română OVIDIU DUMITRESCU, DOREL RADU
Abstract
In order to better understand oxide glass systems, one approach is based on the composition-structure-properties triad.
In the present article, a series of glasses, belonging to the system Na2O-Al2O3-B2O3 has been analyzed. For this analyze, data determined by authors, presented in a previous work, have been used.
Using the experimental determinations of the percentage basicity of glasses, pB, resulting from spectroscopic measurements and also the calculated values, the fractions BO3, BO4, AlO4 and AlO6 have been determined.
Using the experimental data of the measured properties, mathematical functions have been assessed for these, depending on the oxide composition. The values obtained approximate with high confidence the experimental data, thus validating the proposed approach.
Keywords
Na2O-Al2O3-B2O3 glass, basicity, BO3, BO4, AlO4 and AlO6, density, refraction index, thermal expansion coefficient, vitreous transition temperature
ELISABETA VASILESCU , VLAD GABRIEL VASILESCU, ION PĂTRAŞCU, CORNEL FRĂŢILĂ
Abstract
The quality of the biomaterial in implantology is assessed by its ability to allow rapid osseointegration. Tissues react differently to implant depending on the type of biomaterial while the nature of reactions at implant - tissue interface makes a clear distinction between bioinert, biotolerated, bioactive materials. Achieving tissue biointegration requires the presence of a biocompatible material, and also an optimally designed biosurface of the implant. Increasing the biosurface area , possible through various processing methods (mechanical, chemical, electrochemical, etc.), favors the implant osseointegration by the size of the implant - bone contact zone that influence the process of adherence, proliferation and cell growth. This study analyzes the results of the research on the conditions for modifying the surface microtopography of a new material, Ti10Zr bio alloy, by machining, anodic oxidation and acid corrosion and the cell response to surface modification.
X-ray diffraction indicated the presence of oxides TiO2 ( anatase ) and scanning electron microscopy analysis of experimental surfaces processed revealed a special configuration of the surface oxidized , particularly from those obtained by anodizing.
Keywords
bioalloy, citotoxicitaty, biocompatibility, anodic oxidation, biosurface, cell proliferation, cell adhesion
ALIN GIONEA , ECATERINA ANDRONESCU, CORALIA BLEOTU, GEORGETA VOICU
Abstract
The aim of this study is to investigate the influence of different thermal histories and yttrium oxide molar ratio on zirconia dental ceramics properties. Zirconia powders used in this study were stabilized with 2 mol%, 2.5 mol% and 3 mol% yttrium oxide. Final dense ceramics were obtained through hot isostatic pressing at temperature of 1300°C, plateau of 1 and 2 hours, under 150 MPa, in argon atmosphere. Phase composition and microstructure were determined through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Density of specimens was investigated through gas displacement method on a helium pycnometer. Compressive strength and Young’s modulus tests were also performed in order to evaluate the effect of HIP treatment. Finally, the ceramics were tested for biocompatibility, showing good results.
Keywords
ceramics, density, compressive strength, biocompatibility, dental
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Year
2016
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Issue
46 (1)
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Pages
17-24
AZZEDINE BENYAHIA, ALI REDJEM, ZINE EL ABIDINE RAHMOUNI, ABDELLAH MERROUCHE
Abstract
Composite materials based on woven Alfa and unsaturated polyester resins were manufactured by hand layup technique. The Alfa fibers were collected from the M’Sila region (Algeria). Different chemical treatments such as mercerization, permanganate, acetylating and dichromate have been used in order to modulate the mechanical properties of these composites. According to tensile and flexural tests, the treated composites showed better mechanical performances compared to their untreated counterparts. Actually, the permanganate treated fiber-reinforced composites showed 43.02 % of increase in tensile strength and 31.59 % in Young’s modulus, while the acetylated fiber-reinforced composites showed maximum improvement in flexural strength of about 23.80 %. Furthermore, the flexural modulus was also improved by 35.7 % compared to the untreated Alfa fiber composites. FTIR characterization of Alfa fibers showed that the quantity of hydroxyl groups (-OH) decreased and the crystallinity index increase by 20.53% after alkali treatment. SEM observations on fibers surface showed that the different chemical treatments modified the fiber which improved the fiber–matrix adhesion.
Keywords
Alfa fibers, composites, chemical treatment, tensile test, mechanical properties.
NASTASIA SACA, LIDIA RADU, CLAUDIU MAZILU, MARIA GHEORGHE, IONELA PETRE, VIOREL FUGARU
Abstract
The main objective of this work is to identify, based on experimental physical characteristics investigation, the grout types with potential capacity of residual radionuclides stabilization into storage container of low level radioactivity waste (LLW).
The grouts matrix based on Portland cement or special cement with lead slag addition and various fillers (limestone, L or pulverized fly ash, PFA) were carried out with river fine sand or lead slag recycled fine sand. The Portland cement /PFA or L ratios have had values of 30/70; 50/50 and 70/30, and cement/sand ratio was of 1/1.
There were tested on the physical characteristics – fluidity which assesses the filling ability of the LLW storage container, the density which reflects radionuclide shielding capacity, the shrinkage correlated with the microcracking potential and mechanical strengths evolution required of the long time secure LLW management.
Keywords
grout, special cement, lead slag, pulverised fly ash, encapsulation, low level radioactivity waste
MÜNIR TASDEMIR , UMUT YERLESEN
Abstract
In this study low density Polyethylene (LDPE)-based composites are prepared using mussel-oyster shell powder as natural filler. Filler contents in the LDPE were 5, 10 and 15 wt%. The mechanical properties of the polymer composites were investigated. Some mechanical properties of low density polyethylene bio composites have effected much by the addition of mussel-oyster shell powder. For example, the results showed that the elasticity modulus, Izod impact strength, hardness and density of composites improved with increasing the mussel and oyster contents. The addition of fillers to the LDPE changed the wear rate of the composites. LDPE filled with a high level content of mussel and oyster showed higher wear rate than pure LDPE under dry sliding. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM). This study has shown that the composites treated with mussel-oyster shell powder as natural additive and as an inorganic particle-filled polymer will be attractive due to their improved mechanical properties of LDPE.
Keywords
low density polyethylene, mussel, oyster, mechanical properties, wear
IOSIF HULKA , VIOREL AUREL ŞERBAN, DRAGOŞ UŢU, NARCIS MIHAI DUŢEANU, ALEXANDRU PASCU, IONUŢ ROATĂ, IOANA MAIOR
Abstract
Laser cladding NiCrBSi composite coatings were deposited on the surface of stainless steel substrates using different scanning speeds. The influence of scanning speed on dilution rate and the coatings microstructure were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray diffraction. Analysis of microhardness, porosity and the wear behaviour of the obtained coatings were revealed. The coatings were analysed and finally compared to each other. It was found that the microstructure and wear resistance of the coatings were influenced by the scanning speed and dilution.
Keywords
laser cladding, coatings, wear resistance
CRISTINA-ELISABETA PELIN (BAN), ECATERINA ANDRONESCU, GEORGE PELIN, ADRIANA ŞTEFAN, ROXANA TRUŞCĂ
Abstract
In aeronautics applications, there is an increasing interest to replace the use of thermoset matrix in fiber reinforced composites with thermoplastic matrix. This paper presents the obtaining of hybrid carbon fabric reinforced laminated composites based on montmorillonite nanofilled polyamide matrix, using an innovative and cost efficient method involving polymer solvent dissolution, montmorillonite dispersion in different weight contents (1, 2, 4%) relative to the polymer, fabric impregnation with the obtained solution and high temperature pressing. The new laminated nanocomposites were characterized by FTIR spectroscopy to establish nanofiller/polymer chemical interaction, and they were tested in terms of mechanical and thermo-mechanical properties, the fracture cross section being analyzed by SEM and optical microscopy. The hybrid nanocomposites exhibited high mechanical performance, comparable to extensively used carbon fiber reinforced epoxy composites, 4% montmorillonite content generating significant enhancements of both strength and stiffness, as well as heat deflection temperature, results due to both the mechanically improved matrix due to uniformly dispersed montmorillonite, as well a strong fiber/matrix interface due to solvent impregnation processing.
Keywords
carbon fiber fabric, montmorillonite, laminated composites, tensile strength, young’s modulus
A. HADRI, B. FARES, A. AMARI, M. TAIBI , A. MZERD
Abstract
Transparent conducting Al-In codoped ZnO thin films were successfully synthesized onto glass substrates by spray pyrolysis technique. The influence of doping and codoping on the structural, optical and electrical properties was investigated. X-ray diffraction results showed that the samples have the hexagonal Würtzite structure with a preferred orientation toward the c-axis. No peaks belonging to In and Al or their oxides was observed in the limit of XRD technique detection. EDS analysis confirmed the presence of In and Al elements in ZnO thin films. The atomic percentage of In and Al elements was nearly equal to their nominal stoichiometry. The surface morphology of the codoped films showed well-defined hexagonal grains. Examination through transmission electron microscopy depicted that these films consists of an agglomeration of small grains with hexagonal shape. A high transmittance above 75% and electrical resistivity around 3×10-2 Ω.cm were reached after annealing.
Keywords
Spray pyrolysis, Hall Effect, ZnO, aluminum-indium codoped ZnO.
GEORGE STANCIU , NICU DOINEL SCĂRIŞOREANU, VALENTIN ION, MARIUS DUMITRU, ECATERINA ANDRONESCU, MARIA DINESCU
Abstract
Calcium doped strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN:50) is a tungsten bronze ferroelectric material with a tetragonal unit cell. SrxCayBa1-x-yNb2O6 (SCBN) compositions with (x = 0.5; y = 0.14 and 0.28) were obtained by solid-state reaction method. The phase structure, microstructure and dielectric properties of obtained SCBN ceramics were systematically investigated. XRD results showed that SCBN phase with tungsten bronze structure could be obtained in all ceramic samples. Higher Ca content (y = 0.28) lead to occurrence of a secondary phase of CaNb2O6. SEM micrographs show the formation of crystallites with sharp boundaries with an average grain size of about 4 ÷ 12 μm for all SCBN compositions. Compared with pure SBN:50 composition, Ca doping results in a reduction of the dielectric constant value, but the dielectric losses are found to be smaller for this compositions.
Keywords
SBN, SCBN, TTB structure, Dielectric properties
A.UĞUR OZTURK, R. TUĞRUL ERDEM
Abstract
Compatibility of different based superplasticizers with air-entraining admixture has been investigated. Physical and mechanical properties such as flow, setting time and compressive strength of cement mortars incorporating an air-entraining admixture (HS) with naphthalene sulfonate (SPNS) and modified polymer (SPMP) based admixtures have been determined. Also, the effects of their combinations on the freeze-thaw resistance of cement mortars have been determined. All admixtures are used with three different ratios and one of them is for overdosage effect. Results indicate that cement mortars having lowest early strength values are mortars incorporating 1.5% SPMP and 2.0% SPNS by mass of cement. The most effective series for the ultimate highest strength values were series with 0.05 % HS and 0.8 % SPMP. The freeze-thaw resistances of cement mortars were investigated for 50, 100, 150 and 200 freeze-thaw cycles. Indeed, the most effective series for freeze-thaw resistance were series with 0.05 % HS and 0.8 % SPMP.
Keywords
Admixtures; superplasticizer; compatibility; compressive strength; freeze-thaw
JANNE PESONEN, JUHO YLINIEMI, TOIVO KUOKKANEN, KATJA OHENOJA, MIRJA ILLIKAINEN
Abstract
Combustion affects the physical and chemical characteristics of fly ash. Peat and biomass are typically combusted using fluidized-bed combustion (FBC) technique, which causes the fly ash to have a low chemical reactivity. Especially low-Ca FBC ashes have very weak hardening properties, which reduce their utilization potential in many applications. This study examined the effect of adding alkaline activator and Portland cement on the hardening of two peat-wood fluidized bed combustion fly ash samples—one of high-calcium fly ash (24.9 % Ca) and the other low-calcium fly ash (9.7 % Ca). The reactive components of the raw materials, the mineralogical compositions, and compressive strengths of the resulting mortars were studied. Significant improvement to strength development was achieved. The addition of Portland cement proved necessary for low-Ca ash to harden at all. The ash cannot be considered solely as a filler material, since the reactive component (Ca, Si, Al, and S) contents of the ash, especially the Ca content, affect the strength development. Strength development of the mortars can be partly explained by the Ca/(Si + Al + S) ratio and the sum of the reactive components.
Keywords
fly ash, biomass, peat, Portland cement, alkaline activation, fluidized bed combustion
BORDJIBA ABDELHAK, HACEN-CHAOUCH ABDELMADJID, GUENFOUD HAMZA, GUENFOUD MOHAMED
Abstract
The design of a safe and respectful roadway to the environment must meet the users’ requirements in the present without compromising those of future generations. Under the traffic action, always more constraint and the climatic blitzes, the pavements crumbling occurs rapidly, which leads to severe impairments that are reflected on the surface layers: rutting, cracking, substances rejection, polishing and pulling out the aggregates on surface. This situation often involves the renovation of the surface’s layers. It is, therefore urgent to appeal to a new vision of pavement design based on optimizing the use of local materials, non-renewable, and respect for the environment. The recycling of bituminous substances are one of the relevant solutions. It has the advantage of reusing building materials by mixing them with a proportion of refined ones to achieve the required performance. This assignment researches for different rates of coated aggregates, the effects of manufacturing temperature and blending time in the mixing of the constituents during production as well as the additive plastomers of polyolefins on the improvement of the recycled asphalt rutting. Rutting is one of the most encountered degradation phenomena in the Algerian roads. The formulated hypothesis used here assumes that the elastomer polyolefins additive have an influence on the mechanical performance (rutting) of the recycled asphalt and also on the rate of the used asphalt aggregates. To justify this hypothesis it is mandatory to go through the manufacture of the asphalt with different rate of asphalt aggregates. To reduce the number of experimental tests necessary for this study, we used the experimental approaches method.
Keywords
asphalt, Recycling, polymers, environment, binder, penetrability
ZHOU LINA , WANG ZHENG, LU SHUANG
Abstract
The leaching behaviour of hydraulic concrete can’t be ignored for its long-term exposure to surrounding water resulting in irreversible damage of durability, such as strength loss and porosity increase. The coupled effect of leaching and freeze-thaw cycles on the durability of hydraulic concrete in severe cold regions is a bigger challenge. For the quite slow process of natural leaching, electrochemical accelerated leaching method (EALM) was proposed to investigate the damage evolution under two test schemes (scheme one is only leaching for 50 days and scheme two is first 100 rapid freeze-thaw cycles and then leaching for 50 days) designed in this work. The electrical resistivity and calcium oxide dissolved mass were measured through electrode impedance spectroscopy (EIS) and EDTA titration method, respectively. Based on electrical resistivity measurement, the measurable damage can be discussed during above-mentioned single and coupled tests. The results indicate that compared with single leaching the coupled leaching with the freeze-thaw cycling leads to over 50% electrical resistance loss, the largest difference of both calcium oxide dissolved mass and pH in cathode room on the 21st day.
Keywords
leaching, hydraulic concrete; coupled effect; EALM; damage evolution; EIS; calcium oxide dissolved mass
ELENA DUMITRESCU, ECATERINA ANDRONESCU
Abstract
This paper presents experimental results for solid waste (with heavy metals content) inertization in chemically bonded phosphate ceramic (CBPC) matrix. This process turns hazardous waste in non-hazardous waste.
It was studied the inertization of contaminated soil with 2000 mg/kg heavy metals (Cu, Ni, Pb and Zn) in chemically bonded phosphate ceramic versus inertization in Portland cement paste. Waste load was 50%, 70% and 80%. As the CBPC is a fast setting system, it was also used a retarder (i.e. boric acid and calcium lignosulfonate) in concentration of 1% (based on the amount of magnesium oxide and potassium dihydrogen phosphate). To determine the effectiveness of inertization were performed leaching tests in water and in acid solution, and the obtained values were compared with regulated limits.
All wastes stabilized with portland cement and CBPC meet specific criteria for compressive strength for accepting waste in landfill, but stabilization in CBPC is more effective.
In terms of nickel leachability in water, stabilizing of waste in CBPC allows soil waste loading of 80% compared with those stabilized in cement that allows waste loading of 50%.
Keywords
waste inertization, contaminated soil, heavy metals, chemically bonded phosphate ceramic, portland cement, leachate.
DANIELA LAURA BURUIANĂ, ŞTEFAN BALTĂ, CĂTĂLINA ITICESCU, LUCIAN P. GEORGESCU, DĂNUŢ LEFTER, INA I. HUMENIUC
Abstract
The paper presents the study of crops in rural areas along the Siret River basin near the industrial area of Galati, affected by heavy metal pollution.
The city of Galaţi is situated in the geographic center of the largest hydrographic basin in Europe being in the same time, together with Brăila city one of the most important industrial area in Romania. The present research in are on multicriterial monitoring points complex with prognosis using Kriging method. Interpolation methods estimate the values in unsampled locations. The mapping and spatial analysis often requires converting the field measurements into continuous space.
Keywords
kriging, pollution, soil, vegetation
LAVINIA GABRIELA POPESCU , FLORIAN ZAMAN, ENIKÖ VOLCEANOV, ILDIKO ANGER, MIRCEA MIHALACHE, EUGENIA GAMENT
Abstract
This approach is dealing with the recovery procedure of LF slags in agriculture as acid soils amendments. LF slag (slag from secondary treatment of steel) occurs in the form of a powdery material.
By using these slags in improving of acid soils seeks the calcium oxide high basicity from the slag, so this type of slags can be an active amendment in acidic soil treatment technologies.
We have identified various sources of LF slag, such as: 1) steel manufacturer for fabrication of equipments for energy industry, 2) alloyed steel manufacturer for the production of rolling stocks and 3) manufacturer of long semi-finished steel products.
LF slag collected samples was done in order to establish uniform sample batches.
The replacement of natural materials used to relieve acid soil with an unconventional material, like waste - slag LF was effective and leads to positive environmental effects.
Keywords
ladle furnace, LF slag, amendent, acid soil
MIHAI BRATU, OVIDIU DUMITRESCU , OVIDIU VASILE, IOAN ROPOTĂ, LUOANA FLORENTINA PASCU
Abstract
Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health.
In this paper we present our research on making a new type of composite material and testing its properties of noise attenuation level. Tests were carried out in the anechoic chamber using barrier attenuators of sound waves made of composite material consisting of 50% formaldehyde resin reinforced polypropylene granules formed from waste 50%.
It was also determined the efficiency of the panel by calculating the diffraction pression according to the sound waves dispersion on the acoustic panel’s surface and mapping the attenuation of noise levels due to the composite material..
Keywords
composite materials, waste, acoustic panel, anechoic chamber, sound waves
RUXANDRA- ELENA GEANALIU - NICOLAE, ADRIAN - ALEXANDRU PÎRVAN, ECATERINA ANDRONESCU, ROXANA TRUȘCĂ
Abstract
In order to obtain a drug delivery system used in tumoral treatment, this study presents the synthesis of mineral clay /antitumor drug hybrid materials. There were used three types of mineral phases with different structural characteristics as matrix and epirubicin, fludarabine, gemcitabine as active substances. The obtaining process was performed by mixing an aqueous solution of the drugs with the swelled clay. For the active substances incorporation, drug-solutions were heated and added slowly in clays suspensions (at 60°C, using magnetic stirring - 350 rpm). The dried hybrid materials were obtained after the separation was performed by centrifugation of cooled suspension.
The synthesized hybrid materials were characterized using different experimental techniques as X-ray diffraction, thermal analysis, scanning electron microscopy etc.. The characterization gave information about the proper interlayer intercalation of cytostatic, the good adsorption of drug into the matrix and the microstructure.
Keywords
epirubicin, fludarabine, gemcitabine, kaolinite, halloysite, montmorillonite, hybrid materials, drug delivery systems
MĂDĂLINA-ANCA LAZĂR, MIUŢA FILIP, MIHAELA CECILIA VLASSA, LIDIA ADRIANA SORCOI, RADU SEPTIMIU CÂMPIAN, CRISTINA PREJMEREAN
Abstract
The aim of the present study was the elaboration and the characterization of new fiber-reinforced composites (FRCs) that will serve cranial bone reconstruction, particularly in the cases of large bicortical calvarial defects. A series of resins containing dimethacrylate and urethane-dimethacrylate monomers were prepared and characterized. The most promising resin was selected in order to be reinforced with continuous unidirectional and woven E-glass fibers, respectively. The elaborated FRCs were investigated in vitro by scanning electron microscopy (SEM) and by determining the flexural properties and in vivo by intramuscular implantation test. The results of this study pointed out that the FRCs based on urethane dimethacrylic resin reinforced with woven E-glass fibers could be good candidates for the reconstruction of large cranial bone defects.
Keywords
biomaterials, bone reconstruction, fiber-reinforced composite, residual monomer, flexural strength, biocompatibility
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Year
2016
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Issue
46 (2)
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Pages
142-151
MAHAMASUHAIMI MASAE, LEK SIKONG, KALAYANEE KOOPTARNOND, PARNUMART CHOOPOOL, ANURAK BONBANG
Abstract
The extract from mangosteen pericarp (MP) was applied to a silk fabric. Its dye ability of silk fabric has been studied together with its colorfastness, antibacterial activity and UV protection properties. The mordant are aluminum potassium sulfate, ferrous chloride and sodium hydroxide were used to dye fabric. The color fastness to washing, water, perspiration, light and crocking of the dyed samples was determined according to AATCC test methods. In this study the UV protection properties were investigated on silk fabrics. The chemical functional groups of the dyes that were characterized by using fourier transform infrared spectroscopy (FTIR). Our results revealed that MP dyed silk fabric exhibited fair to good and good to very good fastness to washing and crocking, fair to very good light fastness, except for fabric mordanted with sodium hydroxide, whose rating were very poor to poor light fastness. The water and perspiration fastness ratings were good to very good, except for fabric mordanted with aluminum potassium sulfate. Silk fabrics mordanted with ferrous chloride and dyed with MP usually showed good UV protection levels even if undyed. Antibacterial activity of this dyed silk was confirmed by exposing the fabric to Staphylococcus aureus. The fabric dyed with MP extract reduced the number of viable organisms by 98% mordanted with ferrous chloride. These extracts gave polyphenols, gallic acid and carboxylic acid contents. Therefore, it was suggested that MP has the potential in producing functional dyes that could be imparted into the silk dyeing natural colorant system and incorporated in several kinds of cloths.
Keywords
antibacterial, natural dyes, color fastness, UV protection
CLAUDIU ACIU, CECILIA ROMAN, DANA - ADRIANA ILUŢIU - VARVARA, CARMEN PUIA, OANA CADAR
Abstract
This study was focused on the development of plastering mortars with good antibacterial and antifungal properties and adequate physical and mechanical characteristics regarding the mechanical strengths (CS IV), good adhesion to the substrate and low water absorption by capillarity (W2). As testing microorganisms, four bacterial (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa) and two fungal species (Aspergillus niger and Penicillium chrysogenum) as suspensions with density 106 cells/ml were used. In order to obtain antibacterial and antifungal effect on mortar surface, concentrations of more than 5% Ag/ZnO nanopowders (0.05 wt.%) are required. As a result, the obtained plastering mortars can be used for inhibiting the growth of pathogens of environmental and hygienic concern.
Keywords
mortar, zinc oxide, silver, antibacterial and antifungal properties
BOJAN MILOŠEVIĆ, ŽARKO PETROVIĆ, MARINA MIJALKOVIĆ, SLOBODAN RANKOVIĆ
Abstract
Self-compacting concrete (SCC) is intensively used in civil engineering due to its excellent characteristics both in fresh and in hardened state. In the several recent years, there is a growing need for testing of recycled aggregate use for making of concrete, which protects the environment and solves the problem of construction rubble disposal sites. The goal of this paper is to test the potential of usage of coarse recycled aggregate, obtained by crushing of concrete elements mechanically damaged in the production process of prefabrication elements, for making of SCC. Three concrete mixes were prepared for the experiment: the mixture made with the river aggregate as a reference mixture, the mixture where the coarsest fraction of the river aggregate was replaced by the recycled aggregate and the mixture in which both coarse fractions of the river aggregate were replaced by the recycled aggregate. In making of these concrete mixes, the principle of equal consistency of mixtures was followed. The mechanical characteristics determined for all the mixtures were: compressive strength, splitting tensile strength and modulus of elasticity. The obtained results indicate that the properties of these concretes exhibit minimal differences, and the application of the recycled aggregate obtained by crushing of prefabricated elements mechanically damaged in production process is justifiable for making of SCC.
Keywords
Self compacting concrete, recycling aggregate, compressive strength, tensile splitting strength, tangent and secant elasticity modulus
ELENA DUMITRESCU, ECATERINA ANDRONESCU
Abstract
This paper presents experimental results for liquid waste inertization in chemicaly bonded phosphate ceramic (CBPC). This process turns waste hazardous in non-hazardous waste.
It was studied the inertization of liquid wastes containing heavy metals (Ba, Cd, Cu, Ni, Pb) with concentrations between 3000 mg/l and 30000 mg/l in CBPC versus inertization in portland cement paste. As the CBPC is a fast setting system, it was also used boric acid as retarder in concentration of 3% (based on the amount of magnesium oxide and potassium dihydrogen phosphate). To increase the efficiency of cadmium inertization, phosphoric acid was added. Also it was studied the influence of sodium dimetilditiocarbamate. It was determined the maximum temperature of the obtained systems, the setting time and compression strength. To determine the effectiveness of waste inertization it was performed leaching tests in water and in acid solution, and the obtained values were compared with regulated limits.
Keywords
waste inertization, heavy metals, chemically bonded phosphate ceramic, CBPC, portland cement, leachate, TCLP
S. PERILLI, M. REGI, S. SFARRA, I. NARDI
Abstract
The aim of this work is the study of the thermal flux through a multilayer insulation specimen, whose final panels could be designed for the green building field. The specimen was fabricated using an expanded styrofoam base, the mortar and milk cements, a fiberglass, and hemp fibers chopped and scattered into a surface smoothing. The dimensions of the specimen are 230 x 75 x 30.2 [mm]. The need to analyze a reduced surface in the development of a 3D visualization follows a computational aspect, i.e., to limit the number of degrees of freedom to be solved. Specifically, the research is focused on a comparative analysis among numerical simulations through the data processing by means of Matlab® - using the finite difference method (FDM) in the 1D domain -, and Comsol Multiphysics® - using the finite element method (FEM), both in 2D and 3D domains -. In addition, an experimental analysis centred on the detecting of the sub-superficial fiberglass by means of infrared thermography (IRT) technique is carried out. A specific Matlab® script was also implemented.
Finally, can be observed that Comsol Multiphysics® not only allows a visualization of the flow, as it is done in Matlab®, but also of the entire specimen geometry with the possibility of realizing a video of the thermal transient during the heating and cooling phases.
Keywords
Finite difference method, Finite element method, Infrared thermography, hemp fibers, sub-superficial discontinuities
VASILE RUS, HORAŢIU VERMEŞAN, ANDREEA HEGYI, ANCUŢA ELENA TIUC
Abstract
The scope of the paper is to find a model for the evolution of corrosion products formed on hot dip galvanized rebars in fresh concrete, regarding layer thickness and density. In this study, non-passivated and passivated hot dip galvanized rebars were used, with various passivation solutions. Tests were performed using Electrochemical Impedance Spectroscopy (EIS). The corrosion products layer evolution was analyzed using the equivalent circuit model, best fitted with the EIS experimental plots. The layer evolution model was built by monitoring the layer thickness variation with time, and based on polarization resistance data.
Experiment results show the formation of two corrosion products layers, one in the rebar vicinity and the other in the concrete matrix vicinity. The two layers density and resistance evolutions are different; their thickness and density variations are independent from each other. The presence and effects of hot dip galvanized rebar passivation before the embedment in fresh concrete, was also emphasized.
Keywords
Electrochemical Impedance Spectroscopy, hot dip galvanized rebar, corrosion, fresh concrete interface
VASILE MIRON, ENIKÖ VOLCEANOV, GINA GENOVEVA ISTRATE
Abstract
This paper presents a study on the corrosion behaviour of coatings by electroless deposition on the steel strips surfaces. For Ni-P and Ni-P-Al2O3 composite and nanocomposite layers, the variation of corrosion rate in two representative corrosive environments: an acid environment (H2SO4 solution of 5% concentration) and basic environment (NaOH solution of 10% concentration), it has been established, respectively. The corrosion rate was appreciated by using the gravimetric method (mass loss) reported to the area submitted to corrosive attack and the process duration. The study was conducted over a period of 7 days (168 hours) for the acid environment and 28 days (672 hours) in basic environment. The macroscopic appearance of the corroded surfaces was also investigated. The experimental results have emphasized a better behaviour in basic environment of composite coatings, comparatively with the Ni-P coatings with high phosphorus content. In acidic environment, a remarkable behaviour presented the composite Ni-P-Al2O3 and Ni-P alloy coatings, while samples with nanocomposite coating of Ni-P-Al2O3 were completely destroyed.
Keywords
electroless deposition of steel strips surfaces, composite coatings
QINGFENG WANG
Abstract
The calcium magnesium aluminate cement often presents a longer setting time than the conventional calcium aluminate cement containing 70wt. % Al2O3, owing to the presence of the MgAl2O4 spinel in the cement clinker. In this paper, calcium chloride was used to control the hydration rate of the cement containing MgAl2O4 spinel. The temperature development of cement pastes was employed to characterize the hydration and setting behavior of the cement. The electrical conductivity measurement was utilized to evaluate the dissolution-precipitation rate of the cement. X-ray diffraction was conducted to identify the hydrates after halting cement hydration by vacuum freeze drying at a certain curing time. And scanning electron microscopy was used to observe the microstructure development during the cement hydration. These results reveal that calcium chloride addition intensifies the hydration of the calcium magnesium aluminate cement.
Keywords
calcium chloride, calcium magnesium aluminate cement, hydration, dissolution-precipitation rate, microstructure
KSENIJA JANKOVIĆ , LJILJANA LONCAR, DRAGAN BOJOVIĆ, MARKO STOJANOVIĆ
Abstract
Adequate measures must be taken during the determination of the concrete composition for ensuring the durability of concrete exposed to an aggressive environment. The influence of the cement type on the freeze/thaw resistance with and without de-icing salt of concrete was tested. Samples were made using five types of cement. All types of concrete made according to the recommendations of the Serbian and European norms had the required frost resistance. Besides the respected recommendations, concrete made using cement with 35% mineral additions of fly ash and lime was not freeze/thaw resistant with de-icing salt.
Weathering resistance for paving units is determined according to EN 1338 and EN 1339 for freeze/thaw resistance with de-icing salt or water absorption. Taking into account previous investigations, only samples which were made in accordance with the recommendations of the Serbian Building code requirements for concrete and reinforced concrete - BAB 87 and European norms EN 206-1 were tested. Regarding water absorption, it is expected that in the case of established production all types of concrete would be integrated into class 2 according to EN.
Also, for two representative types of concrete with different air content and degree of damage done by destructive test, non-destructive test by device RapidAir 457 was done (specific surface, spacing factor, void frequency and average chord length).
Keywords
types of cement, concrete durability, freeze/thaw resistance, scaling, spacing factor, weathering resistance
IONELA PETRE, MIRELA MENICU, ILEANA MOHANU, FLORIN BERNEA, CAMELIA ȘERBAN
Abstract
In the clinkerization process a negative influence on the kiln operations and the quality of clinker has the presence of volatile compounds (alkalis, sulphur, chlorine). These are brought into the system by the raw materials and fuels. At the international level an efficient method for reducing the negative effects of volatile compounds is the bypass introduction. In this paper the results of theoretical calculations of bypass revealing the influence of bypass degree on reducing of the alkali content from clinker are presented.
Keywords
bypass, alkali volatility, clinker, clinkerization installation, cement
DAN GEORGESCU , ADELINA APOSTU
Abstract
The article presents a proposal with a view to extending the application of the equivalent durability procedure (EDP). It proposes and applies criteria for determining the freeze-thaw of concrete in the context of extending the field of application of the procedure of equivalent durability to existing buildings. The proposed method represents an extending of EDP procedure considering: reducing uncertainties related to the placing of concrete, finishing, curing of concrete and the rate of improving the performance of concrete over time. The application of standardized test methods in Europe also for assessing the freeze-thaw resistance of concrete in existing buildings represent a step forward in increasing concrete durability and prolonged working life of the buildings. The proposed method is similar to the one used in assessing concrete resistance.
Keywords
concrete, durability, assessing, performance, existing building
IULIANA HUDIȘTEANU, NICOLAE ȚĂRANU, IOANA-SORINA ENȚUC, SEBASTIAN GEORGE MAXINEASA
Abstract
Composite structures subjected to complex states of stresses require tailored strength and stiffness characteristics in certain directions, while the properties of the unidirectional lamina are disproportioned and unequal in different directions. Therefore, a multi-layered composite is needed, with various stacking sequences of elementary laminas and different fibre orientations. An accurate prediction of the elastic engineering constants is essential, in order to evaluate the stiffness properties of composite laminates.
The paper presents a comparative analysis of the in-plane elastic engineering constants of continuous fibre reinforced laminated composites, pointing out the influencing parameters of the stiffness properties of multi-layered composites. Three types of laminates, made of composite laminas reinforced with S glass fibres or E glass fibres, embedded in an epoxy resin, with different geometric arrangements of laminas are analysed: an asymmetric general laminate, an anti-symmetric angle-ply and a symmetric angle-ply laminate. The obtained results, illustrated by the graphical distributions of the engineering constants, reveal superior stiffness properties in case of particular laminates.
Keywords
in-plane engineering constants, composite laminates, fibre orientation, glass fibres
M. HRAITA, Y. EL RHAFFARI, G. FADILI, A. SAMAOUALI, Y. GÉRAUD, M. BOUKALOUCH
Abstract
The importance of capillary imbibition and evaporation processes in the alteration of building stones under the action of salt crystallization can be estimated by various experimental techniques. The aim of this study is to understand the direct relationships between salt weathering, petrophysical and structural properties. We chose to work on calcarenite stone which was commonly used as building material in historical monuments in Morocco. Laboratory wetting-drying cycles were tested on calcarenite specimens with sodium chloride solutions of different concentrations. Results show that the permeability and specific mass of precipitated salt depend on the material porosity and solution concentration. Moreover, variations of thermal conductivity and permeability during applied cycles are less important for samples taken parallel to the sediment bedding than for those taken perpendicularly. The material anisotropy will also be discussed.
Keywords
Calcarenite stone, Salt weathering, Moroccan historic monuments, Permeability, Thermal conductivity.
MIHAI ROHAN
Abstract
In Romania, there are several industries that already apply the concept of circular economy, amoung which the cement/concrete industry that turns waste into alternative sources of raw materials and energy and already recovers significant amounts of waste from other industries as well as sorted household waste. Waste co-processing in cement industry is a waste recovery method, recognized as being one of the best practices for an efficient use of resources. By co-processing take place simultaneously, both the recycling of waste mineral content as well as their energy recovery, which leads to the reduction of indirect CO2 emissions.
Also, the product of wide consume of this industry – cement concrete – can be 100% recycled as alternative aggregates used in building the transport infrastructure or getting a new concrete.
Thus, the cement/concrete industry contributes to the conservation of natural resources by replacing them with alternative resources from waste, and becomes an integrant part of the circular economy - European goal for an efficient use of resources and ensuring energy security.
Keywords
cement, concrete, waste, recycling, circular economy, recovery
ANGEL PALOMO, OLGA MALTSEVA, ANA FERNANDEZ-JIMENEZ
Abstract
Coal fly ash can be subject to large variations in characteristics as a function of the type of coal burned, the operation status of the coal power plant and the ash separation technology employed. Good quality fly ash is in demand in the cement industry (and in the concrete plants) due to its ability to partially substitute some Portland cement (typically between 10% and 25%). On the other hand, coal bottom ash, due to its coarser nature, is generally considered as a low value by-product that may at best be used as a partial replacement for aggregates in concretes or as geotechnical fill material. In this paper authors propose a procedure (mechanical-chemical combined procedure) by which to transform regular coal combustion products (fly ashes and/or bottom ashes) into Ultra-Reactive Ashes (URA).
URA is a product with very interesting cementitious characteristics which can become the most important component of a new family of extra-durable and cheap ecoconcretes.
Keywords
Fly ash, chemical activation, mechanical activation, geopolymer concrete
CARMEN MUNTEANU, MARIA GEORGESCU
Abstract
The paper brings information obtained by own researches regarding manufacture and characterization of some concretes in which the binder was Portland cement with variable content of fly ash. As aggregate, an old crushed concrete was used, which substituted partially or totally the conventional aggregate (of ballast-pit). A polycarboxilic type superplasticiser (dosed as 0.9% relative to the cement content) was used for all the concretes.
Based on the experimental data, some useful correlations between compositions and properties (mechanical strength, impermeability, and freeze-thaw resistance) could be established. These allow the assessment that it is possible the manufacture of some concretes by simultaneous use of the fly ash and recycled concrete, without significant change in the principal properties (mechanical strength, impermeability, freeze-thaw resistance). Such waste valorization has favorable influences on the environment.
Keywords
concrete, recycled aggregate, fly ash, properties
GORDANA TOPLIČIĆ ĆURČIĆ, DUŠAN GRDIĆ, NENAD RISTIĆ, ZORAN GRDIĆ
Abstract
The share of aggregate in concrete composition, in terms of volume is 70%-80%. The properties of fresh and hardened concrete depend on the aggregate properties, primarily on particle size distribution. The paper considered impact of particle size distribution of aggregates from two screening plants from the South Morava river on the properties of concrete. The intention was to make concrete mixtures with the aggregate which would have as identical particle size distribution, as similar consistency of fresh concrete as possible and same compressive strengths. For making of afore mentioned concrete mixes, the same sort of cement and same admixtures were used.
It was concluded that the difference in the particle size distribution of aggregate fractions had an impact on the composition of concrete mixes of the identical properties. Specifically, the quantities of cement, admixtures and water were different in the afore mentioned mixtures.
The technical specifications of the cement manufacturers include a recommended quantity of cement for specified concrete classes. It is concluded that these values are only rough guidelines. The same holds for the recommended quantities of admixtures. For that reason, every required concrete mixture must be verified in laboratory, i.e., previously tested.
Keywords
river aggregate, particle size distribution, cement, admixture, concrete
CHRISTU ŢÂRDEI, CLAUDIA MARIA SIMONESCU, CRISTIAN ONOSE, BOGDAN ALEXANRU SAVA, LUCICA BOROICA, BEATRICE-GABRIELA SBÂRCEA
Abstract
This study aimed to investigate the effect of preparation conditions on different hydroxyapatite nanopowders (n-HAP), obtained on the laboratory scale, by the solution–precipitation and sol-gel methods, and to correlate the main characteristics like crystallinity and specific surface area with the ion Pb2+ immobilization capacity. It is tested the increasing performance of nano-HAP so obtained, to remove heavy metals from aqueous solutions through dispersant addition (0.1…1.5%) and isomorphic substitution (Six-HAP, x=0.5; 1). Batch experiments were carried out using different synthetic nano-hydroxyapatites; powders were comparatively tested for lead removal process from aqueous solutions, under different conditions, i.e. initial metal ion concentration, and pH of the solutions. Results showed that all HAP powders obtained by precipitation contain hydroxyapatite as the only crystalline phase instead, the sol-gel HAP powders contains minor quantities of β-TCP. Experimental results shown that, the amount of metal ions (Pb2+) removed correlates to the nature of the adsorbents (morphology and specific surface area), and to the concentration of the synthetic solution in metallic ions.
Keywords
nano crystalline hydroxyapatite, heavy metals, lead removal, adsorption
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Year
2016
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Issue
46 (3)
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Pages
289-297
COSMIN VANCEA, GIANNIN MOȘOARCĂ, ADINA NEGREA, ADINA LAȚIA, ROMUL MARIUS JURCA
Abstract
The present paper proposes an alternative recycling method for two common glass wastes: window panes and funnel CRT glass, together with Bojidar kaolin as new glass matrix for chromium waste immobilization. The kaolin was previously used as adsorption support for the soluble Cr6+ waste from residual waters. Tree different weight ratios glass waste:kaolin (60:40, 70:30 and 80:20) were used for the glass-ceramic synthesis. The raw materials as powders (granulometric fraction under 0.1 mm) were mixed together and then pressed into cylinders having the diameter and height around 35 mm. The heat treatment was conducted at three different temperatures 900, 1000 and 1100°C respectively for 60 minutes. The compactness of the obtained glass-ceramic samples was characterized using their apparent porosity and apparent density. The obtained values range from 0 to 22.93% for the apparent porosity and from 1.93 to 2.25 g/cm3 for the apparent density respectively, depending on the glass waste type and heat treatment temperature. The microporous structure was illustrated using SEM. The phase composition of the studied samples was established by RX diffraction, cristobalite, diopside, tridymite and wollastonite being the main crystalline phases. The compressive strength of the obtained glass-ceramic products was measured and correlated with the heat treatment temperature. The highest values range from 136 to 175 N/mm2, corresponding to the samples obtained at 1000°C. The hydrolytically stability and chromium leachability were determined according to the ISO 719/1985 and American Extraction Procedure Toxicity Test respectively. All the studied samples completely immobilized the chromium ions in the glass-ceramic matrix so that no chromium extraction was recorded for the acid and neutral mediums. The glass ceramic matrix have a low sensibility to the alkaline medium, the total chromium extracted being less than 0.014% after 28 days. The obtained results suggest that the immobilization of the chromium wastes adsorbed on kaolin in glass ceramic matrix is a viable solution having multiple economic advantages.
Keywords
glass wastes, glass recycling, chromium wastes, glass ceramic
DOREL RADU, ZENO GHIZDĂVEȚ
Abstract
Nowadays clinker processing technology has been, already, reached the highest performance level that can be attained in industry. No significant improvements of a constructive/functional type of the present day’s best clinkering plants can be foreseen in the next future. As a consequence, further fuel savings can be obtained by, only, a proper selection of the raw materials that require less heat in order to obtain clinker. The evaluation of the burnability of the raw mix, either by computing or experimentally, provides the most valuable information from both scientifical and industrial viewpoints. In this paper, we briefly analyze existing theoretical indices used for evaluating burnability; afterwards, we explore the possibile interrelations among them. In that purpose, a comprehensive database of 119 raw mixes from both industry and laboratories, from Romania and abroad were used in this investigation.
Keywords
clinker, burnability, correlations
R. TUĞRUL ERDEM , A. UĞUR OZTURK, ENGIN GÜCÜYEN
Abstract
Due to several advantages of cementitious materials especially mortars, they are widely used in construction works. It is important to determine the mechanical properties of cementitious materials to understand their behavior under different effects. In this study, Artificial Neural Networks (ANN) analysis is used to predict the 7 and 28 days compression strength values of cement mortars. Physical-mechanical properties such as flow, setting time and compressive strength of cement mortars incorporating of different chemical admixtures such as air-entraining admixture (HS), naphthalene sulfonate based (SPNS) and modified polymer (SPMP) based admixtures have been determined. The aim of the usage of combinations of air-entraining admixture with two different based superplasticizers is to form different inner structure affecting on compressive strength. All admixtures are used with three different ratios by cement weight and one of them is for overdosage effect. ANN analysis has been performed to predict the compression strength values after 7 and 28 days, in correlation with experimental part of the study. According to this view, 28 sets have been prepared with different combination of admixtures. At early ages, HS015-SPNS2.0 series had the lowest strength whereas the highest compressive strength at 28 days were obtained for HS005-SPMP0.8 series. Obtained compression strength values after 7 and 28 days have also been predicted by ANN analysis. It is stated that the established ANN model indicates a great capacity to predict the compressive strength values in the end.
Keywords
ANN; admixtures; superplasticizer; compressive strength; cement mortars
Behaviour of reinforced concrete beams subjected to dynamic loading in various stages of degradation
CONSTANTIN GAVRILOAIA, NICOLAE ȚĂRANU, RALUCA ONOFREI, MIHAI BUDESCU, PETRU MIHAI, IOANA-SORINA ENȚUC
Abstract
The dynamic characteristics of a building element are represented by vibration frequency, damping coefficient and stiffness. The vibration frequency of a reinforced concrete element modified with respect to the degradation state caused by the cracking of concrete and the yielding of reinforcement is analyzed in this paper.
An experimental program, carried out at the Faculty of Civil Engineering and Building Services in Iasi, revealed a specific relation between the vibration frequency and the damage level of some reinforced concrete elements. In this experimental program four reinforced concrete beams with the same concrete class but different reinforcing ratios have been tested in bending up to various levels of degradation. The experimental results have been validated through numerical modeling using the software package LUSAS based on finite element analysis.
Keywords
reinforced concrete beams, vibration frequency, damage level, numerical modeling
MICHAL HORA, PAVEL REITERMAN
Abstract
This research is focused on concrete with rubber powder content exposed to low (freezing) temperatures. Rubber powder serves as air-entraining agent and should provide better freeze-thaw protection. On the other hand, rubber powder limits maximum compressive strength of concrete. The main purpose of this research is to find an optimal rubber powder content in order to satisfy needs for the minimal loss in strength of concrete as well as high freezing-thawing resistance. A freeze-thaw test was carried out on five concrete mixes with different contain of several rubber fractions to determine the optimal rubber grading. Specimens with rubber powder were tested on compressive strength, splitting tensile strength, tensile strength and moduli of elasticity. The specimens with rubber content were tested at laboratory temperature as well as at freezing temperatures. Influence of rubber addition was assessed on the base of original and residual values of studied properties after freeze-thaw loading. Resistance to frost damaged was determined by splitting tensile strength test and tensile strength test. Non-destructive methodology was predominantly used to monitor gradual deterioration during freeze-thaw cycling.
Keywords
freezing, thawing, rubber powder, compressive strength, air-entrainment
GENG LIN, CHANG-LONG WANG , CHUN-YU QIAO, HAN-LONG CUI, LIE CHEN, SHUO YU
Abstract
To comprehensively utilize lead-zinc tailings (LZT), it was used as main siliceous materials in autoclaved aerated concrete (ACC) in this study. The effects of fineness and content of LZT on the properties, hydration products and microstructures of AAC were investigated by the mechanical test, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric/differential scanning calorimeter (TG-DSC) and scanning electron microscope (SEM). And the composition and morphology of the hydration products in AAC at varying stages were detected. The results show that the ACC containing 62% LZT (in mass percentage) with a specific surface area of 325 m2 kg-1 can achieve a bulk density of 587 kg m-3 and compressive strength of 4.94 MPa, which qualifies the requirements of A3.5, B06 level of AAC sample regulated by the composition and morphology GB/T 11969-2008. The mobility of slurry and hydration activity both increase as the fineness of LZT decreases. However, the small size of LZT particles and the high thickness of the slurry are harmful to form a good pore structure, which would influence the properties of AAC. When the blending percentage of LTZ is too high, the unreacted LTZ particles increase and accumulate within the system, which reduces the space among them and thus influences the growth and crystallization of hydration products. The main hydration products before curing are AFt and C-S-H gels. And then AFt decomposes and some amount of C-S-H transitions to tobermorite after curing and autoclaved.
Keywords
lead-zinc tailings, autoclaved aerated concrete, fineness, content, tobermorite
FAEZEHOSSADAT KHADEMI, MAHMOOD AKBARI, SAYED MOHAMMADMEHDI JAMAL
Abstract
Ultrasonic pulse velocity (UPV) test method is used in this study for evaluating the compressive strength of concrete. A series of UPV tests were performed to evaluate the 28-day compressive strength of concrete and examine the effect of concrete mixture parameters on the UPV of concrete. It was found that concrete with higher 28-day compressive strength gives higher UPV and that an exponential relationship exists between the UPV and 28-day compressive strength of concrete. The results showed that the aggregate size has a significant effect on the strength of concrete. Concrete with larger aggregate size was found to give lower UPV and compressive strength. UPV results also indicated that the UPV and compressive strength of concrete consistently decrease with increase in water-cement ratio of concrete. The effect of using microsilica (Silica fume) in concrete is also studied. It was found that as the microsilica to cement ratio increases in concrete, the UPV and compressive strength of concrete increase. The effects of the ingredient materials on UPV were analyzed and potential mechanisms were proposed. To make the results applicable, the artificial neural network (ANN) method was used to predict the compressive strength of concrete based on the evaluated concrete mix parameters and ultrasonic pulse velocity. The ANN analysis demonstrated high reliability in predicting the compressive strength values of concrete.
Keywords
Concrete, Compressive Strength, Ultrasonic Pulse Velocity, Aggregate, Water-Cement Ratio, Microsilica, Artificial Neural Network.
AYED KADA, KERDAL DJAMEL EDDINE, SOLTANI RABAH
Abstract
The study carried out herein aims at investigating the instantaneous and deferred mechanical behaviours of self compacting concrete (SCC). The survey was carried out in three steps. In the first step, local industrial waste fines, such as limestone (L), siliceous (S) and natural pozzolanic (PZ) fillers, were used in the preparation of the self compacting concrete; in the second, a study was performed to optimize the SCC formulation by varying the volume of paste; and finally, the effect of varying the volume of paste on the mechanical strength and shrinkage of the SCC was examined in the third part. Results showed that the addition of local fillers, according to international recommendations, in the preparation of SCC mixes gives better compressive strength and shrinkage behaviour than that of vibrated concretes.
Keywords
Self compacting concrete; Limestone fillers; Siliceous fillers; Natural pozzolana; Shrinkage; Compressive strength
RUXANDRA – ELENA GEANALIU - NICOLAE, ADRIAN-ALEXANDRU PÎRVAN, ECATERINA ANDRONESCU, ROXANA TRUȘCĂ
Abstract
In this study, the bioevaluation results of drug- clay hybrid materials obtained in Synthesis and characterization of drug - mineral clay hybrid materials for biomedical applications as drug delivery systems – part I [1] are presented, in order to obtaine drug delivery systems used in cancer treatment. The bioevaluated materials were the nine types of hybrid materials, synthesised using three types of mineral phases with different structural characteristics as matrix and epirubicin, fludarabine, gemcitabine as active substances.
For morpho- structural characterization were used the following experimental techniques: X-ray diffraction, thermal analysis, scanning electron microscopy, which offered information about the proper interlayer intercalation of cytostatic, the good adsorption of drug into the matrix, the microstructure. In this study, the characterization was continued with bioevaluation, presenting informations about the kinetics and drug release. Thus, analysis performed was the in vitro cytotoxicity which established the potential use for biomedical applications showing the antitumoral activity.
Keywords
epirubicin, fludarabine, gemcitabine, kaolinite, halloysite, montmorillonite, hybrid materials, drug delivery systems
MARIA COLIE, DAN MIHĂIESCU, ADRIAN SURDU, ANTON FICAI, DANIELA ISTRATI, ECATERINA ANDRONESCU
Abstract
In this paper we describe the synthesis of superconductor powder by a modified autocombustion route. The purpose was to obtain YBa2Cu3O7-δ with nanosized crystallites by a new synthetic pathway, since the literature data reported so far are limited, using stoichiometric amounts of yttrium acetate with barium and copper nitrate without the addition of organic fuel. The auto-combustion reaction transformed the precursor gel into a dark-brown ash powder, during an intense self-ignited exothermic reaction. After calcination at 900oC the obtained black powder was sintered using Spark Plasma Sintering (SPS) at 510oC. The final material was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).
Keywords
autocombustion, acetate-nitrate, supraconductors, plasma sintering
MAHAMMADALI A.RAMAZANOV, ABEL. M.MAHARRAMOV, FLORA V.HAJIYEVA, FEYZA KIRAÇ, OLGUN GÜVEN
Abstract
In the present work, thermal and mechanical properties of nanocomposites PP+ZrO2 are studied. The presence of zirconium dioxide in PP increases its thermal stability and mechanical properties of nanocomposites. The AFM studies show that a change in upper molecular structure of polypropylene as well as a chipping of structure elements of surface morphology occur with addition the nanosize powder to the polymeric matrix. The thermal stability and mechanical properties generally increases with increasing amount of zirconium dioxide. Improvement in thermal stability of PP occurs by the addition of 5% ZrO2. It was experimentally shown that increasing of volume content of ZrO2 changes the mechanical durability of nanocomposite PP+ZrO2 with extremum, i.e. the concentration of ZrO2 up to 5% increase durability, and more than 5% decrease it. These results prove that ZrO2 nanoparticles with concentration up to 5% are the centers of structure nucleation, and further increasing of nanoparticles concentration leads to destroying of physical structure of polypropylene.
Keywords
Nanocomposites, mechanical properties, strength, mechanical testing, thermal analysis
NALAN KALKAN, RECEP KANIT
Abstract
The importance of capillary imbibition and evaporation processes in the alteration of building stones under the action of salt crystallization can be estimated by various experimental techniques. The aim of this study is to understand the direct relationships between salt weathering, petrophysical and structural properties. We chose to work on calcarenite stone which was commonly used as building material in historical monuments in Morocco. Laboratory wetting-drying cycles were tested on calcarenite specimens with sodium chloride solutions of different concentrations. Results show that the permeability and specific mass of precipitated salt depend on the material porosity and solution concentration. Moreover, variations of thermal conductivity and permeability during applied cycles are less important for samples taken parallel to the sediment bedding than for those taken perpendicularly. The material anisotropy will also be discussed.
Keywords
Masonry Structure, Out of plane loading, Steel reinforced shotcrete.
D.N. ISOPESCU, L. DUMITRESCU, I.D. ZĂPODEANU, O. NECULAI
Abstract
The paper findings are focused on the embodied impacts of building materials and component combinations that influence, generally, on the environment, and, particularly, the greenhouse gas emissions of a case study based on a new developed hybrid building system applicable to low-rise buildings located in seismic zones. The hybrid system has been designed as a masonry made of autoclaved aerated concrete blocks strengthened with composite frames made of rolled steel profiles embedded in concrete. The results obtained in design calculus, those obtained for global coefficient for thermal insulation, and those obtained in Life Cycle Assessment, have highlighted the good performance of the proposed hybrid system regarding its environmental impact.
Keywords
greenhouse gas emissions; Global Warming Potential; hybrid structure; Life Cycle Assessment; energy efficiency; low-rise buildings for seismic zones
LAVINIA GABRIELA POPESCU, ENIKÖ VOLCEANOV, ILDIKO ANGER, ALEXANDRA GEORGIANA MOISE, ADRIAN VOLCEANOV, ECATERINA MATEI
Abstract
Present paper presents a comparative assessment of environmental factors by using an industrial waste from secondary metallurgy, such as white slag. LF slag generated at two sources as powder and subsequently as pelletized form were investigated. The chemical composition of the investigated slags were analysed by x-Ray Fluorescence (XRF).
Leachability tests and the chemical analysis were carried out by various methods. Consequently, the chemical composition of the leachate for various particle size fractions of the waste LF slag was determined by using flame atomic absorption spectrometry (FAAS) and by induction coupled plasma optical emission spectrometry (ICP-OES) to determine the content of heavy metals - Ni, Cu, Pb, Zn, Cd, brought by slag.
The values of pH and electrical conductivity on leachate samples, prepared with solid / liquid ratio of 1:2 and 1:10 were also measured.
The advantage of LF slag using as pellets consist in decrease the LF slag instability, comparatively with the initial powdered slag, which leads to dispersion as dust in the environment. This is possible by processing the slag to an optimal grain size distribution in conjunction with physical and chemical characteristics to obtain a homogeneous product. Their use as acid soil amendment in agriculture is effective.
Keywords
pellets, LF slag, leachability, acid soil amendment, agriculture
RODICA-MARIANA ION, MIHAELA-LUCIA ION, ADRIAN RADU, RALUCA-IOANA ŞUICĂ-BUNGHEZ, RADU-CLAUDIU FIERĂSCU, IRINA FIERĂSCU, SOFIA TEODORESCU
Abstract
In the field of architectural restoration, ancient materials and their decay in aggressive environments are studied, through case-histories. Some properties (capillarity, porosity) are tested on different façade surfaces, in order to identify the existing materials and to select the proper materials useful for restoration. The achieved microscopy (MO, AFM) studies allow observing the presence of the main weathering signs and the previous consolidation results. The EDXRF and ICP-AES techniques offer informations about the elemental composition of sample, while GC-MS allow the identification of the previous coniferous resins from the glue used for restoration. The identification of mainly of terpenes and derivative patterns highlighted the presence of plant oils and pine resins. Also, the CIELAB color parameters are a proof of the efficacy of the conservation process. Moreover a comparison between traditional mortars (based on cement) and those based on nanomaterials (calcium hydroxide, hydroxyapatite and their controlled mixture) used in restoration are investigated in this paper.
Keywords
nanomaterials, façade preservation, analytic characterization
PAVEL KRIVENKO, OLEG PETROPAVLOVSKII, HRYHORII VOZNIUK
Abstract
At present, a tendency to substitute hazardous organic adhesives in the majority of building materials is clearly observed. This is connected with the more strict than before requirements for health safety, fire safety and durability. The most important task is substitution of organic binders, traditionally used as adhesives for gluing concrete, brick and ceramics with non-hazardous inorganic binders. To solve this problem an adhesive for concrete, brick and ceramics based on ecologically friendly alkaline aluminosilicate binder (geocement) has been developed. This binder is itself an inorganic polymer, which combines properties of inorganic substances (high strength and frost resistance) and those of organic substances (elasticity, adhesion to various materials etc.) and is analogue to alkaline aluminosilicate materials occurring in nature: zeolites, feldspathoids, etc. Bonding strength of the geocement-based adhesives to various surfaces is higher than 1 MPa. With taking into account high pH of the geocement stone a proper choice of fillera and additives is important. The purpose of the study was to reveal influence of the geocement-based adhesive composition on properties and, accordingly, on structure of the interfacial transition zones: "concrete−concrete", "concrete−ceramics", "ceramics−ceramics".
Keywords
aluminosilicate structures, geocement-based adhesives, metakaolin, mica, feldspathoid, quartz sand, zeolite formation
IOANA GOMOIU, MADALIN ENACHE, ILEANA MOHANU, ROXANA COJOC, SIMONA NEAGU, DAN MOHANU
Abstract
Microbial colonization and biodeterioration of mural paintings in historical monuments have as result structural and aesthetic damages due to degradation of organic binders, biomineralization, colored biofilms and discoloration.The original and infilling mortar from refectory of Hurezi monastic complex-Romania was analyzed from structural point of view as well as from microbiological point of view. Visual inspection performed in situ on the northern and western walls revealed: cracks, small and large pink areas on the pictorial layer, original and infilling mortar, small black areas on the infilling mortar and white and pink efflorescences appearing mostly on the infilling mortar. Microscopical observation performed both in situ and in laboratory (Optical Microscope and Scanning Electron Microscope) revealed a pink biofilm and small black colonies. Microbiological analysis confirmed the bacterial origin of the pink biofilm and fungal origin of black colonies. The characteristics of the mortars sustain adhesion of the bacteria and fungi and organic deposits favor their multiplication which is reflected in colonization of the substrate.
Keywords
microbial colonization, pink biofilm, black biopigmentation, mortar, pictorial layer
ILEANA MOHANU, DAN MOHANU, IOANA GOMOIU, ADRIANA MOANŢĂ, LILIANA RADU, CRISTINA SERENDAN
Abstract
The wooden churches painted in fresco, present exclusively in south zone of Romania, represents a limited category, very little explored and, additional, threaten with disappearance. The main problem of preservation is represented by remaking of the adherence of fresco at wood support.
This paper presents the results of the first researches regarding the obtaining of some materials which will serve in the process of consolidation of mural pictures on wood support. For this purpose were performed a series of mortars based on hydrated lime, river sand and fibers of hemp. For improvement of the adherence an acrylic additive was added. Different characteristics of mortars in hardened state were evaluated, such as: apparent density, water absorption, water vapor permeability, flexural and compressive strength, and resistance at the phenomenon of biodegradation. By using the fibers the flexural and compression strengths of the mortars were improved.
Keywords
fresco, lime mortar, fiber, mechanical strength, water vapor permeability, biodegradation
Coating magnetite nanoparticles with mesostructured silica shell of different pore size and geometry
RAUL-AUGUSTIN MITRAN, DOINA GEORGESCU, NICOLAE STĂNICĂ, CRISTIAN MATEI, DANIELA BERGER
Abstract
Composite nanomaterials combining magnetic properties and porosity have various applications as catalysts, in targeted drug delivery, depollution, energy storage etc. However, the synthesis of magnetite nanoparticles coated with SBA-16-type mesoporous silica is very challenging due to the acidic medium required, which leads to the dissolution of iron oxides. Here, we report a simple synthesis of Fe3O4@SBA-16 composite with high content of magnetic nanoparticles in a weak acidic medium. The influence of reagents addition order was also studied. The resulting materials have been investigated by small- and wide-angle X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, nitrogen sorption analysis and magnetic measurements. The properties of Fe3O4@SBA-16 samples are discussed and compared with a Fe3O4@SBA-41 material, obtained in basic medium. All magnetic composites present high porosity and superparamagnetic behavior.
Keywords
superparamagnetic, mesoporous silica, SBA-16, Fe3O4@SBA-16, magnetite, MCM-41
GEORGE PELIN, ECATERINA ANDRONESCU, CRISTINA-ELISABETA PELIN, OVIDIU OPREA, ANTON FICAI
Abstract
The paper presents a study regarding obtaining, characterization and testing of carbon fiber felt-phenolic resin composite and nanocomposite materials with neat phenolic matrix and nanofilled with silicon carbide nanoparticles added in two different weight contents (1 and 2 wt. %). The effect of the nSiC presence and content is evaluated taking into consideration mechanical, tribological and thermal behavior. Mechanical testing consisted of compression and 3-point bending tests, the results indicating that the strength and stiffness are improved in the case of nanofilled sample. Tribological testing illustrated that friction coefficient increased with nSiC content increase. Thermal behavior was evaluated by TG-DSC analyses and thermal shock tests (at 1100°C), the post-test mass loss analyses showing that nSiC is able to act as a thermal protection agent, improving thermal resistance of these materials. The experimental results indicate that adding silicon carbide nanoparticles in the phenolic resin matrix of carbon fiber felt based ablative type materials improves their mechanical, tribological and thermal properties and recommends them as potential candidates for ablative applications.
Keywords
carbon fiber felt, ablative materials, nano-silicon carbide, thermal shock resistance, TG-DSC
ZENO GHIZDĂVEȚ, DANIELA NĂSTAC, MIHAI EFTIMIE, B. ȘTEFAN, IONELA STANCIU, ADRIAN VOLCEANOV
Abstract
Multivariate Analysis (MVA) on a complex database has been performed, aiming to reveal correlations composition-processing conditions-microstructure for some clinkers. Database was made of cement clinker chemical analysis, information extracted from image analysis on clinker micrographs and clinkering plant process parameters. Clinkers were burned in different conditions in industry (19) or in laboratory (14 different clinkers in two groups). Image analysis of each clinker has been made by computing Shape Parameters, Fractal Dimension and a parameter derived from Shannon Entropy, called the Uniformity Degree. Also, the intermixed C3A and C4AF minerals as interstitial phase of the clinkers have been isolated and analyzed. MVA results clearly identified the influential parameters on the database. It was found that the free CaO content in clinker was influential on both composition-microstructure and process parameters. Therefore, we concluded that the free CaO can be seen as a link between laboratory and industrial parameters in understanding these complex correlations.
Keywords
Image Analysis, Multivariate Analysis, clinker, optical microscopy, Shannon entropy, Fractal Dimension, Interstitial Phase
YU HAN, BAO-MIN WANG , SHUAI LIU
Abstract
Mechanical performances of carbon nanotubes reinforced cement-based composites have been studied separately. The autogenous shrinkage of cement-based composites doped with multi-walled carbon nanotubes (MWNTs) were investigated with low MWNTs concentration of 0, 0.05%, 0.1% and 0.15% by weight(wt%) of cement in the early age in this paper. Ultrasonic processing and a commercially surfactant were utilized to achieve homogenous MWNTs suspensions. The addition of MWNTs decreased the autogenous shrinkage of cement composites compared to the reference sample. When the MWNTs dosage was 0.15 wt%, the autogenous shrinkage of specimen was the minimum, which was 28% lower than the reference sample. The water-cement ratio affects the early-age autogenous shrinkage more obviously. The results indicated that MWNTs can also have a beneficial effect on the early strain capacity, the early-age and long term durability of the cement-based composites
Keywords
Multi-walled carbon nanotubes; cement-based composites; durability; early-age autogenous shrinkage
J.S. POZO-ANTONIO, J. FEIJOO
Abstract
Concrete lime- and NHL-based mortars were prepared with river sand and a standard ASTM sand as aggregate. The mortar samples were subjected to different curing conditions for 28 days in order to achieve the acceptable mortar strength in a shorter period of time, with the aim to move the repaired artworks from the restoration departments of museums while avoiding possible contamination or damages. The results are provided under the study of the influence of the curing conditions, the binder nature, the binder/aggregate ratio relation and the aggregate nature. The test results showed that ASTM sand was a good alternative to river sand; it even improved the mechanical characteristics and drying shrinkage of the NHL-based mortars and lime cement-based mortars. NHL5, with a lower amount of aggregates, achieved higher values of flexural tensile and compressive strength and performed mortars with lower shrinkage values, being the ASTM sand the aggregate that provided better properties. Synthetically, the lime based mortar NHL5 (1:1.75) with ASTM sand under 14 days at a RH of 90 ± 5% and 14 days at a RH of 60 ± 5% seemed to be a satisfactory solution to be used as repair mortar in order to achieve good mechanical and physical properties without long periods in restoration departments.
Keywords
Portland cement, lime, mortar, aggregate, curing, Compressive strength, Modulus of Elasticity, Mechanical properties, Drying shrinkage
CAI JUN, LI GENGYING
Abstract
Self-compacting concrete (SCC), also known as self-consolidating concrete, can be classified as an advanced construction material. SCC is a highly flowable concrete that can achieve full compaction without the need of vibration. In this study, the influence of fly ash on workability, mechanical properties and drying shrinkage of SCC specimens were investigated. The amount of fly ash was varied from 0% to 60% by mass of the binder material. Workability of SCC was characterized by the slump flow and the V-funnel tests. Test results showed that the workability of fresh SCC is improved by increasing the amount of fly ash. Compressive strength, splitting tensile strength and flexural strength decrease with the increase of fly ash. Fly ash can obviously reduce the drying shrinkage of SCC.
Keywords
self-compacting concrete, mechanical properties, drying shrinkage
RADU VOINIȚCHI, CONSTANTIN DORINEL VOINIȚCHI, VIOREL CRĂCIUN, ALINA BĂDĂNOIU
Abstract
This paper presents new insight regarding the influence of aggregate particles dosage and shape on the main properties of pervious concretes. The results presented in this paper show a correlation between the permeability coefficients assessed on aggregate mixture and corresponding previous concretes with various cement contents. This suggests that is possible to design pervious concretes with a prescribed permeability value, using as imput values the results obtained in permeability test of aggregate mix and applying a correction coefficient which depends on cement matrix content.
The replacement in the coarse aggregate fraction (8/16 mm) of polyhedral particles with flat particles (length to thickness ratio higher than 3) do not exert a major influence on the values of permeability coefficient of aggregate mixtures and derived pervious concretes. Nevertheless, a significant decrease of compressive strength is observed when the polyhedral aggregate particles of the coarse aggregate fraction (8/16 mm) are replaced with flat particles.
Keywords
pervious concrete, aggregate shape, water permeability, compressive strength
G. MURALI, A.S. SANTHI , G. MOHAN GANESH
Abstract
The aim of the study is to investigate the loss of mechanical properties such as compressive and splitting tensile strength of fiber-reinforced concrete (FRC) when exposed to impact load. Two different steel fibers i.e. hooked end and crimped end having the length of 50 mm and an aspect ratio of 50 were used as reinforcing materials in 0.5%, 1.0% and 1.5% volumes with a water-binder ratio of 0.42. The American concrete institute (ACI) committee 544 drop weight test was performed on 28 days cured cylinders, in order to determine the impact failure energy. In order to identify the loss of compressive and splitting tensile strength due to the effect of impact, another set of samples were prepared from the same concrete mixtures and exposed to impact loads of 25%, 40%, and 55% of their impact failure energy. Based on the results obtained from the experimental work, multivariate linear regression (MLR) models were developed using SPSS software to predict the percentage loss of compressive and splitting tensile strength due to the effect of impact load and the validity of the proposed model were verified with the test data of an earlier research. The results showed that the loss of compressive and splitting tensile strength in FRC significantly decreased compared with concrete without fiber, when exposed to impact loads. The results of the proposed model provided good agreement with the experimental results.
Keywords
Compressive strength, Tensile strength, Fiber, Impact, loss of strength
ASLAM HUSSAIN , SALEEM AKHTAR
Abstract
Structural Health Monitoring (SHM) plays an important role in retrofitting of concrete structures. In this paper, soundness of concrete material in three domes of a structure was evaluated by the use of Schmidt Rebound Hammer test and X-ray Diffraction (XRD) test after initially investigating the whole structure visually. It has been realized that value addition in the field of NonDestructive Testing (NDT) of Civil Engineering Structures is possible only through combination of various testing techniques. By successfully combining the results of visual inspection, strength based physical test and chemical test, authors have succeeded in introducing a novel idea for further research. XRD test, which has generally not been categorized as an NDT tool for structural evaluation, gives satisfactory results when combined with a strength based NDT tool.
Keywords
Structural Health Monitoring; Soundness of Concrete Material; X-ray Diffraction; Visual Inspection; NonDestructive Testing; Combination of Testing Techniques
AREF MOHAMAD AL-SWAIDANI
Abstract
The objective of the present work is to predict the compressive strength, water permeability, chloride penetrability and porosity of concretes containing volcanic scoria as cement replacement after 2, 7, 28, 90 and 180 days curing. Concrete specimens have been produced with three different water-binder ratios of 0.5, 0.6 & 0.7 and replacement levels ranging from 10 to 35%. Test results revealed that curing time, the scoria content and the water-binder ratio had a large influence on all the examined properties of scoria-based concrete. An estimation equation has been developed by the authors to predict the studied properties depending on the water-binder ratio, the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported, as well.
Keywords
Blended cement, Volcanic scoria, Concrete, Prediction of properties
VLAD LUPĂȘTEANU, NICOLAE ȚĂRANU, PETRU MIHAI, GABRIEL OPRIȘAN, RADU LUPĂȘTEANU, DRAGOȘ UNGUREANU
Abstract
The interface behaviour of carbon fibre reinforced polymer composite (CFRP) strips bonded to steel surfaces is a key aspect in assuring an efficient strengthening solution for structural or non-structural steel elements.
The experimental program which is presented in this paper was developed at the Faculty of Civil Engineering and Building Services from Iasi, and it focused on the investigation of the behaviour of the CFRP-to-steel bonded interfaces. A number of 25 single lap shear specimens were prepared and tested up to failure. The parameters considered in this study were: the type of the CFRP composite strip, the type of the adhesives and their thicknesses. In addition, the influence of the surface preparation was analysed by comparing the results obtained for specimens with grit-blasted steel surfaces and for untreated ones. The specific failure modes were identified and commented on the basis of the performed tests; the load-displacement curves were plotted and the strain distributions along the bond lengths were investigated at different load stages.
Keywords
CFRP composite strips, steel, interface behaviour, bonded single lap shear joints
V. KARAYANNIS, K. NTAMPEGLIOTIS, S. LAMPRAKOPOULOS, D. KASITEROPOULOU, G. PAPAPOLYMEROU, X. SPILIOTIS
Abstract
In the current research, clay-based bricks with beneficial utilization of industrial “scrap-soil” as admixture were developed and characterized, in order to contribute to circular economy, environmental protection and conservation of natural resources. “Scrap-soil” is an industrial soil containing residues of steel scrap and/or steel making by-products as a result of their temporary storage in open steel industry soil spaces. Brick-shaped specimens were formed by extrusion of clay/”scrap-soil” mixtures in various proportions up to 9 %wt. industrial soil, and then fired at different peak temperatures (850-1100oC). Shrinkage and weight loss upon sintering as well as bulk density, porosity, mechanical strength and thermal conductivity of sintered ceramic microstructures were determined and studied as a function of the admixture percentage and firing temperature. The experimental results confirm that incorporation of “scrap-soil” into standard red ceramic bodies is feasible, as their shape, density, mechanical performance and thermal conductivity remain practically unaffected with increasing the admixture percentage. Moreover, the sintering temperature can be optimized either to obtain specific characteristics of the brick bodies or to attain energy savings.
Keywords
“scrap-soil”, steel industry, clay bricks, extrusion, sintering, characterization
DOREL RADU, OVIDIU DUMITRESCU , IRINA PINCOVSCHI
Abstract
Vitreous oxide systems can be described at several structural levels. Thus, the first considered is the atomic level, where typical structural entities are oxygen ions and various cations in fixed proportions. In this case, the determined properties of the glass are the molar volume, the molar volume of oxygen ion and compactness.
In our research work all these properties were calculated based on the experimental data obtained by analyzing glasses with (35–x) Na2O·xAl2O3·65B2O3 molar formula, where x = 0; 5; 10; 12.5; 15; 17.5. Practically, there were established mathematical relations for quantities such as structural compactness - chemical composition, structural compactness – structural characteristics of the studied glasses, respectively.
Keywords
Na2O–Al2O3–B2O3 glass, molar volume, molar volume of oxygen ion, compactness, density, correlation
MIHAI EFTIMIE, EDUARD MARINESCU, ALINA MELINESCU, ANDREEA MONCEA
Abstract
In recent years, electronic equipments containing cathode ray tubes (CRTs) have ceased to be produced in developed countries and were replaced by modern equipment, more economical and lighter. The glass waste resulting from the cathode ray tube is a valuable raw material which can be used to obtain other materials such as glass-ceramics, with different applications.
Present paper aims to study the crystallization of CRT glass with low barium oxide content with 15% by weight added nucleating agent (TiO2, ZrO2 and ZnO). For the obtained samples X-ray diffraction analysis were carried to determine the crystalline phases and scanning electron microscopy to examine the microstructure and the resulting phases from heat treatment. Thus, the influence of nucleating agent and heat-treatment temperature on the properties of the glass ceramic were revealed.
The material has applicability in constructions, e.g. decorative or insulation tiles. Its advantages result from the high percentage of waste reused, with positive impact on the environment, and from the low temperature needed for manufacturing [1-3].
Keywords
cathode ray tubes, glass-ceramics, low barium oxide content
EMILIA MOSONYI, NICOLETA COBÂRZAN
Abstract
The paper presents an interdisciplinary study based on: site inspections, petrographical and mineralogical research (staining methods, transmission polarizing microscopy, XRD analyses) and water absorption tests performed on amples extracted from replaced masonry units (tiles, blocks), weathered and non-weathered Portland cement mortars and tuff tiles from fortifying walls of a monumental tuff-made construction. The main outlined weathering processes were: intensive cracking (drying shrinkage; alkaline-aggregate-reaction, carbonation and salt crystallization, frost attack) and leaching associated with secondary carbonation and sulphate (intrinsic and extrinsic) attack induced expansive phenomena. The chemical and physical incompatibility between tuff, brick and cement based mortar beside the high level of stagnant humidity along the zeolites- bearing tuff blocks surfaces appears to be the first cause of decay and deleterious effects.
Keywords
historical building, volcanic tuffs, petrographic microscopy, sulphate-attack, staining methods, compatibility.
FLORENTINA ALINA BURLACU, CARMEN RĂCĂNEL, ADRIAN BURLACU
Abstract
Road safety has an increasing importance, especially after UN proclaiming 2011-2020 the Decade of Action for Road Safety. As many factors contribute to producing traffic accidents, infrastructure has its own part in this. Studies related to road surface are very important, especially due to the fact that the quality of the tyre-road surface contact could influence the occurrence of road accidents. Aspects like skid-resistance, permeability, and evenness are the main properties that should be taken into consideration for a road surface. The present research paper has the aim to correlate the characteristics of materials used in the wearing layer with the risk of producing road accidents, by calculating the braking distance, as a sub-component of stopping sight distance. The results of the laboratory tests undertaken on aggregates will show that only by varying the source of materials, stopping sight distance can differ with up to 20 meters.
Keywords
road materials, road safety, laboratory tests, roughness, polishing, stopping sight distance