română NASTASIA SACA , MARIA GEORGESCU
Abstract
The behaviour of the blended cements, containing limestone filler in corrosive environments is an important aspect for assesing the durability of concrete prepared with such cements having a diminished „clinker factor”. Such cements are of great interest from economic and environmental point of view. The present paper provides information regarding the behaviour of blended cements, with 10-40% limestone filler (Blaine specific surface area of 4600 cm2/g and 7000 cm2/g respectively), immersed into 5% MgSO4 solution, from 28 to 580 days.
X-ray diffraction (XRD) and scanning electron microscopy (SEM+EDAX) data allow the formulation of some possible interactions that occur between the binding matrix and sulphate solution. As a result of such reactions some hydrates as gypsum, ettringite, brucite are formed. Corrosive processes are carried out progressively from the surface towards the inside of the samples, which involve compositional and structural differences between the two areas. The corrosive effect of MgSO4 solution is highlighted by the decreasing in mechanical strength of the mortar samples for long period of exposure, up to 580 days.
The behavior of mortars in magnesium sulfate solution seems to be positively influenced by using finer limestone filler (Blaine specific surface area of 7000 cm2/g), due to a higher compactness for samples.
Keywords
limestone filler, sulfate corrosion, mechanical strength, X-ray diffraction, scanning electron microscopy SEM
MARIA GHEORGHE, NASTASIA SACA, LIDIA RADU, RACHILA IEREMIE
Abstract
This paper reports on the results of a research about utilization of inorganic sludge (IS) produced by paper industry as cement and fine sand substitute secondary raw material in concrete. The inorganic sludge IS valorization as cement partial substitute into concrete has been supported by experimental data concerning the pozzolanic potential evaluated by Al and Si content of IS waste compounds solubility into leachant of pH=12 and by the compressive strengths time evolution. The concrete samples with the addition of inorganic sludge from paper industry have been characterized by overtime variation of the following characteristics: water absorption, dimensional changes, compressive and flexural strengths. There have also been determined leaching properties by monolithic leaching test. The evolution of the physical and mechanical characteristics suggest the inorganic sludge can be used as a substitute for fine sand in concrete in an amount up 50%, and / or substitution of up to 20% cement. The heavy metal leaching properties measured by the concrete monolithic samples leaching test with the highest content of IS, showed a heavy metal Pb, Cr and Cu release trend diminishing during time, after a logarithmic plot.
Keywords
Inorganic sludge from paper industry, pozzolana, concrete, leaching, mechanical properties
MARIN AMĂREANU
Abstract
The investigations suggested by the objective of this work are focused on the calculation of the confinement pressure, for concrete structural elements with circular section, and of the effective lateral compression stress at the ultimate limit state (ULS) due to the confinement of these elements with carbon fiber fabric. The paper also refers to the execution and consolidation of concrete structural elements by confinement with carbon fiber fabric, so that following the concrete structural elements tests for obtaining the mechanical strength values, these would be comparable with the ones obtained from the calculation.
Keywords
confined concrete, mechanical strength, design calculation
WENZHONG ZHENG, BAIFU LUO, SHUANG LU
Abstract
This paper presents the effect of temperature on mechanical properties of reactive powder concrete (RPC) at elevated temperatures. The influences of temperatures, polypropylene (PP) fibre and steel fibre content, hold time, dimension of specimens and explosive spalling were investigated. The microstructure of RPC was identified by scanning electron microscope (SEM). The experimental results show that adding 2% steel fibres and 0.2% PP fibres can prevent explosive spalling and significantly increase compressive and tensile strengths of RPC. PP fibre and steel fibre content played an important role in failures modes, explosive spalling, compressive strength and tensile strength. Cube compressive strength decreases at 100°C, increases between 200 and 500°C, and decreases beyond 600°C. Tensile strength decreases at 200°C, increases from 200 to 300°C, and decreases beyond 300°C. Pores and small channels created are beneficial for mitigating the explosive spalling at elevated temperatures.
Keywords
elevated temperature, reactive powder concrete, mechanical properties, explosive spalling, hold time
KSENIJA JANKOVIC, ANDJELIJA ILIC, MARKO STOJANOVIC
Abstract
The investigation of posibilities of concrete structure modification by silica fume to improve concrete properties was presented in this report. Percentage of silica fume in regard to cement varied between 0% and 20%. Concrete was cured as follows: in water, steam – curing regime at +60oC and +90oC. The results of the compressive and tensile strength, freeze / thaw resistance with de-icing salts, and depth of penetration of water under pressure.
Keywords
silica fume, steam – curing regime, concrete durability
ANDREI TIBERIU CUCURUZ, ECATERINA ANDRONESCU, CRISTINA DANIELA GHIŢULICĂ, ANDREIA ILIE
Abstract
The purpose of this study was to improve the knowledge in the field of composite materials based on poly(methyl methacrylate) (PMMA) and silica (SiO2). For this purpose, two types of silica were taken into account: i) silica was synthesised in situu by sol-gel technique and ii) commercial silica was used. In both cases the polymer matrix was obtained by radical polymerisation.
The composite materials were then characterized from the phases point of view by Fourier transform infrared spectroscopy (FT-IR) and X-ray Diffraction (XRD) and from the morphology and compatibility between phases point of view by scanning electron microscopy (SEM).
The results showed that in situu formation of the silica network is preferred over commercial silica addition because it allows a better compatibility between the organic and inorganic compounds.
Keywords
poly(methyl methacrylate), silica, composite material, dental application
SORIN ION JINGA
Abstract
The paper deals with the analysis of LiF single crystals growth conditions in order to establish the main parameters that are involved in the crystal quality. Taking into account the experimental data, correlations between the growing conditions and the single crystals quality used as active media or Q-switches were made. The dependence of the crystals length, fixed as driving property function, on the growth process independent variables was achieved.
Keywords
lithium fluoride, optical materials, Q-switches, high purity, crystal growth
ANDREIA ILIE, ECATERINA ANDRONESCU, CRISTINA DANIELA GHIŢULICĂ, ANDREI TIBERIU CUCURUZ
Abstract
The scope of the present work was to study the release of methylene blue from a composite material based on collagen and hydroxyapatite.
The obtaining of the composite material was achieved by co-precipitation of hydroxyapatite in the collagen matrix (at a pH of 10.5). Later, methylene blue was added dropwise because the composite material is intended to act as support for releasing methylene blue; the release of methylene blue ensuring the antiseptic nature of the material.
The composites were then characterized by: Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) while the release process was monitored by UV-Vis spectroscopy.
The characterization of the collagen/hydroxyapatite composite material revealed a good mineralization of collagen matrix a high stability of the mineral phase, as well as the capacity to bind/absorb methylene blue.
From the point of view of the release process, the results showed a gradual release that was evidenced by UV-Vis spectroscopy, the release evolution being monitored at a wavelength of 663 nm, characteristic.
Therefore, studies suggest the use of collagen/hydroxyapatite composite material as support for tissular regeneration of bone tissue, methylene blue providing antiseptic properties.
Keywords
hydroxyapatite, collagen, drug release, methylene blue
CRISTIAN MATEI, CRISTINA ILEANA COVALIU, BOGDAN ŞTEFAN VASILE, DANIELA BERGER
Abstract
Ceria nanoparticles were synthesized by two different wet soft chemistry routes, the thermal decomposition of a tartrate-based precursor and the reverse microemulsion method. The tartrate-based precursor was characterized by FTIR spectroscopy and thermal analysis, whereas the sample isolated from the microemulsion by X-ray diffraction. The precursors were calcined at 500°C, 3h in air and oxide nanopowders were investigated by X-ray diffraction, transmission electron microscopy and selected area electron diffraction. Ceria sample obtained by decomposition of tartrate-based precursor has nanoparticles in the range of 6 - 12 nm with a slight tendency of agglomeration and a specific surface area of 28 m2/g, whereas the sample synthesized by reverse microemulsion method has nanoparticles of 6 nm average size, with very narrow size distribution, and higher specific surface aria, 68 m2/g.
Keywords
ceria nanoparticles, reverse microemulsion, thermal decomposition method, tartrate-based precursor
CRISTIAN ANDRONESCU, VICTOR FRUTH, ENIKÖ VOLCEANOV, RAREŞ SCURTU, CORNEL MUNTEANU, MARIA ZAHARESCU
Abstract
Sr2+ and Mg2+ simultaneously doped lanthanum gallate (LSGM) powders, prepared by a modified Pechini route using polyvinyl alcohol (PVA) as polymeric alcohol, were densified using an activated microwave technique at 2.45 GHz, to develop a dense stable electrolyte for application in intermediate temperatures solid oxide fuel cells (IT-SOFC). Thermal behaviour of precursors was investigated by means of differential thermal analysis combined with thermogravimetric analysis (DTA/TGA). The powders and sintered samples were characterized using scanning electron microscopy and energy dispersive analysis (SEM-EDAX), X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The thermal expansion coefficient (TEC) and ionic conductivity of the sintered samples were also evaluated. Fine, homogeneous and high density pellets of almost pure LSGM phase were obtained after sintering at 14000C for a short period time in an activated microwave field. Using activated microwave field, due to the volumetric in situ heating, the sintering process is highly specific and instantaneous, leading to a faster kinetics compared to the conventional process (electric oven). With an optimized sintering schedule, a fine grained and dense microstructure of the samples were obtained.
Keywords
solid electrolytes, LSGM, microwave technique, IT-SOFC
MARIA SONMEZ, DENISA FICAI, ANTON FICAI, LAURENŢIA ALEXANDRESCU, GEORGETA VOICU, ECATERINA ANDRONESCU
Abstract
In this paper, the technology for obtaining polypropylene (PP) based composite materials reinforced with functionalized glass fibers (GF) is described. In the first step, glass fibers were functionalized by hydrolysis/condensation with (3-aminopropyl) trimethoxysilane as functionalization agent and in the second step, these materials were compounded at 180oC in a Brabender mixer with isotactic polypropylene. The obtained composites were morphologically and structurally characterized by X ray diffraction (XRD), infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Based on the obtained results it can be concluded that GF functionalization leads to a better glass fiber - polymer interaction, GF being covered by an intimate PP film.
Keywords
glass fibers, polymer composites, glass fibers functionalization
TIBERIU PASCU, DAN GEORGESCU
Abstract
Determination of performance of materials for repairing of concrete must be based on experimental research. It should, on the one hand, individual testing of the properties of the various materials for repairing of concrete and, on the other hand, testing the properties of concrete repair systems, made up of individual materials previously tested, especially in the case of specific applications. This paper presents in particular the test methods and results of experimental researches carried out.
Keywords
concrete, repair systems, test methods
Formation of alpha-C2S hydrate in the mixtures with CaO/SiO2=1.75 by hydrothermal treatment at 2000C
KESTUTIS BALTAKYS, TADAS DAMBRAUSKAS, RAIMUNDAS SIAUCIUNAS, ANATOLIJUS EISNAS
Abstract
The parameters of α-C2SH hydrothermal synthesis from a non-stoichiometric composition of CaO and SiO2·nH2O mixtures (the molar ratio CaO/SiO2 = 1.75) in unstirred suspensions were determined and a sequence of intermediary compounds formation was examined and explained. It was evidenced that α-C2SH is formed already after 4 h of hydrothermal treatment at 2000C. However, together with this compound a fair amount of some intermediary compounds (C-S-H(I) and C-S-H(II)) are formed. It was determined that after 24 h of hydrothermal treatment, α-C2SH starts to recrystallized into kilchoanite which dominates in the products after extending the duration (48-72 h) of synthesis.
Keywords
α-C2S hydrate; calcium silicate hydrate (C-S-H); hydrothermal synthesis; kilchoanite
DOREL RADU, CORINA MITU
Abstract
The formation and the properties of the oxide compounds are determined by intrinsic factors (depending on the reactants) and extrinsic ones (the reaction conditions). The formation reactions are defined by a series of thermodynamic functions. In this paper we highlight the correlation between the Gibbs free energy of formation, the reaction energy and the basicity of the reacting oxides, respectively, evaluated through the basicity percentage, pB, in % in the CaO - SiO2 system.
At the same time, for a series of properties (interaction with water, hydration degree, mechanical resistance to compression, shrinkage) of some mineralogical constituents of the Portland cement clinker it is highlighted their interdependence with basicity.
Keywords
basicity percentage, standard free energy of reaction, properties of oxide compounds, properties of clinkers.
MIHAI EFTIMIE, IOANA ŢACU
Abstract
Our experiments on the recovery of the glass waste resulted from cathode ray tubes - CRT were focused to designing compositions of glass-ceramic from glass waste with possible applications in composite materials. The recipes were calculated using as much waste as possible, using various nucleating agents and varying percentages, showing in this study the influence of ZrO2. The report of CRT glass used for the neck:funnel:panel components were 5:30:65%, identical to the ones in CRT. We determined the following physical and mechanical properties: density, porosity, absorption, thermal expansion, hydrolytic stability. In order to characterize in terms of compositional and microstructural, the analyses were carried out by X-ray diffraction and scanning electron microscopy measurements, showing the influence of the nucleating agent and thermal treatment temperature on the properties of the glass ceramics.
Keywords
glass-ceramics, cathode ray tubes, waste, composites
GEORGETA VELCIU, ALINA MELINESCU, VIRGIL MARINESCU, VICTOR FRUTH, RAREŞ SCURTU, MARIA PREDA
Abstract
Four compositions in the range of 85-90 % CeO2, the other being SrO, CaO or 2O3 combined two or three were studied. The mixtures have been homogenized by a wet route for 10 hours. After drying the obtained powders were subjected to thermal analysis which showed that in the process of grinding chemical changes occur. The apparent and relative densities were measured on the samples sintered at temperatures of 1350 and 14000C resulting that the relative densities of the samples are between 79 and 92%. X-ray diffraction revealed that the main mineralogical compound of the samples, thermally treated in the range of 1300-14000C, is a solid solution with a structure of fluorite type specific to CeO2. For some samples were also identified CaY4O7 and SrCeO3, compounds resulting by solid-phase reactions and two solid solutions of the type SrCe0,85Y0,15O2,95 and (Ce,Y)2O3.The microstructure of the studied samples was investigated by electron microscopy and the results showed that the samples exhibit rounded and needle-shaped grains of different sizes. Electrical measurements have shown that three of samples have a corresponding behavior to solid electrolytes usable for IT-SOFC cells.
Keywords
solid electrolytes, LSGM, microwave technique, IT-SOFC
LAVINIA POPESCU, FLORIAN ZAMAN, ENIKÖ VOLCEANOV, MARIANA ENE, MIHAELA ULMANU, ILDIKO ANGHER
Abstract
The development of an analysis methodology with embedded identification of significant issues regarding the use of steelmaking slags from secondary metallurgy in agriculture for acidic soils improvement leads to "elimination” of "waste" term assigned for Ladle Furnace (LF) slag and determines its conversion into useful by-product and environmentally friendly. This paper analyzes comparatively three Romanian sources of LF slag:
1) a steel manufacturer for power industry equipments fabrication (Source 1) ,
2) an alloyed steel manufacturer for the obtaining of rolling stocks (Source 2),
3) a steel manufacturer as long semi-finished forms (Source 3).
Each of these sources (companies) have specific characteristics of the steel manufacturing and LF slags storage which have been investigated in the paper in an attempt to exploit them as secondary resources to obtain materials for acidic soils amelioration.
Keywords
environmental management, recycling, ladle furnace, white slag, acid soil amelioration, lime
ABDELAALI RAHMOUNI, ABDERRAHIM BOULANOUAR, MOHAMED BOUKALOUCH, ABDERRAHIM SAMAOUALI, YVES GERAUD, JAMAL SEBBANI
Abstract
Physical properties of rocks are measured and analyzed, and their relationships are discussed in this paper. Permeability and mercury porosimetry methods, porosity, and pore size distribution are determined. Furthermore, bulk and particle densities of rocks are determined. The morphology of the porous medium has been approached by mercury porosimetry which gives an appearance to the pore distribution of the material. The permeability of a variety of natural materials is characterized using a relatively new laboratory apparatus. Permeability and porosity are in close relation, and it could be assumed that its relationship is linear, i.e., with increasing porosity, permeability increases as well. This relationship is influenced by other rock properties, such as the amount of open and closed pores within the rock sample, size, and distribution of pores. From this point of view, it is necessary to study these physical properties of natural materials as well, because this enables an overall analysis of rocks and their possible use for construction.
Keywords
rocks, permeability, porosity, mercury porosimetry, bulk density, TinyPerm II
Y.EL RHAFFARI, M. HRAITA, A. SAMAOUALI, M. BOUKALOUCH, Y. GERAUD
Abstract
This paper presents a study on the thermal and petrophysical characteristics of porous calcarenites, sampled from a quarry located near the historical monument of Chellah (Rabat).
We measured the thermal conductivity using box method and Thermal Conductivity Scanner (TCS). The sample’s thermal conductivity map generated by exploiting the values produced by (TCS), gives a clear view of the thermal heterogeneity of the studied rock.
The measurement of mercury intrusion porosimetry shows two porous networks (macropores and micropores); the value of porosity is between 16,52% and 34,9%. We have also found that porosity is one of the main parameters that control the transfer of heat in the calcarenites of Rabat.
Keywords
calcarenites, thermal conductivity, mercury intrusion porosimetry, box method, TCS method
MIHAI BRATU, OVIDIU DUMITRESCU, OVIDIU VASILE, ALINA CONSTANTIN (CRISTEA), MARCELA MUNTEAN
Abstract
Noise is a ‘non-periodic sounds’ complex which affects biological and psychological state of people and other natural organisms. The present paper is dedicated to some new polymeric composites with sound-absorbing properties. The originality consists in obtaining new polymeric composites from formaldehyde resin and various waste types used as reinforcing agents. The sound-absorbing capacity of the new composites varies depending on the proportion of waste used. The absorbing coefficient is presented for each sample; it depends on the porosity of the composite material obtained at the interface between the matrix and reinforcing agent.
Keywords
sound-absorbing properties, wastes, absorbing coefficients, porosity, interface
ADRIAN STROIA, CRISTINA ILEANA COVALIU, CRISTIAN CĂPITĂNESCU, GABRIELA GEORGESCU, IOANA JITARU
Abstract
Lucrarea de faţă prezintă sinteza unui nanomaterial Ni/Ag care a fost obţinut într-un sistem argint macroporos granular (suport) – carboxilat de Ni– alcool benzilic. Produsul sintetizat a fost caracterizat chimic şi structural prin următoarele tehnici de caracterizare: spectroscopie de absorbţie atomică (AAS), difracţie de raze X (XRD), spectroscopie de infraroşu cu transformată Fourier (FTIR), microscopie electronică în transmisie (TEM), spectroscopie de razei X cu dispersie de energie (EDX) şi măsurători ale magnetizaţiei. Materialul prezintă proprietăţi feromagnetice datorate conţinutului de Ni şi poate avea aplicaţii electrochimice şi / sau catalitice.
Keywords
macroporous silver, nickel carboxylates, Ni/Ag nanomaterial.
MIHAELA NORIŞOR, EDUARD MINCIUC, ROXANA PĂTRAŞCU, GEORGE DARIE, DIANA TUTICĂ
Abstract
The aim of the paper consists in optimising the integration of CO2 post-combustion capture technology using chemical absorption within the fluidised circulating coal combustion (FCCC) with direct application in glass and cement industries. The authors have performed some comparison of the effects of using primary amines (MEA) and tertiary amines (TEA) in order to reduce energy consumption of regeneration process, and, at the same time, keeping the efficiency of CO2 capture over 85 %. The paper presents results of an experimental study using laboratory equipment for fluidised circulating coal combustion, and also simulation results of CO2 post-combustion capture using specialised software HYSYS 3.2.
Keywords
Cuvinte cheie (engleza)
SORINA STROE, VLAD NAICU, ION PĂTRAŞCU
Abstract
The main objective of our research was to evaluate the PRF potential in bone regeneration of the periodontal bone defect. Using platelet gel for improving bone regeneration is a recent technique in oral surgery and implantology. In this study, based on casuistry, we have evaluated PRF’s local effect combined with the autogenous graft and freeze-dried bone allograft in order to improve bone regeneration in periodontal bone deficiency.
The personal study was accomplished on 5 subjects with various sized periodontal bone deficiencies. From the treated lot, we have selected the most significant clinical case, having an important bone defect in the maxillary frontal area. In the treatment lot we have resolved 3 clinical cases where we have applied peri implantary a mixture of synthetic bone and PRF, plus PRF superjacent membranes. We accomplished a sealing and colonization of the bone defect with the most biocompatible material, assuring quick local bone regeneration and healing. The mixture of PRF – autogenous bone and membrane (PRF), were also used to augment the sinus floor needed for the procedure of elevating the maxillary sinus.
Keywords
platelet concentrate, periodontal defects, maxillary sinus elevation
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Year
2014
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Issue
44 (2)
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Pages
189-194
SORINA STROE, VLAD VASILESCU, CLAUDIU CĂLIN, ION PĂTRAŞCU
Abstract
The working hypothesis on the interaction between the addition biomaterial – peri implant bone is based on the idea that current addition biomaterials based on ceramic and / or collagen form de novo bone interface, are biocompatible and biointegrable. It was evaluated which of the products has the highest clinical success rate and is approaching the gold standard - autogenous bone. Quantitative and qualitative characteristics, determined from histological regeneration of bone, secondary to the application of an autogenous transplantation, namely the addition of different types of biomaterials are reflected by biological reactivity of each implant and systemic reactivity. Results of the osteoscintigrafical investigations necessary for the exposure of the osteogenesis process dynamics are useful when correlated with histological results also with the integration of the implant and new bone formation. The process of "osteostimulation" occurs when an implanted substance influences the osteoreparation, inducing the formation of bone tissue in the periodontal bone defect. So, an experimental study was conducted to test the capacity of some addition biomaterials to induce new bone growth, using the electronic sweeping microscope and EDS spectroscopy as methods to analyze the process of osteointegration.
Keywords
EDX, biomineralization, osteointegration, bone de novo
RADU CONSTANTIN VOINIŢCHI, VIOREL CRĂCIUN, CONSTANTIN DORINEL VOINIŢCHI, ALINA BĂDĂNOIU, GEORGETA VOICU
Abstract
In order to improve the properties of recycled aggregate resulted by the crushing of concrete from construction and demolition waste stream, a thermo-mechanical treatment was applied. This treatment, performed in a muffle furnace and a Los Angeles machine, simulates the conditions specific for a rotary kiln. Recycled concrete aggregate (RCA) was obtained by the crushing of a concrete C20/25 class. The crushed concrete aggregate (RCA), the one resulted after the thermo-mechanic treatment of RCA and the initial natural aggregate where compared from the point of view of physical properties (apparent and bulk densities). A good efficiency of thermo-mechanic treatment was appreciated based on these results.
New concretes were prepared using the recycled concrete aggregates (before and after thermo-mechanic treatment) in order to determine the density and compressive strength. Thus, the compressive strength values, determined on concrete prepared with recycled concrete aggregates subjected to thermo-mechanical treatment, are similar with those prepared with natural aggregate.
The thermo-mechanic process applied for the removal of cement paste/mortar adhered to natural aggregate grains is a possible solution for the improvement of recycled aggregates quality.
Keywords
recycled aggregate, thermo-mechanic treatment, concrete
ANJA TERZIĆ, LJUBIŠA ANDRIĆ, MILAN PETROV, ZAGORKA RADOJEVIĆ, LJILJANA MILIČIĆ
Abstract
Four types of refractory concretes were studied at various temperatures ranging from ambient to adopted maximal 1400°C. The concretes had same matrix composition: K concretes were based on corundum aggregate; B concretes were based on bauxite aggregate and chamotte filler; while K2 and B2 concretes had 30 % of fly ash replacement in bonding agent. Fly ash was mechanically activated by means of planetary ball mill. Samples were dried at 110°C during 24 hours to create standard specimens. Afterwards, the samples were preburned at 1100°C and subsequently subjected to compressive uniaxial creep test conducted at various temperatures (1200, 1300 and 1400°C). Thermal behavior was also investigated by dilatometry analysis starting from room temperature up to 1400°C. The evolution of the refractory concretes behavior from quasi-brittle to visco-plastic was investigated and correlated to their microstructure evolution induced by sintering process. The influence of the burning temperature and procedure duration on the concretes behavior is also discussed. Creep test and dilatometry analysis helped in defining of the sintering mechanism and its parameters, and additionally explained deformation nature of the refractory concretes.
Keywords
sintering, thermal treatment, composites, thermal properties, environment
ALEXANDRINA CUIBUŞ, ZOLTAN KISS, MARIA GOREA
Abstract
This study presents the physical-mechanical characteristics of the concretes (7 compositions) accomplished with 10% fly ash (FA), 10% metakaolin (MK), 10%FA+10%MK, 10% silica fume (SF), 10% SF+10%FA, 10%SF+10%MK additions by substitution of 10% respectively 20% cement. According to the analysis performed on the fresh concrete - density, slump, flow and entrapped air volume, this concrete is of normal volume mass concretes type. The compressive strengths of the concretes with additions of fly ash, silica fume and metakaolin to 28 days are closely to those of the reference concrete i.e. 55.01 MPa, or even higher. The flexural tensile strengths are higher after longer hardening periods of time, except the 10% FA + 10% MK concrete composition (S-4). The elasticity modulus, for all the studied compositions, has higher values than the minimum allowed value for C35/45 concrete class. The experimental studies showed that the reduction of the cement quantity in the concretes, without altering the properties, is possible by using of some industrial byproducts or wastes (fly ash or silica fume) and fired clay(metakaolin).
Keywords
concrete, fly ash, metakaolin, silica fume, pozzolan
NICOLAE ŢĂRANU, SERGIU POPOAEI, GABRIEL OPRIŞAN, PAUL CIOBANU, PETRU MIHAI, VLAD MUNTEANU
Abstract
The paper presents the results of a study including experimental tests and numerical modelling performed to investigate the influence of the edge distance and of the tightening torque on the behaviour of steel bolted lap joints of composite plates made of glass fibre reinforced polyesters (GFRP) manufactured by pultrusion.
The experimental program analysis and testing of eighty samples corresponding to four assembly configurations with a variable number of bolts, with different marginal distances and two steps of tightening torques.
Numerical models based on finite elements using ANSYS software package were designed for each assembly configuration tested experimentally, and the obtained results on bearing capacities for the studied joints have been compared.
Keywords
glass fiber reinforced polyesters, pultruded elements, bolted joints, bearing failure
BAO-MIN WANG, YUAN JIA, TING – TING ZHANG
Abstract
The ability to resist at chloride ion penetration and compressive strength of ocean high performance concrete (HPC) with nano-SiO2 (NS) addition was studied. The 6 hours direct current coulometry method (6-hours DC Method) in ASTM C1202-97 was adopted. The experimental results show that the ability to resist at chloride ion penetration of HPC including NS is heightened effectively, the charge through high-performance concrete with 3%, and 5% NS is reduced with 5% and 15% respectively, and the ability to resist at chloride ion penetration can be heightened gradually with of the age; the charge through high-performance concrete with NS decreases with reducing of W/B of concrete.
Keywords
nano-SiO2(NS), ocean engineering, high performance concrete(HPC), chloride ion penetration, compressive strength
MÜNIR TASDEMIR, SEZGIN ERSOY
Abstract
In comparison to metals, generally unfilled polymers have low thermal conductivity and low wear resistance. Therefore, various filler and reinforcements are frequently added to the unfilled polymers to improve their tribological and thermal properties. So, filled polymers are preferred for many industrial sectors such as aircraft, automotive, electrical/electronic and household application. Friction and wear behaviour is one of the most important properties of polymer and its composites. Therefore, many studies on friction and wear properties of polymer and its composites have been carried out.
In the present work, the friction and wear properties of high density polyethylene/talc and high density polyethylene/calcite polymer composites were studied. Fillers proportions in the HDPE were 5, 10, 15, and 20 wt%. The morphologies of the fracture surfaces of specimens were observed with a scanning electron microscopy (SEM). The result showed that the addition of fillers to the composite changed the friction coefficient and wear rate. For a specimens, wear loss increases with increasing load and sliding distance; meanwhile the friction (static and dynamic) coefficient increases. Wear rate of all HDPE composites is larger than that of pure HDPE. The static and dynamic friction coefficient of HDPE/talc (80/20) composite is slightly less than that of pure HDPE at each load. The modulus of elasticity, elongation, Izod impact strength and hardness values of the composites were also determined.
Keywords
Friction and wear performance of HDPE-talc-calcium carbonate polymer composites against sliding distance and applied load
ALIONA ILJINA, KESTUTIS BALTAKYS, MARIUS BALTAKYS,RAIMUNDAS SIAUCIUNAS
Abstract
In this work the possibility of neutralizing or removing compounds containing fluoride ions from waste silica gel was investigated. The elution of F– ions from waste silica gel to the liquid medium was performed under static and hydrothermal conditions. It was determined that waste silica gel consists of silicon dioxide (77.77%) and other compounds containing 8.64% F– and 4.03% Al3+ ions, which are stable during the drying process (500C; 48 h). It was determined that under static elution conditions it is possible to remove only 6–7 wt. % F– ions into a liquid medium from waste silica gel. It was found that CaO additive has a positive influence on the decomposition of AlF3·3H2O and the formation of CaF2. It was found that silica gel is a prospective raw material for synthesis of Z-phase because the kinetics of compound formation is faster than in pure mixtures. A principal technological scheme has been designed for waste silica gel neutralization and utilization by using Ca(OH)2 under static or hydrothermal conditions.
Keywords
silica gel, waste, fluoride, aluminum fluoride trihydrate, neutralization
LORETTA BATALI, HORAŢIU POPA, GHEORGHE PANTEL, NATALIA BUTNARCIUC, ERNEST OLINIC, SANDA MANEA
Abstract
Construction materials made of polymeric fibres (geosynthetics) are a viable alternative to traditional materials (concrete, granular materials) as proven the last years. Their use in association to mineral materials as soils or granular fills leads to composite materials having improved physical and mechanical properties and allowing to build more efficient structures both from structural and environmental point of view. Paper presents the main aspects related to physical and mechanical properties of geosynthetics, the main applications, focusing on reinforcement, filtration and drainage functions. It presents the various interactions between geosynthetics and mineral materials and the properties of the resulted composite material.
Keywords
geosynthetic, mineral material, composite material, physical properties, mechanical properties, laboratory tests
DANIELA COVACIU ROMONŢI, GEORGETA VOICU, DANIELA IONIŢĂ, IOANA DEMETRESCU
Abstract
CoCrMo alloys are extensively used in tissue engineering in both dental and orthopaedic applications and are highly recommended due to the good ratio quality /price comparing with other metallic biomaterials. The present approach is related to electrodeposition of fluoridated phosphate masses with good ratio calcium to phosphorus close to the one existing in bone.
SEM and EDX analysis confirm that the electrochemical method for deposition of fluoridated apatite on CoCrMo is efficient and the results were quantified using electrochemical and mechanical measurements.
Keywords
CoCrMo alloys, electrochemical deposition, SEM, EDX, artificial saliva, physiological serum
IRINA FIERĂSCU, RADU CLAUDIU FIERĂSCU, RODICA MARIANA ION, CONSTANTIN RADOVICI
Abstract
Most of the artefacts of cultural and / or historical value are exposed to fungal attack often causing irreversible damage. The need for new methods of antifungal protection led to the development of a recipe based on hydroxyapatite and barium hydroxide, with promising results. We synthesized and analytical characterized (trough energy dispersive X-ray fluorescence, X-ray diffraction and Fourier transform infrared spectroscopy) several materials based on hydroxyapatite. The efficiency of the synthesized materials was evaluated by diluted inoculums on the culture media technique and a modified Kirby-Bauer method, using simulated artefacts, previously reported to replicate the real artefacts.
Keywords
artefacts, biodeterioration, hydroxyapatite, X-ray methods
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Year
2014
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Issue
44 (3)
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Pages
292-297
HERI SUTANTO, ILS NURHASANAH, H. HADIYANTO
Abstract
The objective of this research was to study the change of Mn mole fraction to the structure and magnetic properties of GaN:Mn thin film by sol-gel method. A thin film ferromagnetic semiconductor of GaN:Mn has been deposited on Si(111) substrate by using Chemical Solution Deposition method (CSD) and spin coating technique. Atomic composition, crystal structure, morphology and magnetic properties of the GaN:Mn thin film were characterized using Energy dispersive of X-ray (EDX), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Scanning Probe Microscopy (SPM) and Vibrating Sample Magnetometer (VSM). The results showed that the GaN:Mn thin film still contains carbon atom impurity and non-stochiometri. The GaN:Mn thin film has polycrystalline form in which the 2θ angle of GaN peaks have been shifted (~ 0.22o) for that with Mn composition of 5.24% at 32.62° angle. SEM and SPM investigation show the surface of GaN:Mn thin film with 6% Mn distributed by homogeneous grains and the level of surface roughness was 15.3 to 29.90 nm. However, the other magnetic phases (Ga5.2Mn) and oxide phases of Mn, Si and Ga were also detected in the GaN:Mn thin films. Sample with 7.43% Mn exhibits optimum composition results in appearance of ferromagnetic properties. The remanent magnetic (Mr) and saturation magnetic (Ms) of sample were achieved at 5.04 emu/cm3 and 91.5 emu/cm3, respectively.
Keywords
GaN:Mn; Chemical Solution Deposition; spin coating; Si(111) substrate; magnetic properties; ferromagnetic
MARIAN DIMA, CĂTĂLIN FRÂNCU
Abstract
This paper presents a method, tested experimentally by designing a stand for fatigue testing of glass fibre reinforced polymer composites (GFRPs) with polyester matrix used in construction. The test is carried out by applying a repeated stress (0 to max) cycle load. Through operating parameters of the stand the method allows the testing of joints (adhesive or mechanical) between parts of composites. The stand is designed for simultaneous testing of six samples and is characterized by high energy efficiency with a power of only 5.5 kW as opposed to 65 kW as required by a classical tensile testing machine with hydraulic drive.
Keywords
composites, fatigue testing, joints testing, repeated stress cycle load
LUMINIŢA DANIELA URSU, ILEANA CRISTINA VASILIU, IONUŢ FERARU, LUCICA BOROICA, BOGDAN ALEXANDRU SAVA
Abstract
Present paper presents a study of the colorful glasses in the SiO2-Na2O-B2O3-K2O-ZnO system, to which there were added the borosilicate glass waste and copper oxide or nickel oxide from the sludge obtained from the electrochemical deposition industry. The use of borosilicate waste glass (that comes up with important components such as B2O3, CaO, Al2O3), leads to saving of raw materials and energy while being sustainable at the same time. Structural studies of the obtained vitreous materials were made, using FTIR and Raman spectroscopy. FTIR absorption maxima and Raman shifts were identified and discussed according to literature data.
Keywords
decorative glass, borosilicate cullet, copper containing sludge, nickel wastes, ftir, raman spectroscopy
NICOLAE ŢĂRANU, PAUL CIOBANU, SERGIU POPOAEI, PETRU MIHAI, MIHAI BUDESCU, VLAD LUPĂŞTEANU
Abstract
În această lucrare se analizează din punct de vedere teoretic, experimental şi prin modelare numerică, răspunsul structural al unor grinzi din beton armat consolidate cu fâşii înguste din compozite polimerice armate cu fibre din carbon (CPAFC), montate în zona din imediata apropiere a feţei întinse (NSM). Probele consolidate au fost testate la încovoiere sub încărcare monoton crescătoare până la cedare. Inserţia fâşiilor înguste din CPAFC a condus la o creştere semnificativă a capacităţii portante la încovoiere, de până la 220% şi la o reducere a deplasărilor transversale maxime de până la 49%, în comparaţie cu grinzile de control, neconsolidate. Validitatea rezultatelor experimentale a fost verificată analitic şi prin modelare numerică, utilizând programul pe bază de element finit ANSYS.
Keywords
reinforced concrete beams, carbon fibre reinforced polymer composites, strengthening with composite strips, structural response, numerical modeling
P.VALDEZ, R.X.MAGALLANES-RIVERA, A. DURÁN-HERRERA, C.A. JUÁREZ, G.FAJARDO
Abstract
Results of interrelated tests for physical-chemical and microstructural properties of four synthetic pozzolanas evaluating the hydration rate in blends with calcium hydroxide are presented. The pozzolanic activity of silica fume, classified fly ash, raw fly ash and commercial metakaolin was estimated. Results showed a clear relationship between the calcium hydroxide consumption and the reactive phase content, specific surface area and porosity of the pozzolans. The calcium hydroxide-silica fume blend consumed 98% of portlandite after 21 days, whereas the system with metakaolin also presented an effective pozzolanic activity with 94% depletion. The fly ashes were the less effective pozzolans of the study.
Keywords
D. Pozzolans; D. Mortar; C. Mechanical properties; B. X-ray methods; B. Porosity
ALIREZA FIROOZFAR, SEYED MAHDI SAJJADI, MOHD ZULKIFLI BIN MOHD YUNUS, SEYED AMIR HOSSEIN BEHESHTI, TAHA MEHMANNAVAZ
Abstract
Research on ways to increase the resistance of weak soils to build structures on it has been increased in recent years. The present article provide the effects of different mixtures containing microsilica, cement, polypropylene waste fiber and dune sand on mechanical parameters such as, compressibility, compressive strength, bending strength and durability characteristic. In this study also is investigated evaluation the effect of road subgrade based on proposed material. The used dune sand in this research was obtained from Kashan city where is located in central desert of Iran. The obtained results show that the microsilica and cement could play a major role in reducing the cost and required time for building roads and also building foundation on these types of soils.
Keywords
dune sand, fiber, cement, microsilica, stabilization
Y.A. SORVACHEVA, T.M. PETROVA, A.V. POLETAEV, E.Y. CHISTIAKOV
Abstract
Accelerated tests were conducted to evaluate the potential reactivity of one of the potentially dangerous aggregates from the point of view of combination with high alkaline cement with the measurement of linear expansion deformations in order to study the impact of nano-silica on the process of alkaline corrosion of the concrete and formation of cement matrix. It was revealed by using electron microscopy that the addition of nano-silica in concrete mixture promotes the formation of alkali-silica gel in the cement matrix, but not in the pores of the sample, which contributes to slowing, but not prevention of an alkaline corrosion of concrete.
Keywords
Alkali-aggregate reaction, nano-silica, reactivity aggregates, durability
R. RAMAMOORTHI, P.S. SAMPATH
Abstract
This paper presents the investigations of thermo mechanical and free vibration properties by reinforcing halloysite nanotube (HNT) with various weight proportions (0,2,4,6,8, and 10wt%) in glass fiber reinforced epoxy (EP/GF/HNT) nanocomposites. Theoretical study was also carried out to study the vibration characteristics of EP/GF/HNT nanocomposites. It was found that the addition of HNT improved the thermo-mechanical and damping properties. Dynamic mechanical analysis showed an increase in the storage modulus and glass transition temperature up to 4wt% of HNT. Vibration analysis proved that the addition of HNT enhanced the internal damping and increased the natural frequency up to 4wt%.
Keywords
Composites, HNT, Epoxy, Vibration, Damping , DMA
MOHAMMED HRAITA, YOUNES EL RHAFFARI, ABDERRAHIM SAMAOUALI, YVES GÉRAUD, MOHAMED BOUKALOUCH
Abstract
This article consists in studying the petrophysical, petrographical, mineralogical and structural properties of implemented stones. Our study was conducted on one of the stones most commonly used in building monuments of coastal cities in Morocco, particularly in the Rabat-Salé region: the Plio-Quaternary calcarenite. This work is a first phase of a more overall study taking into account the severe conditions to which these building materials were subjected. At this level of advancement, no expertise can be conducted. A good knowledge of various calcarenite stone characteristics allows to better understanding the alteration mechanisms of this material and to consider solutions limiting their progress. So, we have also chosen to work on unaltered samples taken from the original quarry. Experimental analysis performed on sample fragments of unaltered calcarenite rock using the X-ray diffraction (XRD) and the Scanning Electron Microscopy (SEM) observations, allow characterizing the stone both from the mineralogical and the structural point of views. Moreover, the pore size distribution according to pressure-volume analysis has been established by using the mercury intrusion porosimetry method. We will also present petrophysical results concerning the imbibition kinetics, thermal conductivity and permeability for tests performed on specimens taken parallel and perpendicular to the sediment bedding.
Keywords
calcarenite rock, mercury porosimetry, XRD, SEM, TCS, permeability, historical monuments
VERGIL MURARU, ION PIRNĂ, CORNELIA MURARU-IONEL, GHIŢĂ IONIŢĂ, PETRU CÂRDEI, IOAN GANEA
Abstract
The paper presents studies regarding variability of soil chemical properties in Romania. Determination of soil physical and chemical properties is performed using laboratory instrumentation. The soil samples are taken directly from the field using specific instruments. The samples are generally stored in airtight plastic bags and vacuumed eventually. They are transported to the laboratory in order to be analysed or the analysis is immediately made with the aid of some portable analysers It is possible to increase the number of the soil samples and accuracy using VIS–NIR (Visible - Near Infrared Spectrophotometry) and scanning of agricultural surfaces with the aid of specialized equipment that simultaneously can scan the optical properties of the soil, temperature and soil moisture, all being stored in data files. Information obtained from a GPS device is added to files. In this way, the information is geospatial located in order to be also processed in terms of their position. On the other hand, this information can be used after their processing together with other factors to improve the soil quality from agronomic point of view and reducing its pollution. The experimental results on acquiring the soil spectra on a given surface, as well as, the achievement of maps afferent to them are also presented.
Keywords
soil, soil variability,maps,VIS- NIR, GPS, pollution
ERNEST OLINIC, HORAŢIU POPA, SANDA MANEA, LORETTA BATALI, TATIANA IVASUC
Abstract
For the construction of embankments or compacted cushions, the cheapest solution is to utilize the excavated material from the site or from the vicinity. But when the backfilling material is composed of clayey expansive soil it’s use may be impropriate. Expansive soils have a high activity in relation to water and are classified as material “very bad” for the construction of earthworks.
The legislation in force imposes the removal of expansive clays and their replacement with a better material. The high cost of expansive soil replacement has caused the necessity to use a stabilized soil for these constructions.
Keywords
compacting (A), composites (B), mechanical properties (C), expansive soils
OANA STĂNILĂ, DORINA ISOPESCU, NICOLAE ŢĂRANU
Abstract
Fibre reinforced polymeric (FRP) composites have been successfully utilized for strengthening elements made of traditional materials, such as wood. A research program carried out at The Faculty of Civil Engineering and Building Services of Iaşi tested the structural response of wood beams strengthening using carbon fibre reinforced polymeric composites, in different solutions.
The need for realistic analysis of structural behaviour of strengthened timber beams pushed researchers to find analytical and numerical evaluation methods that can correctly replace experimental programs, thus lowering the costs imposed by laboratory tests. The paper presents analytical computations and numerical modelling studies, involving three strengthening methods of timber beams using FRP composites.
Keywords
wood beams, reinforcing, FRP composites, numerical modelling, analytical computation
CRISTIAN OLIVIU BURADA, COSMIN MIHAI MIRIŢOIU, DUMITRU BOLCU, MARIUS MARINEL STĂNESCU
Abstract
In this paper, we have built some new composite sandwich platbands with different core (made of polypropylene honeycomb and polystyrene) and different reinforcement (glass-fiber, carbon-fiber and steel wire mesh). Starting from the dynamic response of these sandwich beams with damping, that are in free vibration, we have established a way to determine the damping factor. We have experimentally determined the damping factor per unit mass for the beams and the stiffness.
Keywords
composite, damping factor, glass-fiber, carbon-fiber, steel wire mesh
DOINA PRODAN, MARIOARA MOLDOVAN, GABRIEL FURTOS, RADU CHISNOIU, VIOLETA POPESCU, OVIDIU PĂSTRAV
Abstract
The root canal sealers have the most important role, being responsable for the final sealing of the tooth root. The novelty elements of this study are represented by the endodontic sealing materials developed-the basic monomer, the coloured bioactive glass, hydroxyapatite in combination with the various metal oxide (all obtained in the laboratory), combining the organic monomers or the inorganic powders, as well as the selection of the appropriate ratio between the organic and inorganic phase and of the optimal polymerization system. All the physicochemical properties of the experimental sealers tested are in accordance with ISO 6876:2001 and the literature data.
Keywords
biomaterials, optical microscopy, endodontic sealers, composites, push out test