română ANDREI TIBERIU CUCURUZ, ECATERINA ANDRONESCU, ANDREIA CUCURUZ, GEORGE PELIN
Abstract
The aim of this work was to prepare via in situ radical polymerization polymethacrylic acid/Al2O3 composite materials and to modify the structure of alumina with two silane coupling agents, 3-aminopropyl-trimethoxysilane (APTMS) and dichlorodimethylsilane (DMDCS). Also, the influence of silanization on the physico-mechanical properties of the resulting composite materials was studied. The surface modification of inorganic particles appears as an efficient technique to improve interactions between polymer matrix and nanoparticles.
The modification of alumina was investigated using transmission Fourier transform infrared spectroscopy that confirmed the success of the silanization procedure. The crystalline phase was identified using XRD analysis and the presence of alumina in the composite materials is demonstrated according to ASTM. Scanning electron microscopy revealed in all the analyzed samples alumina particles with spherical morphology that are embedded homogeneously in the organic polymer matrix. Also, the mechanical properties of composites were investigated based on xylene porosimetry and compression testing.
The composite materials synthesized in this study demonstrated a good potential for application in dentistry as dental resins or denture base materials.
Keywords
Alumina, Polymethacrylic acid, Composite materials, Denture base materials
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Year
2019
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Issue
49 (1)
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Pages
3-11
ELISABETA VASILESCU, VLAD GABRIEL VASILESCU, ION PĂTRAȘCU, BOGDAN GĂLBINAȘU
Abstract
The quality of metal - ceramic restorations is closely related to the quality of the metal - ceramic bond, where the rigidity of the metallic structure that prevents the occurrence of the flexural forces in the plating ceramic and in the interface area is an essential condition. Typically cast, the metallic component is made up of various metals and noble alloys or non-noble alloys.
Titanium and titanium alloys are at present an ideal solution due to their exceptional properties such as: corrosion resistance and high mechanical strength, density, thermal conductivity and reduced thermal expansion coefficient.
The research carried out aimed at studying the behavior of a new titanium alloy in metal - ceramic technology (Ti10Zr), a preliminary study on metal - ceramic bonding compared to conventional alloys (Ti6Al4V) and pure titanium (TiCp). The evaluation of the Ti10Zr-ceramic bond T22 Noritake was performed by mechanical tests, namely the shear resistance measurement and the determination of the final value of the force at which the ceramic component of the metal substructure is detached.
Mechanical tests were complemented by indirect, non - destructive methods of assessing the strength of metal - ceramic bonding.
The experimental results obtained confirm some results from the literature on the behavior of non - alloying alloys as substructures in metal - ceramic restorations, and on the other hand they can constitute novelty elements regarding the behavior of a new titanium alloy (Ti10Zr) as a component metallic in metal - ceramic technology.
Keywords
non - noble alloys, Ti10Zr bioalloy, metal - ceramic connection, mechanical tests metal – ceramic (M – C) prosthetic restoration, oxide, layer thickness, SEM analysis
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Year
2019
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Issue
49 (1)
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Pages
12-22
ADRIAN-IONUȚ NICOARĂ, ALINA-IOANA BĂDĂNOIU, GEORGETA VOICU
Abstract
Intumescent materials have the ability to swell when are subjected to fire or thermal treatment. This type of materials is used for passive fire protection in buildings, providing thermal protection or sealing the penetrations in walls preventing fire spreading in adjacent rooms.
In this paper is presented the synthesis of intumescent alkali activated borosilicate inorganic polymers (AABSIPs) by the alkaline activation of waste glass powder (WGP) with NaOH or/and KOH solutions and borax additions.
The partial substitution of NaOH with KOH, in alkaline activator composition, improves the workability of fresh AABSIP pastes, as well as the volume increase during the intumescence process. By fine tuning of various parameters (alkali activator composition, water to solid ratio) is also possible to modify the activation temperature of intumescence process.
Keywords
Geopolymer, intumescent, fire protection, alkaline activation, waste glass
CRISTINA GHITULICĂ, SIMINA ȘTEFAN, OTILIA RUXANDRA VASILE, ROXANA TRUȘCĂ, IONELA ANDREEA NEACȘU, BOGDAN ȘTEFAN VASILE
Abstract
The aim of this study was to synthesize and characterize a ceramic material with a high porosity, which can be used as a support for the microorganisms’ colonies for water purification. Given the target application, in order to obtain a composition of the ternary system MgO - Al2O3 – SiO2, there were selected two natural materials: kaolin and talc powders. The chosen processing method involves mixing the ceramic powder with a porogen organic compound, in order to achieve a homogeneous suspension. Sintered ceramic samples were characterized in terms of ceramic properties, microstructure and phase composition using laser granulometry, Hg porosimetry, X-ray diffraction and scanning electron microscopy. The growth and activity of biofilm was investigated.
Keywords
silicates, environment, biomaterials, ceramic filter, microorganisms
MARIA P. NIKOLOVA, STEFAN VALKOV, RODICA IOSUB, EMIL YANKOV, PETER PETROV
Abstract
An approach to surface modification for direct formation of nanosized anatase over cathodic arc PVD deposited (Ti,Al,V)N coating at a temperature of about 150 °C is proposed. In order to determine the surface structure influence on the electrochemical properties, bare and coated samples were exposed to Ringer-Braun physiological solution. The aim was to compare their corrosion performance (impedance characteristics, obtained by means of EIS and cyclic voltammetry (CV)) during immersing over an extended period of time - 2 hours, 1 and 7-days while the average temperature was close to the human body level (37±1°C). The capacitive behavior of the coated sample indicates a phase angle close to 71º and slightly decreasing impedance modulus /Z/ because of disruption by the high initial hydration and ions diffusion from the saline. The corrosion resistance of the coated system decreases as a function of time as a result of the thin oxide dissolution and lack of re-passivation of the nitride. The characterization of the surface layer of the coating was obtained by scanning electron microscopy (SEM), glow discharge optical emission spectrometry (GDOES), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis of core electron levels.
Keywords
biomaterials, nanostructures, metallic materials, materials research, PVD coating
VAN-HUONG NGUYEN, NORDINE LEKLOU, PIERRE MOUNANGA
Abstract
Delayed ettringite formation (DEF) is a type of internal sulphate attack caused by heat-induced decomposition and/or prevention of normal ettringite formed during the initial hydration of cement at elevated temperature (above about 70°C) and its re-crystallization in the hardened matrix. DEF is a physico-chemical phenomenon inducing an expansion of the cement paste that could lead to cracking of concrete. In this paper, the effect of metakaolin on DEF of the heat-cured mortars was investigated. To fulfil the aim of this study, a portion of cement was replaced by metakaolin, with three different dosages (10, 20 and 30%). The mortars were heat-cured at early-age, and the tests of expansion, strength, dynamic elastic modulus and thermogravimetric analysis were carried on these mortars a period of 650 days. Additionally, scanning electron microscopy (SEM) observations were realized. The test results obtained highlighted the mitigation effects of metakaolin on DEF.
Keywords
Metakaolin, Delayed ettringite formation (DEF), heat-cured mortar, expansion, concrete
G. SKRIPKIUNAS, G. YAKOVLEV, E. KARPOVA, P.L. NG
Abstract
The application of accelerating admixtures is required in construction work where fast-setting is required or in an environment of low temperature. This type of admixtures allows to regulate the setting and hardening time of cement composites and could influence on their strength and performance. The accelerating admixtures are exemplified by chloride, nitrate and other salts. Some investigations demonstrated the application of different types of nano- and complex additives as a method to accelerate the hydration processes of cement composites.
The present study focuses on the investigation of the combined action of multi-walled carbon nanotubes (MWCNT) dispersion and various types of accelerating admixtures such as calcium chloride, calcium nitrate and magnesium chloride. The amount of accelerating admixtures ranged from 1% to 3% by weight of cement, the amount of MWCNT for all compositions remained equal to 0.005% by weight of cement. The setting time of cement pastes modified by different types of accelerating admixtures and MWCNT dispersion was determined. The combined effects of MWCNT dispersion and accelerating admixtures on compressive and flexural strength, water absorption and porosity of cement mortar modified by calcium chloride and MWCNT were studied. Besides, the cement hydration products were evaluated by FT-IR spectroscopy and XRD analysis. The individual and combined effects of accelerating admixtures and MWCNT addition are reported in the article.
Keywords
Cement, Accelerating admixtures, Setting time, Calcium chloride, Multi-walled carbon nanotubes
NORDINE LEKLOU, PIERRE MOUNANGA
Abstract
This article presents a study on the microstructural evolution of the cementitious matrix at early stages of hydration. The main objective was to follow the development of the interfacial zone between cement paste and granular inclusions during the hardening process. For this purpose, the “simple replica” method was used. This technique consists in observing a facsimile of the polished sample surface. This prevents drying and cracking of the sample during observation under vacuum with a scanning electron microscope (SEM). The study was conducted on Portland cement mortars containing glass beads with diameters of 3 and 8 mm. The effects of inclusion size and temperature were analysed at different time of observation, between 8 and 120 hours of hydration. The results showed a progressive separation between cement paste and glass beads, and the presence of microcracks in the matrix kept at 40°C.
Keywords
Cementitious matrix, glass beads, microstructure, replica method, endogenous microcracking
YUE LI, ZHONGZHENG GUAN, ZIGENG WANG, PENG WANG, GUOSHENG ZHANG, QINGJUN DING
Abstract
This paper presents an integrated investigation of deterioration process of corroded concrete by experiments and theoretical model. First of all, the porosities of concrete samples with different corrosion periods were measured by the mercury intrusion porosimetry (MIP). Then the distribution of sulfate ions in the concrete was measured by the spectrophotometric method. Afterwards, the compressive strength were measured. The results indicated that the porosity and the compressive strength of concrete in water firstly increased and then progressively stabilized at a constant value due to the hydration of cement. However, those values of concrete soaked in 5wt.% Na2SO4 solution increased and then decreased, resulted from the combination of cement hydration and the corrosion of sulfate ions. Moreover, a Stratified-Theoretical calculation model was established with the input parameters of corrosion depth of sulfate ion, length of concrete specimen, strength of concrete immersed in water and in sulfate solution. At last, the corrosion resistance coefficient of corrosion layer was firstly put forward to evaluate the deterioration process of concrete with high effectiveness.
Keywords
concrete; ternary copolymer fibers; dispersion; compressive strength
DAMIR ZENUNOVIC , NESIB RESIDBEGOVIC, RADOMIR FOLIC
Abstract
The experimental tests were carried out with the aim to develop a rapid procedure for predicting chloride penetration into concrete, without stimulating the migration of chloride ions with electricity. Pressure Penetration Test (PPT) results were compared with the results obtained using the standardized Bulk Diffusion Test (BDT). The testing was carried out on 15x15 cm concrete cubes. Chloride penetration into concrete samples was modeled by analyzing previous studies and selecting suitable mathematical models. The two models were modified by introducing chloride penetration coefficients, experimentally determined by comparing PPT and BDT chloride profiles. The study confirmed the possibility of applying the PPT procedure for the rapid prediction of chloride penetration into concrete.
Keywords
concrete, chloride, diffusion, penetration, modeling, comparison
YANG LI, ZHENDI WANG, LING WANG
Abstract
Air entraining admixture is often used to improve fluidity and freeze-thaw resistance of concrete through introducing dispersed micro bubbles. Driven by the Great Western Development Strategy and the Belt and Road Initiative of China, a large amount of concrete are used for the construction at high altitude areas of western China. But it was found that the fluidity and freeze-thaw resistance of concrete decreased a lot due to low atmospheric pressure at high altitude. To explore the influence of low atmospheric pressure on the performance of cementitious material, flow-through time of cement paste and pore size of hardened cement paste were tested. The flow-through time at 20 kPa was increased by 27.6% to 135.0% compared to normal atmospheric pressure (100 kPa). As the atmospheric pressure decreased from 100 kPa to 40 kPa, the average pore diameter of the high W/C hardened cement paste decreased to 75.3% to 71.3%, whereas the average pore size of the low W/C hardened cement paste increased by 39.0%. This reflects that the fluidity and the freeze-thaw resistance of cementitious material will decrease more or less at lower atmospheric pressure. The changes of fluidity and freeze-thaw resistance durability may be explained by the increased diameter of bubbles in fresh cement paste at lower pressure.
Keywords
Low atmospheric pressure; Pore; Bubble; Air entraining admixture
LINGJIE WU, LINZHU SUN, FANG YANG, DONGYAN WU, JUNLIANG ZHAO
Abstract
Based on the fiber dispersion and concrete compressive strength tests, the effects of mixing method, mixing time and fiber content on the dispersion performance of ternary copolymer fibers in concrete were studied. The experimental results show that a modified dry mixing method benefits the dispersion of the fibers in concrete and obtains a desirable mechanical performance as compared with wet mixing and ordinary dry mixing methods. With an increase in mixing time, the fiber dispersion coefficient and the compressive strength of concrete increased at initial stage and then decreased. In addition, the fiber dispersion coefficient and the compressive strength of concrete decreased with the increase of fiber content. Taking both the strength properties of the concrete and economic factors into consideration, the modified dry mixing method was considered the most desirable mixing method, with an optimum mixing time of 6 minutes and an ideal fiber content of 0.14%.
Keywords
concrete; ternary copolymer fibers; dispersion; compressive strength
RĂZVAN LISNIC, CRISTINA BUSUIOC , GEORGETA VOICU, SORIN-ION JINGA
Abstract
Two types of natural gypsum from different regions of Romania and two types of synthetic gypsum resulted in the flue gas desulfurization (FGD) industrial installation where characterized from compositional, structural and morphological point of view by thermal analysis, X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and laser granulometry. The mortars developed based on portland cement and different proportions of gypsum were also investigated in terms of setting time and mechanical properties (flexural strength and compression strength), in correlation with the visualization of the hydration products through scanning electron microscopy. The results were correlated with the purity and homogeneity of the analysed gypsum specimens.
Keywords
Portland cement; Natural gypsum; FGD gypsum; Setting time; Flexural strength; Compression strength
AGNE SMIGELSKYTE, RAIMUNDAS SIAUCIUNAS, MATTHIAS WAGNER, LIUDVIKAS URBONAS
Abstract
Rankinite binder material was synthesised from the mixture (C/S = 1.5) of locally (Lithuania) available materials – opoka and limestone – at 1250 °C for 45 min. Its suitability as a non-hydraulic binder for carbonation curing has been assessed.
Mortar samples prepared of binder and sand mixture (15:85 wt%, w/c = 0.35) were pressed and cured in a pressure reactor using gaseous (5 and 50 bar at 20 and 50 °C) and supercritical CO2 (150 bar at 50 °C) for 4 and 24 h. It was determined that with increasing pressure, exposure time and/or temperature the carbonation process is intensified, sample compressive strength is highly increased. Hardening samples at the highest conditions led to full carbonation and the highest strength. For the first time it was shown, that at the supercritical CO2 conditions the compressive strength of the rankinite binder samples was higher than the OPC ones. The study showed that rankinite as a binder material is suitable for carbonation curing and could be used to produce carbonated construction materials.
Keywords
Rankinite, non-hydraulic binder, carbonation curing, CO2, opoka, limestone
KAMILE TOSUN FELEKOĞLU, EREN GÖDEK
Abstract
In this study, the matrix rheology, mechanical performances and thermal insulation properties of high tenacity polypropylene fiber (HTP) incorporated lightweight engineered cementitious composites were investigated. Matrices were prepared by using air entraining admixture 2, 4 and 8% of cement weight and HTP fibers added to matrices by 2% of total matrix volume. Before fiber addition, rheological properties of matrices were investigated by using a ball type rheometer. After fiber addition, the air entrainment percentages of composites were determined through theoretical calculations, aerometer test, and image processing methodology for comparison purpose. Specimens were cast into: 25x60x300 mm prismatic molds for flexural strength and thermal tests; dog-bone molds for tension tests; 50x50x50 mm cubes for compression tests. Crack numbers and crack widths of specimens were measured additionally to the mechanical test by using a portable hand microscope at unloaded state in order to investigate crack properties after flexural and tensile test. Thermal properties of composites were also investigated by thermal conductivity and thermal permeability measurements. The thermal conductivity values of composites were achieved by using prismatic specimens before flexural tests. Correlations between air-dry densities and thermal conductivities were calculated. Additionally, thermal permeability of composites were obtained by using a novel thermal camera integrated test setup, which simulates actual site conditions, and related with the thermal conductivity test results. In conclusion, composites were lightweightened by 19-35%. The accuracy of the aerometer test was confirmed by image processing technique. Yield stress and viscosity of matrices were decreased by increasing air entraining admixture dosage and 8% of air entraining admixture dosage was found much preferable in terms of consistency preservation. First crack (in both flexural and tensile tests) flexural, tensile and compressive strengths of composites were decreased by increasing air entrainment percentage. By taking air entrained composites into account, deflection and strain capacity of HTP-LECCs were increased by increased admixture dosage. Also, crack numbers were increased and crack widths were decreased by increasing admixture dosage within air entrained composites. Thermal permeability of composites were investigated by novel thermal camera test setup. Strong correlation (R=0.96) was found between thermal conductivity and thermal permeability tests.
Keywords
Lightweight ECC, air entrainment, rheological, mechanical, thermal, HTP
RADU KUNCSER, MARIA PARASCHIV, CRISTINA CIOBANU, OTTO BOSNIAK, MALINA PRISECARU, MOHAND TAZEROUT
Abstract
In this moment plastics provide a fundamental contribution in all activity fields: cars, aircraft, electronics, building, domestic daily activities, packing, etc. so the consumption of plastics has increased drastically. The disposal of plastic composite wastes is a serious environmental problem as they are not biodegradable. As a consequence, our work is focused in recycling of carbon fibers and glass fibers from waste composites through pyrolysis and partial oxidation.
Keywords
recycling, carbon fiber, glass fiber
The compressive behaviour of aggregates cemented with fly ash collected from coal-fired power plants
ANCUŢA ROTARU, VASILE BOBOC, NICOLAE ȚĂRANU , MONTHER ABDELHADI, ANDREI BOBOC, OANA-MIHAELA BANU
Abstract
The paper analyses the compressive behaviour of aggregates stabilized with fly ash in Romania, investigating the possibility to use the fly ash residue obtained from the combustion of lignite type coal as a cement substitute material for road construction works. The experimental testing of some proposed mixes embedding 20%, 25%, and 30% of fly ash by weight of total mixture, collected from Iaşi and Vaslui coal-fired power plants, reveals that only the mixtures of aggregates stabilized with 30% of fly ash fulfill the acceptability conditions to be used as a base layer in road construction works. Instead, the mixtures stabilized with 20% and 25% of fly ash could be used as sub-base layers.
Keywords
compressive strength, fly ash, aggregates, cement-like material, road building work.
DAN GEORGESCU, LAURENȚIU RECE, ANCA IONESCU, ADELINA APOSTU
Abstract
The use of admixtures in the preparation of cement and concrete is already a widespread solution at national and European level. There is often the issue of promoting new compositions with varying percentages and types of additions for certain applications and exposure environments, the main issue being to ensure good behavior over time and to ensure a proper working life. The article presents the applications of performance-related methods used at European level to check the possibility of using new compositions in certain exposure environments. These methods stand for useful tools in completing the water/cement equivalent ratio method,expected to provide similar time behaviors to a reference composition. The article presents the 1frost-thawing resistance of concrete based on the results of experimental research carried out by the authors.
Keywords
concrete, cement with mineral admixture, compressive strength of concrete, k-value concept, performance methods.
PENG ZHAO, QIN LEI, XIUZHI ZHANG, WENJUAN HUAN, HAIJIAN MA
Abstract
This experiment takes the mass loss rate and relative dynamic elastic modulus as indicators to study the damage degradation process of black bricks in freezing-thawing environment and sulfate corrosion environment under pressure load, it compares and analyzes the characteristics of freezing-thawing damage and mutual influence of various failure factors. This paper also performs experimental research and theoretical analysis of the process of damage degradation of black bricks under action of freezing-thawing cycles. The study finds that under the action of only freezing-thawing factor, the relative dynamic elastic modulus of the black brick test piece decreases to about 0.60 after 80 cycles of freezing-thawing, reaching the failure criteria of the test piece. The coupling effect of the load and sodium sulfate accelerates the decline of the relative dynamic elastic modulus of the test piece under the action of freezing-thawing. Finally, this paper combines with the freezing-thawing fatigue damage equation model, through the number of indoor freezing-thawing cycles of the black brick, uses the Geographic Information System (GIS) software TopMap7 to draw various freezing-thawing life distribution maps of the black bricks under water freezing, load and salt freezing environment.
Keywords
Black Brick; Durability; Freezing-Thawing; Life Prediction; Model
GEORGETA VELCIU, ALINA MELINESCU, VIRGIL MARINESCU, VICTOR FRUTH, CRISTIAN HORNOIU, MARIA PREDA
Abstract
Two types of La0,6Sr0,4Co3-δ and La0,5Sr0,5Co3-δ compositions were studied. The preparation of mixtures from La2O3, SrCoO3 and Co3O4 was made by mechanical activation. The obtained powders have a monomodal distribution of particle sizes and low dispersion. Reactions occurring in the formation of compounds in these mixtures were studied by complex thermal analysis. The two compositions have been sintered at a temperature of 1250°C. The mineralogical composition determined on thermally treated samples showed that in case La0,6Sr0,4Co3-δ compound a solid solution was formed with the cubic structure derived from LaCoO3, and for La0,5Sr0,5Co3-δ a solid solution with a hexagonal structure corresponding to SrCoO3. The samples formed single-phase at 12500C. The electrical conductivity measurements showed a semiconductor behavior for La0,6Sr0,4Co3-δ, and conductor behavior for La0,5Sr0,5Co3-δ.
Keywords
solid solution, electrical conductivity, SEM
MERUYERT KAYGUSUZ
Abstract
The sol-gel process has received a great deal of attention in the past decade due to advantages such as low temperature processing and high homogeneity of final products. The preparation of TiO2-SiO2-GLYMO composite by the sol–gel method is efficient at producing thin, transparent multi-component oxide layers. In this study, the preparation of TiO2-SiO2-GLYMO composite and its characterization were investigated. TiO2-SiO2-GLYMO nanocomposite was prepared from tetraethoxysilane (TEOS), titanium n-butoxide (TBO) and GLYMO (3-glycidoxypropyl)-trimethoxysilane) catalyzed with acid. Scanning electron microscopy (SEM) was employed to characterize the surface properties of composite films. The chemical structure of the composite was evaluated by means of Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Particle size was determined by a particle sizer. In summary, transparent and uniform nano colloidal TiO2-SiO2-GLYMO composite solutions were successfully synthesized though the sol-gel method. The turbidity values of the TiO2-SiO2-GLYMO composites were in the range of 8.4±0.4–12.7±0.6 ntu, and the pH values were in the range of 4.8 to 5.2. The particle sizes of the obtained composites were in the range of 5.9±1.3–22.1±1.2 nm. It was determined that the viscosity of the TiO2-SiO2-GLYMO composite solutions was approximately equal to 3-7 mPas. The thin transparent coatings obtained from these solutions were evenly distributed.
Keywords
TiO2-SiO2-GLYMO nanocomposite, Sol-gel, Leather, Finishing, Coating
I.M. SUTJAHJA , A. O. SILALAHI, S. WONORAHARDJO, D. KURNIA
Abstract
Determination of thermal conductivity based on temperature history (T-history) method is low in cost and can be applied directly to some samples, as it depends only on the number of temperature sensors used in a measurement. However, very little published data has reported the solid and liquid thermal conductivities of phase-change materials (PCMs) based on this analytical method. The thermal conductivity based on T-history data is related to other thermophysical parameters of the PCM, such as the solid and liquid specific heats and the latent heat of the solid–liquid phase transition. This report analyses the solid and liquid thermal conductivities of CaCl2·6H2O as an inorganic PCM, using thermophysical parameters obtained from two methods of analysis, namely the T-history method proposed by Zhang et al. and its improvement by Hong et al. (Z/H) and Marin et al. (M) based on the temperature-dependent enthalpy curve. The data predict the enhancement of thermal conductivity with 1 wt.% ZnO nanoparticles as a dopant, which permit effective heat transport in the material in response to environmental heat.
Keywords
Phase-change material (PCM), CaCl2·6H2O+ ZnO dopant, T-history method, solid and liquid specific heats, heat of fusion, enthalpy-temperature curve, solid and liquid thermal conductivities
VASILE MÎNZATU, CORNELIU MIRCEA DAVIDESCU, ADINA NEGREA, PETRU NEGREA, MIHAELA CIOPEC, COSMIN VANCEA
Abstract
Cellular glass is an insulation material that competes with polymeric and fibrous insulators on the market, having significant advantages such as the constant insulation efficiency, fire protection, corrosion and moisture resistance and long term dimensional stability. The present paper proposes a green solution to harness the exhausted composite adsorption material resulted from the removal of arsenic from wastewaters, by vitrification using two types of common recycled glasses: window panes and cathode ray tubes (CRT). Based on the high carbon amount present in the exhausted adsorption material, it was used as porogen material for cellular glasses. The apparent porosity, determined using the saturation under vacuum method, ranged between 40.25 - 62.15%. The optimal porous microstructure, having small uniform pores (under 150 m) and narrow dimensional scattering, was obtained using both exhausted adsorption material and silicon carbide. The hydrolytically stability, measured according to the ISO 719/1985, classifies all the investigated glasses in HGB1-HGB3 stability classes. The arsenic, lead and iron ions leachability were determined in accordance with the American Extraction Procedure Toxicity Test. No discernable losses of arsenic or lead (in the case of samples containing CRT recycled glass) were measured, regardless of time or environment’s pH. The amount of iron extracted after 28 days was very low, ranging from 0 to 0,056 % of the total iron. The thermal conductivity of the obtained cellular glasses range from 0.092 to 0.133 W/mK, classifying them as insulators. These results confirm the viability of the proposed alternative for immobilizing the exhausted adsorption material containing arsenic together with common recycled glasses as cellular glasses having high chemical stability and good thermal conductivity with multiple economic advantages.
Keywords
arsenic adsorption, arsenic wastes, glass recycling, cellular glass
ZENO GHIZDAVET, ALINA CORNELIA BACIU, DANIELA ILIE, MIRELA IONELA LECHES
Abstract
A technological issue was addressed in the part I of the paper, i.e. recipes of different proportions of materials were used to obtain ceramic bodies (seven raw mixtures). Shaped materials were fired in industrial tunnel kilns for biscuit/glost firing. Resulting ceramic bodies were tested for industry-relevant properties. Correlations composition-properties for the ceramic body were, initially, empirically identified, by observation. Regression analysis was used, afterwards, to scientifically quantify these correlations. Results confirm the existence of fair to up to strong correlations composition – properties; therefore, properties can be easily obtained by using the composition of the raw mix. In industry, these simple calculations can serve as a preliminary assessment of the properties, to reduce the amount of experimental efforts, given a set of raw materials. Multiple-Criteria Analysis was used to show that it is possible to select, on a scientifically basis, the best available alternative of the raw materials’ proportions used i.e. the alternative that fulfills most requirements, as concerning properties. In a future, second part of the paper, the correlation processing – properties will be explored to demonstrate the influence of grinding on the glaze properties.
Keywords
tableware ceramics, correlations, Multiple-Criteria Analysis
S. JANANI, A.S. SANTHI
Abstract
Concrete, being one of the most commonly used building materials in construction industries, has, cement as its principle component. Cement paste is responsible for bonding and strength gain in concrete. The production of cement releases an equal amount of CO2 to the atmosphere causing environmental pollution. This Study identifies the property enhancement of concrete due to the partial replacement of cement with pozzolanic materials such as fly ash and silica fume at 40% and 7% respectively. Tests were conducted to identify mechanical properties – compression, split tension, flexure; and Impact resistance. Steel fibres were also incorporated at 0.75%, 1.15% and 1.55% to the mix. Addition of steel fibre to blended concrete showed an increase of 33-77% on mechanical properties and 186% on impact resistance of concrete at 28 days. A Multiple linear regression model was formulated using SPSS, and consequently, equations were derived to predict the mechanical properties and impact resistance of concrete. The equations were found to be in a good agreement with the experimental results obtained by various other researches with significance level lesser than 0.05 in ANOVA.
Keywords
fly ash; silica fume; steel fibres; mechanical properties; impact resistance; regression
AVUTHU NARENDER REDDY, T. MEENA
Abstract
Cement is one of the essential constituent for the production of concrete. However, large amounts of carbon dioxide (CO2), green house gases etc are emitted during the calcinations of limestone; for the production of one tonne of cement, the raw materials of about 2 tonnes is required and it releases approximately 1 tonne of CO2. Since, the production of cement involves excessive emission of greenhouse gases that leads to damaging of ozone layer and many environmental problems, a substitute or alternative material to cement for a sustainable construction was required. Research works are being carried out for finding out the alternate cementing material which will replace cement partially or fully due to its ill effects on the environment. The present paper reports an attempt in this direction by experimental examination on the hardened properties of concrete by replacing cement with combination of Fly ash (FA), Alccofine (AL) and Colloidal Nano Silica (CNS) in order to form a blended concrete (BC). From the experimental results, it was clearly observed that the combination of FA, AL and CNS had shown a high early age strength gaining property. Incorporation of a combination of these admixtures enhanced the mechanical and water absorption properties of the concrete. BC mix with a combination of 25% FA, 10% AL and 1% CNS with a total of 36% replacement of cement has achieved higher mechanical and water absorption properties as compared with all other mixes. The relationship between compressive strength and splitting tensile strength as well as between compressive strength and percentage water absorption is also investigated.
Keywords
Colloidal Nano Silica; Fly Ash; Alccofine; Blended Concrete; Compressive Strength; Split Tensile Strength; Flexural Strength and Water Absorption
GIDEON BAMIGBOYE , ADEOLA ADEDEJI, DAVID OLUKANNI, KAYODE JOLAYEMI, OLALEKE FASANYA
Abstract
This study focus on durability to saline environments of self-compacting concrete (SCC) made of granite-gravel combination as coarse aggregates in concrete production. In this study fine aggregates, water, superplasticizer and cement were kept constant. The percentages replacement of gravel in place of granite aggregates were 10, 20, 30, 40, and 50, while 100% granite serves as control. A total of 162 cubes of 100 x 100 x 100 mm concrete specimens were immersed over the initial curing in a water container and further cured in 5% sodium chloride (NaCl) and sodium carbonate (Na2CO3) solutions for 28, 56 and 91 days in line with ASTM C39 (2003). The tests results indicate that concrete cured in five percent (5%) of NaCl solution have compressive strength accelerating properties at early age that could not be sustained for long. While those cured in 5% of Na2CO3 solution reduced significantly the compressive strength of concrete.
Keywords
Self-compacting concrete, concrete, durability, sodium chloride, cement, sodium carbonate, compressive strength
ODAY M. ALBUTHBAHAK , ASHRAF A. M. R. HISWA
Abstract
As a non-destructive technique for concrete compressive strength assessment for existing concrete structures, Ultrasonic Pulse Velocity (UPV) test method has been widely used. Since the UPV affected by many factors, it is not easy to accurately assess the concrete compressive strength. Effect of some factors which are coarse aggregate grading type, slump, the water-cement ratio (w/c), sand volume ratio, coarse aggregate volume ratio, testing age, concrete density, and pressure of steam curing, were analyzed on the relationship between ultrasonic pulse velocity and concrete strength. 436 records of data, extracted from published research work, were used to build seven supervised machine learning regression models which are; Artificial Neural Network (ANN), Support Vector Machine (SVM), Chi-squared Automatic Interaction Detector (CHAID) decision tree, Classification and Regression Trees (CART) decision tree, non-linear regression, linear regression, and stepwise linear regression models. Also, the independent variable importance for each predictor was analyzed and for each model. With an adequate tuning of parameters, ANN models have produced the highest accuracy in prediction, followed in sequent with SVM, CHAID, CART, non-linear regression. Linear and stepwise linear regression models have present low values of predictive accuracy. w/c was observed to be the highest importance factor in prediction of concrete strength, and the forecasting of the concrete strength was efficient when using w/c and UPV only as predictors in any of the used predictive models.
Keywords
Concrete Compressive Strength, Ultrasonic Pulse Velocity, Machine Learning Models, Artificial Neural Network ANN, Support Vector Machine, Decision tree, Regression.
RIMVYDAS KAMINSKAS, IRMANTAS BARAUSKAS
Abstract
The study aims at investigating the possibility of using Autoclaved Aerated Concrete Waste (AACW) as an additive (replacement) for Portland cement. 5%, 10% and 15% (by weight) of Portland cement were replaced with this additive. The specimens of cement paste were hardened for 28 days under normal conditions in water. It was estimated that recycling of AACW as the micro-filler required one and a half less energy than a natural additive of limestone and four times less energy than conventional construction and demolition wastes i.e. cement mortar. Under normal conditions, Autoclaved Aerated Concrete Waste additive accelerates the initial hydration of ordinary Portland cement (OPC), promotes the formation of additional calcium silicate hydrates, and increases the density of cement stone. It was estimated that up to 10 % wt. of the OPC can be replaced by AACW additive without impairing the strength properties of cement paste samples.
Keywords
Portland cement, Autoclaved Aerated Concrete Waste, additives, energy consumption
QUAN WAN , MINLI ZHENG, SHUCAI YANG, WEIWEI LIU
Abstract
Micro-texturing can greatly improve the cutting performance of tools. Thus, this paper attempts to disclose the effects of laser machining on the morphology and surface performance of micro-textured tools. Firstly, the 2D and 3D morphologies of micro-textures were explored and the effects of different laser machining parameters were analyzed. After that, the author examined the microstructure and the composition of the heat affected zone (HAZ) around each micro-texture. Furthermore, the micro-hardness and nano-hardness in different areas of HAZ were subjected to comparative analysis. The results show that laser parameters directly affect the micro-texture morphology and surface material properties. With the same total energy, high power density and the number of scans can reduce the deposition of sputtering materials, improve the size accuracy of micro-texture, and increase the performance of micro-texture surface materials. The research findings lay the basis for the fabrication of micro-textured cemented carbide cutting tools.
Keywords
Cemented Carbide Tool; Micro-Textured Surface; Laser Machining; Heat Affected Zone (HAZ)
S PRAVEENKUMAR , G SANKARASUBRAMANIAN
Abstract
In this study, the experimental investigation on the flexural test of bagasse ash blended high performance concrete (HPC) and influence of steel fibre (STF) and polypropylene fibre (PPF) are carried out. The flexural test was done for beam size of 150 mm x 200mm x 1800mm with two point loading system. The concrete was considered for M60 grade (P series) as recommended by P.C.Aitcin. The blend mix included both free STF (Q series) and PPF (R series), and furthermore the hybridization of STF and PPF (S series) at a total volume fraction of 1.0% by volume of concrete with 10% bagasse ash as a substitution of cement. Structural behavior of eleven bagasse ash blended high performance concrete beams reinforced with steel, polypropylene and hybrid fibres were examined. The behavior of each beam was assessed with respect to initial crack, ultimate load, ultimate deflection, flexural strength, ductility and toughness. The inclusion of fibres increased the failure load and ensured the ductile behavior of the beams. The results demonstrated that adding hybrid fibres enhanced the mechanical properties as well as the structural behavior of beams
Keywords
bagasse ash, high Performance concrete, steel fibres, polypropylene fibres
LIVIA INGRID DIACONU, DIANA PLIAN, NICOLAE ȚĂRANU , OANA MIHAELA BANU, ADRIAN CONSTANTIN DIACONU, DĂNUȚ TRAIAN BABOR
Abstract
The aim of this paper is to present an assessment method for the modification of some essential characteristics of the concrete mixes embedding fly ash subjected to an accelerated corrosion process using softened warm water. In the construction elements exposed to water, the dissolving – levigation corrosion phenomenon occurs by washing the calcium hydroxide from the cement stone, affecting the durability characteristics. A special equipment that enables the acceleration of the processes developed in concrete structure when exposed to softened warm water was designed and constructed to subject the concrete samples to this type of corrosive attack. After subjecting the concrete specimens to softened warm water, several physical and mechanical tests were performed to determine the unit weight, the water absorption, the permeability and the compression strength. A total number of 117 cubic samples were tested for a period of 36 months to observe the behaviour of fly ash concrete mixes subjected to the corrosive attack of softened warm water.
Keywords
concrete, ash admixture, corrosion, dissolving – levigation
LIANA IUREŞ, CORNELIU BOB, REMUS CHENDES, CĂTĂLIN BADEA, RADU POPA
Abstract
The concrete it is delivered on the construction site having two main characteristics: it will harden and it will present drying cracks. The cracks due to hardening of the concrete will lead to complains of the beneficiary and to shortening of the durability of the concrete structure. The drying shrinkage sensibly influences the resistance structures’ integrity. It was noticed that for the elements that have the free shrinkage constrained, it is possible to appear cracks. The present paper propose the introduction of two new coefficients: - characteristic shrinkage and - cracking indices, that are for a facile characterisation of the efficiency of an admixture used in concrete, on the reduction of the shrinkage effects and cracking tendency.
Keywords
concrete, durability, shrinkage, admixtures
COSMIN MIHAI MIRIŢOIU, CRISTIAN OLIVIU BURADA
Abstract
In this paper it is experimentally determined, using some known methods, the loss and damping factors, equivalent dynamic Young modulus and flexural rigidity for composite platbands with natural reinforcement. There were created created the next samples: from hemp and cotton, with 15 mm width and 4 respectively 6 mm thickness. Four layers were used for the cotton fibers with different proportion for the epoxy resin, obtaining samples with the mass of 38 and 98 grams. Four and five layers for the hemp fibers were used, obtaining samples with the mass of 38 and 98 grams. In addition to the dynamic values, the static mechanical characteristics (tensile strength, yield strength, static elasticity modulus, and so on) by tensile testing were obtained.
Keywords
damping factor, loss factor, Young modulus, bast, seed, hemp, cotton
RUI-XI DAI, HUA CHENG, GUO-XIN ZHENG, JUN-RU REN, CHAO-SHAN YANG, XIN-HAO ZHENG
Abstract
In this study, a new type of concrete brick, which is suitable for island environment and non-autoclaved, is developed, and the mechanical properties of the bricks are tested. The results show that the compressive strength, flexural strength and compression ratio of the concrete brick can reach 28 MPa, 4.58 MPa and 0.16 respectively after 28 days. The study also discusses the binder which can be used in the brick material, and puts forward the design idea of the special binder. These experimental and theoretical results can be applied to the construction of new masonry structure in island environment, and have certain guiding significance and application prospect for island engineering.
Keywords
non-autoclaved; concrete brick; superabsorbent polymer; special binder; island environment
T.P. MASHIFANA , F.N. OKONTA, F. NTULI
Abstract
The generation and disposal of phosphogypsum (PG) is a worldwide challenge, due to the environmental pollution posed by the material. The contaminants laden in the material are the major limitations for the utilisation of PG. Other materials considered as wastes such as fly ash (FA) and basic oxygen furnace slag (BOF slag) are generated by numerous industrial activities and disposed into environment. This study investigated the use of three wastes materials for the development of a composite applicable for road construction. Two types of PG were investigated, namely citric acid treated PG (TPG), for the removal of the contaminants and raw PG (RPG). Lower content PG containing 20% and 30% were investigated and modified with FA, Lime (L) and BOF slag. The effect of particle size distribution (PSD) on unconfined compressive strength development, durability of the composites and hydration products contributing to strength development were studied. Modification of PG with FA-L-BOF slag significantly improved the unconfined compressive strength of PG. The PG content of 20% for the RPG and TPG yielded the highest strengths of 7.4 MPa and 5.4 MPa, respectively when cure at elevated temperatures. Normal curing of the composites over 7 days and 28 also showed an increase in strength development. Particle size played a significant role in the unconfined compressive strength development. Kieserite, calcium aluminium sulphate and calcite were the predominant hydration products formed during the curing process.
Keywords
Phosphogypsum, environment, hydration, fly ash, slag
ENIKÖ VOLCEANOV, CRISTINA GEORGIANA POPA, ADRIAN VOLCEANOV, SORIN CIUCA
Abstract
In this study, the effects of simultaneous admixture of CaO and MgO on the crystalline phases, crystallite sizes and sintering properties of coprecipitated zirconia-alumina powder are investigated using complex thermal analysis (TG, DTA, DTG), X-ray diffractometry (XRD), scanning electron microscopy (SEM) coupled with EDS. Correlations among composition - microstructure and properties of the coprecipitated 85ZrO2. 15Al2O3 powder after sintering at 1050 oC, 1350 oC, and 1500o C with 2 hours soaking time at each temperature were performed. The results showed that development of tetragonal phase of zirconia stabilized with Ca2+ and Mg2+ was effective at 1500 oC. In dental applications, dental materials are soaked in saliva, which contains a large number of ions which in turn may accelerate the corrosion of materials. In such context, the chemical stability in modified Fusayama-Meyer type artificial saliva of sintered zirconia- alumina ceramics was also investigated. The ceramic samples sintered at 1500 oC show a better chemical stability, as the pH variation is lower when using a starting immersion solution with pH = 7.4. However, the variation of pH after immersion in artificial saliva is obvious after 216-288 hours due to the ionic transport between ceramic and the solution, even after sintering at 1500o C.
Keywords
Zirconia, Alumina, bioceramic, chemical stability, artificial saliva, corrosion
SIMONA NEAGU, CRINA ANASTASESCU, IOAN BALINT, MARIA ZAHARESCU, IOAN ARDELEAN, MĂDĂLIN ENACHE
Abstract
This study was undertaken as an attempt to assess the effects of ZnSe based materials toward Escherichia coli cells. ZnSe materials with spherical and flower-like morphologies were obtained in hydrothermal conditions. Qualitative and quantitative assays were conducted to evaluate the antibacterial activity. The effect of materials on the bacterial cells was observed by electron microscopy. Repetitive Sequence-Based PCR (rep-PCR) and polymerase chain reaction (PCR) of the 16S rRNA gene analyses were performed after the interaction of the samples with the bacterial cells. The results demonstrate that the antibacterial activity was influenced by concentration, size, time exposure, and shape of the material. Thus, ZnSe with flower-like morphology exhibited higher antibacterial activity on Escherichia coli reference strain compared with the micro-sized ZnSe spheres, related to their different morphology and their higher surface area
Keywords
zinc selenide, antibacterial activity, Escherichia coli
ADRIAN VOLCEANOV, RĂZVAN STATE, COSMIN MĂRCULESCU, ENIKÖ VOLCEANOV
Abstract
Pyrolysis and gasification as well as the product upgrading can be performed by conventional heating or microwave heating, the latter being preferred lately due to its advantages, such as fast heating and start-up or short processing time. The resulting products from gasification and pyrolysis have certain limitations and cannot be used for application in their current state. Pyrolysis and gasification are accompanied using catalysts to improve the yields or quality of reaction products.
The main goal of our research was to study the synthesis and structural characterization of ZSM-5 zeolite type catalysts, as well as to simulate their potential behavior in pyrolysis and gasification process of different vegetal waste.
As starting raw material has been used ZSM-5 zeolite that was subjected to protonation to obtain HZSM-5 form of zeolite. Then, substitution of H from protonated form with different transitional metals (Me = Ni, Mo, Co, Fe2+, Fe3+) was employed. The purpose was to establish the catalytic ability of Me-ZSM-5 substituted zeolite during pyrolysis.
To establish composition and structural-morphological characteristics of Me-ZSM-5 catalysts there were performed X-ray analysis and Fourier Transformed Infrared (FTIR) spectroscopy before and after pyrolysis process. The results have shown the preservation of structural features even after use, confirming their good stability after calcination at 6000C, the simulated temperature of pyrolysis. Morphological analyses have been done using Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray Analysis (EDAX) for elemental distribution and analysis.
The results were considered satisfactory and the first tests on both thermochemical and microwave assisted pyrolysis seem to be very promising.
Keywords
pyrolysis, catalyst, zeolite, synthesis ZSM-5
DOREL RADU, OVIDIU DUMITRESCU, IRINA PINCOVSCHI
Abstract
In the Na2O–Al2O3 system, six glasses were synthesized having the (35–x)Na2O·xAl2O3·65B2O3 molar composition, where x = 0; 5; 10; 12.5; 15; 17.5. For these synthesized glasses the following physical properties were measured: density; refractive index; linear thermal expansion coefficient; glass transition temperature. The structural compactness, the molar volume and the volume of oxygen ion, considered as structural characteristics for the first level of analysis (atomic), at a sub-nanometric scale, were also calculated. The correlation analysis of the properties indicated that these structural characteristics, even at this atomic level, sub-nanometric, influence the physical properties considered at a macroscopic scale. Moreover, the dependency graphs show a series of particular points (return points) that suggest structural transformation areas generated by the [BO3]-> [BO4] and [AlO6] -> [AlO4] transformations, according to the chemical composition of the glasses.
Keywords
Na2O–Al2O3 glasses, structural compactness, properties, correlations, sub-nanometric scale
NESE KEKLIKCIOGLU CAKMAK , GULER BENGUSU TEZEL
Abstract
In this study, graphene oxide nanoparticle (NGO) was fabricated via modified Hummers’ method and then modified with amine terminated 4-armed PEG to enhance the biocompatibility and stability of nano drug carrier. In our strategy, Doxorubicin (DOX) was used as a model drug. DOX loading onto NGO–PEG was synthesized by simply mixing with the NGO-PEG solution at pH 7 overnight. NGO, NGO-PEG and NGO-PEG-DOX was characterized by power X-ray diffraction, scanning electron microscopy, and UV spectroscopy. Stability analysis was performed with zeta potential. The experimental results showed that the zeta potential analysis values were above ±40 mV. NGO-PEG-DOX is still had very good dispersion stability even after 45 days. Therefore, this drug loaded product can be good candidate for treatment of cancer.
Keywords
nanographene oxide (NGO) , nanostructured drug carrier, stability, DOX, PEGylated
TAHA H. ABOOD AL-SAADI , ZAINAB HASHIM MAHDI, ISAM TAREQ ABDULLAH
Abstract
Foamed geopolymer (inorganic polymers materials) were successfully produced from alkali activated glass waste powder, after thermally treated at temperatures between 500 and 700ºC for 1 hour. These geopolymers were synthesized by mixing the mixed color glass waste powder with (potassium hydroxide and sodium silicate) solutions. Thermal treatment of these new materials at temperatures ranging from 500ºC to 700ºC recorded an important volume increase 18-41%, during to a foaming process specific for sodium or potassium silicate (aluminate) hydrates. For these compositions and due to foaming process, the increase of volume is noticed at 600ºC and partial melting occurs at 700ºC. The formation of glass foams leading to large changes in volume associated with different sizes of open porosity. This method for creating a foaming geopolymers represents a novel reuse of the waste glass in engineering applications as thermal and sound insulations coupled with low cost and environmental benefits.
Keywords
glass waste, foamed geopolymers, alkali activators, thermal treatments
LEONID DVORKIN, VADIM ZHITKOVSKY , YURI RIBAKOV, OLEH BORDIUZHENKO , ANTON STEPANUK
Abstract
The paper deals with the features of obtaining a composite binder containing cement kilns dust, blast furnace slag and Portland cement, in which increased complex activation of blast-furnace granulated slag is achieved, due to the increased content of alkalis in cement dust, as well as the effects of hydroxide and calcium sulphate, contained in the cement. The influence of composition, fineness of grinding and content of chemical additives on the hydration degree and strength of low water demand binders was studied. The optimal relationships between the binder composition and the required fineness of the grinding are established, which ensure the strength characteristics and the hardening speed. The influence of superplasticizers naphthalene formaldehyde and polycarboxylate types, which provide low water demand of binder and high fineness of its grinding, is studied. Using the method of the experiment mathematical planning, equations for the regression of compressive and flexural strengths in different compensations were obtained, which allow predicting strength, taking into account the composition and features of the technology for obtaining the binder.
Keywords
binder, dust, kiln, grinding, hydration degree, strength
R. GOPI , V. REVATHI
Abstract
This paper presents the finding of an experimental study on strength and durability performances of self compacting concrete (SCC) with pre-saturated light expanded clay aggregate (LECA) and fly ash aggregate (FAA). The fine aggregate was replaced in the mixes in the range of 0% to 25% with 5% interval on volume basis. Also, the blend of LECA and FAA was used to make Self Compacting Self Curing Concrete (SCSCC) mixes. The influence of LECA and FAA on the fresh properties, strength, acid resistance (HCl) and sulphate resistance (MgSO4) on SCC and SCSCC were studied. From the results it was observed that replacement of fine aggregate by presaturated LECA and FAA as self curing agent to SCC mixes gives cost-effective and technical benefits.
Keywords
Self compacting concrete, Curing, Strength, Micro structure, Durability
CHUNQUAN DAI , YANXIA LONG, ZEJUN SHI, GUANGXUE XING, WENZENG HOU
Abstract
Considering the high permeability and low strength of weathered granite in tunnelling and underground projects, this paper develops strong permeability grouting (SPG) materials with good fluidity, excellent impermeability and long durability based on the features of the weathered granite formation. The materials can repair and reinforce the weathered granite formation through permeation grouting. Besides, the author tested the basic mechanical properties of the proposed SPG materials, and applied them to a tunnelling project of Qingdao Metro. The test and application results show that the SPG materials enjoy great wettability and permeability to granite; the SPG materials can meet the requirements for grouting projects in granite formation, due to the good strength and impermeability of their concretions; the SPG slurries require easy steps and a low grouting pressure in construction. The promotion and application of the proposed SPG materials will definitely bring good economic and social benefits, owing to the huge demand for high-performance grouting materials at home and abroad.
Keywords
Grouting Material; Weathered Granite; Orthogonal Test; Permeability
KADIR GÜÇLÜER , İSMAIL DEMIR
Abstract
This study aimed to use metakaolin and blast furnace slag as main raw materials in the production of autoclaved aerated concrete (AAC). AAC is a light building material obtained by bringing of silica sand, cement, gypsum, lime and pore-forming agent together and hardening it in autoclave. In this study, instead of silica sand, samples of AAC were produced using metakaolin and blast furnace slag (BFS). Experimental measurements were carried out to determine the physical, mechanical and thermal properties of the AAC samples. The micro structural investigations were carried out using SEM and XRD technique.
Keywords
Autoclaved aerated concrete, Metakaolin, Blast Furnace Slag, Microstructure, Mechanical Properties
KARTHIK PRABHU.T, SUBRAMANIAN.K , JAGADESH.P , NAGARAJAN.V
Abstract
Experimental programme is conducted on steel slag blended concrete, by partially replacing offline aggregate by steel slag up to 50%. The mechanical properties were determined by conducting cylinder compressive strength (CRCS), modulus of elasticity (MSE) and modulus of rupture (MSR).Comparison was done with conventional concrete and steel slag blended concrete in terms of strength and economy. Further modeling of relationships between the mechanical properties as CRCS, MSE and MSR of the concretes with fine aggregate replacement was done and validated with NZS:3101 (New Zealand Standard code 3101), AS: 3600 (Australian Standard code 3600) and ACI: 318 (American Concrete Institute code 318)
Keywords
Steel Slag, Cylinder Compressive Strength, Modulus of rupture, Modulus of Elasticity
LIU LIN , HAIXIA ZHANG, KAI GUO
Abstract
In terms of curing method for buried heat-source concrete in winter, internal temperature field of concrete shows characteristic opposite to temperature field in the traditional concrete curing period during the curing process, with surface temperature higher than internal temperature. Therefore, based on porous structure characteristics of concrete, concrete moisture movement control equation is established according to the mechanism of moist heat transfer. The effects of ambient temperature, heat source temperature and heat source heating time on moisture transfer of buried heat-source concrete columns during the curing period in winter are analyzed by numerical simulation. Studies have shown that before the end of hydration, for the influencing factors, the higher the concrete-casting temperature and ambient temperature is, the lower the relative humidity is. After the end of hydration, the lower the ambient temperature is, the lower the relative humidity is, while the effect of surface exothermic coefficient on humidity is exactly opposite. The effect of heat source heating time on relative humidity is shown after the end of hydration. That is, for a longer heating time, vapor pressure in the pores increases due to the temperature field, and the relative humidity increases. The heat source temperature rises in the hydration stage accelerates hydration, and shortens the time for relative humidity to reach the reduction inflection point.
Keywords
heat and moisture coupling; winter construction maintenance; moisture movement
ANITA JESSIE. J., SANTHI A. S
Abstract
Steel Fibre Reinforced Concrete (SFRC) has been very widely used in the structures such as thermal power plants due to its bonding effect, ductility, durability and stability of the structures at high temperatures. The concrete structure when exposed to high temperatures, shows the numerous chemical changes in the concrete which leads to deterioration of the structure. The flexural behaviour of the concrete prism with steel fibre volume fraction of 1.35% and without steel fibre, at room temperature (28ºC) and when exposed to elevated temperatures of 150ºC, 350ºC, 550ºC and 750ºC for the time period of 1 hour were observed. The Finite Element Analysis was done for the prism, to find the deflection on the plain concrete and steel fibre reinforced concrete when subjected to the same temperatures as mentioned above. The main objective of this study was to decrease the structural element failure when exposed to elevated temperature, which in turn increases the evacuation period of the occupants during fire accidents.
Keywords
SFRC, High temperature, Flexural strength, FEA, Deflection, ABAQUS
R.MANJU
Abstract
The structural integrity of concrete is known to improve by the incorporation of fibres in recent days. A 10% of Ground Granulated Blast furnace Slag (GGBS) and 10% of Silica Fume (SF) were used as replacements for cement binder along with 1.5% of fibre content dispersed in the mixture. This research discusses the influence of steel fibres, polypropylene fibres and supplementary cementitious materials in attaining High Strength Fibre Reinforced Concrete (HSFRC). Manufactured sand (M-sand) is employed as fine aggregate now that river sand has a commercial ban due to its scarce availability. A superplasticizer (SP) commercially marketed as Conplast SP430 is proportioned to 1.5% by weight of cement to improve the workability of the mixture. The study investigates the flexural behavior of three HSFRC beam specimens casted for a design characteristic compressive strength of 60MPa (M60 grade) under normal water curing conditions. The specimens were supported by a two-point loading setup and tested as per the Indian standards. It was evident from the results that the flexural strength of beams increased notably with the use of fibres in comparison with normal plain reinforced concrete beams and the same was validated through an analytical study using ANSYS software. The formation and width of cracks was much reduced in HSFRC beams compared to the conventional concrete beams. Reduction in cracks are an advantage in building up the durability of the specimens.
Keywords
High Strength Fibre Reinforced Concrete (HSFRC), Ground Granulated Blast Furnace Slag (GGBS), Silica Fume (SF), Polypropylene fibre, Steel fibre and M-sand
RADHIKA SRIDHAR, RAVI PRASAD
Abstract
This paper describes an experimental study on the behavior of engineered cementitious composites (ECC) accompanied by compressive, flexural and uni-axial tensile strength. In this experimental program, six sets of ECC mixtures with 2% total volume fraction of fibers were produced for each set of mixture and was proportioned to have the same material quantity such as silica sand, micro-silica and cement in order to determine the optimal percentage of polyvinyl alcohol (PVA) and steel fibers (SF). ECC mix proportion is designed experimentally by adjusting the amount of micro-silica and silica sand by conducting four-point bending, compressive and uni-axial tensile strength test of the ECC specimens. The test results emphasize that there is an improvement in ultimate flexural strength and ultimate tensile strength of the hybrid fiber reinforced cementitious composites with the addition of 1.5% of PVA and 0.5% of Steel fibers. High tensile strain capacity of about 25% has attained for the addition of 2% of PVA fibers, which indicates a superior ductility behavior of ECC specimens. Furthermore, the experimental results emphasize that there is a good correlation between flexural deflection capacity and tensile strain capacity.
Keywords
Hybrid fiber, four-point bending, uni-axial tensile, PVA, ECC
XIAOGANG WU, SHUREN WANG, JIANHUI YANG, SEN ZHU
Abstract
In view of the significant influence of fibre type and dosage on the mechanical properties of lightweight concrete, an experimental study was undertaken to analyze the mechanical performance characteristics, including compressive strength, splitting tensile strength, energy absorption, high temperature deterioration performance, fracture toughness and dynamic mechanical properties of steel fibre reinforced all lightweight concrete (SFRALWC), polypropylene fibre reinforced all lightweight concrete (PFRALWC), and basalt fibre reinforced all lightweight concrete (BFRALWC). Results showed that the specific strength, energy absorption index and dynamic peak stress of shale ALWC/FRALWC improved with the increase of the compressive strength, and the relation exhibites strong correlation characteristics, which ccould be expressed by quadratic polynomial. SFRALWC with optimal fibre dosage had the highest splitting tensile strength, specific strength, compressive strength and fracture toughness values. Steel fibre (SF) could significantly increase the plasticity, high temperature resistance to deterioration and dynamic impact resistance of all lightweight concrete (ALWC). Polypropylene fibre (PPF) could improve the plasticity and inhibited the high temperature bursting performance of ALWC. BFRALWC was most sensitive to the strain rate of dynamic impact. The conclusions obtained in the study can provide the reference to the similar engineering.
Keywords
Lightweight concrete, Fibre, Shale ceramsite, Dynamic impact, High temperature deterioration performance
ZHANG YICHAO, WANG YING, ZHOU JINGHAI, KANG TIANBEI, WANG QINGHE
Abstract
Phosphogypsum is a byproduct of the manufacture of phosphoric acid by dehydrating process. The discarded phosphogypsum not only occupies considerable land resource, but also leads to serious environmental contamination. In order to improve the utilization rate of phosphogypsum, hemihydrate phosphogypsum was used as raw materials for manufacturing energy efficiency wall materials in this paper. Comparing with the conventional structure, the optimized structure was designed based on energy efficiency wall materials. The heat transfer of optimized structure was simulated to evaluate the energy efficiency of wall. The results show that the prepared material has suitable setting time, compressive strength and low thermal conductivity. Two-dimensional heat transfer coefficient of thermal bridge is decreased by 18.5%, and the average heat transfer coefficient of wall structure is decreased by 13.9%. The optimized structure can effectively improve the thermal insulation properties of walls.
Keywords
Hemihydrate phosphogypsum, vitrified microsphere, energy efficiency wall materials, heat transfer characteristic
YIGITALP OKUMUS, GOKTUG GUNKAYA
Abstract
In this study, the aim is to synthesize borosilicate glass powder with a particle size of approximately 50nm by the sol-gel method to be used as a hierarchical surface agent in hydrophobic coatings. Precursors used in the sol-gel reaction are Tetraethoxysilane (TEOS) as a source of silicon, boric acid as a source of boron and potassium hydroxide as a source of alkali. For this purpose, process optimization was simply investigated in three stages; solution, catalysis and reaction temperature parameters, respectively. In the first stage of the study, gelling behavior and amorphous structure formation were examined by using solutions prepared with different solvents at different pH values. The solution, which had an ethyl alcohol-water mixture as a solvent with an acidic start and alkaline second step, was found to be suitable. In the second step, the effect of catalysis was investigated by changing the catalyst type and amount in the solution which was found to be most suitable in the previous stage. Ammonium hydroxide and urea solutions that contain ammonium groups were used as catalysts. It was observed that the urea solution did not function as a catalyst due to its neutral character versus the base character of the ammonium hydroxide. In the last step of the study, the effect of reaction temperature was investigated. Upper and lower temperatures are limited due to the solution-based process. A temperature close to room temperature was included in the experiment in order to increase the controllability of the temperature. The gelation behavior at all stages was recorded with photoshoots of tilted beakers, the amorphous structures were examined using x-ray diffractometer (XRD) and microstructures were visualized with scanning electron microscopy (SEM). As a result of all the steps, a solution mixture of ethyl alcohol with a water molar ratio of 44.6: 33.9 and a starting pH of 2.3, a catalyst solution of 0.102 mol of ammonium hydroxide and a reaction temperature 30°C, were determined as optimal parameters.
Keywords
Sol-gel, glass powder, catalysis
ADRIAN-IONUȚ NICOARĂ, RUXANDRA- ELENA GEANALIU-NICOLAE, ECATERINA ANDRONESCU, ROXANA TRUȘCĂ
Abstract
The scope of the present study is the synthesis and characterization of mesoporous silica. using two different methods, the classic sol-gel and a novel microwave- hydrothermal process. There were synthesized nanostructured mesoporous silica materials with average particle size dimensions between 87-500 nm presenting a structure with symmetrical hexagonal pores with the average size of 4 nm.
In order to obtain mesoporous silica, the precursor has been characterized using TG-DSC analysis. Nanoporous silica materials, MCM-41, have been characterized using different techniques as X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and the Brunauer– Emmett–Teller (BET) analysis.
Keywords
MCM, mesoporous silica, hexagonal, mesostructured, biomaterials
HÜSNÜGÜL YILMAZ ATAY, BERK ENGİN
Abstract
In our previous studies, we observed excellent flame retardant properties of mineral reinforced polymer composites. However, it was investigated that some mechanical properties of the composites were deteriorated concurrently with adding minerals. In this study, it was aimed to improve those features by using glass fibers and glass spheres. Polyproplyene is used as a matrix material. Huntite hydromagnesite and glass fibers/spheres were embedded to the matrix in different loading levels. Prior to the composite production, crushing, grinding and screening processes were applied to the mineral. After fabrication of the mineral and glass fibers/spheres reinforced polyproplyene composite samples, they were characterized by using Scanning Electron Microscope - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) to investigate the elemental analysis and morpology. Tensile and flexural tests were applied to determine the mechanical behaviours. Finally Flame retardancy test was undertaken to observe the flame retardant properties of the composites. It was concluded that the use of glass fibers is a beneficial way to improve mechanical properties of mineral reinforced flame retardant composites.
Keywords
Flame retardant; Polymeric composites; Mechanical properties; Glass fibers; Glass spheres; Huntite hydromagnesite
ECATERINA MATEI, CRISTINA ILEANA COVALIU, ANDRA PREDESCU, GEORGE COMAN, CLAUDIA DRĂGAN, CRISTIAN VASILE NIȚU, CRISTIAN PREDESCU
Abstract
A Fe3O4@SiO2@TiO2 composite type was obtained using two synthesis methods in order to select the optimal method for future environmental applications, especially for the degradation of organic pollutants compounds found in water. Thus, a nanostructured magnetic core of Fe3O4 was coated with a SiO2 protective layer and subsequently functionalized using a Ti precursor. The functionalization process was developed both by the hydrothermal method (to obtain Fe3O4@SiO2@TiO2 -A) and by the sol-gel method, followed by evaporation (to obtain Fe3O4@SiO2@TiO2 -E). In both cases, the material was calcinated at 550 °C to obtain the stable form of anatase, known for its photocatalytic properties. It was found, following structural, morphological and stability investigations, that a composite with well-controlled homogeneity was obtained in the case of Fe3O4@SiO2@TiO2-E having also a higher tendency of agglomeration, which resulted in an increased particle sizes compared to Fe3O4@SiO2@TiO2 -A. Investigations on both composite materials have sustain their future use in photocatalytic processes.
Keywords
magnetic composite, photocatalyst, titanium dioxide, silicon oxide
I.V. MATSUKEVICH, I. ATKINSON, S.V. BASARAB, G. PETCU, S. PETRESCU, V. PARVULESCU, V. FRUTH
Abstract
The aim of the paper is to obtain nanocomposites based on magnesium oxide and metal nanoparticles, as well as to establish the influence of the preparation methods on the properties and photocatalytic activity of these materials. Magnesium oxide was obtained by two preparation methods namely precipitation and combustion synthesis. The obtained samples were characterized from the structurally, morphologically and compositionally point of view. Further, nanocomposites based on obtained MgO, were prepared by reducing metal ions to zero-valent metal nanoparticles immobilized on the surface of the MgO carrier (Cu and Ni). The photocatalytic activity of the synthetized nanocomposites was evaluated by monitoring the degradation of amoxicillin (AMX) aqueous solution under irradiation (365 nm).
Keywords
MgO, metal nanoparticles, nanocomposite, photocatalytic activity
LIGIA TODAN, DOREL CRIŞAN, NICOLAE DRĂGAN, DANIELA C. CULIȚĂ, CRINU CIUCULESCU, SANDA MARIA DONCEA
Abstract
In this paper the adsorption of pyridine, a toxic pollutant, on naturally occurring clay, namely bentonite, was studied at a basic pH and room temperature. Sodium saturated bentonite as well as modified with a cationic surfactant were used and the results compared. The influence of contact time and of the initial pollutant concentration on the pyridine uptake was determined by GC-MS. The adsorbents were characterized before and after being in contact with the pyridine solution by BET specific surface area and porosity, XRD and FTIR analysis.
The hydroxyl groups of bentonite in contact with pyridine solution led to protonated pyridine forms which can be responsible for hydrogen bonds formation and electrostatic interactions with the clay and for surfactant removal. Chemical adsorption prevailed over the partition/physical adsorption in both cases and the process followed the pseudo-second-order kinetics with the Freundlich isotherm model representing well the equilibrium adsorption data. The equilibrium adsorptive efficiency was 82.88% for the surfactant modified bentonite and 97.82% for sodium bentonite, the latter being a better alternative for sequestering pyridine from solution.
Keywords
bentonite, infrared spectroscopy, X-ray diffraction, kinetics, pyridine adsoption
ZENO GHIZDĂVEȚ, ALINA CORNELIA BACIU, ANTON FICAI, DIANA ANCA TIT
Abstract
This second part of the paper aims to identify the influence of the mechanical processing of the raw mix on glaze properties.
Preliminary tests on grindability were run on each main raw material, showing an initial, large dispersion of the grains size distribution between raw materials at the lowest number of mill rotations. As the number of rotations increases, it was found that the mechanical behavior tends to link to the hardness of the raw materials. Specifically, grains size distributions fall into two different groups of very close, almost identical values: one group for the raw materials having a higher hardness (sand, feldspar) and the other for the lower hardness materials (dolomite and calcium carbonate).
Two sets of raw materials compositions, one for obtaining matte glaze and the other for obtaining glossy glaze were used; each of them was grinded in a laboratory, planetary ball mill at the same number of mill rotations (1000, 2000, 3000, 5000, 7000, 10000 and 13000 rotations) and grain size distributions were measured. The resulting raw mixes were used to glaze already-made ceramic biscuits. Glost firing was made in an industrial tunnel kiln at 1200°C and it was followed by the investigation of optical properties. Also, glaze thermal expansion was measured.
Results reveal that the particle size distribution of the raw mixtures strongly influence glaze color parameters and glaze thermal expansion. This shows a direct influence of the particles size on the investigated properties, as they interact with light. Specifically, as the grinding gets more advanced, the smallest crystals can enter the melt so lowering the number of crystalline particles existing in the glaze. On the other hand, smaller particles scatter the light more than bigger ones; consequently, they behave like opacifiers.
FTIR images of the glazes surface show that the glazes contain a considerable number of crystalline particles embedded in the vitreous matrix. FTIR spectra and maps revealed a decrease in transmittance as the fineness increases.
According to the results, there is no reason to increase the number of rotations higher than 7000 rotations.
Keywords
tableware ceramics, grinding, glaze, color
ENIKÖ VOLCEANOV, ADRIAN VOLCEANOV
Abstract
The densification of pure Al2O3 and Al2O3–SiC composites (with 5%,10%, 20% and 30 % SiC) manufactured by the SPS process was remarkably enhanced due to additional diffusion mechanisms induced by the spark plasma even at low temperature (830 oC - 1050oC). The densification enhancement was attributed to the acceleration of the diffusion process due to additional mass-transport mechanisms induced by the spark plasma. The onset for densification of Al2O3– SiC composites was delayed with increasing amounts of SiC compared with the pure Al2O3 compact, respectively. The delay of the densification is thought to be due to the decrease in the grain boundary and lattice diffusivity, resulting from the second phase SiC dispersion. Therefore, in the composite case, higher temperatures for fully densification should be required to supplement the decrease in the diffusivity, compared with pure Al2O3. The thermal conductivity of SiC material is higher than that of Al2O3 particularly at elevated temperatures and consequently, the addition of SiC might be expected to promote heat transfer from the graphite die to the compacts. Finally, the enhancement of densification for the SPS process can also be attributed by considering the additional diffusion due to Joule heating, impact force and the electric field effect in which the diffusion of ions for sintering is accelerated by an applied electric field. It is reported that the generation of spark plasma at the insulating particle-to-particle contact points enhance densification. The monoclinic moganite-SiO2 was identified in the composite with 10% SiC particles as well as rombohedral α-Al2O3 and distortioned hexagonal and rhombohedral SiC polytypes. Also, a hexagonal AlC0.5O0.5 compound was revealed in the composites with 5-20% SiC and cubic Si was identified only in the composition with 30% SiC
Keywords
Spark plasma sintering, Al2O3–SiC ceramic, densification behavior, microstructure
İLKNUR BEKEM KARA
Abstract
This study investigates the effects of nano silica admixture on the behavior of cement mortars containing micro silica exposed to elevated temperatures. The cement mortars were incorporated with an optimized ratio of 5 wt% micro silica and 0,1,2,3wt % of nano silica admixtures. The specimens were exposed to elevated temperatures of 300 and 600 °C. After cooling, the mass loss, ultrasonic pulse velocity and compressive strengths of the specimens were determined. The investigations undertaken in this study were supported by scanning electron microscopic images. As a result, there is an optimum nano silica content which can be beneficial for improving the thermal resistance of cement mortars. Nano silica (2 wt%) improved the resistance of cement mortars containing 5 wt% micro silica at elevated temperatures.
Keywords
Cement mortar, nano silica, micro silica, elevated temperature
K.SRINIVASREDDY , S.BALAMURUGAN
Abstract
Using the geopolymer concrete/mortar in the construction industry can reduce CO2 emissions by consuming low embodied energy and fewer natural resources than the Ordinary Portland Cement (OPC). Most of the previous works on geopolymer concrete/mortar were cured in elevated temperature to attain the strength. This is considered to be a limitation in using the geopolymer technology in the construction industry. The present study investigated the effect of alccofine 1203 in the ternary blended geopolymer mortar and concrete with msand as fine aggregate and geopolymer specimens cured at ambient temperature. The results showed that with increasing the percentage of alccofine 1203 content in the ternary blended binder has significantly influenced the consistency, setting times and the compressive strength than the mix without alccofine 1203. Using fly ash, GGBFS and alccofine 1203 with msand can replace the use of OPC completely. The study also includes the effect of setting times and the SiO2 to Al2O3 ratio on the compressive strength of geopolymer specimens.
Keywords
fly ash, GGBFS, alccofine 1203, alkaline solution, and compressive strength
ALIREZA AFSHAR , AMIRHOSSEIN NOBAKHTI, ALI SHOKRGOZAR, AMIRHOSSEIN AFSHAR
Abstract
In this research, we simulate the corrosive behavior of steel reinforcements on 5 different mixtures to investigate the effect of two powerful protective methods, including pozzolanic additives and corrosion inhibitor on concrete, by artificial neural networks (ANNs).
Related to this model, fly ash (FA), micro silica (MS), and slag were used as pozzolanic materials at an optimum 25%, 10%, and 25% of cement weight, respectively. Moreover, Ferrogard 901 as an inhibitor was also utilized. The producer recommends using12 kg/m3 to get the best possible results. The non-linear corrosion of concrete into a marine solution (3.5% NaCl) was simulated by the feed forward back propagation (FFBP) algorithm. Data acquisition happened over a period of 180 days, and according to the ASTM C876 standard for simulating harsh conditions, a period of 10 years was selected as the simulation period. The simulated results all align with collected data. The mixture with 10% of MS has the lowest corrosion current density and corrosion rate at the end of 3600 days, which are 0.38 µA/cm2 and 0.20 mpy, respectively. It provides the best protection against reinforcement corrosion.
Keywords
pozzolanic concrete, inhibitor, corrosion, simulation, artificial neural networks
SADIK ALPER YILDIZEL , GOKHAN CALIS
Abstract
In this study, physical, mechanical and durability properties of basalt fiber reinforced lightweight pumice concrete including water absorption, bulk density, strength and sulfate attack resistance were investigated. Taguchi method was proposed to optimize compressive strength, flexural strength and sulfate resistance properties. Ground Calcium Carbonate (GCC), Basalt Fiber (BF), and Pumice Aggregate (PA) ratio were used as three factors in the L16 Taguchi array. GCC was partially replaced with cement at the rates of 0 %, 5%, 10% and 15 % by weight. BFs (6mm) were added in four contents of 0.25 %, 0.50 %, 0.75 % and 1 % by volume of the mixtures. PA to aggregate content ratio were considered as 25 %, 30 %, 34 % and 38 %. 16 series of laboratory tests were performed on the prepared samples. The contribution of each factor was also evaluated with analysis of variance (ANOVA) method to determine the optimum levels. Experimental tests were also conducted in order to validate Taguchi optimization and ANOVA results.
Keywords
Lightweight concrete, basalt fiber, pumice concrete, optimization, Taguchi method, GCC
MURAT MOLLAMAHMUTOĞLU , EYUBHAN AVCI
Abstract
The effect of superplasticizer on the grouting performance of superfine cement and the engineering properties of grouted sand were investigated. At first, the bleeding, setting time, and viscosity tests were conducted to determine the rheological characteristics of superfine cement grouts with or without superplasticizer at different water-cement ratios. Thereafter, the groutability of superfine cement grouts into various graded sand specimens with or without superplasticizer were tested. Those specimens grouted successfully were then subjected to unconfined compression tests at different time intervals. The addition of superplasticizer to superfine cement grouts increased their bleeding, initial and final setting times but decreased their viscosities. As the unconfined compressive strength (UCS) of superfine cement grouted sand specimens increased with the addition of superplasticizer. It was shown that the engineering properties of superfine cement grouted sand specimens were better improved with the addition of superplasticizer.
Keywords
Superplasticizer; Superfine cement; Groutability; Unconfined compressive strength; Permeability
JIANGANG NIU, JIAN LIANG, JINGJUN LI , XIAOPENG WANG
Abstract
In this work, to decrease the chloride ion penetration of high-performance polypropylene fiber reinforced lightweight aggregate concrete (HPPLWAC), mineral admixtures were added into concrete mixtures in two forms. One was added in powder form and the other was using the mineral admixture paste to prewet the lightweight aggregates. The mineral admixtures including fly ash, slag, silica fume added in the separate or composite mixed forms. The scanning electron microscope (SEM) was used to observe the microstructures of concrete to reveal the improvement mechanism of permeability. The results showed that the separate mineral admixtures could decrease the chloride ion penetration of HPPLWAC. When 10% silica fume was added, the chloride ion diffusion coefficient of HPPLWAC decreased by 71.1% compared to the reference group and obtained the best resistance to chloride ion penetration compared to other groups. Composite mixed mineral admixtures could effectively improve the resistance to chloride ion penetration of HPPLWAC. The optimal resistance to chloride ion penetration was obtained when adding 20% slag and 10% silica fume into the reference group and its chloride ion diffusion coefficient decreases by 73.2% compared to the reference group. The lightweight aggregates prewetted by using mineral admixture paste could improve the chloride ion penetration of HPPLWAC, and the slag paste had the best effect. Using DPS to prewet lightweight aggregates had more significantly effect on improving the resistance to chloride ion permeability of HPPLWAC than lightweight aggregates prewetted by using mineral admixture.
Keywords
high-performance polypropylene fiber; lightweight aggregate; chloride ion penetration; prewetting; microstructure
NENAD RISTIĆ, ZORAN GRDIĆ, GORDANA TOPLIČIĆ ĆURČIĆ, DUŠAN GRDIĆ, DEJAN KRSTIĆ
Abstract
Rapid technological and industrial development in the recent decades caused considerable environmental problems, and one of the most significant is, undoubtedly, disposal and recycling of waste materials and by-products of industrial production. Since concrete is a composite material, waste materials can suitably be used in its composition. In this paper, the research of effects of milled recycled glass from cathode tubes, flotation tailings from a copper mine, red mud and fly ash as mineral admixtures on properties of fresh and hardened self compacting concrete was presented. The test results indicated that the addition of such materials does not cause a decline in physico-mechanical characteristics and properties of durability of self-compacting concretes (SCC), and they even improve some aspects of concrete performance in comparison with SCC made with limestone filler as mineral admixture. Waste materials such as fly ash and recycled glass of cathode tubes (CRT) exhibit a puzzolanic activity, so the performances of the concretes with these admixtures proved to be better after ageing than the concretes with other admixtures.
Keywords
self compacting concrete, recycled CRT, flotation tailings, red mud, fly ash, limestone filler, fresh and hardened properties, durability
MONTHER ABDELHADI, ANCUŢA ROTARU, NAFETH ABDEL HADI, NICOLAE ȚĂRANU, ANDREI BOBOC, OANA-MIHAELA BANU
Abstract
The western part of Amman, the capital of Jordan, holds a layer of 4 to 5 meters depth of problematic brown clay that exhibits a wide range of plasticity, swelling, settlements and low shear resistance. On the other hand, south Jordan holds large deposits of bituminous oil shale that extend to considerable depths. The government of Jordan has decided to start using the bituminous oil shale for power generation and oil production resulting large amounts of ash. This research work studies the effect of bituminous oil shale ash, rich in lime, on the characteristics of the silty-sandy brown clay that spreads on large areas in the middle and northern areas of Jordan. The oil shale ash has been mixed with brown clay in different percentages and some geotechnical parameters of the resulted mixtures have been measured and analysed. The outcomes of this work show that there is a significant effect of the bituminous oil shale ash on reducing the plasticity index of the mixture, on decreasing its dry unit weight, as well as on increasing its compressive strength and permeability to a certain percentage of added ash. In addition, the mixture has a positive effect on reducing the compression index (Cc) and the swelling index (Cs) of brown silty-sandy clays.
Keywords
bituminous oil shale ash, silty-sandy brown clay, plasticity index, compressive strength
ADRIAN VOLCEANOV, ENIKÖ VOLCEANOV, COSMIN MĂRCULESCU
Abstract
The purpose of the present paper is to investigate the influence of ash coming from the complete burning of poplar wood and willow wood, respectively. For this purpose, plaster mortar with ash with 2 and 5% admixtures to a commercial reference mortar was prepared. The major elements in the investigated wood ash are calcium, magnesium, potassium and carbon. Sulfur, phosphorus and manganese are present at around 1%. Silicon, sodium, iron, aluminum, copper, zinc, and boron are present in relatively smaller amounts. Strong peaks corresponding to Ca(CO3)2 were identified in both ash. The willow ash contains relatively higher amounts of potassium compared to poplar ash and show strong peaks corresponding to K2Ca(CO3)2. Willow ash being richer in sulphur and potassium has K2Ca(SO4). Similarly, poplar, being richer in sodium, displays very weak peaks corresponding probably to Na2Ca(SiO2)3 compound. The addition of ash, regardless of its nature (poplar or willow) or its amount did not contribute to the increase of the resistance of the commercial reference mortar after 3 days, 7 days or 28 days of hardening. Their role was mainly of filler together with pre-existing silica aggregates from the commercial mortar. Finally, the compressive strengths determined experimentally after 28 days of hardening place these mortars with ash admixtures below the values accepted by the starting reference mortar class. However, the use of poplar or willow ash generated after calcinations at 650oC as admixtures for binder materials in mortar seems to be effective for their recycling in plastering mortars.
Keywords
Ash, Willow, Poplar, Wood, Mortar, Waste Recycling
ERGANG XIONG , KUN ZU, TUANJIE FAN, LINBO LIU , LIANGYING SONG , QIAN ZHANG
Abstract
This paper attempts to disclose the shear behavior of reinforced concrete (RC) beams designed by compressive force path (CFP) method. For this purpose, three beams were designed by the CFP method and another three by GB 50010-2010. For each type of beams, the three beams were prepared with different shear span ratios, respectively 2.0, 1.5 and 1.0. Then, a monotonic loading test was performed on all the beams. To identify the effect of shear span ratio on shear behavior, the author compared the CFP beams with GB beams in terms of ultimate load, failure process and failure mode. In addition, the load-deflection curve and load-strain curves of concrete, reinforcement and stirrups were analyzed in details. The results show that the shear capacity of RC beams is mainly affected by the stress transmitted along the CFP; Compared with the GB method, the CFP method, despite using fewer number of stirrups, effectively guaranteed the shear capacity of the beams with any of the three shear span ratios, and did not significantly change the ultimate load; the amount of stirrups saved by the CFP is negatively correlated with the shear span ratio of the beam. To sum up, the CFP method was proved as a feasible and rational way to design RC beams.
Keywords
Compressive Force Path Method; Shear Capacity; Shear Span Ratio; Mechanical Properties; Stirrup