bluuebunny/crossref_metadata_2025 huggingface dataset:
Autogenous Shrinkage in Plain Cement Mixtures
Authors: Rajayogan Vinod , Kayali Obada
Published: March 2009

Determination of a realistic model for the estimation of autogenous shrinkage in plain cement mixtures has been an ongoing research among researchers in high performance concrete. While no standard test method exists for the determination of autogenous shrinkage, various researchers have designed different test methods for measurement of autogenous shrinkage. Current study involved the experimental determination of autogenous shrinkage using the test method developed by O.M.Jensen and co-workers, complimented with non-contact eddy current sensors. Measurements were conducted from as early as 1.5 hours from the time of casting. The samples were placed in a constant temperature chamber and the temperature of the sample was also monitored using a thermocouple. The study was carried out on plain cement mixtures at three water cement ratios of 0.25, 0.32 and 0.38. Measurements were also conducted on simple sealed prismatic samples but these measurements could only be collected after 24 hours of casting. The work is supplemented with CEMHYD3D simulations of the samples at similar water-cement ratios under sealed conditions so as to understand the development of the microstructure of the cement responsible for autogenous shrinkage. While experimental determination of internal relative humidity is quite difficult, data regarding chemical shrinkage, amount of water left and the development of the discontinuous capillary network from the simulations help to understand the determined experimental values of autogenous shrinkage. A detailed explanation on the causes of autogenous shrinkage and the basic mechanism responsible for it has been presented.
Effect of Calcination Temperature on the Microstructure, Activity and Expansion of Mgo-Type Expansive Additive Used in Cement-Based Materials
Authors: Mo Li Wu , Deng Min , Tang Ming Shu
Published: March 2009

Shrinkage compensating by the expansion generated by the hydration of expansive additive is one of the important measures to improve the dimensional stability of cement-based materials. Due to the slow hydration of MgO, it may cause delayed expansion in cement and thus has been used as an expansive additive to compensate thermal shrinkage at late age in mass concrete. The relationship among the microstructure, activity and expansion properties of MgO-type expansive additive (MEA) has not been clearly demonstrated, though many researches have been focused on its expansion mechanism and expansion properties. So the industrial production and application of MEA depend much on empirical methods. Three different types of MEA are produced by calcining magnesite at 900°C, 1100°C, and 1300 °Cfor 1h in an electrical furnace. The specific surface area, activity, inner pore structure, microtopography and expansion properties of the MEA have been investigated. Results show the effect of calcination temperatures on the expansion properties of MEA results from the changes in its microstructure, specific area, and thus the activity. High calcination temperature causes growth in MgO grain, decrease in specific area and surface defects of MgO, and hence the reduction of the activity value, inducing slow hydration rate and thus delayed expansion. This study will provide a platform for well understanding various activity and expansion properties of MEA produced under different temperatures.
Chloride Penetration into Concrete
Authors: Wan Xiao Mei , Wittmann F.H. , Zhao Tie Jun , Jiang Fu Xiang
Published: March 2009

Reinforced concrete structures may be exposed to an aggressive environment. In this case combined mechanical and environmental actions may act simultaneously and their synergetic influences have to be taken into consideration. In this contribution results of tests on two different types of concrete and mortars are presented and discussed. Capillary absorption of not carbonated and carbonated concrete has been determined. The influence of mechanical load on capillary suction has been studied separately. A moderate compressive load reduces the coefficient of capillary suction, while capillary suction is enhanced by higher mechanical loads as micro-cracks are formed. Chloride diffusion has been measured by means of the diffusion cell test. The diffusion coefficient observed in carbonated concrete is roughly speaking one order of magnitude higher than the value measured on not carbonated concrete.
Effect of Electrochemical Chloride Extraction on the Steel Reinforced Concrete
Authors: Xu Jian Zhi , Ding Zhu , Xing Feng
Published: March 2009

Electrochemical chloride extraction (ECE) is used for the rehabilitation of chloride-contaminated concrete. High current densities of steel surface are applied between the steel and a temporary external anode which is placed on the concrete surface. Anions are pushed away from the cathode (steel reinforcement), and cations are accumulated at the cathode. In this study chloride ions were found in the electrolyte during ECE. The extraction efficiency of chlorides was obvious. After treatment, the amount of chlorides around the reinforcement was greatly reduced. ECE had insignificant effect on the compressive strength. Steel potentials in treated specimens showed a strong shift towards more positive values, while potentials in control specimens remained strongly negative.
Four Point Bending Experimental Investigation on Reinforced Ultra High Toughness Cementitious Composite Beams
Authors: Li Qing Hua , Xu Shi Lang
Published: March 2009

Ultra high toughness cementitious composite (abbreviated as UHTCC) shows significant pseudo strain hardening behavior and offers prominent tension strain ability of more than 3% when subjected to uniaxial tension load. The failure pattern of the UHTCC components exhibits multiple fine cracks with crack width lower than 100μm even corresponding to the ultimate tensile strain state. Four-point bending investigations of reinforced ultra high toughness cementitious composite (RUHTCC) members without web reinforcement have been carried out due to the excellent crack dispersion and strain energy absorption abilities of UHTCC material, aiming at design issues of strictly anti-cracking structures or aseismic design in key parts of structures such as beam column joint when using UHTCC. The moment-curvature curves have been measured and compared with the theoretical analysis proposed before. There is a reasonable agreement between them, especially that both moment and curvature present little difference before yielding. According to experimental results of RUHTCC beams with three different reinforcement ratios, UHTCC can delay yielding of reinforcements and improve load bearing capacity and ductility of structures or components compared with ordinary reinforced concrete beams, then steel products can be saved. The possibility of corrosion should be evidently reduced in respect that RUHTCC can effectively control crack. Accordingly, durability of structures improves by using UHTCC members.
Experimental Study on Cracking Property of Self-Compacting Concrete
Authors: Jin Nan Guo , Jin Xian Yu , Gu Xiang Lin
Published: March 2009

Taking free shrinkage as the key parameter in evaluating cracking of concrete, the cracking properties of self-compacting concrete with strength grade of C35 and C50 were investigated based on ring and slab restraint tests. Meanwhile, the ultimate tensile strain of self-compacting concrete was studied by using flexural test. Experimental results show that the shrinkage of self-compacting concrete is lower than that of normal concrete. Self-compacting concrete cracks later than normal concrete with the same strength grade. Although the ultimate flexural tensile strains of self-compacting concrete in 7 d and 28 d are a little bit lower than that of the normal concrete, it can still be concluded from the research that the cracking property of self-compacting concrete can be greatly improved by using proper mix proportion.
Preliminary Study on a New Evaluation Method of Concrete Cracking Resistant Behavior
Authors: Ji Tao , Hu Chang Bin , Liang Yong Ning
Published: March 2009

A restrained ring setup with a clapboard was developed. Because the clapboard can cause a stress concentration of concrete annulus placed in the ring setup, a crack of the concrete annulus can rise at the tip of the clapboard at an early age of curing. Then the time-span of the evaluation of concrete cracking behavior is shortened. The new evaluation method can avoid the disadvantages of applying the conventinal restrained ring setup without a clapboard when evaluating the cracking resistant behavior of concrete, such as the longer time-span, randomicity and chanciness of concrete cracking. Based on experimental data, in which the effect of polypropylene fiber and expansive agent on the cracking resistant behavior of concrete was investigated, the cracking age of concrete loops and the ratio of tensile strength to compressive strength of concrete were obtained, and the validity of the proposed ring setup has been verified.
Grey Correlation Analysis of Sensitive Factors of Concrete Structures Durability
Authors: Liu Jian Xin , Liang Ben Liang
Published: March 2009

Concrete structures durability is affected by a number of factors which have different sensitivity. According to level of sensitivity classified the influence factors could promote concrete structures durability design. The disadvantage of traditional methods of sensitivity analysis in concrete structures durability is the larger number of samples. The grey correlation theory was used to analyze the degree of the sensitivity of the influence factors and comparison with traditional methods of calculation. The results show that the grey correlation analysis method could quantify the levels of the sensitive factors and with higher reliability. A new way to study the durability of concrete structures was provided.
Durability Experimental Study on RC Beams Strengthened with CFRP
Authors: Wang Qiang , Lu Chun Ling
Published: March 2009

The principle of electrochemistry is adopted in this test. The current is switched on 7 RC beams strengthened with CFRP of different measures (include: not strengthened L-0, strengthened with one layer of CFRP on the bottom L-1, coated only with epoxy resin L-2, strengthened with one layer of CFRP on the bottom and coated with epoxy resin on the lateral L-3, strengthened with two layers of CFRP on the bottom L-4, strengthened with one layer of CFRP on the bottom and alternately on the lateral L-5, strengthened with CFRP entirely L-6) when the beams are working in corrosive environment. So the corrosion speed of the beams becomes fast. Comprehensive comparison of mechanical property and transformation rule among them has been made. The different effects of the enhancement in durability are analyzed and its reason is researched. The test results indicate that the durability of the beams strengthened with CFRP can be enhanced significantly especially in the beam strengthened with CFRP entirely L-6.
Study on Combining Performance of Young and Old Concrete with Mechanical Joint Element
Authors: Zhao Xiao Yan , Tian Wen Ling , Jiang Xin Liang , Wang Xiao Wei , Zhou Ming Jie
Published: March 2009

The new way of using mechanical joint element (MJE) to cross the interface of new and old concrete to reinforce the combination is put forward. The splitting strength tests of young and old concrete were carried out to investigate the effects on splitting strength of MJE and different materials used to embed the MJE. The working mechanism of the MJE in split test is discussed emphatically. The shear tests of young and old concrete were carried out too. The effects on shear strength of MJE and interface agent are discussed. The mechanism of MJE in shear test is analyzed synchronously.
Experimental Research on Seismic Behavior of Strengthened R.C. Frame with Special-Shaped Columns
Authors: Zhou Ming Jie , Tian Wen Ling , Xun Jing Chuan , Cui Jian Xin , Zhao Xiao Yan , Wang Xiao Wei
Published: March 2009

In this paper, a damaged R.C. frame with special-shaped columns has been strengthened for earthquake resistance. The strengthening method combines wrapping steel outside and stick steel. The experimental research on seismic behavior of the strengthened frame was performed. Through the quasi-static test, the load-displacement hysteretic curves under horizontal low-cycle loading are given, and the failure modes of the strengthened frame structure are summarized. This paper gives the analysis of its bearing capacity, stiffness deterioration, energy dissipation capability and ductility property. After comparing the strengthened frame with that before damaged, we draw a conclusion that the method of seismic strengthening in this paper can effectually improve the carrying capacity of damaged R.C. frame with special-shaped columns, and make the strengthened frame have better ductility.
Seismic Response of a Multi-Span Bridge Based on Remote Testing Platform NetSLab
Authors: Fan Yun Lei , Guo Yu Rong , Xiao Yan , Cai Xin Jiang
Published: March 2009

Seismic response of a multi-span bridge is investigated in this study using an Internet based testing platform. The platform, NetSLab, was developed based on client/server concept along with a proposed data model and communication protocols. The platform is capable of transferring control and feedback data and signals among remotely located structural testing laboratories or computers connected by Internet. In these tests, a three-pier bridge system was simulated in which a Glass Fiber Reinforced Plastic (GFRP) retrofitted reinforced concrete pier was tested physically in Hunan University and a Carbon Fiber Reinforced Plastic (CFRP) reinforced concrete retrofitted pier was tested physically in Harbin Institute of Technology and the third one was simulated numerically in Tsinghua University. The bridge was loaded to simulate the responses under ground motions corresponding to earthquake hazards for a highly seismic location with 63%, 10%, 2% chance of exceedance in 50 years. The experiments demonstrate that the bridge structure with retrofitted piers has adequate behavior under earthquake loading even in areas of high earthquake intensity.
Service Performance of Bridge Approach Slabs and Replacement Alternatives
Authors: Chai Y.H. , Chen Y.T. , Hung H.J. , Rocha G.N
Published: March 2009

Approach slabs are commonly used to provide a smooth transition between the roadway and the highway bridge. Conventional construction of approach slabs uses cast-in-place reinforced concrete slabs that are anchored to the abutment. Maintenance of bridges, however, often requires repair or replacement of approach slabs due to damage from traffic, washout of fill materials, and settlement of the approach embankment etc. This paper describes recent tests of full-size approach slabs with conventional steel reinforcement as well as pultruded fiber-reinforced polymer grating and glass fiber- reinforced polymer rebars.
Development of α-β SiAlON Ceramics from Different Si3N4 Starting Powders
Authors: Acikbas Nurcan Calis , Kara Ferhat , Mandal Hasan
Published: March 2009

- SiAlON ceramics were produced from different starting Si3N4 powders including
β-Si3N4 and α-Si3N4 powders and mixtures of these powders. Gas pressure sintering was used for sintering. After sintering, resultant fracture toughness values were correlated with microstructure and starting powders. By optimizing chemistry and process parameters; - SiAlON ceramics with reasonable fracture toughness can be produced from rather coarse β-Si3N4 powder. This could improve the economic viability of SiAlON ceramics since -Si3N4 powders are less costly.
Dielectric Properties of β-SiAlON at High Temperature Using Perturbation Method
Authors: Seong Young Hoon , Kim Ha Neul , Kim Do Kyung
Published: March 2009

-SiAlON with various z-values (z = 0.5~4.0) were produced by hot pressing. The dielectric properties (dielectric constant and tangent loss) of -SiAlON were characterized by the post-resonator method at room temperature and by the perturbation method from room temperature to 1200 oC at 2.45 GHz, respectively. Effect of z-values and temperatures with -SiAlON were investigated.
New Theory of Transformation Induced Grain Growth in Porous SiC
Authors: Tanaka Hidehiko
Published: March 2009

- and -SiC powder mixtures with 0.3 mass% of AlB2 were sintered at 2200oC. Porous materials having 43-45% porosity were obtained. Grains in the powder mixtures grew into plate-shaped grains of 6-8 m size, and -SiC transformed into -SiC. Free energy due to the polytype transformation enhanced material transport very much. The new rate theory proposed here explained very well the behavior of the grain growth.
High Temperature Oxidation of SiC Powder in Oxidizing Atmosphere Containing Water Vapor
Authors: Akashi T. , Kasajima Miho , Muraoka Chiharu , Kiyono Hajime
Published: March 2009

Oxidation of SiC powder was studied at 1373 K to 1873 K in Ar-O2, Ar-H2O, and Ar-O2-H2O using thermogravimetry. At 1373 K to 1573K, the weight gain increased with increasing water vapor pressure. The oxidation rate was evaluated on the basis of the Ginstering-Brounshtein kinetic model. In this temperature region, the apparent activation energy for the oxidation was almost the same (139-191 kJmol-1) independent of the atmosphere, suggesting that the same oxidation process proceeds. On the other hand, at temperatures >1673 K, the weight gain in the dry O2 (Ar-O2) was greater than that in the wet and wet O2 (Ar-H2O and Ar-O2-H2O). The apparent activation energy in the dry O2 (442 kJmol-1) was much greater than that in the wet and wet O2. We propose that water molecule diffused in silica layer in the wet and wet O2 atmosphere at 1373 K to 1873 K.
Low Temperature Sintering of Si3N4 Ceramics and its Applicability as an Inert Matrix of the Transuranium Elements for Transmutation of Minor Actinides
Authors: Yano Toyohiko , Yamane Junichi , Yoshida Katsumi
Published: March 2009

For the transmutation of the very long half-lived isotopes which are separated from the spent nuclear fuels, it is necessary to find proper inert matrices these are stable under heavy neutron irradiation at high temperature. Silicon nitride ceramics is a candidate since it is very tolerant for heavy neutron irradiation and keeps relatively high thermal conductivity. For these reasons, we try to sinter Si3N4 ceramics containing large amounts of CeO2 as a simulant for Am2O3, a typical transuranium element. The low-temperature pressureless-sintering behavior of the ceramics and chemical and thermal properties of the obtained sintered bodies are reported.
Effect of Second Phase After-Heat Treatment on the Thermal Conductivity of AlN Ceramics
Authors: Lee Hyeon Keun , Kim Do Kyung
Published: March 2009

The high thermal conductivity of Aluminum nitride, coupled with its high electrical resistivity and nontoxic nature, makes it a very promising material for electronic substrate. In this study, microstructural characterization on the thermal conductivity of AlN ceramics was investigated. An AlN ceramic was prepared with a dopant Y2O3 under a reducing nitrogen atmosphere with carbon. In order to obtain high thermal conductivity, cooling rate control and after-heat treatment was carried out. Morphology of the second phase was characterized using scanning electron microscopy (SEM). SEM studies showed that the microstructural change caused by after-heat treatment have a major influence on the thermal conductivity.
Synthesis and Refinement of β-SiAlON by Nitriding and Post-Sintering of Si Mixture
Authors: Park Young Jo , Noh Eun Ah , Ahn Joong Ho , Kim Hai Doo
Published: March 2009

A cost-effective route to synthesize β-SiAlONs from Si mixture by reaction bonding followed by post-sintering was investigated. Three different z values, 0.45, 0.92 and 1.87 in Si6-zAlzOzN8-z, without excess liquid phase were selected to elucidate the mechanism of both SiAlON formation and densification. For the RBSN(reaction-bonded silicon nitride) specimens, nitridation rate of more than 90% was achieved by multistep heating up to 1400oC in flowing 5%H2-95%N2 and residual Si was not detected by XRD analysis. Increase in density was observed with z values for the post-sintered specimens and this tendency was well explained by the presence of higher amount of transient liquid phase with larger z values. Measured z values of the synthesized -SiAlONs were nearly similar to calculated values using starting compositions. The slight deviation in the two z values was successfully explained by the reasonable assessment of nitriding and post-sintering process.
Experimental Investigations on Material Removal Rate and Surface Roughness in Lapping of Substrate Wafers: A Literature Review
Authors: Cong Wei Long , Zhang Peng Fei , Pei Zhi Jian
Published: March 2009

Lapping is an important material-removal process for manufacturing of substrate wafers. Objectives of lapping include removing subsurface damage in sliced wafers, thinning wafers to target thickness, and achieving a high degree of parallelism and flatness of wafer surfaces. This paper reviews the literature on lapping of substrate wafers. It presents reported experimental results on effects of input parameters (lapping pressure, plate rotation speed, abrasive grain size, slurry concentration, and slurry flow rate) on material removal rate and surface roughness.
Technology of Ultra-High Strength / High Performance Concrete Applied to Guangzhou Xita Tower Construction
Authors: Ye Hao Wen
Published: March 2009

This paper introduces development and application of ultra-high strength/high performance concrete in construction of the Xita tower high-rise building at Zhujiang New City of Guangzhou, China. The goal of the concrete construction in the Xita Tower project will be realized via research of mix proportion and optimization of pumping equipment. In regard to mix proportion of concrete, low water/cement (W/C) ratio, low water content lower than 150 kg/m3 and employment of superplasticizer are essential to acquire high strength. A series of parameters have been measured to research workability of concrete from C70 to C90, such slump, slump flow, flow time from inverted cone, L-box flow, and bleeding under pressure et al. Properties of hardened concrete should also be considered, including durability, autogenous shrinkage caused cracking, and fire resistance.
Progress in Study of Concrete Pumping Construction Techniques in Super High-Rise Building
Authors: Ba Ling Zhen , Yang Yi Bo , Liang Song , Mo Hai Hong , Cao Hong , Liu Ting Jin , Chen Jun Sheng
Published: March 2009

To super high-rise building, concrete pumping construction is an inevitable choice. This paper introduces the application status and development trend of concrete pumping construction in the super high-rise projects at home and abroad, introduces high-rise pumping concrete from the selection of raw material, mix design, performance evaluation and so on, sums up technical specification of concrete pump and pumping concrete pipe-laying method, in order to provide reference for the high-rise concrete pumping construction in Guangzhou West Tower.
Influence of Mineral Admixtures on Dispersion of Poly Carboxylate Superplasticizers with Different Characteristics
Authors: Wang Dong Min , Zuo Yan Feng , Xiong Wei Feng
Published: March 2009

Naphthalene sulfate based superplasticizer and poly carboxylate superplasticizer (characterized by different polymerization of graft chain and backbone chain, different reaction temperature and different carboxyl/graft chain ratio) were applied to investigate their influences on fluidity of mineral admixtures (fly ash, granulated ground iron blast furnace slag, silica fume) -Portland cement-water system.
Study on Durability of C100 Concrete in Shenyang Royal WAN XIN Hotel
Authors: Zhang Da Li , Wang Yuan , Chen Cui Hong
Published: March 2009

Durability of C100 concrete in Shenyang WAN XIN Hotel engineering including long-term mechanical properties, dynamic modulus of elasticity, and chloride ion resistance was tested and analyzed. Test results appeared that C100 concrete had very good density and extremely good durability. Simultaneously we suggest improving the evaluation method to test the durability of super-high strength concrete in order to enhance the evaluation level effectively. It will provide one according of durability to apply super-high strength concrete.
Research on Performance of Cement with Kiln Dust-Activated Coal Gangue
Authors: Wang Chun Mei , Wang Jing , Yang Li Rong
Published: March 2009

The setting times and strength of cement substituting kiln dust-activated coal gangue for part of clinker was tested. The performance of sulphate resistance and restraining alkali silica reaction (ASR) of cement with 30% kiln dust-activated coal gangue was studied. The results indicate: the setting times of cement mixed with kiln dust-activated coal gangue is delayed and the early strength and later strength of cement with 10% kiln dust-activated coal gangue is improved to some extent, but the strength is reduced with farther increasing the content of kiln dust-activated coal gangue that replaces clinker, and obviously decreased when content of kiln dust-activated coal gangue is 30%; the performance of resisting sulphate of cement with 30% kiln dust-activated coal gangue is better enhanced; ASR is restrained to some extent.
Effect of Aggregate Volume Fraction on the Charge Passed of Mortar and Concrete
Authors: Niu Quan Lin , Li Chong Zhi
Published: March 2009

Charge passed of mortars with different aggregate volume fractions was tested according to ASTM C1202, and the differential expression of the Ohm law was introduced to explain the relationship between charge passed data and aggregate fractions.Cl- penetration depth of the corresponding mortars and concretes was measured to illustrate the influence of the aggregate volume fraction on their chloride permeability. It was shown that the charge passed of mortar was negatively correlated with aggregate volume fractions, and high aggregate fraction bearing concrete with low charge passed did not necessarily mean low permeability. As a result, the influence of aggregate fraction on charge passed should be taken into consideration when charge passed data was employed to evaluate Cl- permeability of concrete.
Research on the Strengthening Effect of Phosphorus Slag Powder on Cement-Based Materials
Authors: Liu Dong Mei , Fang Kun He , Yang Hua Shan
Published: March 2009

The strengthening effect of phosphorus slag powder (PSP) in cement-based materials was researched by model of strengthening effect of mineral admixes, and the mechanism of strengthening effect of PSP was also studied by SEM. The results indicate that, in early hydration period, the strengthening effect of PSP on strength of cement mortars is zero. At 90 days, strengthening effect has been exerted, and increases with the amount of PSP when that is no more than 40%, but decreases with larger content of PSP. At 180 days, the strengthening effect was further enhanced, the greater the amount of PSP, the greater its effect. For compressive strength of cement mortars, the strengthening effect of PSP is more than that of PSP on flexural strength. The results analyses of SEM show that, strengthening effect of PSP mainly come from its pozzolana reaction. With double excitation of cement hydration product hydroxide and gypsum, the low alkalinity C-S-H was produced.
Study and Application of Salt-Scaling Resistant Admixture in Concrete
Authors: Wang Yuan , Zhang Da Li , Chen Cui Hong
Published: March 2009

This paper investigated a new type of admixture which can be used to enhance the resistance of concrete surface to deicing salt deteriorating. Physical and mechanical properties of concrete incorporating this salt-scaling resistant admixture were measured. Practical application on site has proved that this admixture is effective for concrete to resist salt-scaling action.
Research on Creep Performance of C60 High Performance Concrete
Authors: Yin Jian , Li Yi Jin , Zheng Ke Ren , Luo Shi Dong , Yan Ai Guo , Liu Zhen Biao
Published: March 2009

It was tested creep performance of C60 high strength concrete and C60 HPC to calculate the long-term creep of C60 HPC accurately, which was combined with engineering construction of Yichang Chang Jiang Railway Bridge. It was concluded the creep degree and creep coefficient of C60 HPC by means of optimization fit calculation, which gives scientific foundation for the design and construction of this bridge.
Study on Low-Cost Reactive Powder Concrete and its Application
Authors: Zhang Ming , Xing Feng , Deng Liang Peng , Cao Zheng Liang , Huang Zhan
Published: March 2009

Reactive powder concrete (RPC) is a new kind of material with very high mechanical behavior and durability, however, high cost and complex procedure to make RPC result in hardly apply to engineering in large scale. a new low-cost RPC that compressive strength exceeds 130MPa was prepared with the replacement of quartz sand, crushed quartz and partial of silica fume by fly ash, slag and natural fine aggregate in the paper. Manhole cover that made from the low-cost RPC can meets the requirements of different situations, such as special road, motorway, etc.
Experimental Study on Vacuum-Assisted Pumping Technique of Steel Tube-Confined Concrete
Authors: Hu Shu Guang , Peng Yan Zhou , Ding Qing Jun , Luo Shi Dong
Published: March 2009

A new technique for construction of steel tube-confined concrete (STCC), i.e., vacuum-assisted pumping technique was put forward in this paper, and the simulation research both in laboratory and on the building site had been done. The test results showed that the formation of air membrane between steel tube and core concrete could be effectively inhibited by controlling the air content of concrete through optimizing design for mix proportion of concrete and by regulating the vacuum pressure in steel tube during the process of concrete pumping, and thus the density of concrete was increased and the bond between steel tube and concrete was improved. Therefore, the performance of STCC structure such as the ultimate load-bearing capacity was enhanced. Moreover, this new technique can decrease the difficulty of concrete pumping. The technology had been applied in the construction of Yichang Yangtze River Bridge in Yichang-Wanxian railway.
Rheological Properties of Fresh Cement Paste and its Relation to Adsorption Behavior of Superplasticizer
Authors: Lin Dong , Fang Man Man , Xi Xiao Lin , Wang Heng Chang , Yin Su Hong , Wen Zi Yun
Published: March 2009

This paper studied rheological properties of fresh cement pastes and adsorption behavior of superplasticizers which are FDN-5R, a type of naphthalene sulfonic acid based condensate, 3350, a type of polycarboxylate superplasticizer, by R/S-SST rheometer and UV Visible Spectrometer. Results show that superplasticizers can reduce the flocculation structure of fresh cement paste obviously and reduce the yield stress and apparent viscosity. The turn of thixotropic property is: blank sample > FDN-5R > 3350, especially the sample with 3350’s curve of upward and downward almost match together and the thixotropic property drives to zero. Shearing stress, apparent viscosity and thixotropic property are decreased, adsorption capacity is higher by the superplasticizer adding. The bigger effectual adsorption, the better dispersive action of flocculation and rheological properties of fresh cement pastes. Therefore, we can understand the effect mechanism and properties of superplasticizer much better by combining the molecular structure, adsorption capacity, dispersive action and rheological properties.
Kinetics of the Decomposition of Crocidolite Asbestos: A Preliminary Real-Time X-Ray Powder Diffraction Study
Authors: Gualtieri A.F. , Levy D. , Dapiaggi M. , Belluso E.
Published: March 2009

This work is a preliminary kinetic study of the crocidolite decomposition followed in situ at high temperature using real time conventional powder diffraction and DTA in the temperature range 720-795 °C. The data analysis using the Avrami models indicates that the rate limiting step of the reaction is monodimensional ion diffusion (n=0.5) with an activation energy of 129 (10)kcal/mole.
Characteristics of Fe2O3/SiO2 Nano-Composites Particles Prepared by a Diffusion Flame with Premixed Precursor
Authors: Ahn Kang Ho , Ahn Jung Ho , Jeon K.-S. , Choa Yong Ho
Published: March 2009

Fe2O3 nano-particles coated with SiO2 are synthesized using H2/O2 co-axial diffusion
flame with the state-of-the-art electro-spraying (e-spray) technique at atmospheric condition.
Fe(CO)5 and TEOS (tetra-ethyl-ortho-silicate) mixture in liquid phase is injected directly into the
center of the flame using the electro-spraying method. The synthesized particle characteristics are
analyzed with HRTEM, XRD, SQUID. The core (iron oxide)-shell(silica) structured spherical
particles are obtained. Most of the particles synthesized are magemite() regardless of the particles
sampling positions inside the flame.
Properties of Catalytic Filter for the Hot Gas Cleaning
Authors: Lee J.S. , Shin K.H. , Shin Min Chul , Cho D.H. , Lee Hyung Seok
Published: March 2009

Porous filter was manufactured using cordierite powder and it was loaded with V2O5
catalyst by vacuum impregnation method. The removal efficiency of NOX and simultaneous
removal efficiency of NOX /Dust were measured by passing NO and dust through catalystloaded
ceramic filter. The cordierite porous filter had the apparent porosity of 61.6%, the
compressive strength of 12.3 MPa and the pressure drop of 1200 Pa at the face velocity of 5
cm/sec, at 400oC. NOX removal efficiency of filter loaded only V2O5 catalyst was 80% and it
could be improved up to 90% by the acid treatment (which increased specific surface area of
filter elements); then this result is equal to the removal efficiency of the commercial V2O5/TiO2
catalyst, which was used at SCR(Selective Catalytic Reduction) process. Dust & NOX
simultaneous removal efficiency of filter loaded V2O5 catalyst was about 99.6% of dust and
90% of NOX. Crack generated by thermal shock or pressure was not found. We found that
catalytic cordierite filter is good candidate for simultaneous removal of particulate and
hazardous gas from this result.
Fabrication of Activated Carbon Fibers from Stabilized PAN-Based Fibers by KOH
Authors: Lee Young Jae , Kim Jae Hyung , Kim Jang Soon , Lee Dong Bok , Lee Jae Chun , Chung Yun Jung , Lim Yun Soo
Published: March 2009

Activated carbon fibers were prepared from stabilized PAN-based fibers by chemical activation using potassium hydroxide at different concentration. The experimental data showed variations in specific surface area, microstructure by the activated carbon fibers. Specific surface area of about 2545 m2/g was obtained in the KOH/stabilized PAN-based fiber ratio of 1:1 at 800°. An abrupt reduction of specific surface area was observed in the experiments with the ratio of 3:1 of OH/stabilized PAN-based fiber, being dissimilar with the result of KOH/fiber ratios of 1:1 and 2:1 in the similar experiments. The high concentration of KOH led to the destruction of micropore walls instead of forming mesopores.
Observation of Metal Flow Phenomenon of Lap Joints during Friction Stir Welding
Authors: Shinoda Takeshi , Suzuki Junki
Published: March 2009

Two kinds of aluminum alloys have been used as lap joint in FSW. Experiments are
selected to observe metal flow by metallurgical procedures. One is for the effect of probe type and pre-friction time on metal flow at start point. Another is for the effect of probe type on metal flow for stable traveling stage. Thermal analysis also has been carried out.
Friction Welding of A 6061 Aluminum Alloy and S45C Carbon Steel
Authors: Shinoda Takeshi , Kawata Shiniti
Published: March 2009

Many researches for friction welding of aluminum with either carbon steel or stainless steel have been carried out. From those results, it is concluded that the greatest problem is the formation of brittle intermetallic compounds at weld interface. However, it is not clearly demonstrated the effect of friction welding parameters on the formation of intermetallic compounds. This research purposes are to evaluate the formation of intermetallic compounds and to investigate the effect of friction welding parameters on the strength of welded joint. For these purposes, A6061 aluminum alloy and S45C carbon steel were used with a continuous drive vertical friction welding machine. Tensile test results revealed that the maximum tensile strength was achieved at extremely short friction time and high upset. The joint strength reached 92% of the tensile strength of A6061 base metal. Tensile strength of friction welding was increasing with increasing upset pressure when friction time 1sec. However, tensile properties were deteriorated with increasing friction time. It was observed that the amount of formed intermetallic compound was increasing with increasing friction time at weld interface. Partly formed intermetallic compound on weld interface were identified when friction time 1sec. However, intermetallic compound layer were severely developed with longer friction time at weld interface. It was concluded that intermetallic compound layer deteriorated the tensile properties of weld joints.
Recrystallisation and Grain Growth in Batch Annealed Ti-IF Steels
Authors: Petitgand Hélène , Réglé H. , Zimmermann Uwe
Published: March 2009

In order to optimize the batch annealing cycles and increase the productivity of this process, the impact of the chemical composition and the processing parameters on the recrystallisation and grain growth kinetics were investigated on different Ti IF steels. A simple model based on an Avrami formulation has been developed for the prediction of the recrystallisation kinetics.
Study of Nucleation Mechanisms during Dynamic Recrystallization of a Coarse Nb Microalloyed Austenite
Authors: Fernández-Calvo Ana Isabel , López Beatriz , Rodriguez-Ibabe J.M.
Published: March 2009

The dynamic recrystallization (DRX) behavior of a coarse grain sized Nb microalloyed austenite (∼ 800 µm), typical of thin slab casting processes, has been studied. Continuous torsion tests were carried out at different, Z, Zener-Hollomon parameter values. It has been observed that as Z increases the curves move to higher values of stress and both the peak, εp, and steady state, εss, occur at larger strains, with an increase in the εss - εp strain difference. Consequently, an
increment in Z produces a delay in the beginning and the progression of the DRX process. In the present work, it has been found that the pre-existing grain boundaries are the most favorable nucleation sites for DRX for all Z values, the nucleation mechanisms being related to strain induced migration of high angle grain boundaries. However, in the case of high Z values, intragranular nucleation on defects generated during deformation is also observed. The microstructure analysis
denotes also that dynamic recrystallization is a process dominated by repeated nucleation with limited growth.
Influence of TiN Particles on Dynamic and Static Recrystallization in Microalloyed Steels
Authors: Medina S.F. , Vega M.I. , Gómez Manuel
Published: March 2009

This work has studied the influence of different Ti and N compositions on hot deformation strength by determining the peak stress of flow curves and the activation energy (dynamic recrystallisation). It has also assessed their influence on static recrystallisation by means of the statically recrystallised fraction versus time and the activation energy. A precipitate study performed by SEM and TEM has yielded a better understanding of the influence of the Ti/N ratio and precipitation state in hot deformation (dynamic and static recrystallisation). A correlation was found between for the finer distribution of precipitates, Ti/N ratio close to 1.5, smaller austenite grain, maximum activation energy for hot deformation (dynamic recrystallisation) and maximum activation energy for static recrystallisation.
The Effect of Hydrogen on Dynamic Recrystallization in α-Titanium Alloys
Authors: Murzinova Maria A. , Salishchev Gennady A. , Afonichev D.D.
Published: March 2009

The influence of hydrogen content on the mechanical properties and size of dynamically recrystallized grains in commercially pure (CP) titanium and Ti-5Al-2.5Sn alloy was investigated. The alloys with hydrogen contents from 0.1 to 5.2 at.% were deformed in the a-field at temperatures of 650°, 750°С with initial strain rates of 5×10-4 s-1. A decrease of the deformation temperature leads to a reduction in grain size and to a stress increase for all compositions. This is in good agreement with the well known relation between the recrystallized grain size (d) and the steady flow stress ss=kd-n. At a given test temperature the steady state flow stress is four times lower and the grain size is about ten times greater in CP titanium in comparison with the Ti-5Al- 2.5Sn alloy. Hydrogen alloying of the Ti-5Al-2.5Sn alloy does not lead to a noticeable change in ss and d. However, an increase in hydrogen content from 0.1 to 5.2 at.% in CP titanium leads not only to a decrease in grain size by a factor of 2 but also to a decrease in flow stress (about 28%). This result is not in agreement with the above relation. This unusual behaviour may be due to two reasons: the influence of hydrogen on grain growth and the hydrogen effect on dynamic strain ageing. Both these effects are stronger in CP titanium.
Diffusion Creep during Grain Growth in Nanocrystalline Metals
Authors: Estrin Yuri , Gottstein Günter , Shvindlerman Lasar S.
Published: March 2009

Diffusion controlled creep in nanostructured materials is considered for the case when grain growth occurs concurrently. The Nabarro-Herring and Coble mechanisms that would predict creep rate reduction are re-considered to include the effect of grain-growth induced vacancy generation. It is shown that under such conditions creep is accelerated during an initial stage of grain growth as compared to the case of constant grain size. This creep enhancement stage is followed by a
period of reduced creep rate. The predicted strain rate behaviour resembles primary and secondary creep.
Structural Evolution of IF Steel during Annealing after ECAP
Authors: De Messemaeker Joke , Verlinden Bert , Van Humbeeck Jan
Published: March 2009

IF steel processed by equal channel angular pressing to an equivalent strain of 9.2 via route BA was annealed for different times at 500°C and 600°C. At both temperatures the microstructural evolution shows continuous recrystallization followed by grain growth, in absence of primary recrystallization. At 600°C a slightly bimodal grain size distribution develops.
Thermal Stability of CP-Aluminium during Annealing after ECAE
Authors: Poortmans Stijn , Verlinden Bert
Published: March 2009

Samples of a hot-rolled AA1050 Aluminium alloy have been deformed by ECAE for 4 and 8 passes following route C. The structural stability of the samples after annealing treatments in the range 200°C to 350°C during 1 to 1000 minutes has been investigated. After 4 ECAE passes, the microstructure is not homogeneous. EBSD-scans show that the former grains can still be identified and that these grains show a different stage of subdivision. After 8 passes the structure is more homogeneous. During subsequent annealing the (sub)structure changes following a common pattern, but with different kinetics in all former grains. At first the dislocation density decreases, illustrated by an increase in image quality of the EBSD-scans and a sharpening of the (sub)structure can be observed. The (sub)grain size remains practically constant during this phase. At a given time, different from one (original) grain to another, some (sub)grains start to grow following an ‘abnormal grain growth’ pattern. This happens at all investigated temperatures. The kinetics and mechanisms of this microstructural evolution will be discussed.
On the Production of Randomly-Oriented Recrystallization Nuclei for Selective Growth Experiments
Authors: Nave Mark D. , Verbeken Kim , Kestens Leo
Published: March 2009

The ideal starting condition for selective growth experiments is one having a layer of
randomly-oriented nuclei adjacent to a matrix with negligible orientational variation but sufficient stored energy to promote growth. In practice, cutting or deformation processes are used in an attempt to approximate these ideal conditions, but the degree to which this is achieved has not been rigorously quantified. In this work, Fe-3wt%Si single crystals were cut or deformed using six different processes. The variation in texture with distance from the cut or deformed surface was measured using electron backscatter diffraction (EBSD) in a field emission gun scanning electron microscope (FEG-SEM) in order to assess the ability of each process to create conditions suitable for selective growth experiments. While grooving with a machine tool produced the best spread of orientations at the cut surface, the suitability of this process is diminished by the presence of a differently-textured deformed layer between the cut surface and the single crystal matrix. Grinding
produced a less ideal distribution of orientations at the cut surface, but the presence of these orientations in a very thin layer adjacent to the matrix makes this process preferable for preparing crystals for selective growth experiments, provided the results are corrected for the deviation in the distribution of nuclei orientations from a random distribution.
Difference in Recrystallization Behavior between Martensite and Deformed Ferrite
Authors: Futamura Y. , Natori Masahide , Tsuchiyama Toshihiro , Takaki Setsuo
Published: March 2009

Microstructural change and soft ening behavior during annealing were investigated for deformed ferrite and lath martensite in an ultralow carbon 1.5mass%Mn-0.0018mass%B steel, and then the difference in recrystallization behavior between the materials was discussed in terms of the nucleation site of recrystallized grains. The ferritic and martensitic materials were obtained by furnace-cooling and water-quenching, respectively, after solution treatment. The ferritic material was cold-rolled at a reduction of 80% to give the same dislocatio n density as of the martensitic material. The deformed ferritic material contains a large number of geometrically necessary boundaries with large misorientations, while the martensitic material does only contain original grain boundaries such as prior austenite grain boundaries, packet boundaries and block boundaries. The recrystallization during annealing is markedly retarded in the martensitic material compared with the deformed ferritic
material. As a result, the time for completing the recrystallization was roughly a hundred times longer in the martensitic material than in the deformed ferritic material. This is due to the difference in nucleation site of recrystallized grains, that is, the geometrically necessary (GN) boundaries introduced by the deformation for the ferritic material, and only the original grain boundaries for the martensitic material.
Study of Deformation Microstructure and Static Recovery in Copper after Cold Drawing
Authors: Benyoucef Mustafa , Jakani S. , Baudin Thierry , Mathon Marie Helene , Penelle Richard
Published: March 2009

The analysis of the microstructure deformation and the static recovery were investigated by transmission electron microscopy (TEM) observations, after cold drawing in copper. The observed microstructures according to the orientation of grains are composed of dislocation cells, deformation bands and dense dislocation walls. In <001> grains, the cells are equiaxed, regular and surrounded by sharp walls, whereas in the <111> grains the cell creation is also in progress. During the annealing, the microstructure of <001> grains evolves to a stable configuration composed of very thin walls and coalesced cells that correspond to the first recrystallization nuclei.