United Kingdom

The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longitudinal size shorter than the plasma wavelength, λp, instead of a periodic plasma wave, a cavity free from cold plasma electrons, called a bubble, is formed behind the laser pulse. An intense charge separation electric field inside the moving bubble can capture the electrons at the base of the bubble and accelerate them with a narrow energy spread. In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The carrier–envelope phase（CEP） breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional（2D） particle-in-cell（PIC） simulations show that the frequency-chirped laser pulses are more effective in controlling the pulse depletion rate and consequently the effect of the CEP in the bubble regime. The results indicate that the utilization of a positively chirped laser pulse leads to an increase in rate of erosion of the leading edge of the pulse that rapidly results in the formation of a steep intensity gradient at the front of the pulse. A more unstable bubble structure, the self-injections in different positions, and high dark current are the results of using a positively chirped laser pulse. For a negatively chirped laser pulse, the pulse depletion process is compensated during the propagation of the pulse in plasma in such a way that results in a more stable bubble shape and therefore, a localized electron bunch is produced during the acceleration process. As a result, by the proper choice of chirping, one can tune the number of self-injected electrons, the size of accelerated bunch

关键词： bubble regime plasma wake field positively chirped laser pulse

A modified averaging scheme with application to the secondary hopf bifurcation of a delayed van der Pol oscillator

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Acta Mechanica Sinica 2008年第4期24卷 449-454页

作者： z.h.Wang h.Y.hu Institute of Sciences PLA University of Science and Technology Nanjing 211101 China Institute of Vibration Engineering Research Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In this paper, a modified averaging scheme is presented for a class of time-delayed vibration systems with slow variables. The new scheme is a combination of the averaging techniques proposed by hale and by Lehman and Weibel, respectively. The averaged equation obtained from the modified scheme is simple enough but it retains the required information for the local nonlinear dynamics around an equilibrium. As an application of the present method, the delay value for which a secondary hopf bifurcation occurs is successfully located for a delayed van der Pol oscillator.

关键词： Time delay ·Secondary hopf bifurcation·The averaging technique van der Pol oscillator