bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulphate expansion and permeability of concrete with limestone aggregate
Authors: Piasta W. G. , Hebda L.
Published: October 2009

The Paper describes the results of an experiment which was carried out to compare the sulphate expansion of granite and limestone concretes. In spite of the higher porosity of limestone aggregate, lower expansion and permeability as well as higher strength were observed in limestone concrete. Better functional properties of this kind of concrete result from the formation of calcium monocarboaluminate hydrate mainly in the cement paste aggregate interface.
Marine performance of PFA concrete
Authors: Thomas M. D. A.
Published: October 2009

Results are presented from a study of the performance of reinforced concrete in a marine environment. Reinforced concrete specimens from three series of concrete mixes of nominal strength grades C25, C35 and C45 and with a range of PFA levels (0–50%) were placed in the tidal zone of the BRE marine exposure site. Measurements of reinforcement weight loss and chloride ion penetration were carried out on the specimens after two years' exposure. The results indicate that chloride ion penetration during early exposure is controlled by sorptivity rather than diffusion, and predictions of diffusion coefficients derived from chloride concentration profiles are not valid. No significant increase in the chloride content at depths below 10 mm were observed between one and two years for concretes containing 30% or more PFA, whereas substantial increases were observed for the OPC control concretes. The PFA concretes were far more resistant to the penetration of chloride ions than the OPC concretes and consequently corrosion of steel reinforcement was reduced in the PFA concrete. It is concluded from results to two years that in marine conditions PFA concrete provides much improved protection to steel reinforcement, compared with OPC concrete of equal strength grade, cementitious content (OPC + PFA) or water–cementitious ratio. Further assessments will be carried out after 5 and 10 years exposure. These results are discussed in the context of current specifications for concrete exposed to marine conditions.
An improved model to predict the ultimate drying shrinkage of concrete
Authors: Almudaiheem J. A.
Published: October 2009

An improved model to predict the ultimate drying shrinkage of concrete is proposed. The model is derived from the theory of elasticity, composite theory, and microstructural considerations. The model includes the effects of the drying shrinkage of paste, the relative restraining volume of the aggregate and unhydrated cement, the elastic modulus, and Poisson’s ratio of the shrinkage active phase (hydration products), the shrinkage restraining phase (aggregate and unhydrated cement) and the concrete. The model requires the ultimate drying shrinkage of a paste of the same w/c ratio as the concrete. It was found that the elastic modulus of concrete can be accurately predicted by using a model intermediate between the extreme boundaries described by Paul. The improved model proposed was tested on shrinkage data for thin mortar specimens at 50% relative humidity (RH) found in the literature for a wide range of aggregate content and curing times, and the results confirm the validity of the model.
Competitive nature of alkali-silica fume and alkali–aggregate (silica) reaction
Authors: Wang H. , Gillott J. E.
Published: October 2009

Silica fume is an effective pozzolan in controlling alkali-aggregate (silica) reactionwhen used in appropriate amounts as a cement replacement. The experiments described in this Paper showed that silica fume reacts in a similar way to alkali-expansive opal with CaOH)2 and/or NaOH. Pastes of silica fume and Ca(OH)2, silica fume and NaOH, and silica fume and Ca(OH)2 plus NaOH showed the same expansive properties as corresponding pastes made with opal and these three alkalis. The role of silica fume in controlling alkali-aggregate (silica) reaction is attributed to a competitive reaction between alkali-silica fume and alkali-aggregate (silica) reactions.
Confinement of reinforced concrete columns by rectangular ties and steel fibres
Authors: Alsayed S. H.
Published: October 2009

The effect is studied of steel fibres on the confinement in a reinforced concrete column subjected to high axial load, and, in turn, on the peak load and the corresponding strain and ductility. 14 short columns with and without steel fibres were tested. The main variables in the study were the volume fraction and the aspect ratio of the steel fibre. The measured ultimate strength, the corresponding strain and the energy-absorbing capability were found to be in excess of the corresponding values obtained when confinement was provided by stirrups only. On the contrary, strains in the transverse reinforcement were signicantly reduced by the addition of steel fibres.
Strength and chloride permeability of concrete containing red tropical soils
Authors: Cabrera J. G. , Nwaubani S. O.
Published: October 2009

Red tropical soils are produced by natural chemical weathering. They contain appreciable quantities of amorphous silica and alumina and also large proportions of very poorly ordered clay minerals. For this reason they are considered to be a good source of pozzolanic material and may be used as raw feed for the manufacture of cement or as cement replacement for the production of concrete. This Paper presents the results of an investigation into the engineering properties and performance of concrete made with a mixture of cement/pozzolan, where the pozzolan consisted of two types of red tropical soil. The Paper highlights the strength properties and chloride ion permeability characteristics of these mixtures and discusses the beneficial effects of using red tropical soils in concrete.
Shear and flexural strengths resulting from confinement of the compression regions in circular section structural concrete beams
Authors: Ziara M. M. , Haldane D. , Kuttab A. S.
Published: October 2009

This paper examines the effect of confinement of the compression regions on the behaviour of structural concrete beams with circular cross-sections. The programme of experimental work included eight 200 mm diameter beams traditionally designed to resist shear; however, the stimy, configurations inseveral of the beams were determined by the shape of the compressive force path. The results obtained from the test programme confirmed that the confined compression concrete regions in such beams are the main contributors to shear resistance and that the development of truss action is not necessarily required to transmit the applied loads to the support. It is concluded that the enhancement of the concrete strength in the compression regions due to the confining influence of the stirrups offsets the reduction in the flexural capacity of the beams due to the shear effects. The flexural capacity and ductility of the beams resulting from confinement were found to be higher than the corresponding values for traditionally detailed beams. A flexural-shear interaction model has been derived from a more general approach to determine the number of confinement stirrups required to prevent diagonal failures and also to evaluate the flexural strength of such beams. There was good agreement between the results obtained from the model and those obtained from the test programme. Eight structural concrete 200 mm diameter beams reinforced with semi-circular and/or circular shaped stirrups, were included in the investigation. The shape of the compressive force path was used to determine the stirrup configurations in several of the beams. The experimental results indicated that the ductility and strength of these beams were more than 50% and up to 32 % (depending on the level of confinement) greater than found in beams detailed according to current Code provisions. A flexure—shear interactive analytical model which recognizes the importance of the compression concrete in resisting lateral loads was found to closely predict the results obtained from the investigation.
Influence of early curing on the sub-surface permeability and strength of silica fume concrete
Authors: Austin S. A. , Robins P. J.
Published: October 2009

The difficulties of producing durable concrete in hot climates is widely appreciated, along with the potential benefits of using cement replacements. However, there is relatively little published data on the influence of curing methods or hot climate on the Permeability of condensed silica fume (CSF) concrete. This paper reports on part of a research programme on the performance of silica fume concretes cured in temperate and hot climates. More specifically, it describes the influence of early curing on the sub-surface air and water permeabilities of CSF concretes up to the age of 6 months and compares these with the development of surface permeability and compressive strength. The effect of curing duration, method (water and polyethylene) and environment (temperate and hot) on three strength grades (C25, C40 and C55 are reported, the conditioning involving appropriate diurnal temperature/humidity cycling. The work has demonstrated that curing duration, method and climate have a large impact on silica. fume concrete's permeability and hence its potential durability, in terms of resisting carbonation and ingress of other aggressive mediums such as chlorides. The silica fume concretes responded, favourably to the hot climate if at least two days moist curing was provided, the greatest improvements occurring with the lower strength grades. Good correlations were, found with surface air and water permeabilities; the surface tests have the advantage of being totally non-destructive and easier to perform in situ (although they are still sensitive to the moisture state of the concrete). Protective quality categories are proposed for each test method.
A new explanation for size effects on the flexural strength of concrete
Authors: Carpinteri A. , Chiaia B. , Ferro G.
Published: October 2009

The size dependence of the flexural strength of concrete beams is discussed. It is shown that existing approaches fail to predict the strength of real-sized structures. The scaling of the modulus of rupture σu can be consistently modelled by means of a multifractal scaling law, the influence of microstructural disorder being predominant for the shallowest beams. At larger scales, homogenization comes into play, leading to the definition of an asymptotic constant strength ft. This transition occurs more rapidly in the case of high-strength concrete, where a more brittle behaviour is observed, accompanied by the rapid vanishing of size effects. Validation of the law is pursued by means of best-fitting of relevant experimental data, which allows for determination of the asymptotic value of σu, valid for real-sized members.
Diagonal cracking and shear strength of reinforced concrete beams
Authors: Zhang J.-P.
Published: October 2009

The shear failure of non-shear-reinforced concrete beams with normal shear span ratios is observed to be governed in general by the formation of a critical diagonal crack. Under the hypothesis that the cracking of concreteintroduces potential yield lines which may be more dangerous than the ones found by the usual plastic theory, a physical explanation is given for this phenomenon and a way to estimate the shear capacity of reinforced concrete beams, based on the theory of plasticity, is described. The theoretical calculations are shown to be in fairly good agreement with test results jrom a large number of experiments carried out by previous investigators.
Application of high-strength/superworkable concrete to thin-wall prestressed concrete products
Authors: Nagai T. , Kojimat T. , Miura T.
Published: October 2009

Undertaken to develop a practical vertical casting method that can be applied to manufacture efficiently thin-wall prestressed concrete products with high strength (fck = 70 MPa), the work presented in this paper included the development of superworkable concrete made by adding 15–20% fine limestone powder (Blaine specific surface area 7310 cm2/g) to high-early-strength Portland cement along with a polycarboxylic-acid-type air-entraining superplasticizer and viscosity agent (natural polysaccharide polymer of type β-glucan) solution. This was followed by the laboratory testing and trial production of this superworkable concrete at an actual plant to study its suitability as a material for densely reinforced, thin-wall prestressed concrete products. The study confirmed that neither the addition of a viscosity agent (β-glucan) nor the quantity of fine limestone powder added has any effect on the freezing and thawing resistance or the sulphate resistance of superworkable concrete.
Analytic modelling and experimental study of the porosity and permeability of a porous medium—application to cement mortars and granitic rock
Authors: Aït–Mokhtar A. , Amiri O. , Sammartinot S.
Published: October 2009

In this work an analytic relationship between the permeability and porosity of a porous material is developed. This modelling is based on the use of a statistical pore size distribution, which is first used to establish an analytic expression for the porosity in relation to an average pore radius and a location parameter. Two types of measurement were performed on three cement mortars and a granitic rock: mercury intrusion porosimetry measurements so as to adjust parameters of the distribution law and deduce the ‘theoretical’ permeability from the model, and direct water permeability measurements by the application of the Darcy law so as to validate the analytic model. Globally, the ‘experimental’ permeabilities obtained were inferior to those calculated. The main explanation for these differences may be in the fact that in the calculation of the permeability, all types of pores are taken into account, and not only ‘open’ pores which are the only ones responsible for the flow in porous materials.
Effects of passive confinement on fatigue properties of concrete
Authors: Hooi Tan Teng
Published: October 2009

The effects of passive confinement on the fatigue properties of concrete were investigated by conducting compression tests on spirally reinforced cylindrical specimens. Results shows that lateral confinement increases the fatigue properties, and the classical Aas–Jakobsen S-N equation is modified to include the effects of passive confinement.
Environmentally sound concrete release agents
Authors: de Brito J. , dos Santos R. , Branco F. A.
Published: October 2009

The construction industry contributes to the increase in the levels of pollution of the environment in several ways. The total emissions of volatile organic compounds in Europe alone due to concrete release agents may be up to 30 000 tons annually. Most of these products are mineral-oil-based, non-biodegradable and toxic to humans, air, water and soil. Just as in other industries, the enforcement of environmentally minded laws will force the building industry to change its habits. Vegetable-oil-based release agents present a good alternative to the present situation, with advantages in terms of working conditions, environmental control, economy and technical production performance, which will be described in this paper. A project funded by the European Union aimed at promoting the use of these alternative products has been launched. Some tests have been performed within this project to evaluate the technical performance of this type of release agent and are described here.
Equipment for the analysis of the behaviour of concrete under restrained shrinkage at early ages
Authors: Pigeon M. , Toma G. , Delagrave A. , Bissonnette B. , Marchand J. , Prince J. C.
Published: October 2009

This paper describes an experimental set-up which was built to evaluate the visco-elastic deformations that can occur when a specimen of concrete is placed in a fully restrained condition from the time it is cast. It consists of two distinct devices. The first one allows the measurement of the free autogenous shrinkage from time t = 0. The second one, which includes a movable head, is used to determine the increase in load due to autogenous shrinkage, also from time t = 0. In both cases, the specimen is cast directly into the mould after mixing, and is then sealed. In the equipment with a movable head, the specimen is allowed to shrink (or swell) freely until it reaches a predetermined strain, at which time a sufficient force is applied to pull (or push) it back to its original position. It is then left again to shrink (or swell) while the force that is applied is maintained constant until the predetermined strain is once more reached, at which point the force is increased in order to pull (or push) it back to its original position. Such a procedure allows the determination of the stress build-up in the specimen as a function of time. It also allows the determination of the visco-elastic deformation (and thus of the stress relaxation) in the restrained shrinkage specimen by subtracting (at any given point in time) the cumulative sum of the strains in the restrained shrinkage specimen from the free shrinkage in the companion specimen. The results of a first series of tests on a mortar mixture are presented and discussed.
Finite element analysis and behaviour of pre-cracked reinforced concrete members in shear
Authors: Pimanmas A. , Maekawa K.
Published: October 2009

Reinforced concrete members may be subjected to cracking damage due to environmental attack and past loading. Recent experiments conducted by the authors show that the shear behaviour of pre-cracked beams differs greatly from the uncracked ones. In an uncracked beam, the shear failure is governed by a single diagonal crack. On the other hand, the shear failure of pre-cracked beams is governed by a mutual contribution of pre-crack and diagonal crack or by the pre-crack only. The behaviour of all the pre-cracked beams can be consistently explained by the concept of shear anisotropy along the pre-crack plane. The pre-cracked beam problem poses challenges to the numerical analysis of reinforced concrete members. The finite element method (FEM) is discussed in this paper. It is made clear that a crack model that can handle the pre-cracked beam problem must be able to record and transfer pre-crack and other state variables over load steps, treat multi-directional cracks with mutual interaction and treat shear anisotropy along the pre-crack plane. The four-way fixed crack approach is proposed for numerical analysis. The analysis target includes non-orthogonal two-way crack interaction, three-way crack interaction and crack interaction in which two cracks form an arbitrary angle.
ACR expansion of dolomites with mosaic textures
Authors: Guangren Qian , Min Deng , Mingshu Tang
Published: October 2009

The relationships between expansion of alkali–carbonate reaction (ACR) and types of dolomites with mosaic textures are presented in this article. The results show that dolomites usually appear to have a poor ACR expandability when they start to react with alkali. However, a higher ACR expansion would be produced for dolomites when reaction time is enough. It suggests that dedolomitisation of dolomites could indeed result in ACR expansion. Meanwhile, there are significant differences of autoclaved expansion among different dolomites, which is largely controlled by the intercrystalline gap in the texture of dolomites. Additionally, argillaceous dolomites are found with potentially high ACR expandability.
A maturity approach to the rate of heat evolution in concrete
Authors: Ballim Y. , Graham P. C.
Published: October 2009

This paper discusses the use of the concept of maturity as a means of combining the effects of time and temperature in describing the rate of heat evolution from hydrating cement in concrete. The proposed maturity approach allows the rate of heat evolution determined from an adiabatic test to be expressed in a form which is independent of the starting temperature of the test. This relationship can then be directly used in a time–temperature prediction model that requires a solution of the Fourier equation for heat flow.

The results of an experimental study aimed at assessing the suitability of both the Arrhenius and Nurse–Saul maturity relationships is also presented. Three adiabatic calorimeter tests were conducted on each of two concrete mixtures but starting at different temperatures. The results confirm the suitability of this approach and indicate that, of the two maturity relationships assessed, the Arrhenius maturity relationship is the more suitable in this application.
Flexural strengthening of reinforced concrete beams using carbon fibre reinforced polymer strips
Authors: Hsu C.-T. T. , Punurai W. , Bian H. , Jia Y.
Published: October 2009

This paper explores the behaviour of carbon fibre reinforced polymer (CFRP) strengthened reinforced concrete beams with and without end anchorage provided at the ends of CFRP strips on the tension face of the beams. A total of 12 beams were tested to failure under monotonic and cyclic loads. The beams were originally designed as either under-reinforced or almost over-reinforced concrete beams. The present experimental results show that externally bonded CFRP strips to the tension face of the beam is an effective technique for repair and retrofit of reinforced concrete beams under various loads. This study also shows that ductility of CFRP strengthened beam, in particular for a shorter beam, is adequate if the beam is properly designed and the CFRP strips are properly anchored.
Prediction of ultimate stress in unbonded prestressed tendons
Authors: Au F. T. K. , Du J. S.
Published: October 2009

The behaviour of prestressed concrete members with unbonded tendons is different from that of members with bonded tendons. While the behaviour of prestressed concrete beams with bonded tendons is characterised by that existing at individual sections, analysis of the entire member is necessary for beams with unbonded tendons. This paper examines various design methods for the determination of ultimate tendon stress at flexural failure of prestressed concrete beams with unbonded tendons. Two broad categories of deformation-based approaches have been identified, namely those based on the span–depth ratio together with loading type, and those based on the neutral axis depth. These methods are reviewed critically. A new design formula has been proposed in the light of the available experimental data. It is applicable not only to the conventional high-strength steel prestressing tendons, but also to those made of other materials such as fibre-reinforced polymer.
Mathematical model for complete stress–strain curve prediction of normal, light-weight and high-strength concretes
Authors: Tasnimi A. A.
Published: October 2009

This paper presents a series of compressive tests on concrete cylinders in order to develop a stress–strain model for concrete under axial compressive load. A mathematical model representing the entire range of concrete behaviour under axial compressive stress is developed, generating the ascending and descending portions of the stress–strain curve of the concrete. The main parameter needed to generate the model is the peak compressive strength of the concrete. Complete stress–strain relationships for unconfined normal, light-weight and high-strength concrete are also predicted. The proposed model is based on analysis of the stress–strain curve and one single experimentally determined parameter. Comparison was made with actual test data and some other available models. The comparison indicates excellent prediction of stress–strain behaviour of the specimens.
Transient thermal creep of concrete in service conditions at temperatures up to 300 °C
Authors: Colina H. , Sercombe J.
Published: October 2009

This paper presents experimental results concerning the behaviour of ordinary, high-strength and high-performance concretes under constant mechanical loading and increasing temperatures up to near 300°C. Heat was applied at a rate of 0·1 °C/min such that successive constant temperature levels were reached and maintained sufficiently to ensure internal temperature stabilisation. The analysis of experimental measures focuses on the so-called transient thermal creep, obtained during the transient thermal loading stages. To study the importance of changes in the internal properties, especially those related to free and bound water, some specimens were submitted to a second heating cycle. Test results confirm the existence of transient thermal strains during first heating, and its occurrence during the second cycle only when the maximum temperature of the first cycle was exceeded even if the specimen had spent a recovery period at ambient temperature. The transient thermal creep values were estimated for different temperature levels, above 105 °C, and they were inversely proportional to the water/cement ratio.
Effect of axial restraint on flexural and shear behaviour of high-strength concrete members
Authors: Yang E.-I. , Yi S.-T. , Morita Shiro
Published: October 2009

This paper was developed to examine the effect of sequential axial restraint on flexural and shear behaviour of high-strength concrete beams. This study includes flexural and shear tests conducted under both restrained and unrestrained conditions to provide a comparison in test results. In the early stage of the tests, the bending stiffness of the fully-restrained beam was lower than that of the unrestrained beam due to a crack generated by tensile restraint during concrete curing. However, as the transverse load increased, the restraint force changed from tension to compression, causing the stiffness to be higher. Even though the displacement capacity of the restrained beam at failure decreased, the yield load and displacement of the restrained beam was higher than that of the unrestrained beam. Additionally, it was observed that shear crack propagation and shear capacity were not affected by cracks less than 0·1 mm in width, which penetrated due to the restraining tensile stress that occurred before loading.
Flexural strength of fly ash concrete under elevated temperatures
Authors: Potha Raju M. , Shobha M. , Rambabu K.
Published: October 2009

Concrete elements exposed to fire undergo temperature gradients and, as a result, the surface layers spall, exposing steel reinforcement. Relatively few studies have been undertaken on heat-induced changes in fly ash concrete. The structural property of concrete that has been studied most widely as a function of heat exposure is compressive strength. Less attention has been given to flexural strength as influenced by heat exposure. Therefore, to investigate the effect of temperature on the flexural strength of fly ash concrete, the present study was carried out with M28, M33 and M35 grades of concrete. Concrete specimens 100 mm × 100 mm × 500 mm with partial replacement of cement by fly ash (10%, 20% and 30% replacement levels) were heated to 100°C, 200°C and 250°C for 1 h, 2 h and 3 h duration in an electric oven. The specimens were tested for flexural strength in the hot condition immediately after removing from the oven. The fly ash concrete showed consistently the same pattern of behaviour as that of concrete without fly ash under elevated temperatures during flexure. The fly ash concrete with fly ash content up to 20% showed improved performance compared with the specimens without fly ash by retaining a greater amount of its strength.
Distribution of construction loads in columns and shores during construction of reinforced concrete structures
Authors: Lee T.-G. , Kim S.-Y. , Yi S.-T.
Published: October 2009

Many studies have been performed to apply research results for the time-dependent behaviour of reinforced concrete (RC) framed structures to the design and construction of high-rise buildings. However, shoring, removal of forms, and backshoring at early ages have not been adequately reflected in most studies. Removal of forms and backshoring activities have been dealt with as one construction sequence and the deformation of columns that occurs at an early age before removal of shores was not considered. In this study, a two-dimensional frame analysis program was developed to predict time-dependent behaviour of RC structures. In the program, the actual construction sequence of installation of forms and shores, concrete placement, removal of forms and shores, backshoring, removal of backshores, and application of additional loads are considered to predict axial force variations in RC columns and shores due to the change of concrete member stiffness. In order to evaluate the validity of the developed program, a model RC-framed specimen was tested under the same construction sequence. It was noted that with increasing time the axial forces in columns and shores were increased and decreased, respectively. In addition, column deformations occurred before removal of shores and axial forces in shores were redistributed to columns. Finally, it was also observed that the program predicted experimental results well.
A new approach to testing reinforced concrete flat slabs
Authors: Baskaran K. , Morley C. T.
Published: October 2009

This paper outlines a new experimental method developed to test flat slabs with simple uniform loading and improved boundary conditions. A new form of punching shear reinforcement, which will increase the punching shear resistance without affecting the flexural resistance, is used. Available experimental methods to test flat slabs are reviewed to demonstrate the simplicity of the new approach. To show the effectiveness of both the method and the shear reinforcement, some experimental results are included. In the design of slabs, in addition to self-weight a uniform imposed load is usually considered. But in the laboratory, applying this uniform load is challenging. This is further complicated by the requirements to maintain proper boundary conditions. One way adopted in the past was testing multipanel slabs with multiple point loads. However this is an expensive approach. Therefore in this paper a very simple approach to test isolated flat slab panels with improved boundary conditions is presented. A special vacuum rig was constructed at Cambridge University Engineering Department. Details of the vacuum rig and some experience from experiments are given: the method seems promising. It is concluded that with further tests the shear reinforcement introduced in this paper could be useful in practice.
Safety of VHSC structures under concentrated loading: experimental approach
Authors: Boulay C. , Toutlemonde F. , Clément J. L. , Verók K. , Fakhri P.
Published: October 2009

According to the French design code for reinforced concrete structures, zones submitted to localised compression are checked at the ultimate limit state using limit analysis. These rules apply when concrete characteristic strength is lower than 80 MPa. Joint research efforts were carried out in order to extend the actual design rules to very high performance concrete. Tests corresponding to localised compression on 200 × 200 × 600 mm prisms, reinforced according to the French design rules, were carried out. Four types of concrete with a mean compressive strength of 50, 75, 100 and 120 MPa, as well as an ultra high performance fibre-reinforced concrete were studied. It is shown that the safety margin between the stress corresponding to the first cracking and the stress allowed by the design rules under the localised loading decreases when the compressive strength of the concrete increases. An additional coefficient is proposed to take these observations into account. Complementary provisions for Eurocode 2 are proposed.
Impact resistance of steel-fibre-reinforced lightweight-aggregate concrete
Authors: Wang L. , Wang H. , Jia J.
Published: October 2009

A series of drop-weight tests have been carried out to investigate the enforcing effect of steel fibres on impact resistance of lightweight-aggregate concrete (LWC) with the drop weight test method recommended by the American Concrete Institute (ACI) Committee 544. The tested specimens were prepared as discs with size of 152 × 64 mm and five levels of volume fraction of steel fibres as 0·0%, 0·5%, 1·0%, 1·5% and 2·0% respectively. The experimental results show that the impact resistance of LWC—that is, the number of blows to first visible crack as well as to failure—can be greatly improved by including steel fibres. Moreover, it is observed that with higher volume addition, a greater improvement of impact resistance will be achieved. In view of the variation in impact resistance test results, the two-parameter Weibull distribution was adopted to analyse the test data. It is proved that the probabilistic distribution of the blows to first crack and to failure of steel-fibre-reinforced lightweight-aggregate concrete (SFLWC) can be modelled well by two-parameter Weibull distribution. Lastly, the impact resistance formulae for SFLWC with each steel fibres addition are developed to facilitate the application.
Effect of crimped synthetic fibre surface treatments on plastic shrinkage cracking of cement-based composites
Authors: Won J.-P. , Park C-G. , Lee S.-W. , Jang C.-I. , Won C.
Published: October 2009

The plastic shrinkage and thermal shrinkage cracking of cement-based composites can be controlled by using fibre reinforcing, although the possible effects of fibre length or cross-sectional area or the hydrophilic and hydrophobic nature of the fibres used have not been evaluated comprehensively. In addition, there is some concern over the potential reduction of performance when fibre balling occurs, particularly with increased levels of added hydrophobic fibres. This study evaluated the effects of fibre length, diameter, volume fraction and hydrophilic treatment of crimped polypropylene fibres on controlling plastic shrinkage. The fibre surface was hydrophilised by applying maleic anhydride grafted polypropylene (mPP) granules. The crimped polypropylene fibres proved effective at controlling plastic shrinkage cracking of a cement-based composite, particularly when the fibre surface had been hydrophilised. Fibres with smaller diameters controlled cracking better, regardless of their length or proportion. For a given diameter at low fibre levels, the longer fibres performed best, although shorter fibres gave better results when the fibre amounts were high. Plastic shrinkage cracking control is enhanced significantly when the fibre surface is hydrophilised, regardless of fibre length or diameter.
Seismic performance assessment of reinforced concrete bridge columns with lap splices using shaking table tests
Authors: Kim T.-H. , Hong H.-K. , Chung Y.-S. , Shin H.M.
Published: October 2009

The purpose of this study is to investigate the seismic performance of reinforced concrete bridge columns that have lap splices in the plastic hinge region when subjected to impulsive near-fault ground motions. For this purpose, the paper presents the results of shaking table tests on four reinforced concrete bridge columns. By using a sophisticated non-linear finite-element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, the RCAHEST (reinforced concrete analysis in higher evaluation system technology), was used for the analysis of reinforced concrete structures. A lap-spliced bar element was used to predict the inelastic behaviours of lap splices. The solution to the seismic response of reinforced concrete bridge columns was obtained by numerical integration of the non-linear equations of motion using the Hilber–Hughes–Taylor (HHT) algorithm. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge columns with lap splices when subjected to impulsive near-fault ground motions is verified by comparing the analytical results with test data that were developed by the authors.
Punching shear reinforcing using studs with steel plates in reinforced concrete flat plates
Authors: Cho Y.-S. , Noh S.-Y. , Kim H.-W.
Published: October 2009

Flat plate structures of reinforced concrete buildings have many advantages. However, a drawback of flat structures is that they are vulnerable to punching shear failure at the column–slab connections. This study proposes a new novel technique to improve the punching shear resistance capacity in new flat plate structures using the studs with perforated steel plate reinforcement at column–slab connections. Tests were carried out on specimens of ¾ scale, which were designed to fail as a result of punching shear. The specimen variables were as follows: the first case used a stud rail and a base specimen; the second case used four stud specimens with perforated steel plates with different lengths; and the third case used a perforated steel plate with the same length as the stud with the steel plate. From the test results, the following conclusions were drawn: (a) the ultimate strengths of specimens have been designed to resist punching shear based on ACI 421 and Eurocode 2-04, and shear reinforcement for slabs has been compared with the results from the structural experiments; (b) the studs contributed substantially to the increase of ultimate strength; (c) the studs with steel plates contributed to the increase of the ultimate strength. The ratio of ductility in the specimen was larger than that of the total increase in strength.
Some water resources issues of Central Kazakhstan
Authors: Tanton T. W. , Ilyushchenko M. A. , Heaven S.
Published: October 2009

The key to the 1950s' New Lands policy of the former Soviet Union was the development of the vast steppe of Kazakhstan. Unfortunately, within the centre of the country, water resources are scarce, restricting both agricultural and industrial development. To overcome this problem a huge water-basin transfer scheme was constructed to transfer up to 70 m3 s−1 of water from the River Irtysh, lifting it up to 533 m and transferring it to remote areas up to 1300 km away. As a result, irrigation and water-consumptive industries flourished in the region. Unfortunately, with the transfer to a market economy, operating costs can no longer be covered and the effective operation of the canal has ceased. This paper examines the water supply system for the region and considers the implications of canal closure and the issues of future supply.
The free overfall as a flow measuring device in a circular channel
Authors: Sterling M. , Knight D. W.
Published: October 2009

The critical depth of flow (hc) and the brink depth (hb), for a circular pipe with and without a horizontal bed are used to estimate the channel discharge. The brink depth ratio (hb/hc) for a given cross section geometry is shown to be a constant for subcritical flow. The brink depth ratios for various channel geometries and bed slopes are presented in a form readily accessible to engineers. Two worked examples, one for an irrigation channel and the other for a larger circular sewer, show how the discharge Q can be obtained from measurement of the brink depth.
Estimating transverse mixing coefficients
Authors: Boxall J. B. , Guymer I.
Published: October 2009

The inaccuracy, and prohibitive field costs, involved in the evaluation of mixing coefficients severely limit the predictive capabilities of water quality models. This paper examines the traditional method of evaluating transverse mixing coefficients from field measurements and suggests a new simplified method of evaluation with significantly reduced data requirements. Results are presented from a series of laboratory experiments conducted on a large-scale test facility. Two planform configurations were tested—a straight and a meander channel. Both channels were of trapezoidal cross-section. Velocity measurements are presented together with the results of tracer studies conducted from continuous point source releases.Transverse mixing coefficients have been evaluated using both the traditional method of moments and the new method. The new method is shown to be a viable technique to obtain estimates of transverse mixing coefficients. The results highlight the impact of planform curvature on the rate of transverse mixing. The longitudinal location of a release with respect to a curvature is shown to be critical to the rate of transverse mixing.
From the redwood forest to the Gulf Stream waters: human signature nearly ubiquitous in representative US landscapes
Authors: Cardille Jeffrey A , Lambois Marie
Published: October 2009

What landscapes best represent the land uses and land covers (LU/LC) of the continental United States? Would the set include a cornfield? A forest? A backyard? Combining principles of landscape ecology and computer science, we identified a small set of “exemplar landscapes”, representing distinct LU/LC pattern types of the conterminous US. We first partitioned the 1992 US National Land Cover Dataset into 193 705 landscapes, and quantified patterns with standard measures of LU/LC composition and configuration. Using the values to estimate similarity of LU/LC patterns between landscapes, we applied an algorithm developed to find representatives in large sets. In the resulting 17‐member set of exemplar landscapes, patterns created and managed by human activity are by far the most evident features. This set of representatives summarizes the nation's LU/LC, demonstrating the degree to which human‐influenced patterns dominate: aggregations of rectangular fields, farmlands within cleared forests, shrublands/pasture, and suburbs. The algorithm's selection of an exemplar for each group may have other ecological applications when an objectively determined subset of representative items is needed.
The Influence of Technological Literacy on Students' Writing
Authors: Turner Kristen H. , Katic Elvira K.
Published: October 2009

Many forms of technological communication exist in non-linear environments and there is potential for new approaches to learning and teaching which may more closely approximate naturalistic and authentic approaches to learning. The following study examined the ways in which high school students were influenced by technology as they wrote and how different aspects of emergent technological literacies were appropriated into their writing processes. We found that the complexity of technological affordances largely informed the students' non-linear writing processes and that they exhibited fluency with non-linear frameworks. The students' use of technology no longer seemed an issue of translation. Rather, writing occurred in, around, and with this non-linear framework. It is likely that the more students use such non-linear frameworks, the more their fluency will continue to increase, and the more they will look to accomplish other writing tasks by using this “new” literacy that they have mastered.
Dying to Know: A Community Survey about Dying and End-of-Life Care
Authors: Schrader Susan L. , Nelson Margot L. , Eidsness LuAnn M.
Published: October 2009

A community survey of Sioux Falls, South Dakota was conducted in 2004 to understand knowledge, attitudes, and preferences about end-of-life (EOL) care and to generate conversations about these topics. Questionnaires were sent to 5,000 randomly selected households, with a return of 1,042 (21%). Most respondents said preparation for EOL is very important, yet far fewer had taken steps to ensure their EOL wishes would be known or met. These disparities are examined, with recommendations for future research and public policy. Bivariate analyses revealed significant differences by age, sex, education, marital status, and religiosity. Community studies are important for baseline understanding, evoking conversation, and setting goals for change. Public education is needed to strengthen understandings of hospice care, and professional education is needed to raise awareness about practitioners' roles in resolving discrepancies between what people want and what they get at end of life.
An Internet Tool to Normalize Grief
Authors: Dominick Sally A. , Irvine A. Blair , Beauchamp Natasha , Seeley John R. , Nolen-Hoeksema Susan , Doka Kenneth J. , Bonanno George A.
Published: October 2009

This research evaluated the efficacy of a psycho-educational Internet self-help tool to educate and support recently (1–6 months) bereaved individuals. The goal of the website was to help users normalize their grief to enhance their adaptive adjustment. A randomized controlled trial evaluated the gains in social cognitive theory constructs and state anxiety. Compared to the control group ( N = 34), treatment participants ( N = 33) reported significant multivariate gains (eta-square = .191). Significant program effects were obtained on all three outcome measures: attitude (eta-square = .177), self-efficacy (eta-square = .106), and state anxiety (eta-square = .083). These findings suggest the potential efficacy of an Internet-based grief support tool to enhance adaptive adjustment of the bereaved.
Effects of two kinds of aerobic training on body fat content and serum lipid profile in cadets
Authors: de Souza e Silva Mauro , de Souza Rabelo Adalberto , Vale Rodrigo , Ferrão Max , Gonçalves Leila , de Sá Rego Fortes Marcos , Moreira Sérgio , Dantas Estélio
Published: October 2009

Effects of two kinds of aerobic training on body fat content and serum lipid profile in cadets

Study aim: To assess the effects of aerobic training on body fat content and serum lipid profile.

Material and methods: A group of 45 male members of Brazilian Military Police Academy, aged 18 - 32 years, were subjected randomly assigned into 3 subgroups and to 12-week programmes: aerobic fatmax zone training (FG; n = 18), traditional military training (TM; n = 15) and non-training control group (C; n = 12). Body fat content (3 skinfolds), serum lipid profile (total cholesterol, LDL, HDL and triglycerides), waist circumference (WC) and O2max (12-min test) were determined.

Results: O2max significantly (p<0.05) increased and body fat content decreased in both experimental group compared with the control one. Significant (p<0.05) reductions in WC and LDL vs. control group were observed in the TM group only.

Conclusions: The applied aerobic training induced a decrease in percent body fat irrespectively of the kind of training.
Synthesis and Evaluation of Highly Tolerant Pd Electrocatalysts as Cathodes in Direct Ethylene Glycol Fuel Cells (DEGFC)
Authors: Rodríguez Varela F. Javier , Luna Sergio Fraire , Savadogo Oumarou
Published: October 2009

Highly selective Pd electrocatalysts were synthesized by the formic acid (FA) method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence of ethylene glycol (EG, C2H6O2), Pd/C exhibited a noteworthy electrochemical behavior and full tolerance to the organic molecule. No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the ORR (Eonset) toward more negative potentials was negligible on this cathode. As a comparison, commercial Pt/C was tested under the same conditions showing a poor selectivity for the ORR when EG was present. The detrimental effect of EG on the Pt electrocatalysts resulted in high intensity current density peaks due to the oxidation of EG and a significant shift in Eonset. The evaluation of Pd/C in a DEGFC operating at 80 °C demonstrated its good performance as cathode material. Given these results, it is expected that highly efficient Pd-based cathodes can find application in DEGFCs.
Transformations de l'islam à Pemba au Mozambique
Authors: Bonate Liazzat J.K.
Published: October 2009

Résumé Cet article analyse les récentes transformations de l’islam dans la ville de Pemba au Mozambique à travers le prisme de l’économie morale. Une modification des conceptions et pratiques islamiques s’est opérée au sein des communautés musulmanes, africaine comme indienne, suite à l’établissement dans la ville d’une ONG islamique transnationale, l’Africa Muslim Agency (AMA) en 1987. Une nouvelle génération de leaders islamiques a émergé et défié l’ancienne génération en invoquant la nécessité de « corriger » les normes et pratiques locales appropriées à un comportement musulman et de promouvoir une adhérence plus stricte au Coran et au Hadith. Les changements survenus dans l’économie morale de l’islam sont allés de pair avec ces transformations.