bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanism and rate of attack of sodium sulphate solution on cement and cement/pfa pastes
Authors: Cabrera J. G. , Plowman C.
Published: July 2012

Synopsis

A study of the mechanisms and rates of attack of a sodium sulphate solution on four ordinary Portland cement (OPC) pastes, and four OPC/pfa pastes is presented. Accelerated experiments were carried out on mortar cubes, and samples from different depths were analysed by X-ray spectrometry and X-ray diffraction.

The mechanism of attack was similar for the different cements: initial attack on the hydrated calcium aluminates produced AFt and AFm phases, and subsequent attack on calcium hydroxide resulted in the formation of gypsum. Incorporation ofpfa reduced the rate of attack, due to the finer pore size distribution of the paste, and the formation of Afm in preference to Aft. Subsequent attack on calcium hydroxide was greatly reduced.
Determination of the sulphate resistance of blastfurnace slag cements using small-scale accelerated methods of test
Authors: Osborne G. J.
Published: July 2012

Small-scale accelerated tests using cement paste cubes and mortar prisms have been carried out with Portland cements and blastfurnace slag cements to assess whether any of these methods could be recommended as an acceptance test for determining the sulphate resistance of cements. It is concluded that additional laboratory studies and direct comparison with longer term concrete cube test data would be necessary before any of these tests could be used as a standard sulphate resistance test method. A mortar prism test was considered to provide the best indication of cement behaviour in sulphate conditions. The three accelerated tests indicated that in general the use of ground granulated blastfurnace slag (GGBS) for up to and including class 3 sulphate conditions as recommended in Building Research Establishment Digest 250 is justified even if ordinary Portland cements (OPCs) with high C3A and slags with high Al2O3 contents are used together. The performance of GGBS in more severe sulphate conditions may also be satisfactory provided that medium C3A OPC or low Al2O3 slags are used.
Assessment of sodium molybdate as an accelerator of cement hydration and setting
Authors: Thomas N. L. , Egan P. J.
Published: July 2012

As part of a search for an alternative chloride-free accelerator, the effects of sodium molybdate as an accelerator of hydration for both aluminate and Portland cement are given. Heat evolution, structure development and corrosion testing techniques have been utilized. Results confirm an accelerating action on early hydration but at later ages compressive strengths were significantly reduced. By comparison with other known accelerators, possible mechanisms for the effects of sodium molybdate are suggested.
The hydration of C3S and ordinary Portland cement with relatively large additions of microsilica
Authors: Groves G. W. , Rodger S. A.
Published: July 2012

The microstructure of pastes of ] part of C3S blended with 1·3 parts of precipitated silica, and 1 part of ordinary Portland cement (OPC) blended with 1·4 parts of silica fume, hydrated for two months at 25°C and three months at 40°C respectively, have been studied by analytical transmission electron microscopy and solid state NMR. The hardened pastes were found to consist, solely in the case of C3S/silica and principally in the case of OPC/silica fume, of silica particles embedded in CSH gel with a Ca/Si ratio significantly less than unity. The gel contained silicate units in chains of approximately 8·5 units in average length. Similar pastes prepared with alkali addition differed little in microstructure, but the OPC/silica fume paste with alkali addition contained isolated regions of low calcium and high alkali content with a distinctive morphology.
Influence of superplasticizer on aqueous phase composition in the CaO-Al2O3-SO3-H2O system
Authors: Luke K.
Published: July 2012

The effect of three different superplasticizers on the formation of ettringite during the reaction of Al2(SO4)3·16H2O with Ca(OH)2 and on the hydration of C3A with CaSO4·2H2O was investigated in relation to aqueous phase compositions. The superplasticizers comprised a sulphonated melamine formaldehyde condensate (SMF) and two sulphonated naphthalene formaldehyde condensates (SNF) , with different counter-ions (Na and Ca). The addition of superplasticizer altered to varying extents the aqueous compositions, and this was dependent on the reaction system, the degree of reaction and the type of superplasticizer used. The SNF superplasticizer as the Na salt produced solution characteristics different to those produced by either the Ca salt or the SMF superplasticizer. Compositional variations occurring in the aqueous phases as a function of time, both with and without super plasticizer, have in part been explained in relation to that of the solid phase composition.
Small-scale durability study of gasifier slag—Portland cement blends
Authors: Bland C. H. , Sharp J. H. , Osborne G. J.
Published: July 2012

Gasifier slag (GS), a by-product of the manufacture of substitute natural gas, is a potential new pozzolanic cement replacement material. A small-scale durability study of a series of blended cements as paste systems has been carried out using two Portland cements blended with two gasifier slags, and also with a granulated blastfurnace slag and a pulverized fuel ash for comparison. The compressive strength results indicate that GS could be used successfully as a blending component for cement, generally producing good durability (especially with high replacement levels in aggressive environments). Analyses of the hydrates and their modification by the presence of GS could help to explain these effects.
Rheological properties of belite cement pastes
Authors: Grzeszczyk S.
Published: July 2012

Results of rheological examination of belite cement pastes prepared from clinkers containing various crystalline modifications of the C3A phase are presented. Pastes obtained from be lite cements of comparable C3A contents, prepared from clinkers containing potassium only and both potassium and sodium but no sulphates, have higher plastic viscosity and yield values at the initial stage of hydration than those prepared from alkali-free clinkers. The highest plastic viscosity and yield values are shown by pastes in which the C3A phase has a prismatic morphology. Although C3A type has a marked effect on the rheological properties of cement pastes, it is much less important than the specific surface area of the ground clinker and the waterlcement ratio of the paste.
Borate retardation of cement set and phase relations in the system Na2O—CaO—B2O3—H2O
Authors: Cseteyi L. J. , Glasser F. P.
Published: July 2012

The CaO-rich portions of this system have been determined at 25° and 55°C. Twenty-one closely spaced compositions were prepared from analytical reagent-grade materials and reacted in sealed containers for up to 6 months. Solid phases were characterized mainly by X-ray diffraction and the aqueous phase was analysed chemically for Ca, Na and B. Solubility data were also obtained from singlephase preparations of selected hydrates; in conjunction with data in the literature, extensive thermodynamic modelling of solubility relations was undertaken. The combination of calculation and experimental determinations enabled the equilibrium features to be determined rapidly; cross-checks between calculated and experimental data are presented.
Porosity of oil well cement slurries during setting
Authors: Justnes H. , Skalle P. , Sveen J. , Øye B. A.
Published: July 2012

The phenomenon of ‘gas migration’ during oil well cementing is believed to occur during the transition state between initial and final set of the cement. In order to evaluate the importance of pore openings and total porosity in the critical time gap, a suitable experimental technique was tested on some neat oil well cement slurries. The hydration was effectively stopped every 30 min at 20°C and every 20 min at 60°C by dropping plastic tubes containing the cement slurry into liquid nitrogen (i.e. quenching), cracking the tubes open and letting the frozen bits of paste thaw in ethanol. The change in porosity and pore size distribution was determined by helium pycnometry and mercury intrusion porosimetry as a function of time in the setting period for a plain API class G cement slurry (w/c = 0·50) at both 20°C and 60°C. These data were compared with the amount of chemically hound water in the same samples, and used to predict the total porosity at a given degree of hydration. The excellent correspondance of experimental and theoretical porosities validates the experimental procedure, which can also be used in explaining the variation in gas migration between commercial oil well cement slurries.
Quantification of thaumasite in cementitious materials by 29Si {1H} cross-polarization magic-angle spinning NMR spectroscopy
Authors: Skibsted J. , Hjorth L. , Jakobsen H. J.
Published: July 2012

29Si {1H} cross-polarization (CP) magic-angle spinning (MAS) nuclear nagnetic resonance (NMR) is shown to be a valuable tool for detection and quantification of thaumasite in cementitious systems. A 29Si {1H} CPIMAS NMR method for quantitative analysis of thaumasite employing 1H and 29Si rotating-frame relaxation times TH1p and TSi1p and the 1H—29Si CP time TSiH is introduced. The method is illustrated by determination of the thaumasite content in five laboratory samples containing carbonates and sulphates from different sources. The use of 29Si{lH} CP/MAS rather than 29Si MAS NMR for the detection of thaumasite is shown to reduce the instrument time by up to a factor of IOOO because of the large difference in 1H and 29 spin-lattice relaxation times (TH1 and TSi1) and the 29Si intensity gain by CP for this mineral. The non-standard behaviour of the 1H and 29 spin-lattice relaxation processes observed for some samples is shown to follow a decay exponential in t with time t. 27Al MAS NMR is used to quantify ettringite for some of the samples. In contrast to previous proposals on the mechanism for the formation of thaumasite, it is demonstrated using 29Si{lH} CP/MAS and 27Al MAS NMR that considerable quantities of thaumasite can be produced in virtually aluminium-free materials. 13C {lH} CP/MAS NMR of pure thaumasite shows its potential in characterizing the carbonate anions in this mineral.
The hydration of hydraulic active calcium germanates: Part 2. The early hydration of dicalcium germanate
Authors: Trettin R. , Odler I. , Gerdes A.
Published: July 2012

The reactivity of Ca2GeO4 with water is very small compared with that of tricalcium germanate but similar to that of dicalcium silicate. Only one maximum of heat evolution is visible at the beginning of hydration. The initial reactivity of dicalcium germanate is followed by a period of very slow reactivity. The hydration products are the same as these formed with tricalcium germanate. Crystalline calcium hydroxide is present, and also at least two crystalline calcium silicate hydrate phases. The small reactivity of dicalcium germanate is influenced by the structure and by a reaction layer. This layer comprises hydration products, which cover the surface of dicalcium germanate and form a barrier whose permeability determines the kinetics of hydration.
Early-age hydration kinetics of polymer-modified cement
Authors: Zeng S. , Short N. R. , Page C. L.
Published: July 2012

The hydration kinetics of styrene butadiene rubber latex-modified cement have been studied by isothermal conduction calorimetry. The influence of factors such as polymer concentration, polymer modification, presence of surfactant and alkalinity of cement have been investigated. It has been found that the polymer acts as a retarder first by increasing the induction time, thus suppressing the nucleation of cement hydration products, and secondly by restraining the growth of these phases during the acceleration stage. Reaction rate constants for the acceleration stage have been calculated using modifications of the Jander and Avrami equations and activation energies have been estimated. Small concentrations of polymer were found to influence the growth of phases to a substantial degree but not to change the hydration mechanism. In contrast, larger concentrations of polymer influenced the induction time and changed the hydration mechanism.
The microstructure of steam-cured precast concrete
Authors: Patel H. H. , Bland C. H. , Pool A. B.
Published: July 2012

This work reports on the microstructure of concrete cubes manufactured at 16°C and steam-cured at 42°C, 60°C and 80°C. Increase in curing temperature leads to the development of distinct hydrate rims around both anhydrous cement grains and Hadley grains. In concrete cured at or above 60°C, 20%-30% of the C-S-H rims had a dark inner zone and light outer shell which were not present at room temperature, and up to 80% of the Hadley grains had distinct hydrate product rims, many being partially or completely in filled with either ettringite or monosulphate-type hydrates. As curing temperature increases the proportion of ettringite-type hydrates decreases, while those associated with monosulphate become more predominant. Sulphate concentrations were about twice as large in the light outer C-S-H as in the dark inner C-S-H for specimens cured at 80°C and, within the hydrate rims of the Hadley grains, the sulphate content at 80°C was about twice that observed at 60°C.
Characterization of the microstructure and strength of cement paste by microhardness testing
Authors: Igarashi S. , Bentur A. , Mindess S.
Published: July 2012

The structure and properties of cement paste were investigated by means of microhardness testing. The characteristics of the paste were defined by the microhardness value itself and by the parameters obtained from the evaluation of the indentation size effect. The latter effect is due to the dependence of the microhardness value on the indentation load. In cement pastes higher loads resulted in higher microhardness. which is in contrast to the observations in metals. Analysis of this dependence by two parameters was shown to be effective in quantification of microstructural characteristics. Linear relations between strength and microhardness were obtained, but they differed with testing conditions in the microhardness test. These differences could be interpreted in terms of the microstructural characteristics as quantified by the indentation size effect. The influence of age, silica fume and waterlcement ratio was characterized by these means.
Technical calcium nitrate as set accelerator for cement pastes at low temperatures
Authors: Justnes H. , Nygaard E. C.
Published: July 2012

Technical calcium nitrate (CN) is tested as a set accelerator for five French cements by Vicat needle and isothermal calorimetry at both 5°C and 20°C. All five cements were characterized by standard test methods and X-ray diffraction. CN works as a set accelerator for all five cements tested (but poorly for cement no. 2). The CN dosages tested at 5°C were 0·00%, 1·55%, 3·86% and 7·73% of the cement weight. The optimum dosage was found to be 1·55%, 1·55%, 3·86%, 3·86% and 1·55% CN for cements nos 1, 2, 3, 4 and 5, respectively. However, optimum CN dosages less than 1·55% cannot be excluded for cements nos 1, 2 and 5. The accelerating efficiency of CN is higher at 5°C than at 20°C. In addition to shortening the overall setting time, the CN accelerator often reduced the time gap between initial and final set, indicating a more rapid strength build-up. Isothermal calorimetry revealed a good correlation between the extra heat output during the first five hours and the effectiveness of 1·55% CN (fixed dosage) in accelerating initial set at 5°C. The efficiency of CN as set accelerator for the different cements seems to increase with increasing β-CsS, as partly confirmed by X-ray diffraction, or other cement characteristics promoting belire formation in the clinker process.
Dissolved gas as a problem in oil well cements
Authors: Lile O. B. , Justnes H. , Skalle P. , Backe K. R. , Sveen J.
Published: July 2012

Dissolution of high-pressure gas in drilling fluids and oil well cement slurries may cause problems when the gas is liberated. A literature survey on solubility data confirms that gas may he dissolved and liberated at typical well conditions. Formation gas dissolved in the drilling mud is liberated when the mud returns to the surface, but this is normally not a problem. It is not known whether dissolved gas in the cement slurries may create any problems. A new hypothesis is introduced, claiming that gas from the formation may enter into the cement slurry and eventually lead to a weaker cement and/or to fractures, enabling a continuous migration of gas to the surface. Laboratory experiments have been carried out on cement slurries. Thin sectioned samples of the hardened cement showed that more gas bubbles and fractures had indeed developed in the cements that had been exposed to pressurized gas before and during the hardening process.
Quantitative phase analysis of Portland cements from reactive powder concretes by X-ray powder diffraction
Authors: Mansoutre S. , Lequeux N.
Published: July 2012

As part of a Cooperative research programme between Bouygues, Lafarge and Rh6ne-Poulenc, X-ray powder diffraction has been used to study the effects of heat treatments on very high strength concretes (‘reactive powder concretes’). Three methods of X-ray quantitative analysis have been developed, and the paper reports on the advantages and limits of each. Method A (area measurement) is the fastest and does not require high-speed computers. However, it requires pure reference materials and does not work for belite whose peaks overlap with those of alite. Method B (a Rietveld analysis using structural models) allows good accuracy, although the quality of refinement is affected by the lack of alite crystal models. Method C (a Rietveld analysis using full pattern matching for alite and a structural model for other phases) gives high-quality refinements but is not adequate to determine the alite content, because of the poor accuracy of the Bogue composition. The three methods give nonconflicting data and they can be used to follow the various stages of hydration of cement phases, in particular alite and belite, and to investigate (i) xonotlite formation, and (ii) pozzolanic activity, which is associated with a portlandite decrease.
Hydrothermal synthesis of tobermorite from fly ashes
Authors: Ma Weiping , Brown P. W.
Published: July 2012

The hydrothermal behaviour of oxide mixtures whose compositions simulate those of fly ashes is discussed. These model systems were synthesized using phase-pure starting materials, so that the exact compositions of the mixtures could be specified. Fly ashes were then used as starting materials to compare their behaviour under hydrothermal conditions. The compositions of class F and C fly ashes were adjusted to those of the systems made with the pure oxide starting materials. It was demonstrated that tobermorite can be synthesized from fly ash based materials under hydrothermal conditions, and the process was accelerated at high sodium hydroxide concentrations. The pore size distributions of tobermorites prepared from fly ashes showed an increase in pore volume over the size range from 19 Å to almost 0·1 μ;m.
CaF2 and CaSO4 in white cement clinker production
Authors: Blanco-Varela M. T. , Palomo A. , Puertas F. , Vázquez T.
Published: July 2012

A review of the fluxing and mineralizing effects of CaF2 and CaSO4 during the clinkering process is presented. The simultaneous addition of CaSO4 and CaF2 to compositions in the system CaO—Al2O3—Fe2O2-SiO2 results in formation of phases not found in ordinary Portland cement: for example, C11A7·CaF2, C4A3S, and 3C2S·3CaSO4·CaF2, etc. These modify the compatible equilibrium phases as well as the stable primary fields of C3A and C3S. Finally, CaSO4 and CaF2 are responsible for changing the melt composition together with its rheological characteristics. Clinkerization of raw meals with silica moduli greater than 10 and lime saturation factor greater than 0·95 is possible when CaF2 and gypsum partially replace traditional fluxes. Finally, the results of an industrial test in which a mineralized white cement (AS-SR type) was produced are presented. The clinker has about 80% silicates plus aluminates; fluorellestadite is a characteristic phase of this process. The thermal and economic balances are positive compared to traditional fabrication. The durability properties of the new cement, when subject to attack by sulfates and sea water, are much better than a normal white cement.
Action of admixtures on fondu cement: II. Effect of lithium salts on the anomalous setting time observed for temperatures ranging from 18 to 35°C
Authors: Damidot D. , Rettel A. , Sorrentino D. , Capmas A.
Published: July 2012

Measurement of the conductivity of stirred and diluted suspensions of fondu cement hydrated in water at different temperatures indicates that the duration of the induction period that occurs before the massive precipitation of hydrates passes through a maximum at 27°C. The temperature at which the maximum occurs depends upon the nucleation rates of CAH10 and AH3: the CAH10 nucleation rate is expected to decrease with temperature whereas the AH3 nucleation rate is expected to increase. Thus, one passes from an induction period controlled by the CAH10 nucleation rate to an induction period controlled by AH3 at the temperature that induces the maximum retardation of the hydration. This mechanism explains why lithium salts can reduce or even remove this maximum of retardation.
Metakaolin additions to autoclaved cement—quartz pastes: evaluation of the acid-insoluble residue
Authors: Klimesch D. S. , Ray A. S.
Published: July 2012

Metakaolin (MK) is an important source of reactive aluminous material which accelerates the crystallization rate 11 Å tobermorite (C6S5H5) in autoclaved cement-quartz and lime-quartz based building materials. The acid-insoluble residue (AIR) provides a measure of unreacted MK when excessive additions of MK are made. This paper reports the findings of our evaluation of the AIR, for autoclaved cement-quartz pastes with MK additions of up to 30·5% and autoclaved cement-MK paste, by using a combination of analytical techniques such as X-ray fluorescence and X-ray diffraction spectrometry, scanning electron microscopy and differential thermal analysis and thermal gravimetric analysis.
Investigation of hydration activity and Ca—O bonds of the aluminate minerals CA, CA2 and CA6 with SCF-DV-Xa
Authors: Xiuji Feng , Beixing Li , Qijun Yu
Published: July 2012

The relationship between valence bond structures and the hydration activity of the aluminate minerals CA, CA2 and CA6 has been studied by the SCF-DV-Xa method. Comparing the calcillated results, such as bond ordel; hydraulic activation energy and electronic energy level states, etc., we have confirmed the theoretical reason for the hydration activity sequence of three aluminate minerals being CA > CA2 > CA6.
Chemical shrinkage and autogenous shrinkage of Portland cement—metakaolin pastes
Authors: Wild S. , Khatib J. M. , Roose L. J.
Published: July 2012

Portland cement (PC)-metakaolin (MK) pastes of compositions 0, 5, 10, 15, 20 and 25% MK and water/binder ratio 0·55 have been subjected to tests for chemical shrinkage, autogenous shrinkage and expansion during soaking. Chemical shrinkage was carried out in 200 ml containers on water-covered 12 mm thick layers of paste, and the volume changes were monitored using 1 ml graduated pipettes. Autogenous shrinkage and expansion were determined by monitoring the dimensional changes of 285 × 25 × 25 mm paste bars, in, respectively, a sealed environment and in water. Volume changes are converted to millilitres per gram of binder for all three systems for purposes of comparison. Chemical shrinkage was found to increase for compositions between 0 and 15% MK and then decrease for compositions above 15% MK. Autogenous shrinkage was found to increase for compositions between 0 and 10% MK and then decrease for compositions above 15% MK. Expansion showed little variation for compositions between 0 and 10% MK and then increased for compositions above 15% MK. These changes are discussed in terms of formation of new hydrate phases and self-desiccation due to hydration.
Phase equilibria in the system CaO—Al2O3—B2O3—H2O at 23 ± 1°C
Authors: Bothe J. V. , Brown P. W.
Published: July 2012

Phase equilibria in the four-component system CaO—Al2O3—B2O3—H20 at 23 ± 1°C have been investigated. Data obtained experimentally were used to construct a phase diagram showing the stability regions of the sohd phases Ca(OH)2, Al(OH)3, the ternary hydrate 3CaO·Al2O3·6H2O, and the two quaternary hydrates, 6CaO·Al2O3·2B2O3·39H2O and 4CaO·Al2O3·½B2O3·12H2O. Theoretical calculations were also performed using the speciation program PhreeqC, which gave results that were in close agreement with those obtained experimentally. From this study, the solubility products (PKsp) for 6CaO·Al2O3·2B2O3·39H2O and 4CaO·Al2O3·½B2O3·12H2O were determined to be 44·23 and 28·51, respectively.
Metakaolin additions in autoclaved cement—quartz pastes: a 29Si and 27Al MAS NMR investigation
Authors: Klimesch D. S. , Lee G. , Ray A. , Wilson M. A.
Published: July 2012

Cement-quartz pastes containing 0-30·5% metakaolin (MK) were prepared and autoclaved at 180°C for 8 h. MK was introduced as either quartz or cement replacement. 29Si nuclear magnetic resonance (NMR) spectroscopy employing magic angle spinning was used successfully to detect unreacted MK in situ. thus providing valuable information on the practical limits of MK addition in these autoclaved products. Results were in excellent agreement with evaluations of the acid-insoluble residue; however, in situ detection of unreacted starting materials, particularly MK, using 29Si NMR eliminates the use of reagents which partially or completely dissolve them. 29Si NMR results indicated that MK affects the overall distribution and nature of silicate anions in the product, presumably a consequence of both silica and alumina species participating in the reactions.
Experimental limitations in impedance spectroscopy of cement-based materials
Authors: Mason T. O. , Ford S. J. , Shane J. D. , Hwang J.- H. , Edwards D. D.
Published: July 2012

Impedance spectroscopy is a powerful technique for characterizing the frequency-dependent electrical behaviour of cement-based materials and interfaces, given that certain experimental limitations—machine limitations, stray imittances (e.g. from cables and leads), and electrode effects—are recognized and dealt with. The origins of these effects in impedance spectroscopy are discussed and various remediation strategies are presented, with illustrations from measurements on cement-based materials. The problems encountered and remediation strategies taken are generally applicable to impedance studies of heterogeneous, conductive materials.
Monitoring the early hydration of pozzolan—Ca(OH)2 mixtures using electrical methods
Authors: McCarter W. J. , Ezirim H. C.
Published: July 2012

This paper utilizes electrical methods to follow the early hydration characteristics of pozzolanic materials activated with powdered calcium hydroxide at room temperature (20°C). The electrical response is measured in terms of conductance and capacitance. Four materials are studied: ground granulated blastIurnace slag, microsilica, metakaolin and pulverized fuel ash (the last from three different sources). The work shows that monitoring the temporal change in electrical parameters can exploited as a potentially usefit! test method for identifying the stages of hydration and studying the rate of reaction over these stages. To this end, different formats of data presentation are exploited. It was shown that the capacitance of the material displays a marked frequency dependence over the range of the current study (10a Hz to 10kHz); the influence of frequency of applied field on conductance was less pronounced.
Electrochemical chloride extraction: influence of testing conditions and mathematical modelling
Authors: Castellote M. , Andrade C. , Alonso C.
Published: July 2012

To continue the work developed by the authors, in the field of application of electrical fields to concrete, electrochemical chloride extraction experimental trials were carried out in order to verify the assumptions made on the processes and its mathematical modelling. Studied variables have been: duration of the test (from 1 to 8 weeks of treatment), arrangement of the electrodes, type of regime (potentiostatic or galvanostatic) and the influence of renewing the external anodic solution (anolyte). From the results obtained, the efficiency of the technique regarding the percentage of extraction and chloride transport numbers has been calculated. This work has enabled the authors to demonstrate the reasons why the efficiency decreases with time and in consequence why the diffusion coefficient diminishes as the treatment proceeds, as well as to give the equations that model the extraction processes, allowing the duration of the treatment to be calculated.
Characterization of transport of caesium, strontium, cobalt and iron ions through concrete by steady-state migration and natural diffusion tests
Authors: Castellote M. , Andrade C. , Alonso C.
Published: July 2012

Immobilization of wastes in cement-based matrices is being increasingly used, particularly in the case of elements of medium and low activity. Therefore, characterization of the system in relation to the release of ionic wastes through the cement, and consequently the determination of their diffusion coefficients, becomes of strategic importance. Nowadays, diffusion coefficients of some radioactive elements (mainly of Cs+) can be found in the literature, obtained by natural diffusion tests that are very time-consuming. In the present paper, the calculation of steady-state diffusion coefficients of Cs+, Sr2+, Co2+ and Fe3+ through concrete has been done by migration experiments. The mutual influence of the diffusion coefficients has also been studied, and transference numbers of the different ions have been calculated. The results have been compared with those obtained by natural diffusion tests, having found for Cs+ and Sr2+ that there is a very good accordance between diffusion and migration tests. In contrast for Co2+ and Fe3+ the accordance is not so good, because at migration working conditions they are able to form complex compounds. In consequence, migration tests are reliable for obtaining diffusion coefficients of different elements through concrete, always taking into account the nature of the species that are present at working conditions.
Early strength development and hydration of alkali-activated blast furnace slag/fly ash blends
Authors: Shi C. , Day R. L.
Published: July 2012

This study concerns the effect of two types of fly ash and the addition of lime on the strength development and hydration of sodium hydroxide- and sodium silicate-activated slag/fly ash blends which consisted of 50% fly ash and 50% slag by mass. Performance was compared to that of 100% slag cements. When NaOH was used as an activator, the slag replacement with ASTM Type F fly ash did not show a significant effect on either the strength development or hydration; Type C fly ash did not affect the strength development, but affected the hydration process due to the presence of C3A in the fly ash. Both fly ashes had a significant effect on the hydration and strength development when Na2SiO3 was used as an activator. The addition of a small amount of hydrated lime significantly increased the early-age strength but slightly decreased the later-age strength of the activated slag/fly ash blends. Measurement of the heat evolution during hydration indicated that the addition of the hydrated lime had a slight effect on the hydration during the pre-induction period, but accelerated the hydration thereafter.
Briefing: Speeding up innovation by better ‘first use’ reporting
Authors: Ainger Charles
Published: July 2012

This briefing addresses an urgent issue for engineering innovators, institutions and journals: how can the spread of infrastructure innovation for sustainability be speeded up? It discusses the challenges and the reasons why innovation can be hard and slow, and focuses on a key innovation sequence: doing the ‘first use’ project, and early reporting of it, which ‘enables’ the first copying of the idea – the ‘first follower project’. This starts to validate the new idea for the sector. The briefing finishes with some suggested questions to be answered by a good report paper on a ‘first use’ case study; and calls for more such papers to be submitted.
Use of overstrength and inelastic response in seismic design
Authors: Mwafy Aman
Published: July 2012

Inelastic analysis procedures are more dependable means for predicting the actual seismic response compared with elastic analysis methods. Encouragement to use the former procedures is still limited and designers tend to favour elastic analysis procedures. The permissible reduction in response parameters obtained from elastic analysis unlike those from inelastic analysis procedures discourages the effective use of the latter analysis methods in design. This paper proposes a simple and theoretically-based approach that utilises inelastic structural response in design. To describe the approach, the correlation of seismic demands obtained from ineleastic and elastic analysis procedures carried out using a wide range of reinforced concrete buildings of different characteristics, ranging from 8 to 60 storeys, is investigated. Verified fibre element models and diverse input ground motions are employed in the inelastic simulations. The presented approach enables designers to arrive at a realistic and cost-effective design without compromising safety.
The succession of international treaties in contemporary practice
Authors: Dimitrijevic Dusko
Published: July 2012

Succession of states is a process of substitution of state subjects
concerning responsibility of international legal relations of the territory
to which the succession relates to. No general rules and unwillingness of
states to apply particular rules on succession often caused extreme
difficulties in the past in analyzing the succession of treaty rights and
obligations. As a totally incomplete system that would serve to regulate all
problems caused by the change of the state territorial sovereignty in time
the law of succession has manifested a tendency towards ?adjustment? of
customary rules to the factual situation. The contemporary examples of
dissolution of the USSR, Czechoslovakia and SFR Yugoslavia, re-unification of
Germany, as well gaining of independence by the Baltic States prove the
assertion mentioned above. However, succession does not always prejudice
legal substitution of states with regard to their rights and obligations. The
study of the legal consequences of the process of succession of states
presumes the application of a comparative method in the analysis of the state
practice as well as the implementation of rules and principles of
international law codificated in the 1978 Vienna Convention on Succession of
States in Respect of Treaties.
Evaluation of neurophysiological parameters and good metabolic control in patients with type 1 diabetes mellitus
Authors: Matanovic Dragana , Popovic Srdjan , Parapid Biljana , Dubljanin Emilija , Stanisavljevic Dejana , Ille Tatjana
Published: July 2012

Introduction. Numerous authors have indicated the beneficial effect of
glycoregulation on micro- and macro-angiopathic complications. Objective. The
aim of the study was to examine whether intensive treatment with maintaining
blood glucose concentrations close to normal range could improve
electrophysiological parameters. Methods. The study involved 81 patients with
type 1 diabetes mellitus type 1 randomly assigned to intensive insulin
therapy. The patients were followed for a period of 3 months by metabolic and
electrophysiological control. The metabolic control included daily
measurement of concentration of blood glucose and HbA1c and lipid status,
while the neurophysiological control included nerve conduction velocity (NCV)
of median, peroneal, tibial and sural nerve and latency of F wave. Results.
In the beginning of our study blood glucose was 9.10?3.69 mmol/l and HbA1c
8.12?1.20%. After 3 months of administered intensive insulin therapy, blood
glucose was 7.88?2.79 mmol/l and HbA1c 6.63?1.33. After 3 months NCV improved
in the tibial, median and sural nerve (p<0.05) and latency of F wave.
Conclusion. We found a significant association between the metabolic control
and NCV findings which suggests that good metabolic control influences the
improvement of neurophysiological parameters in patients with type 1 diabetes
mellitus.
In vivo susceptibility of ESBL producing Escherichia coli to ceftriaxone in children with acute pyelonephritis
Authors: Peco-Antic Amira , Paripovic Dusan , Buljugic Svetlana , Spasojevic-Dimitrijeva Brankica , Cvetkovic Mirjana , Laban-Nestorovic Suzana , Milosevski-Lomic Gordana
Published: July 2012

Introduction. The choice of empiric therapy of acute pyelonephritis (APN) in
children should be based on the knowledge of Escherichia coli (E. coli) as
the most common uropathogen and its antibiotic sensitivities considering that
nowadays ESBL-producing [ESBL (+)] E. coli is on the rise worldwide.
Objective. To examine in vivo susceptibility of ESBL (+) E. coli to
ceftriaxone (CTX), and to evaluate the options for empiric therapy for APN in
children. Methods. Retrospective study of CTX empiric therapy of APN in
children treated at the University Children?s Hospital in Belgrade from
January 2005 to December 2009. ESBL phenotypic confirmatory test with
ceftazidime, CTX and cefotaxime was performed for all urine isolates by disc
diffusion method on Mueller-Hinton agar plates. In vivo sensitivity of CTX
documented by clinical response to empiric CTX therapy was compared between
two groups of children: group I with ESBL (+) E. coli and group II with ESBL
(-) E. coli APN. Results. Group I with ESBL (+) APN consisted of 94 patients
and group II of 120 patients with ESBL (-) APN, respectively. All patients
received CTX as empiric therapy at a mean dose of 66.9 mg during 7.2?2.6 days
of therapy. Clinical effect of CTX was similar in patients with ESBL (+)
compared to those with ESBL (-) APN. Conclusions. In vitro resistance of ESBL
E. coli to CTX determined by standard methods is not sufficiently predictive
for its in vivo sensitivity. Therefore CTX may be used as empiric therapy for
acute pyelonephritis in children.
Results of application of external fixation with different types of fixators
Authors: Grubor Predrag , Grubor Milan
Published: July 2012

Introduction. Extra-focal or external fixation is the method of fracture
fixation through the healthy part of the bone using pins or wires. Objective.
The aim was to determine which external splints (Ortofix, Mitkovic, Charnley
and Ilizarov) had the best biomechanical properties in primary stabilization
of spiral, transverse and commutative bone fractures. Methods. To determine
the investigation methodology of biomechanical characteristics of the
external fixator we used mathematical and computer simulator (software),
juvidur physical model and clinical examination. Results. Values of advancing
fragments in millimetres obtained by the study of mathematical and computer
simulator (software): Charnley - 0.080 mm, Mitkovic M 20 - 0.785 mm, Ilizarov
- 2.245 mm and Ortofix - 1.400 mm. In testing the juvidur model the following
values were obtained: the external fixator Mitkovic M20 - 1.380 mm, Ortofix -
1.470 mm, Ilizarov - 2.410 mm, and Charnley - 2.510 mm. Clinical research of
biomechanical characteristics of the effect of vertical force yielded the
following results: Mitkovic M20 - 0.89 mm, Ortofix - 0.14 mm, Charnley - 0.80
mm and Ilizarov - 1.23 mm. Conclusion. When determining the total number of
the stability test splints under the effect of vertical force (compression)
and force effect in antero-posterior, later-lateral plane of cross, spiral
and comminuted long bone fractures, the best unified biomechanical stability
was shown by the following external fixators: firstly, Mitkovic M20 (0.93mm),
secondly, Charnley fixator (1.14 mm), thirdly, Ortofix (1.22 mm), and
fourthly, Ilizarov (1.60 mm).
Outpatient utilization of non-steroidal anti-inflammatory drugs in three largest municipalities in South Backa district
Authors: Horvat Olga , Mijatovic Vesna , Calasan Jelena , Sabo Ana
Published: July 2012

Introduction. Nonsteroidal anti-inflammatory drugs (NSAIDs) are used in the
treatment of musculoskeletal system diseases (MSD) and are associated with
numerous adverse effects. Objective. To determine the amount and structure of
outpatient consumption of NSAIDs and its correlation with musculoskeletal
system diseases in three municipalities in South Backa district with
different levels of health care. To examine whether the cost of drugs and the
level of health care influence the choice of drugs. Methods. Data on the
quarterly consumption of NSAIDs have been collected from all pharmacies in
Novi Sad, Vrbas and Backa Palanka. Data are presented by the number of
defined daily dosage (DDD) per1000 inhabitants. Cost (in RSD)/DDD was also
calculated. The drug utilization 90% (DU90%) methodology was used. Data on
the incidence of MSD from the three municipalities were obtained from the
Institute of Public Health of Vojvodina and were presented as the number of
patients/1000 inhabitants. Results. The highest total outpatient consumption
of NSAIDs was recorded in Backa Palanka, a municipality with the highest
prevalence of MSD. The lowest NSAIDs consumption and the lowest number of
patients were observed in Vrbas. Diclofenac was NSAID with the highest
consummation in all three municipalities, while ibuprofen, meloxicam and
nimesulide were dispensed in much smaller amounts. The cheapest NSAIDs were
found to be piroxicam and naproxen, diclofenac was the third in terms of
price/DDD, while ibuprofen was the sixth. Conclusion. In order to improve
prescription practice and the profile of drug usage in the population, it is
important to educate health care professionals, and to inform general
population about the risks of inappropriate drug use.
A rare case of benign omentum teratoma
Authors: Sforza Marcos , Andjelkov Katarina , Ivanov Dejan , Maricic Zoran , Krstic Slobodan
Published: July 2012

Introduction. Mature teratomas (benign cystic teratomas or dermoid cysts) are
among the most common ovarian tumours; however, teratomas of the omentum and
mesentery are extremely rare. Teratoma in the intraperitoneal cavity is
uncommon and atypical, and it is even more uncommon in adulthood. Case
Outline. An 82-year-old female was admitted to our department with clinical
signs of abdominal tumour. The ultrasound scan and preoperative laboratory
tests were done. Explorative laparotomy revealed tumour with torsion on its
pedicle at the greater omentum. After removal of the mass and the incision a
tooth and hair were found, characteristics of teratoma. Conclusion. The
excision was very effective and also definitive treatment for this case. The
patient recovered well and was discharged 3 days later. The patient probably
carried the tumour all her life asymptomatically until admission.
Across the borders in search of best practices: International comparative criminology at the UN
Authors: Alvazzi del
Published: July 2012

This paper analyzes the changes of the focus of the UN Committee on Crime
Prevention and Control through time and the formation of the new Commission
on Crime Prevention and Criminal Justice. The focus of the paper is the
contribution of Dusan Cotic, the last Chairman of the Committee.
Victimisation surveys: What are they good for?
Authors: Aromaa Kauko
Published: July 2012

The author analyzes the usefulness of victimization surveys. The paper is
focused of surveys in which nationally representative population samples are
surveyed for their personal victimisation experiences, and their attitudes
and opinions of issues related to crime and crime control. The author points
out the benefits of using victimization surveys, but also explains why most
countries have failed to make systematic use of this instrument.
Esteticki perspektivizam - problem metode u estetici Mirka Zurovca - M. Zurovac: Metodicko zasnivanje estetike, Dereta, Beograd, 2008
Authors: Grubor Nebojsa
Published: July 2012

nema
3D-steering and superfocusing of second-harmonic radiation through plasmonic nano antenna arrays
Authors: Reichenbach P. , Eng L. M. , Georgi U. , Voit B.
Published: July 2012

Second-harmonic generation (SHG) of light at nanoparticles provides the possibility to generate light (of a desired frequency) in-situ instead of introducing it by focusing an external light beam. Our theoretical study provides steering SHG light through the superposition of the radiation from a number of nanoparticles which are arranged in a circle. The authors assume cone-shaped or rod-shaped nanoparticles. Their radiation can be modeled as radiating dipoles. The superposition of their fields yields a “hot spot” with a full width at half-maximum of around 100 nm. Even more important, the position of the hot spot within the circular arrangement of nanoantennas can be adjusted in the xy plane simply by changing the incident angle of the exciting beam.
Femtosecond laser-induced periodic surface structures
Authors: Bonse J. , Krüger J. , Höhm S. , Rosenfeld A.
Published: July 2012

The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ ∼ 30–150 fs, λ ∼ 800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength λ are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (∼λ/10) can be generated. For semiconductors, the impact of transient changes of the optical properties to the LIPSS periods is analyzed theoretically and experimentally. In dielectrics, the importance of transient excitation stages in the LIPSS formation is demonstrated experimentally using (multiple) double-fs-laser-pulse irradiation sequences. A characteristic decrease of the LIPSS periods is observed for double-pulse delays of less than 2 ps.
Laser-assisted nanofabrication of carbon nanostructures
Authors: Zhou Yun Shen , Xiong Wei , Park Jongbok , Qian Min , Mahjouri-Samani Masoud , Gao Yang , Jiang Lan , Lu Yongfeng
Published: July 2012

An overview of laser-assisted techniques developed in our group for fabricating carbon nanostructures, including two-dimensional graphene, one-dimensional carbon nanotubes, and zero-dimensional carbon nanoonions, is presented. Unique laser-material interactions provide versatile possibilities in fabricating carbon nanostructures, including localized heating, direct laser writing, tip-enhanced optical near-field effect, polarization, ablation, resonant excitation, precise energy delivery, and mask-free direct patterning. Rapid single-step fabrication of graphene patterns was achieved using laser directing writing. Parallel integration of single-walled carbon nanotubes was realized by making use of tip-enhanced optical near-field effect. High-quality carbon nanoonions were obtained through laser resonant excitation of precursor molecules.