bluuebunny/crossref_metadata_2025 huggingface dataset:
Physicochemical Reactivity after the In Vitro Assays of Synthetic and Natural Hydroxyapatite
Authors: Oudadesse Hassane , Mezahi F.Z. , Harabi Abdelhamid , Camargo Nelson Heriberto A. , Cathelineau G.
Published: March 2009

Bioactive ceramics such as bioactive glasses, calcium carbonate and sintered hydroxyapatite are widely used in biomaterials field because of their high biocompatibility. In this study, natural hydroxyapatite (N-HA) and synthetic Hydroxyapatite (S-HA) were heat treated at 800°C and studied using “in vitro” experiments. Several physicochemical methods like: SRD, FTIR, SEM and ICP-OES were employed to evaluate the effects of the thermal treatment and to compare their behaviour after soaking in the Simulated Body Fluid SBF at different times. The formation of TCP has favours the formation of new phase. Obtained results show that the dissolution occurred more in N-HA than in S-HA and consequently the precipitation of new phosphate phase is more important in N-HA. This is due to the presence of Mg, Sr and Zn in N-HA with concentration higher to that in S-HA.
Cellular Alignment Induction during Early In Vitro Culture Stages Using Micropatterned Glass Coatings Produced by Sol-Gel Process
Authors: Pelaez-Vargas A. , Ferrell N. , Fernandes M.H. , Hansford D.J. , Monteiro F.J.
Published: March 2009

Cell behaviour such as adhesion, morphology, proliferation and functional activity are highly influenced by surface properties including hydrophobicity, roughness, texture and morphology. These surface properties may be controlled using a mixture of additive coating techniques to produce glass coatings by sol-gel process and soft lithography on dental ceramics. The purpose of this work was to compare cell adhesion and early orientation of Human Bone Marrow (HBM) cells cultured on micro-patterned (micro-PGC) and on flat glass coatings (FGC) produced by sol-gel processing. Spin coating was used to apply SiO2 flat coatings on glass substrates as model surfaces. Photolithography was applied to produce master patterns with microscale dimensions. A moulding technique was used to print micropatterned SiO2 glass coatings produced by a sol-gel process. The coatings were then sintered, sterilized and cultured with HBM cells derived from primary cultures, using a standardized protocol, for 1 and 7 days. Cell morphology and orientation were observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Flat and MPGC with line shaped features were produced. Cells presented a typical osteoblastic morphology on flat surfaces while slimmer, preferentially oriented and more elongated morphologies could be seen on line micro-patterned surfaces. HBM cells cultured on flat glass coatings showed increased tendency to spread and to assume more randomized proliferation when compared to the cells on the micro-patterned glass coatings. Micro-patterned glass coatings showed higher orientation control and smaller delay in the rate of proliferation, in early stages of in vitro culture as compared to flat coatings. These preliminary studies revealed that Micro-PGC induce significant morphological changes and controlled orientation of HBM cells during early stages of cell proliferation.
The Interaction between Human Osteoblastic Cells and Titanium Anodized with Sulphuric Acid Coated or not with Human Plasma Fibronectin
Authors: Raybolt dos Santos Aline , Costa e Silva Fernando , de Almeida Soares Gloria Dulce
Published: March 2009

In this study, commercially pure titanium (Ti-cp) sheets grade 2 were used as substrates. To investigate the role of composition and characteristics of titanium surface oxides in cellular behavior of osteoblasts, the surface of titanium were modified by anodic oxidation with sulphuric acid. Subsequently were treated part of anodized samples with FN and cultured with osteoblast cells for 30, 120 and 240 minutes. The chemical composition and topography have influenced the interaction between fibronectin and substrate. Cells were found more associated to the surfaces that have been submitted to anodization and FN coating than to the related controls.
Combustion Synthesis of Hydroxyapatite and Hydroxyapatite (Silver) Powders
Authors: Narayanan R. , Singh Vijay , Kwon Tae Yub , Kim Kyo Han
Published: March 2009

Hydroxyapatite powder is produced using combustion synthesis method. The powder was produced using a low-temperature processing method involving time as short as 15 minutes. As silver is known to have anti-bacterial properties, silver-doped hydroxyapatite was also produced by the same method. Both the powders were fully crystalline. XRD indicated the presence of an additional phase of CaO in both the samples. FT-IR indicated the presence of hydroxide, phosphate and carbonate groups. Silver addition tends to control the reactions of powder with a test Tris buffer environment and maintain a stable pH for a longer period of 500-hour duration.
Hydroxyapatite-Sheet Microstructure of Shinbone
Authors: Chen Bin , Sun Shi Tao , Peng Xiang He
Published: March 2009

Bone is a kind of biomaterial in nature. It behaves favorable strength, stiffness and fracture toughness which are closely related to its fine microstructures. Scanning electron microscope (SEM) observation on a shinbone shows that the bone is a kind of natural bioceramic composite consisting of hydroxyapatite layers and collagen matrix. The hydroxyapatite layers are arranged in a parallel distribution and consist of many hydroxyapatite sheets. The fracture toughness of the bone was analyzed based on the representative model of the microstructure in the bone and the idea of maximum pullout energy. The analytical result shows that the long and thin shape as well as the parallel distribution of the hydroxyapatite sheets increase the maximum pullout energy of the sheets and enhance the fracture toughness of the bone.
Adsorption and Sustained Release of Insulin from Zinc Hydroxyapatite Microparticle with Poly (Lactic Acid) Coating
Authors: Tonegawa Toru , Ikoma Toshiyuki , Yoshioka Tomohiko , Shinozaki Kazuo , Hanagata Nobutaka , Tanaka M.
Published: March 2009

Insulin delivery carriers using low crystalline porous zinc hydroxyapatite (ZnHAp) microparticles with different crystal sizes and novel formulation method of poly (lactic acid) (PLA) have been developed to achieve the sustained-release of insulin. The adsorption isotherm curves of insulin dissolved into acetic acid of pH4.5 onto ZnHAp nanocrystals show non-Langmuir type due to the dissolution of the ZnHAp microparticles; the adsorption amounts were increased with the increase of crystalline sizes. The PLA formulation, coating the outer layer of microparticles, showed the apparent reduction of initial burst for insulin. The amounts of initial release of insulin decreased with the increase of crystalline sizes of ZnHAp, which could be attributed to the different meso-porous structure depending on its crystal sizes.
Biocompatibility Properties of ZrO2 Ceramics and ZrO2-TiN Composites
Authors: Arin Melis , Yazici Hilal , Goller Gultekin
Published: March 2009

In order to study bicompability properties of fully dense ZrO2 ceramics containing 2-3 mol% Y2O3 stabilizer, and ZrO2-TiN composites containing 1-1.75 mol Y2O3 and 1 mol% Nd2O3 stabilizers, and electrical conductive TiN particles (40-60 vol%), cell viability was evaluated based on the reduction of tetrazolium salt to formazan crystals by living cells, the alkaline phosphatase production was investigated, and nitrite quantification was done for indirect evaluation of osteoblast NO production. The samples were defined biocompatible since there is not any significant change observed in the physiological functions of the cells when incubated together.
In Vitro Evaluation of the Antimicrobial Action of Chlorhexidine Associated to Hydroxyapatite
Authors: Souza C.A.S. , Souto Renata M. , Colombo Ana Paula V. , Rossi Antonella M. , Rocha-Leão Maria Helena M.
Published: March 2009

Chlorhexidine (CHX), a cationic antiseptic, is an antimicrobial agent with many applications. In this work, the antimicrobial action of CHX associated with hydroxyapatite (HA) was evaluated for treating oral infections. Based on the determination of MIC (6,25 mg/mL HACHX), the material showed growth inhibition of E. faecalis for up to 08 days.
Lead and Cadmium Immobilization by Polymeric Sponges Coated with Hydroxyapatite
Authors: Mavropoulos Elena , da Rocha Nilce C.C. , Kede M.L.F.M. , Prado da Silva Marcelo Henrique , Moreira Josino C. , Rossi Antonella M.
Published: March 2009

Polymeric sponges coated with hydroxyapatite were used in lead and cadmium uptake experiments in order to mimetizes heavy metal incorporation by bone tissue. The hydroxyapatite-coated sponges (S-HA) were obtained by hydrothermal alkali conversion from monetite. The results showed that S-HA were efficient in immobilizing Pb and Cd. The uptake experiments using hydroxyapatite powder (HA) removed almost 100% of Pb2+ and 59% of Cd2+. When polymeric sponges coated with hydroxyapatite were used, the removal of Cd2+ and Pb2+ decreased, respectively, to closely 14 % and 74%, after 24 hours sorption. Before and after sorption experiment MEV analysis indicated precipitation of pyromorphite on hydroxyapatite-coated sponges.
Phase Evolution of Thermally Treated Amorphous Tricalcium Phosphate Nanoparticles
Authors: Döbelin Nicola , Brunner Tobias J. , Stark Wendelin J. , Eggimann Manuel , Fisch Martin , Bohner Marc
Published: March 2009

X-ray amorphous tricalcium-phosphate nanoparticles (ATCP) produced by flame spray synthesis were heat-treated at temperatures between 500 and 1000 °C and analyzed in situ by X-ray powder diffraction. The main phase occurring after crystallisation at 525 °C was α-TCP, minor phases were identified as β-TCP and hydroxyapatite. More elevated temperatures induced crystallite growth and the transformation of α-TCP into β-TCP. Above 900 °C no α-TCP was traceable anymore. α’-TCP was not observed in the experiment. This study shows that nanoparticulate α-TCP can be obtained by thermal treatment of an amorphous TCP nanoparticle in a temperature range where sintering effects such as particle growth and densification are moderate or nearly negligible.
In Vivo Behavior of Hydroxyapatite Evaluated by Attenuated Total Reflection Infrared Microscopy (ATR-FTIR)
Authors: Calasans-Maia Monica , Santos Silvia R. A. , Rossi Antonella M. , Granjeiro José Mauro
Published: March 2009

The study aimed the evaluation of the effect of osseous repair in the synthetic hydroxyapatite cylinder (HA) implanted in rabbit’s tibia. Fifteen adult animals, weighing around 2.5 and 3.0 Kg, sourced by the Fluminense Federal University Animal Lab were anesthetized with spinal anesthesia, and two perforations were created in right tibia and filled with cylinders (2 x 6 mm) of HA. The animals were killed after 28 days for evaluating the HA cylinder through attenuated total reflection infrared microscopy (ATR-FTIR). The two fragments of tibia with the cylinder were collected and fixed in alcohol 70° prior to dehydration in successive alcohol solutions and then impregnated and embedded in methyl-methacrylate. Not stained neither pasted to lamina, sections of 200 µm thickness were analyzed in a Shimadzu IRPrestige-21 Automatic Infrared Microscope (AIM-8800) with ATR Objective Mirror (ATR-8800M). Prior to implantation, HA cylinder was characterized by X-Ray diffraction (XRD), Attenuated Total Reflection- Infra Red microscopy (ATR-FTIR) and X-Ray Fluorescence (XRF). After the implantation, the spectrum of the ATR-FTIR at the interface to neoformed bone was acquired. The hydroxyapatite synthesized was crystalline and stoichiometric with Ca/P ratio of 1.66, becoming carbonated after 28 days of implantation. We conclude that attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) is a useful tool for biomaterial evaluation and able to detect the modification of the chemical HA cylinder pattern occurred probably by ions migration in the biological environment.
Synthesis of Nanostructured Hydroxyapatite: A Comparative Study between Sol-Gel and Aqueous Solution Precipitation
Authors: Rodrigues L.R. , Motisuke M. , Zavaglia Cecília A.C.
Published: March 2009

Particle size is one of the most important factors to the successful application of calcium phosphate bioceramics as it may have an important role on its final properties such as mechanical resistance and reactivity. Thus, a process which results on very small and homogeneous particles is required, since it avoids further contamination derived from long milling times. On this context, a process such as sol-gel synthesis may be feasible, due to its simplicity on handling and its well known characteristic of producing homogeneous nanoparticles. Moreover, precipitated HA also may lead to satisfactory results regarding particle size and phase purity. The aim of this article was to demonstrate a preliminary characterization study of powders obtained by both methods and to compare them to a commercial sample available in Brazil. Characterization was made by XRD, Scherrer’s equation, XRF, SEM-LV, SEM-FEG and SEM-EDS. It has been found out that all samples consist of pure nanostructured hydroxyapatite with crystallite size between 37nm and 62nm.
Three-Layer Coating for Stents with Nanostructured Surface
Authors: Beck Ulrich , Lange Regina , Lembke U. , Neumann Hans Georg
Published: March 2009

A three-layer coating for stents with a nanostructured surface of calcium phosphate (CaP) is pre-sented. The coating stack consists of (a) a TiNbN layer deposited by physical vapour deposition and acting as diffusion barrier against allergenic ions, (b) a SiO2 xerogel layer providing good adhesion properties and designing the nanoporosity of the outer CaP layer (c) precipitated electrochemically. The verification of the SiO2-layer (and therewith its influence onto adhesion and structure of the outer CaP layer) succeeded only by use of XPS because of the very small amount of the xerogel. SEM results verified a homogeneous nanoscale nanoporous structure of the CaP coating. It is char-acterised by high adhesion strength. If applied for stent covering the nanoscale CaP coating has promising properties to initiate rapid endothelium formation and reduced risk of restenosis.
Modified Gelcasting Process to Prepare Porous Trifasic and Bifasic Hydroxyapatite Scaffolds
Authors: Mendonça Flavia , Louro Luis Henrique Leme , de Campos Jose B. , Rossi Antonella M. , Prado da Silva Marcelo Henrique
Published: March 2009

In the present work, apatite powders were synthesized at pH 10, pH 11 and pH 12 in order to give rise to biphasic and triphasic bioceramics after sintering. A modified gelcasting process, including polyethylene wax spheres addition to the suspension, is proposed in comparison to the original gelcasting method. The aim of the addition is the creation of uniform, open and interconnected pores in the body of samples.
Porous Alumina Scaffolds with Bioactive Coating: Implants in the Rat Tibia and In Vitro Studies
Authors: Camilo Claudia C. , Fortulan C.A. , Parizotto N.A. , de M. Purquerio B.
Published: March 2009

Ceramic scaffolds, mechanically qualified, highly porous, non biodegradable and with bioactive coating have been manufactured. The aim of this study was evaluated mechanical and in vivo responses of the porous alumina scaffolds with bioactive coating. The bioactive coating was performed under vacuum with bio-glass (45S5®)) and hydroxyapatite (HAp). Alumina ceramics (Al2O3) are used for bone implants in function of the biocompatibility and the high mechanical reliability of this material. Unfavourably alumina is a bioinert material and bone ingrowths are hard to occur and any implant anchorage becomes difficult. To improve this, ceramic scaffold samples were made with porosity concentration around 75vol% and with average pores diameters around 190.0µm. They were mechanically characterized through macro and micro structural analyses and mechanical tests and biologically through cell culture tests with fibroblastic VERO cell line for cytotoxicity and animal experiments on tibiae rats – Rattus norvegiicus albinos – aiming histological and line scan analysis in order to check the scaffold-bone cellular interaction. Current results seem to suggest the promising properties of the bioactive coated alumina ceramic scaffolds tested. The concentration of 75vol% alumina showed to be the great alternative for an economical solution for porous alumina ceramic scaffolds related to the mechanical properties and bone integration.
Biological Response to Wollastonite Doped α-Tricalcium Phosphate Implants in Hard and Soft Tissues in Rats
Authors: Minarelli Gaspar Ana Maria , Saska Sybele , García Carrodeguas R. , De Aza A.H. , Pena P. , De Aza P.N. , De Aza S.
Published: March 2009

The biological response following subcutaneous and bone implantation of β-wollastonite(β-W)-doped α-tricalcium phosphate bioceramics in rats was evaluated. Tested materials were: tricalcium phosphate (TCP), consisting of a mixture of α- and β-polymorphs; TCP doped with 5 wt. % of β-W (TCP5W), composed of α-TCP as only crystalline phase; and TCP doped with 15 wt. % of β-W (TCP15), containing crystalline α-TCP and β-W. Cylinders of 2x1 mm were implanted in tibiae and backs of adult male Rattus norvegicus, Holtzman rats. After 7, 30 and 120 days, animals were sacrificed and the tissue blocks containing the implants were excised, fixed and processed for histological examination. TCP, TCP5W and TCP15W implants were biocompatible but neither bioactive nor biodegradable in rat subcutaneous tissue. They were not osteoinductive in connective tissue either. However, in rat bone tissue β-W-doped α-TCP implants (TCP5W and TCP15W) were bioactive, biodegradable and osteoconductive. The rates of biodegradation and new bone formation observed for TCP5W and TCP15W implants in rat bone tissue were greater than for non-doped TCP.
Evaluation: Specific Energy Deposition from 252Cf-Sol-Gel Glass in Brain Interstitial Implants
Authors: Mendes B.M. , Campos T.P.R.
Published: March 2009

Neutron brachytherapy show better results than conventional photon therapy for radioresistant tumors with hypoxic regions. Herein a comparative radiodosimetric analysis is presented considering 125I photon emitter seeds, often applied to brachytherapy, and a proposed Sol-Gel glass, synthesized with incorporated 252Cf neutron emitter, on a brain tumor implant. The proposition is to verify the viability of applying this bioceramic material. The methodology is based on the investigation of the specific energy deposition (dose) from 252Cf-Glass in deep brain interstitial implants through a stochastic computer code (MCNP5) and comparison with 125I seed’s energy deposition. 252Cf-Glass show dose per transition values higher than 125I seed’s set. RBE-isodose curves show a faster decrease of dose with the source distance increasing which can improve healthy tissue sparing.
Adiabatic Temperature Rise of Incompletely Hydrated Cement Concrete
Authors: Ng P.L. , Ng I.Y.T. , Kwan A.K.H.
Published: March 2009

The temperature rise of concrete during hardening is intimately related to the mix proportion, among which the cement content is a major factor. However, high-strength concrete mixes are often proportioned with low water contents which leads to incomplete hydration of cement contained therein. Hence, the conventional rule of determining concrete temperature rise solely based on the cement content may not yield accurate estimations. An experimental program has been launched to investigate the coupled effects of cement and water contents on the adiabatic temperature rise of concrete. Eighteen concrete mixes were tested with a newly developed semi-adiabatic curing test method and their adiabatic temperature rise obtained by applying heat loss compensation to the test results. The results revealed that, when the water/cement ratio is lower than 0.36, both cement and water contents have effects on the adiabatic temperature rise of concrete. Prediction formula and design chart of adiabatic temperature rise, which are accurate to ±1.3°C compared with the test results, are developed. Furthermore, prediction formula of the degree of hydration of concrete is recommended.
Stochastic Damage Constitutive Model for Concrete Considering Strain Rate Effect
Authors: Ren Xiao Dan , Li Jie
Published: March 2009

The present work concentrates on the model of concrete under dynamic loading. The stochastic damage constitutive model for concrete under static loading developed by the authors’ research group is firstly reviewed in this paper. The strain rate effect is considered as viscous effect so that the dynamic generalization of the static model could be developed by analogy with viscous-plastic theory. Combined with static damage expressions, the frame work of dynamic stochastic damage constitutive relationship for concrete is established. The analytical expression of dynamic increase factor (DIF) of peak stresses under tension and compression are derived according to the present dynamic damage model. Several simulation results of concrete under static as well as dynamic loading are provided to demonstrate its capacity of reproducing the salient features experimentally observed.
Selective Use of High Performance Cementitious Composites in Concrete Structures
Authors: Leung Christopher K.Y.
Published: March 2009

Recent advancements in concrete science and technology have made possible the development of high performance fiber reinforced cementitious composites (HPFRCC) with excellent mechanical properties and long-term durability. However, the costs of these materials are many times that of conventional concrete and the construction of complete structures with them is hard to justify. The strategic application of high performance materials, in selected parts of concrete structures, can bring along higher performance/cost and wider acceptance of the material in practice. This paper will investigate several examples of selective HPFRCC application, including the fabrication of permanent formwork for durability enhancement, the replacement of steel reinforcements at the anchorage zone of post-tensioned members to relieve the steel congestion problem as well as the development of simple and narrow joints for pre-cast concrete members. Based on the experimental results obtained so far, the selected use of HPFRCC in concrete structures appears to have good potential for practical applications.
The Numerical Study on Load-Transferring Model for SFRC Double-Column Combined Six-Pile Caps
Authors: Zhang Yuan Yuan , Xu Li Hua , Chi Yin
Published: March 2009

For discussing the mechanism of load-transferring for reinforced steel fiber reinforced concrete (SFRC) double-column combined six-pile caps, the large-scale general finite element software-ABAQUS is used for the tested SFRC caps with computing in the aspects of modeling, cracking load, limit load, load-deformation curve, distribution of stress in caps and cracks and etc. The results of computing is compared with the result of experiments and the comparison is indicated: The results of computing and experiments are coincided well; The destroy pattern of SFRC double-column combined six-pile caps is sheared damage or punched damage and the model of load-transferring accords with spatial strut-and-tie method (STM); The mixture of steel fiber can improve cracking load and limit load for RC caps, delay the crack for caps, block the cracks’ expansion, and enhance the cap’s ductility.
Study and Application on Computational Methods for Ultimate Bearing Capacity of Single Pile
Authors: Yao Ze Liang , Jian Zhen , Bai Guo Liang
Published: March 2009

It is difficult and important to accurately calculate single pile ultimate bearing capacity during pile foundation design. Typical computational methods on single pile ultimate bearing capacity are contrastively analyzed in this paper. Contact element method on single pile ultimate bearing capacity is relatively accurate and economical, but it isn’t used in practical projects until now because its computational process is complicated. 343 different single pile ultimate bearing capacities are calculated with the contact element method in order to study a simple computational formula based on the contact element method. All data calculated are analyzed with a linear recursive multi-analysis program which is programmed with Fortran90. A simple computational formula on the contact element method is presented based on the analysis results. The simple computational formula, the experiential formula in the code, the contact element method and the static load experiment method are respectively used to calculate single pile ultimate bearing capacity in two practical projects in order to test the simple computational formula. The results show that the simple computational formula is relatively accurate. Some advice is presented based on the analysis results.
Inner Force Analysis of Two Typical Frames with Vertical Displacement
Authors: Zhou Wei
Published: March 2009

Finite element method is often used to obtain exact solution in the course of internal force calculation of some complex frames which contain nodal vertical displacement such as frames with transferring layer and mega-frames with sub-structure. In the phase of scheme comparison and schematic design, methods which can quickly produce calculation results of the above said frameworks are necessary. Based on the basic principle of displacement method, this paper proposes a simple analytical method for frameworks that contain nodal vertical displacement. According to the proposal, the basic structure for calculation is the framework in which is added vertical chain-pole at relevant node; the basic unknown quantities are the nodal vertical displacement of the basic structure; the basic equation is fixed according to the equilibrium of node forces; unit vertical displacement as well as bending moment and shear diagram of the basic structure under external load are respectively obtained by using moment redistribution method; nodal vertical displacement is determined through substitution of shear force of relevant rod into the equilibrium equation of the chain-pole node; the actual internal force is determined through superposition of actual vertical displacement and internal force diagram algebra of the basic structure under vertical external load. An engineering example is introduced, which is intended to provide reference for the simple calculation for the above said complex frameworks.
The Influence on Bundled Tube Structure of Super-High Building Caused by Changing-Rigidity of the Ground or the Foundation
Authors: Xie Xiang Dong , Xu Li Hua , Xu Hao Ran , Zhou Jian Min
Published: March 2009

With the rapid development of the subgrade or the foundation over recent years in China, there is a growing tendency for tall building to orient its directions to the more numbers of plies, much higher and more complex in plane layout. Moreover, some buildings adopt tube structure or bundled tube structure and so on to diversified development. The changing-rigidity of ground or foundation has obvious effects on superstructure when the buildings act on much higher and huge type. Therefore, in view of this, taking the bundled-tube structure of super high building for example in the paper, the method, equal the bundled tube structure of super high building and its foundation to stiffening-thin wall-combination, is adopted, then based on the three-dimensional model, the rigidity of subgrade and foundation’s effect on superstructure are given by calculation with semi-analysis. The calculated result indicated that there exist remarkable influence on sideway of the top end, the sideway between layers, the warp of the tube and the stresses between the subgrade and the bottom of the foundation.
Flexural Behavior of Steel Plate-Concrete Composite Beams
Authors: Nie Jian Guo , Zhao Jie
Published: March 2009

In this paper, the steel plate-concrete composite (SPCC) beam is developed, in which traditional steel beam in the steel-concrete composite beam is replaced by a steel plate. The aim to develop this type of composite beam is to provide a theoretical basis for design of SPCC structures and SPCC-strengthened structures. In order to investigate the flexural behavior of SPCC beams, tests were conducted on five specimens with loading cases of four-point or three-point bending. All the beams were identical in geometry, longitudinal reinforcement, stirrup, and concrete strength but various in steel plate thickness, shear connection degree, shear span length and cut-off position of steel plate. The structural behavior of the tested SPCC beams, including strain, deflection, crack width, load carrying capacity and deformability, etc., were measured and analyzed. Based on test results, it can be concluded that by means of appropriate shear connection degree and anchorage length, steel plate and concrete can work together very well and the SPCC beams have a very good ductility. The ultimate strength of the SPCC beams can be calculated by means of the same plastic method as reinforced concrete beams.
Study on the Behavior and Durability of Reinforced Concrete in Boric Acid Environment
Authors: Jin Xian Yu , Jin Nan Guo , Tian Ye
Published: March 2009

By method of artificial simulating acid environment to celebrating corrosion, the effects of boric acid on the physical properties and performance of reinforced concrete were investigated. The experimental study of concrete in nature and in various boric solutions (2000ppm, 8000ppm, 30000ppm) was carried out. The compressive strength, splitting tensile strength and elastic modulus of concrete were measured. The weight losses of steel bars and bond strength of reinforced concrete were calculated to analysis the influence of boric acid on reinforced bars. The ingredient change of concrete submerged in boric acid solution was studied with X-ray diffraction analysis. The experiments show that, in general, the mechanical strength of corrupted concrete increases with time. While comparing to the specimen curried in nature environment, the fundamental properties of concrete in boric acid solution decrease slightly. In this research, the influence of boric acid on the corrosion of the steel bars and the interacting between the concrete and the steel bars are insignificant. Three kinds of borides are detected in the X-ray diffraction analysis. It can be concluded from the research that boric acid will not generate apparent influence on the mechanics performance of concrete and steel bars. The same conclusion can be drawn on the bond properties between concrete and steel bars. Generally, corrosiveness of boric acid to reinforced concrete is quite weak.
Study on Crack Resistance of Steel Fiber Reinforced Self-Stressing Concrete in Old Bridge Reinforcement
Authors: Wang Bo Xin , Huang Cheng Kui
Published: March 2009

Steel Fiber Reinforced Self-stressing Concrete (SFRSSC) is a new type of fiber reinforced composite material. It has various applications in civil engineering for its well known superior properties such as self-expansive performance and high tensile resistance. However, it is not widely accepted as an effective reinforcement in the rehabilitation of the old bridges at present.
The primary goal of this research is to apply SFRSSC to improve the crack resistance in the negative bending moment areas of the old bridges. Firstly, a computer analysis on the internal force of the continuous T-beams with 5 spans is given in this paper. The results show that the expansive action of SFRSSC can effectively decrease the internal force in the negative bending moment area. Meanwhile, based on the experiments of 5 composite concrete inverted T-beams, the crack resistance of the beams reinforced with SFRSSC layers is investigated. The test results obviously indicated that the composite layers enhanced the cracking moments 44.9% more than conventional concrete layers, though its height is only 13.9% of the cross section height.
It is concluded that the continuous beams strengthened by SFRSSC has greatly improved the crack resistance in negative bending moment areas compared with the continuous beams strengthened by conventional concrete. According to the existing theoretical models, a procedure how to determine the self-stress is supplied and a formula which evaluating the crack resistance of composite T-beams in negative moment area is deduced in order to supply references to the old bridge rehabilitation design.
Experimental Study on Behaviors of Unbonded Prestressed Concrete Beams Reinforced with CFRP Tendons
Authors: Zheng Wen Zhong , Bai Chong Xi , Cheng Hui Dong
Published: March 2009

In order to research behaviors of unbonded prestressed concrete beams reinforced with CFRP tendons, static load experiments on 4 partially prestressed simple beams with unbonded CFRP tendons and 9 two spans partially prestressed concrete continuous beams with unbonded CFRP tendons were performed. Based on the experiment results of simple beams, the law of ultimate stress increment in unbonded CFRP tendons in simple beams was obtained. Based on the experiment results of continuous beams, the law of stress increment in unbonded CFRP tendons in continuous beams was obtained at serviceability state and at strength limit state of bending capacity. The calculation formula of length of equivalent plastic hinge for this kind of continuous beam was presented. The calculation formulas of moment modification coefficient with composite reinforcement index for intermediate support as variable and relative plastic rotation for intermediate support as variable were given respectively.
Analysis of Shear Force Transfer Mechanism in Bridge Deck of SFRC-Steel Composite Girder
Authors: Zhen Xiao Xia , Wang Rong Hui , Rao Rui
Published: March 2009

Based on tension-compression and bending equivalences, an equivalent single material plate is formed to substitute bridge deck of composite girder with steel fiber reinforced concrete (SFRC) and steel. Thickness and elastic modulus of the equivalent plate are then formulated. After three dimensional finite-element analyses of the bridge deck, in terms of shell element membrane effect and girder flexion-torsion theory, combined with compatibility of deformation, single material shell element stress is restored to stresses on SFRC plate and steel plate separately; shear force distribution on shear keys between SFRC and steel is analyzed.
Finite Element Modeling of Concrete-Filled Steel Tubular Column after Exposure to Fire
Authors: Huo Jing Si , Qu Hui
Published: March 2009

A computational model, in which the effects of high temperature on steel and concrete’s properties and the composite action and interfacial properties between steel tube and concrete core were considered, was developed using ABAQUS program. Based on a damage model of concrete at ambient condition and tested stress versus strain curves of fire-damaged concrete, a new damage model of concrete after exposure to high temperatures was developed to consider the influence of high temperatures on the damage of concrete. By introducing the damage model of fire-damaged concrete, the reasonable equivalent stress-strain relations of confined concrete and a modified steel tube-concrete interface model into the ABAQUS FE model, the mechanical behaviors of the fire-damaged CFT columns and connections were simulated precisely and verified by some relative test results.
Experimental Study on Anti-Impact Properties of Prestressed Concrete Beams
Authors: Wang Xin Wu , Li Yan Zhao
Published: March 2009

The dynamic displacement ductility and ultimate load-carrying capability of three partially prestressed concrete (PPC) and unbonded beams, has been experimentally investigated by applying impact load to their middle with falling hammers. The typical measurement wave curves are described. Influences of a falling hammer’s gravitational potential energy on the dynamic properties of the PPC beam are analyzed. Based on the analog simulation theory, the impact-load carrying capability of the actual unbonded PPC beam with span 12 m is gained. Results indicate that the unbonded PPC beams have favorable performance of anti-impact properties fragile destruction will not happen, and the unbonded PPC beams can be used in wide-span underground structures.
Analysis of Retrofitted RC Beam with Fixed End Supports against Blast Loads
Authors: Wu Chengqing , Wu C. , Chen William , Oehlers Deric John
Published: March 2009

Currently, there are adequate guidelines available for FRP retrofitting RC structures against static and seismic loads. However, there is still limited information on retrofitting RC structures against short-duration dynamic loading effects such as blast loading. Due to the increasing threat of terrorism in recent years, retrofitting of RC structures against blast loading is of paramount importance in structural engineering. In this paper, a dynamic model that is based on single-degree-of-freedom (SDOF) approach is developed for the analysis of the response of retrofitted fixed end supported RC slabs subjected to blast loads. A previously validated layered capacity analysis method is used to determine the yielded and ultimate blast resistant capacity of a cross-section of a RC slab which allows varying strain rates with time along the depth of the member. The corresponding deflections are determined by plastic hinge analysis. To simplify the calculation process, a tri-linear resistance-deflection function which consists of elastic, elasto-plastic and plastic region for fixed end supported RC slabs is converted to an equivalent bilinear function. This developed model can adequately predict the retrofitted members’ response to blast loading. It is then is used to conduct a parametric study to optimise the retrofitting of RC slabs subjected to blast loading by varying the quantity, material type and technique of retrofitting.
Evaluation of Microstructure of High-Strength Reaction-Sintered Silicon Carbide
Authors: Suyama Shoko , Itoh Yoshiyasu
Published: March 2009

A newly developed high-strength reaction-sintered silicon carbide (SiC), which has two or three times higher strength than the normal sintered SiC, is one of the most promising candidates such as the lightweight substrate of optical mirror, because of fully dense, small sintering shrinkage (±1%), good shape capability and low sintering temperature. In this paper, in order to improve the performance of newly developed reaction-sintered SiC, the microstructure was investigated by paying attention to the crystal structures using the observation of transmission electron microscope and X-ray diffraction analysis. As a result, it made clear that the finer-scale microstructure could be observed as consisting of large particles (~1m in diameter) of starting powder -SiC and small particles (~1m in diameter) of -SiC formed during the reaction (Si+CSiC) with the residual silicon filling the remaining porosity. Also, it was identified that the -SiC formed during the reaction referred to the cubic (3C) polytype and the -SiC of starting powder referred to the hexagonal (6H) polytype.
Microstructural and Mechanical Properties of Ti3SiC2 Composites
Authors: Huang Jow Lay , Lu Horng Hwa
Published: March 2009

Ti3SiC2 has been a spectacular material, as it combines many of the best properties of metals and ceramics. This new material has potential applications for fabrication of jet engines and in bonding phases. Microstructure can further enhance the mechanical properties, such as strength, wear resistance and chemical stability. In the current research the different starting powder systems were used to synthesize Ti3SiC2 by hot pressing. The contents of Si were controlled appropriately to obtain Ti3SiC2/TiC ceramic composites. Preliminary results indicated that the fracture toughness and strength were improved. The influences of TiC contents on the microstructure and mechanical properties were investigated and the fracture mechanisms of Ti3SiC2/TiC ceramic composites are discussed qualitatively.
Fabrication of Electrically Conductive Si3N4 Ceramics by Dispersion of Carbon Nanotubes
Authors: Yoshio Sara , Tatami Junichi , Wakihara Toru , Komeya Katsutoshi , Meguro Takeshi
Published: March 2009

Electrically conductive Si3N4 ceramics were fabricated by dispersion of different characteristics of carbon nanotubes (CNTs). When the sintering aid of Y2O3-Al2O3-TiO2-AlN was used for lower temperature densification, it was confirmed that CNTs existed in Si3N4 ceramics from SEM observation and SiC was not identified in XRD analysis, which means that CNTs did not react with Si3N4. Relative density and electrical conductivity of the CNT dispersed Si3N4 ceramics depended on the characteristics of CNTs. Aggregation of CNTs, which is outstanding in much thinner CNTs, should limit densification of Si3N4. CNTs were well-dispersed by beads milling in ethanol. As a result, beads milling process was confirmed to be effective in unraveling and dispersing CNTs. It was shown that better dispersion of CNTs with higher aspect ratio resulted in higher density and electrical conductivity.
Synthesis of Nano-Sized SiC Powders by Carbothermal Reduction
Authors: Yoshioka Yoshiki , Tanaka Hidehiko , Konishi Mikio , Nishimura Toshiyuki
Published: March 2009

Nano sized SiC powder was successfully synthesized by the carbothermal reduction in SiO2. Precursor for SiC was prepared by using phenolic resin as a carbon source and ethylsilicate as a silicon source. After mixing, hydrolysis, drying and pyrolysis at 1000°C, SiC precursor consisted of C and SiO2 was obtained. The precursor was heat treated at 1500-1800°C in Ar to synthesize SiC by the carbothermal reduction. The carbothermal redction reaction was almost completed at 1700°C and then SiC particle with suitable size was obtained at this temperature. Nano-sized SiC particles could be achieved at 1600 °C, and unreacted SiO2 and C remained in the sample. Pure SiC particles were obtained by oxidation and acid treatment. Nano-sized SiC powder had the diameter of 10-20 nm and BET surface area of 156 m²/g.
Fabrication and Mechanical Properties of TiN Nanoparticle-Dispersed Si3N4 Ceramics from Si3N4-Nano TiO2 Composite Particles Obtained by Mechanical Treatment
Authors: Kodama Eriko , Tatami Junichi , Wakihara Toru , Meguro Takeshi , Komeya Katsutoshi , Nakano Hiromi
Published: March 2009

TiN nanoparticle-dispersed Si3N4 ceramics is one of the typical ceramics used for bearing applications. Because larger TiN particles considerably damage the mating metallic materials, smaller TiN particles must be dispersed in Si3N4 ceramics. In this study, we fabricated TiN nanoparticle-dispersed Si3N4 ceramics from Si3N4–nano TiO2 composite particles prepared by mechanical treatment. The mechanical properties of the fabricated TiN nanoparticle-dispersed Si3N4 ceramics were evaluated. At first, TiO2 nanoparticles were dispersed in ethanol using polyethylene imide as a dispersant with a lower molecular weight. Si3N4 powder was mixed with this slurry to obtain a powder mixture. In this case, the reaggregation of the TiO2 nanoparticles during the drying process is the problem that has to be solved. In this study, TiO2 nanoparticles and Si3N4 particles were mechanically joined by a particle composer to fabricate the composite particles from the powder mixture. TiN nanoparticles were uniformly dispersed in Si3N4 ceramics by using composite powder. The bending strength of the developed Si3N4 ceramics with TiN nanoparticles was improved, and its distribution was narrow due to the homogeneous dispersion of TiN nanoparticles.
The Phase Evolution in the Si3N4-AlN System after High-Energy Mechanical Treatment of the Precursor Powder
Authors: Sopicka-Lizer Malgorzata , Pawlik Tomasz , Włodek Tomasz , Tańcula Marta
Published: March 2009

The high-energy milling uses the mechanical energy to activate chemical reactions by developing structural changes in the powder particles. High-energy milling with an acceleration of 28g was applied for the mechanical activation of the aluminium and silicon nitrides mixture with yttria additive. The activated powders showed the significant damage of the crystal structure and limited formation of a solid solution. Sintering of the activated precursor demonstrated higher ability for densification and started at 300 °C lower temperature in comparison to the standard mixture. The phase evolution during sintering was dependent on the starting composition and degree of powder activation.
Research Progress of Workability Theoretical Research and Simulation Computation of Pumping Concrete
Authors: Chen Jun Sheng , Mo Hai Hong , Cao Hong , Liu Ting Jin , Liang Song , Yang Yi Bo , Ba Ling Zhen
Published: March 2009

With the wide application of pumping concrete， and the increasing of pumping height and distance， more and more attention of researchers focus on the workability of pumping concrete. Traditionally， the research method of workability of pumping concrete is mainly experiment. With the increasing of pumping height and distance，experimental method for workability of pumping concrete becomes more difficult. Combining simulation computation and experimental method to solve pumping construction problems of concrete under complicated conditions is a feasible method. Research progress about experimental method and simulation computation of workability of pumping concrete are presented， which would provide research thinking and research method for combining simulation computation and experimental method.
The Research on Composition Design and Hardening Accelerating Effect of Na+ & K+ Ions-Free Concrete Hardening Accelerator
Authors: Gao Zhen Guo , Yao Bing Wen , Han Yu Fang , Qian Hui Li
Published: March 2009

By means of orthogonal experimental design, the composition (including Calcium formate, Ferric sulfate and Crystal-embryo) of Na+ & K+-free concrete hardening accelerator is designed, and the hardening accelerative effect of the concrete hardening accelerator is studied. The experimental result indicate that there are the interactions between compositions each other, the optimal combination of the factors is 4:5:3 (Calcium formate: Crystal-embryo: Ferric sulfate).By this combination, the concrete hardening accelerator is prepared. The early strength of the concrete which mixed with the concrete hardening accelerator can be enhanced 43%(1-daystrength), 47% (3-day strength), 39%(7-day strength), and 31%(28-day strength) compared with the controlled concrete. By altering the strength grade and the breed of the cement, the adaptability of the concrete hardening accelerator is studied too.
Effects of Fly Ash and Ground Granulated Blast-Furnaces Slag on Properties of High-Strength Concrete
Authors: Wang Ji Liang , Niu Kai Min , Yang Zhi Feng , Zhou Ming Kai , Sun Li Qun , Ke Guo Ju
Published: March 2009

Effects of fly ash and ground granulated blast-furnace slag (GGBFS) on workability, strength, volume stability and durability of HSC are investigated. Results show that fly ash and GGBFS can improve the workability, increase the later strength of high strength concrete (HSC) remarkably, and reduce the brittleness. In addition, the ameliorative effect of GGBFS on HSC brittleness is more remarkable. With the increase of fly ash and GGBFS, the early elastic modulus of HSC reduces. The elastic modulus is similar to the controlled sample when the load is applied after 60d curing. The fly ash and GGBFS can improve HSC’s resistance to chloride ion penetration significantly. However, the effects of fly ash and GGBFS on freezing-hawing resistance of HSC are not obvious. Besides, the fly ash will reduce freezing-hawing resistance of HSC only when the content of mineral powder is up to 36%.