română CRISTINA STANCU
Abstract
The aim of this paper is to present the importance of the laboratories participation in the interlaboratory comparison (ILC) scheme, using the case study called Interlaboratory Test for adhesive for ceramic tiles. At present, the ILC scheme organized by CEPROCIM is the only one addressed to the laboratories for testing adhesives for ceramic tiles.
The paper aims to present, by using several case studies, the influence of continuous participation at the ILC scheme on the performance improvement of the participants, affecting also the coefficient of variation, as well as the influence brought by the joining of new participants. The case studies represent both accredited laboratories according to EN ISO/IEC 17025 and non-accredited laboratories whose performance (z-score) were assessed during their participation of the all 12 editions of the Interlaboratory Test for adhesive for ceramic tiles.
Keywords
Interlaboratory comparison scheme, adhesive for ceramic tiles, initial adhesion strength, tensile adhesion strength after water immersion, open-time, z-score
GHEORGHE DOBRA, SORIN ILIEV, LUCIAN COTEȚ, ALINA BOIANGIU, ILEANA MOHANU, NICOLETA FLORENTINA CÎRSTEA
Abstract
In this paper the possibility of obtaining porous ceramics by using of two commercial sorts of aluminum hydroxide with different fineness (from Vimetco Alum SA Tulcea Romania) was investigated. Proposed method for obtaining a such ceramics is based on a very low-pressing (30kN) of powder mixtures, followed by a thermal treatment at 1550oC. The effect of aluminum hydroxide finesses on the apparent porosity and density, compressive strength and thermal expansion coefficient of the ceramics obtained was investigated. Also, the mineralogical and microstructural characteristics were evaluated by XRD and SEM analyses. The results showed that both samples of aluminum hydroxide led to improve of porosity, density and mechanical strengths properties compared to standard ceramics prepared with calcined alumina. The use of the coarser powder (below 45µm) in the proportion of 25% leads to the obtaining of ceramics with physical-mechanical characteristics close to those of ceramics made with finer powder (less than 10µm) in a proportion of 25-50%, with beneficial effect on production costs. The properties of porous ceramics had suggested that they may be used in filtering applications.
Keywords
aluminum hydroxide, porous ceramics, microstructure, physical and mechanical characterization
ANGELA SPOIALĂ, CORNELIA-IOANA ILIE, GEORGIANA DOLETE, ROXANA-DOINA TRUȘCĂ, LUDMILA MOTELICĂ, OVIDIU-CRISTIAN OPREA, DENISA FICAI, ANTON FICAI, ECATERINA ANDRONESCU, LIA-MARA DIȚU
Abstract
The purpose of this article was to synthesize antimicrobial composite membranes using chitosan (CS) and zinc oxide (ZnO) nanoparticles as adsorbents for the removal of heavy metals. Chitosan/ ZnO composite membranes were prepared through the electrospinning method. The ZnO nanoparticles concentration from the CS/ZnO composite membranes was 1% and respectively, 5%. The synthesized membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), hydration capacity, antimicrobial assessments and, heavy metal retention through the inductively coupled plasma mass spectrometry (ICP-MS) analysis technique. The thickness of the as-prepared CS/ZnO composite membranes was 20µm (CS/ZnO 1%) and 30µm (CS/ZnO 5%). The appearance of the synthesized membranes indicated a smooth and uniform morphology, which suggested the integration of zinc oxide nanoparticles into the obtained membrane. Fourier transform infrared spectroscopic measurements showed the existence of relevant functional groups of both chitosan and ZnO in the composite membranes. ICP-MS measurements provided information regarding the capacity of retention of these membranes, indicating that CS/ZnO 5% had the highest retention rate. The as-obtained CS/ZnO composite membranes are expected to be used as adsorbent materials for water purification applications.
Keywords
ZnO; chitosan; nanocomposite membranes; antimicrobial; water purification
OUADAH NOUREDINE, ABDESSEMED MOULOUD, KECHOUANE FOUAD
Abstract
The use of composites for the reinforcement of concrete structures, sometimes poses the problem of the detachment of the composite plates/fibers from the surface of the concrete support, especially in arid or dry climates. This phenomenon of disbonding, due to the poor performance of the matrix (adhesive glue), affects nearly 8% of the structures reinforced with FRP in Algeria and negatively influences the durability and bearing capacity of the reinforced structure over time. This article presents the results of a study on reinforced concrete structures. It concerns the insertion of carbon nanotubes (CNT) in epoxy resin, used as an adhesive for CFRP composites. The objective is to evaluate the improvement of the mechanical performances of the resin used and to contribute to reduce the phenomenon of disbonding. An experimental work carried out on a set of reinforced concrete beams, strengthened by CFRP plates, with the insertion of carbon nanotube powders (CNT) in the resin used, with percentages varying from 0 to 2%, has been performed. To validate the results obtained, a numerical work based on the finite element method was developed taking the case of a concrete bridge requiring repairs. The results showed that the nano-composites (CNTs) improve the mechanical performance of the epoxy resin and bring an appreciable gain of the order of 50 to 170% to the constraints. Moreover, this technique of moderation of composites by adding nanotubes (CNTs), gives an appreciable gain at vibration frequencies. This was confirmed by the results of the modal analysis of the bridge structure repaired with 2% addition of CNTs.
Keywords
Concrete, reinforcement, composite, adhesive, nanotube, disbonding, frequency, analysis, structure
A nondestructive testing technique for high strength concrete：explosive-loaded nail penetration test
CHAORAN DUAN , SUHANG YANG
Abstract
The traditional nondestructive techniques (NDT) may be insufficient to estimate the compressive strength of high strength concrete used widely in modern architecture engineering. This paper adopts the penetration test for this purpose with some advantages. This method is more convenient and more efficient than the traditional ones. The explosive-loaded nail penetration test (ENPT) can widen the testing rage of NDTs which are used to estimate the compressive strength of high strength concrete. Experimental results shown a good relationship between the compressive strength of concrete specimen (30-80MPa) and the results obtained from the ENPT. Other NDT techniques like Schmidt rebound hammer (SRH) and ultrasonic pulse velocity (UPV) were also applied to concrete specimens as comparisons and the results shown that the ENPT is more reliable. Since the penetration depth is closely related to the large-scale compressive strength obtained from indoor and field tests, the new test method is considered to be effective.
Keywords
Compressive strength; In-situ test; High strength concrete; Nondestructive testing (NDT); Explosive-load nail penetration test (ENPT)
SELÇUK MEMİŞ , ALİ ALSHAAB RAMROOM
Abstract
In this study, the effects of silica fume (SF), fly ash (FA) and granulated blast furnace slag (GBFS) on the design and fire resistance properties of ultra-high performance concrete (UHPC) were analyzed using the Taguchi L16 method. Samples were exposed to temperatures of 300 °C, 450 °C and 600 °C. The composition of the UHPC was: sand/binder ratio = 1, water/binder ratio = 0.19, Polycarboxylate superplasticizer (PCE) /binder ratio = 3.5%, pozzolanic (SF, FA and GBFS)/binder ratio = (0, 10, 15, 20)% and steel fibers = 1% by volume, and a Taguchi L16 program was prepared that consisted of 240 samples (40x40x160mm). The high-temperature properties of the UHPC samples were evaluated. Because several mixtures could withstand a temperature of 450 °C, it was determined that the losses were more effective when the highest temperature reached was greater than or equal to 600 °C, and the twelve mixtures are damaged by breaking them up. When the actual values obtained in the verification test were examined, it was determined that the results were sufficient for the compressive and flexural strength and physical properties of the concrete under various heating conditions and the Taguchi optimization was successfully implemented.
Keywords
Ultra-high performance concrete (UHPC); Cement; Steel fibers; Polycarboxylate ether-based superplasticizers (PCEs); Compressive strength; Taguchi Method; Fire resistance
D. VAIČIUKYNIENĖ , A. KANTAUTAS, A. A. NAVICKAS, V. VAIČIUKYNAS, E. IVANAUSKAS, A. AUGONIS, THIYAGARAJU LOGANATHAN
Abstract
Recently, supplementary cementitious materials are widely used in cements systems. One of these materials could be a zeolitic by-product. The present study carried out experiments with the aim to find out the impact of zeolitic by-product with incorporated CaCl2 on the main features of hardened cement paste. A zeolitic by-product is the cracking catalyst of a fluidized bed. It was treated with saturated CaCl2 solution. Specimens were produced from Portland cement paste with a zeolitic by-product as supplementary cementitious material. It was determined that according to the X-ray the modified zeolitic by-product resulted in the formation of substantial amounts of hydrocalumite (Ca4Al2O6Cl2∙10H2O). The results indicate that the addition of small amounts of this additive can increase the compressive strength of the early and late hydration ages as well. In Portland cement systems the zeolitic by-product with inserted CaCl2 behaved as a hydration accelerator, had the filler effect at early-ages, and acted as a pozzolanic material at later-ages.
Keywords
zeolitic by-product, hardened cement paste, Portland cement hydration, supplementary cementitious material, CaCl2 accelerator
CRISTIAN PETCU, VASILICA VASILE
Abstract
The construction industry uses an ever-increasing amount of thermal insulation materials to meet the building sectors growing energy efficiency demands. Exclusive use of synthetic thermal insulation may lead to a complicated process of re-integrate demolition waste in the economy and potential environmental damage over time. The use of traditional natural materials is ecological and through an appropriate design of the buildings, it offers efficient construction elements. This paper attempts to increase the professionals awareness of some typical industry by-products (straw, sawdust, cellulose), with thermophysical characteristics interesting for the building sector. Besides the information needed for the usual engineering calculation, like thermal conductivity coefficient, we measured data needed for dynamic building simulation, such as thermal diffusivity, volumetric heat capacity, and specific heat capacity.
Keywords
thermal insulation; by-products; sustainability; building materials; sustainable buildings
ALI SABERI VARZANEH, MAHMOOD NADERI
Abstract
Curing and compaction are two major factors in the interface bond strength of concrete and repair mortars. Ignoring these two factors would create fine holes in the concrete-mortar interface and reduce the adhesion. Hence, the present study has aimed to evaluate the effects of initial pressure and fiber on adhesion between mortars and concrete substrates using the twist-off and pull-off tests. The effects of fibers on the shrinkage of mortars are also discussed. The influences of pre-pressure and fibers on the adhesion of the two layers were demonstrated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The results indicated that initial pressure had positive impacts on the interface shear and tensile bond strength in the twist-off and pull-off tests, and the effect of pre-pressure was greater on mortars with more aggregates. Moreover, fibers reduced the mortar shrinkage and increased the adhesion. Considering the high correlation between the twist-off and pull-off results, affordable and available twist-off apparatus can be employed instead of expensive pull-off apparatus to measure the concrete-mortar adhesion.
Keywords
Twist-off, Pull-off, Pre-pressure, Bond, Fiber
MARINELA BARBUȚĂ, PETRU MIHAI , ALINA-MIHAELA NICUȚĂ PRECUL, LILIANA BEJAN, NICOLAE ȚĂRANU, OANA-MIHAELA BANU
Abstract
The article presents the experimental and the numerical results obtained on hollow blocks made of concrete with waste materials, as substitution of the natural aggregates. Two types of waste materials were used, shredded Polyethylene terephthalate (PET) bottles and sawdust, to replace the sand in a dosage of 40%. Fly ash was also used for replacing 10% of cement from the regular concrete mix. The density, compressive strength, modulus of elasticity and compressive force-deformation diagrams were experimentally determined. The constructed concrete hollow blocks were tested in compression and the ultimate load and failure types under loading were relieved. A numerical analysis of the concrete hollow blocks behaviour under compressive load using ATENA software was also performed. It was observed that the failure in compression of the tested blocks was a stepwise, progressive type one, the cracks pattern being matched with areas where tensile stresses exceeded the strength of the analysed materials. The results of the carried out studies showed a good correlation between the numerical and the experimental data.
Keywords
fly ash, shredded plastic bottles, sawdust waste, sustainable development, compressive strength, numerical analysis
SUMATHI A, ELAVARASI D , SARAVANA RAJA MOHAN K
Abstract
The current research was carried out on the effect of natural sand replaced by manufactured sand (M-sand) in fibrous concrete infiltrated with slurry under static and impact loading. The compressive strength, split tensile strength and impact strength of Slurry infiltrated fibrous concrete (SIFCON) with partial replacement of river sand by M-sand. Hooked end steel fibres of 10% by volume fraction and a constant slurry mix of 1:1 with water cement ratio of 0.4 were used. The low velocity impact response is conducted on 150 mm and 60 mm high cylindrical specimen diameters using the drop weight impact test device as per ACI Committee 544-89. By dropping a steel ball of 4.5 kg with a falling height of 457 mm with the use of a self-manufactured drop-hammer impact test setup, the replication of a low-velocity impact on the cylinder was achieved. The test results show that the strength and energy absorption capacity of SIFCON with 50% of natural sand substituted by M-sand significantly improved compared to all other replacement of M-sand. It was found that optimum replacement level of river sand by M-sand as 50%. Regression analysis has been developed from the experimental results to predict the first crack and ultimate energy absorption capacity of SIFCON. The analytical values from the regression model are well correlated with the experimental results.
Keywords
CUVINTE CHEIE (ENGLEZĂ)
ALINA MELINESCU, ENIKÖ VOLCEANOV, MIHAI EFTIMIE, DAN BATALU, ADRIAN VOLCEANOV, LAVINIA GABRIELA POPESCU
Abstract
Our work was focused on enhancing the deposition rate, homogeneity, and hardenability on low carbon steel surfaces of Ni-P-TiO2 nanocomposite comparatively with Ni-P coating. Two bath compositions were developed for the electroless deposition, namely Bath (A), composed of nickel sulphate and sodium hypophosphite aqueous solutions and various admixtures to stabilize and accelerate the deposition rate during plating, and Bath (T): Bath (A) to which nanosized TiO2 particles were added in amount of 10 g/l. The deposition rates, co-deposition of particles, and roughness was influenced by the nano powder concentration, temperature, agitation rate, pH, and deposition duration in the bath. The adhesion and uniformity of the composite layers analyzed metallographically and by SEM are appropriate, so the interface of the composite layer with the support steel is perfectly continuous, without discontinuities and the layer is uniform. After deposition the coating was amorphous. Due to the heat treatment, the hardness of the electroless Ni-P- nanocomposite coating is significantly increased. The performance of the Ni–P-TiO2 nanocomposite coatings is analyzed for their surface morphology, phase composition, wear and hardness to assess wear characteristics, and compared with Ni–P alloy coatings. The change in hardness with heat treatment exhibits a similar trend for these coatings, which suggests that the hardening mechanism upon annealing is the same for both electroless Ni–P and Ni–P-TiO2 nanocomposite coatings.
Keywords
Electroless plating, Coatings, Ni-P-TiO2 nano-composite layer, steel substrate
ALINA IULIA DUMITRU, GEORGETA VELCIU, DELIA PATROI JANA PINTEA, TUDOR-GABRIEL DUMITRU, ILDIKO PETER
Abstract
The influence of dopants, such as Y3+, Sm3+ and Bi3+ and poling conditions on the piezo - electrical properties of (Pb0.91Me0.06)(Ti0.98Mn0.02)O3 compositions have been investigated. The compositions have been obtained at high sintering temperature (1190°C and 1240°C) by solid state reaction methode. In the present research paper the effect of sintering temperature on some properties, in particular on the physical characteristics, on the structural and microstructural features and on the dielectric and piezo-electric properties of the bulk materials have been considered and investigated.
From the studies carried out, it comes out that the type of dopant has an effect on the structure and microstructure, as well as on the dielectric and piezoelectric properties. The structure has been identification by X-ray measurements and the crystallite size has been monitored by SEM analyses. At room temperature, all the sintered samples show a tetragonal perovskite structure. Piezoelectric parameters (kp) determinations have been performed using resonance - antiresonance methods. The obtained results indicate that the sintered compositions (doped PT) can be used in obtaining active elements as well as targets for deposition.
The obtained results indicate that the sintered compositions (doped PT) can be used in obtaining active elements as well as targets for deposition.
Keywords
doped PZT, dielectric and piezoelectric properties, ferroelectric properties
LÜTFIYE DAHIL, KHALED NIMER MOHAMMED AL-NIMER
Abstract
In the present study, crash simulations for thin-walled circular and square cross-section samples made of intra-layer glass-carbon/epoxy hybrid composite, and aluminum have been conducted; and energy absorption capacity and deformation modes are obtained. Results related to some post-collision parameters such as variation of displacement and force are presented for each combination of cross-sectional geometry and material, as well. Numerical method is validated by a previous experimental drop-weight study. Numerical calculations have shown that the hybrid composite sample of square cross-section exhibits the highest load resistance and maximum crash energy absorption, while aluminum samples have a low load resistance and energy absorption capacity the circular Al samples have smaller displacement than that of the square samples.
Keywords
Intra-layer hybrid composites, numerical modeling, drop weight impact test, folding
I. REGINA MARY , T.BHAGAVATHI PUSHPA
Abstract
This paper shows the study of a statistical approach for finding the optimum values of the dependent and independent factors in Geopolymer concrete (GPC) composites using 75:25 of fly ash and Ground Granulated Blast Furnace Slag (GGBS). The input parameters considered in this study were alkali/binder, binder content and water/solids ratio. These factors affect the fresh and hardened properties of Geopolymer concrete such as slump value, compressive strength and split tensile strength for 28 days ambient curing. Response Surface Methodology (RSM) technique was used to optimize the trial mixes using Box-Behnken Design (BBD) by considering three factors. Results show that the optimum compressive strength of 57.05 MPa, optimum tensile strength of 4.52 MPa and optimum slump value of 135.034 mm was achieved by using optimum alkali/binder ratio, binder content and water/solids ratio of 0.386,420 kg/m3 and 0.17 respectively. The desirability achieved for the optimum value is 0.9212 and the mean error was less than 5%. ANOVA results of the regression studies showed that each factor contribute significantly to the strength development of GPC.
Keywords
Response Surface Methodology, ANOVA, regression, Box-Behnken, Geopolymer concrete, optimum value
MARIAM FAROUK GHAZY, METWALLY ABD ALLAH ABD ELATY, MOHAMED FATTOUH ABD EL HAMEED
Abstract
In this study a hybrid method including a response surface methodology, technique for order preference by similarity to ideal solution (TOPSIS), and a particle swarm optimization (PSO) algorithm were proposed to determine optimal parameter settings of the geopolymer (GP) mortar. Compressive strength, flexural strength, splitting tensile strength, and weight loss were used as the most important characteristics. Six factors (metakaolin, cement, sodium silicate solution, polypropylene fibers, curing temperature, and elevated temperature) each at three levels with 54 experiments was selected. TOPSIS method was used to convert the single-responses to an equivalent single-response known as a multi-performance characteristics index (MPCI). The significance of the process parameters was also evaluated using the analysis of variance. The PSO was used to predict optimal parameter settings of the GP-mortar process. The approach and the methodologies employed in this work can be utilized in solving the mixture proportions of the optimization problem.
Keywords
Geopolymer motar; Response surface methodology; TOPSIS; Particle swarm optimization; Mechanical properties; elevated temperature
VIRGIL PENTA, CAMELIA UNGUREANU, ANDREI BOGDAN STOIAN, CRISTIAN PIRVU
Abstract
Candida albicans is the most frequently isolated pathogen yeast and is present in the oral cavity of almost half of the population. Since there have been several seemingly contradictory studies on the effect of electricity on C. albicans behavior, we propose a new method of measurement: Electrochemical Impedance Spectroscopy (EIS) coupled with Surface Plasmon Resonance (SPR). Along with other electrochemical methods and high-resolution Atomic Force Microscopy (AFM) imagery we investigated the effect of electric potentials measured between metallic intraoral restorations materials on C. albicans.
Keywords
Candida albicans, biofilm, Surface Plasmon Resonance, Electrochemical Impedance Spectroscopy, Atomic Force Microscopy
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Year
2022
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Issue
52 (2)
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Pages
145-155
ZENO GHIZDĂVEȚ, OVIDIU DUMITRESCU, MIHAI EFTIMIE, ADRIANA MOANȚĂ, IONELA PETRE, NICOLETA CÎRSTEA
Abstract
Two classes of glass wastes, colored (C) and transparent (A), will be used for the partial substitution of the raw mixes, i.e. especially sand, in cement clinker production. Advanced statistical methods will help to identify and extract correlations composition – raw mix grinding – clinkering – cement grinding – properties. Investigations aim to clarify if and how the partial substitution of the raw materials with glass cullet could influence the most important cement properties, via clinker quality.
It is expected to find out, also, if the various mixes of raw materials and glass waste will show different raw mix grinding behavior; the same question will be answered for cement grinding. The major concern when sand is entirely substituted with glass is the higher alkali intake, that can influence both clinker phase composition and, therefore, quality and clinkering plant operation. Being one of the indices that define clinker quality, grindability directly affects operational costs, so it is an important feature that will also be evaluated and correlated; among other factors, grindability is related to the amount of alkali in clinker.
Keywords
glass waste, clinker, partial substitution, correlations
CORNELIA-FLORENTINA DOBRESCU, RAMONA PINȚOI
Abstract
The paper aims to analyze the potential use of glass waste for the production of construction materials and the improvement of clayey soils. Experimental applications based on the integration of recycled products as binders have shown that glass waste contributes positively to the micro-structural properties of the mixture through an obvious improvement in mechanical performance. Within the paper, an experimental program is structured which represents a preliminary stage for small-scale modeling applied in the design of structures and eco-sustainable elements useful in construction works. The obtained results confirmed the efficiency of using recycled glass as a construction material in engineering applications. The advantages of using glass waste in the manufacture of construction elements consist in the durability of the material, the improved abrasion resistance of concrete, the improved rheological properties of fresh concrete, without using superplasticizers in the mixtures.
Keywords
stability, performance, improvement, alternative materials, clayey soils, waste glass
VIOLETA TSAKIRIS, DORINEL TĂLPEANU , MAGDALENA VALENTINA LUNGU, DELIA PĂTROI, GABRIELA BEATRICE SBÂRCEA, VIRGIL EMANUEL MARINESCU
Abstract
For the replacement and regeneration of hard and damaged tissues, it is preferable to use orthopedic implants from Mg-based biomaterials. It is desirable that orthopedic implants have mechanical properties similar to those of natural bone to avoid the effect of stresses due to the difference in properties of materials, i.e. between bone and implant. Numerous studies have shown that of all metallic biomaterials, Mg used as an orthopedic biomaterial can promote bone reconstruction and accelerate the healing process, having both density and modulus of elasticity close to cortical bone.
In this paper, Mg-Zn-(Mn) biomaterials with 5 wt.% Zn and/without a small addition of Mn (0.3 wt.%) were synthesized by high-energy mechanical milling of the component powders mixtures and consolidated by Spark Plasma Sintering technique, at different sintering temperatures (350, 400 and 450°C) to be used as orthopedic implants. The influence of the mechanical milling and sintering parameters, on the chemical, structural and physical characteristics was investigated. Properties suitable for the intended application, in terms of physical properties such as density 1.77-1.78 g/cm3, hardness (95-112 HV), and Young Modulus (36-46 GPa) recommend the alloys obtained from Mg-Zn-(Mn), as potential biomaterials. These biomaterials resulted from the composite powder mechanical milled for 5 h and sintered at the highest sintering temperature (450°C).
Keywords
doped magnesium, biomaterial, SPS technique, osseous implants
LEONID DVORKIN, VADIM ZHITKOVSKY , VITALIY MARCHUK, YURI RIBAKOV
Abstract
The research is focused on obtaining high-strength mortars from composite cements, containing up to 50% of fly ash and a polyfunctional modifying admixture. The polyfunctional modifier contains a superplasticizer and an intensifier for cement grinding. Using mathematical experiments planning, experimental-statistical models of mortars strength in bending and compression at 2 and 28 days were obtained. The models take into account the influence of the fly ash amount, superplasticizer content and type and cement grinding fineness. Analytical results based on the obtained models and the influence of the investigated factors are presented. The obtained mathematical models of mortar strength allowed optimization of the required technological solutions that provide the necessary mechanical characteristics of mortars at minimum cost.
Keywords
mortar, fly ash, composite cements, superplasticizer, grinding, experimental-statistical models, optimization
V. VOLCHUK, S. KROVIAKOV, V. KRYZHANOVSKYI
Abstract
Macrostructure of the modified expanded clay concrete in the matrix-filler form system was considered. Statistical criteria of the macrostructure expanded clay concrete elements using a topological composition and fractal invariants were determined. The criteria describe metric discrepancy of length, diameter and area of macrostructure elements with their topological equivalents. It is shown that taking into account the indicators of metric discrepancy between length of the interphase and intraphase diameter boundaries, pore and coarse aggregate area leads to accuracy increase and is consistent with the theoretical prerequisites for influence of the investigated structural elements on strength. It has been established that the empirical model, taking into account the metric area deviation of expanded clay gravel fractions, has the highest accuracy in concrete strength predicting (R2=0.92), and the model for flexural strength assessing taking into account the diameter of its fractions has the lowest accuracy (R2=0.44). As the study results have shown, the statistical criteria for metric discrepancy of structural elements can be used as correction coefficients or constants in existing empirical models for strength assessing of lightweight concrete, taking into account the macrostructure effect.
Keywords
concrete, structure, strength, fractal dimension, metric discrepancy, topological equivalent, model
ANIL NIŞ, TAHA SALAH WAHHAB AL-ANTAKI
Abstract
In this study, volcanic pumice aggregate incorporated different lightweight concretes (LWC) were investigated under a 5% sulfuric acid environment. For this purpose; OPC, OPC-FA, OPC-S, OPC-FA+S with 0%, 50%, and 100% pumice incorporations were manufactured considering cement efficiency factors for fly ash (FA) and slag (S) given in the TS13515 and EN 206-1 to evaluate the applicability of cement efficiency factors in the water and sulfuric acid environments. The visual appearance, weight change, and compressive strength tests were executed, and strength gain index and strength loss index parameters were utilized for the evaluation. The results indicated that the cement efficiency factors for the fly ash and slag were found appropriate for the pumice aggregate replacements up to 100% for the LWC incorporating only fly ash or slag. However, when the fly ash and slag were used together, the cement efficiency factors should be reduced from 0.4 to 0.35 for FA and from 0.8 to 0.75 for slag materials.
Keywords
volcanic pumice aggregate, lightweight concrete, cement efficiency factor, durability, sulfuric acid resistance
DENG CHEN, LI-WU MO, KAI-WEI LIU, AI-GUO WANG, SHI-PING ZHANG, QIN-FENG DI, JUN YAN
Abstract
In order to investigate the hydration and pore structure evolution of wet white cement paste at early age, the transverse relaxation time (T2) spectrum signals of wet white cement paste were tested by 1H low-field nuclear magnetic resonance (NMR). The effects of water to cement (W/C) ratio on the T2 spectrum, T2 geometric average values, hydration degree and pore structure of the cement paste samples hydrated within 168 h were studied. The results show that the T2 can characterize the hydration process and pore structure of wet white cement paste. With the increase of hydration time, the T2 peak area and T2 geometric average values decrease gradually. The hydration degree of cement increases rapidly within the first 24 h, and then slows down gradually after 24 h. For the cement pastes hydrated from 0 h to 7 h, most of the evaporable water is filled in the capillary pores in the range of 10 nm ~1000 nm. With the continuous hydration of cement, the water in these pores is consumed and the peak pore radius decreases constantly. The increase of W/C ratio can improve the hydration degree, but results an increase in the porosity and the proportions of larger pores.
Keywords
1H low-field NMR; hydration; pore structure; white cement
NAZMI EKREN, CEYLIN EDA KARACAN
Abstract
Electrospun patches have attracted interest in different biomedical fields, including tissue engineering and drug delivery. Portable electrospinning guns promise faster and more practical interventions in these areas. In this article, the design, construction and testing of a portable electrospinning gun are described to produce fiber and particle products. Results were discussed depending on the electrospinning gun’s working system and properties of the products. The electrospinning gun system could have a high voltage of up to 30 kV. Also, no heating problems were encountered during high voltage values. Due to the uniformity, reproducibility and tunability of the produced PCL and PMSQ fibers, it can be said that electrospinning gun can be used in nanotechnology, drug delivery systems and wound dressing applications.
Keywords
Electrospinning, electrospinning gun, fiber, wound dressing, biomedical
LÜTFIYE DAHIL, KENAN KAYA, ÖMER FARUK ERKENDIRCI, CIHAN SEZER
Abstract
The present study experimentally investigates tensile strength and impact toughness of plain composites made of carbon, glass, Kevlar, and steel wire mesh fabric; and hybrid composites of carbon-Kevlar reinforcement with polyethylene matrix. Composites are prepared by employing a hot press technique, where reinforcement fabrics, as well as polyethylene film are stacked in varying number of layers. Samples were cut from the composite plates for uniaxial tensile loading and low-velocity Charpy impact tests, as well as for resin burn-off process. It is shown that number of layers affects tensile and impact characteristics, as in general, tensile strength of composites increases with number of layers. Also, impact energy absorbed by the specimens is also proportional to number of layers.
Keywords
CUVINTE CHEIE (ENGLEZĂ)
ANDRADA-ELENA ALECU, ȘTEFANIA-ANDREEA GIRJOABA, MIHAELA BEREGOI, SORIN-ION JINGA, CRISTINA BUSUIOC
Abstract
In this work, polyvinylidene fluoride was obtained in the form of one-dimensional structures with the help of electrospinning technique. Several types of precursor solutions were tested to find the optimal experimental conditions to produce smooth, continuous and beadless fibres, morphologically suitable for the development of piezoelectric scaffolds dedicated to tissue engineering applications. Thus, the influence of solvent type, polymer concentration, as well as electrospinning parameters (feeding rate, spinneret-collector distance, and applied voltage) was assessed and the best situation was the one with a 2:3 ratio between dimethylformamide and acetone, 20 % polymer concentration, 1 mL/h flow, 20 cm distance and 18 kV voltage. In the end, the fibres were loaded with barium titanate commercial particles, as first attempt to produce a piezoelectric composite with potential in the medical field.
Keywords
polyvinylidene fluoride, barium titanate, fibres, electrospinning, morphology
I. GOMOIU , M. ENACHE, S. NEAGU , R. RUGINESCU, M. DUMBRĂVICIAN, R. RADVAN, L. GHERVASE, I. MOHANU, R. COJOC
Abstract
Biological cleaning of the restored of artworks is a green methodology which avoids the toxicity of solvents used in dry cleaning and protects restorers and environment. Biocleaning with viable bacteria cultures has been used successfully to remove black crust, mineral salts deposits, and organic matter residues, due to selective and specific metabolites proving to be more effective than chemical methods. Biocleaning treatments were applied for removing of the organic materials used in previous restoration or accidentally filed onto an artwork. Gels captured the attention of restorers and their applicability quickly extended to murals, stone, paper, even metals. Agarart hydrogel is recommended both for cleaning of artworks and as a delivery system. This study aimed to remove consolidants (acrylic resin Paraloid B72, Transparent Dispersion of Casein) and accidental organic deposits (beewax, sunflower oil and soot) from the surface of the murals with esterolytic enzymes produced by halotolerant bacteria Bacillus sp. BA N P3.3, applied directly or integrated in Agarart. The experiments were carried out on laboratory models aged by exposure to variations of temperature and humidity respectively to UV-A/UV-B radiation. Although biocleaning was achieved by applying of the esterolytic enzymes entrapped in Agarart gel (E-Agarart) or directly on the surface of organic deposit and then covered with Agarart gel (E+Agarart), to avoid the development of efflorescences, treatment with esterolytic enzymes integrated in Agarart gel is recommended.
Keywords
halotolerant and halophilic microorganisms, biotechnologies for conservation and restoration, hydrolytic enzymes, integrated esterase in hidrogels, biocleaning with fungal cultures
CONSTANTIN DORINEL VOINIȚCHI , DAN CARAGHEORGHEOPOL, FĂNICA CĂPĂȚÂNĂ, ANDREEA MATEI
Abstract
The aim of this paper is to estimate the number of fibers that cross a section.
Two methods were used, considering a uniform distribution the average number of fibers in any section of a prism with width and thickness considered infinite.
The probabilistic method was used for the central area of the prism, in which the wall effect is not taken into account.
The second method involved a Monte Carlo simulation; the results obtained by the two methods were close.
Experimental validation involved the use of two different dosages, one usual (25kg /m3) and a much larger one (125kg/m3), trying to highlight a possible interinfluencing effect of the fibers.
The effect of large granules that could change the distribution of fibers was also studied, by performing concrete samples with only a small 0/4mm aggregate and one with larger 0/16mm aggregates. The experimental results, close to those provided by the two methods, showed a minor influence of the fiber dosage as well as the size of the aggregate granules.
Keywords
Monte Carlo simulation, fiber, distribution, concrete
CICI JENNIFER RAJ J , VINOD KUMAR M , SHABARISH S
Abstract
The earthquake related destructions in buildings is alleviated by uncomplicated methods with the implementation of sand-tire mix as the base isolation material below the footing. Rubber which is the major raw material for the elastomeric bearings shall be replaced with sand-rubber mix. The mix is placed below the footing to determine the deflections of the footing for trials such as 0%, 10%, 20%, 30 % and 50% crumb rubber (CR). Furthermore, the behaviour of the footing is studied with these trials under static and cyclic loading. The research is exclusively dealt to determine the energy dissipation capacity and stiffness degradation of the footing with and without base isolation material (sand-rubber mix). From the investigation it was evident that 30% crumb rubber combination have better seismic energy mitigating capacity.
Keywords
Sand, crumb rubber, footing, static, cyclic, energy dissipation capacity, stiffness degradation
KRISHNA KUMAR P , CHINNARAJU K
Abstract
This paper demonstrates the comparative study of properties of foam concrete with polypropylene fiber and carbon fiber. The experimental investigations were done between foam concrete with 10% and 20% foam volume. As well as cuttle bone powder was partially replaced with cement as bio-filler in the aspect of cost cutting in foam concrete production and reducing environmental hazard. Both polypropylene and carbon fibers were added in the foam concrete in the percentage of 0.5%, 1%, 1.5%, 2%, 2.5%, 3% by mix volume fraction. The physical, mechanical, thermal and durability properties of foam concrete were investigated. The result showed inclusion of fibers in foam concrete increases the compressive strength with minimal reduction in densities. The hydrophobic properties of foam concrete were improved with polypropylene fiber addition, which decreases the adsorption and sorptivity characteristics. Irrespective of the type of fiber added the thermal conductivity of foam concrete also decreases when compared to conventional foam concrete. Polypropylene fiber in foam concrete showed the highest reduction in thermal conductivity. With the gainful impact saw on the density and strength performance and from the cost investigation, 2% Polypropylene fiber with 25% cuttlebone powder as cement replacement in foam concrete is recommended for the production of low cost and sustainable foamed concrete.
Keywords
Foam concrete, polypropylene fiber, carbon fiber, cuttle bone powder, compression strength, density, thermal conductivity, sorptivity
QUN GUO, XIAOZHEN LI, JUNZHE LIU
Abstract
The effect of rust inhibitor on the composition and microstructure of the passive film on the surface of the rebar in carbonated concrete was studied through XPS and other microstructure testing techniques.The mechanism of the rebar passive film formation under the action of rust inhibitor was clarified. The results show that the main components of the passive film are FeOOH, Fe3O4,FeO, and Fe2O3. The reaction of sodium molybdate (Na2MoO4) with Fe2+ resulted in the formation of the FeMoO4 protective layer.Benzotriazole (BTA) and Fe combined to form N-Fe bonds, which adhered to the surface of rebar and prevented corrosion. According to the composition and compactness of the passive film, Na2MoO4 + BTA has the best corrosion resistance effect.
Keywords
carbonation; passive film; rust inhibitor; microstructure characteristics
MURAT OZOCAK, CAN BURAK SİSMAN
Abstract
The depletion of traditional energy sources and environmental problems have increased the orientation to new and renewable energy sources. In this context, studies have intensified on the use of wastes generated in different sectors for energy production. As a result of these studies, fuel briquettes were produced from hazelnut shells and put into use for heating purposes in different structures. In this study, it was aimed to prevent environmental problems caused by the ash formed as a result of burning the briquettes produced from hazelnut shells and to investigate its usability as a pozzolan in the production of economical and durable concrete with high insulation properties in the construction sector. In this way, it will be possible to convert ash, which is the waste of a useful product produced from an agricultural waste, into a product with high added value in the construction sector. For this purpose, the effects were investigated on the physical, mechanical and thermal properties of concrete of using briquette ash in different proportions (0, 5, 10, 15 and 20%) as a substitute for cement in concrete production. As a result of the research, it is recommended to use briquette ash up to 5% in order to produce concrete with sufficient strength and good insulation, as it is possible to use briquette ash as a pozzolan in concrete production.
Keywords
Briquette ash, nutshell, agricultural wastes, concrete, pozzolan material
SANJEEV KUMAR VERMA , HITESH KODWANI, SOURABH ASANGE
Abstract
The characteristics of ingredients used for performing construction will affect the performance of prepared concrete. Aggregates are major constituents of concrete and it has been observed by researchers that characteristics of material used as aggregate significantly influence the strength and workability of concrete.
Here, in the present work effect of flaky aggregates and steel slag as partial replacement of coarse aggregate on the characteristics of concrete composed by replacing cement by sand has been investigated. Two types of mixes have been prepared by varying the ratio of sand and marble powder which is 1:1 and 1:0.5, coarse aggregates are partially replaced by flaky aggregate and steel slag in 10%, 15%, 20%, 25% and 30% by weight. It has been observed that increase in proportion of flaky aggregate reduces the strength and workability of concrete and increase in steel slag increases the strength of concrete but reduces the workability. Mixing both the materials simultaneously increases the early strength of concrete and then lowers the percentage increase of strength, however, produces the concrete with low workability.
Keywords
Cement, Concrete, Aggregates, Steel slag, Marble powder
SEYED VAHID RAZAVI TOSEE , IMAN FARIDMEHR
Abstract
In this research, from zero to 100% every 10%, normal aggregates were replaced with heavy aggregate (a mixture of iron ore and barite) in the concrete. A total of 110 cylindrical specimens (15x30cm) and cubic specimens (15x15cm) were used to examine the specific gravity, compressive strength, and tensile strength of Heavyweight Concrete (HWC). The test results confirmed that by substituting Heavyweight Aggregate (HWA) iron ore and barite mixture for 10% (or higher) of regular aggregates, a specific weight greater than 2600 kg/m3 might achieve, and the resulting product classified as HWC. In the second phase of the research, to develop the Generalized Regression Neural Network (GRNN) for estimating compressive and tensile strength, 48 data records from the specimen tests were selected randomly to find the best network with minimum mean square error (MSE) and correlation coefficient. The results confirmed that the proposed informational model could adequately estimate the mechanical properties and simplify the design processes in computational intelligence structural design platforms in the future.
Keywords
Material Science, Material Property, Material Structure
B.RANJITH BABU, R.THENMOZHI
Abstract
In this study, a high strength-lightweight concrete of 50 MPa compressive strength was developed using an artificial neural network through MatLab programming. For the structural application of lightweight concrete, density and strength are more crucial. According to IS 456-2000, the concrete used for structural elements such as beams, columns, and slabs must have a minimum compressive strength of 20 MPa. Historically, additional materials like silica fume and fly ash were utilized to partially substitute cement. Nowadays, fly ash is processed systematically into pelletized aggregates and heated to temperatures up to 1500 degrees Celsius and is used as aggregates in lightweight concrete adding to sustainability. A high-strength lightweight concrete was modeled using neural networks, and its compressive strength was validated using laboratory measurements. A total of 57 data sets were used to construct this mix, which was based on earlier research.
Keywords
Lightweight Concrete, sintered fly ash aggregate, MATLAB, Neural Networking
SREENATH SREEKUMARAN , SARAVANA RAJA MOHAN KALIYAPERUMAL
Abstract
Reactive Powder Concrete (RPC) mixes consume a very high volume of cement in which a part only can undergo hydration due to the adoption of a very low water to binder (W/B) ratios. The unhydrated part of cement can act as a filler in the mixes. In this study, for the sustainable development of RPC mixes, the filler part of cement was replaced with Ground Granulated Blast furnace Slag (GGBS). Further reactive Rice Husk Ash (RHA) was introduced to the mix as a replacement for inert Quartz Powder (QP) filler to bring in a better pozzolanic activity. Flow characteristics of the mixes were evaluated. Compressive strength of the mixes was also evaluated. For the optimization of results, regression models were established based on Box-Behnken method of Experiment Design. Sustainability Indicators such as Embodied Energy (EE) and Embodied Carbon (EC) of the mixes were also evaluated. It was observed that flow of the mixes was improved considerably due to the addition of GGBS and got reduced due to the incorporation of RHA. Improved strength was observed up to 30% replacement of cement with GGBS. For all the cases, 100% replacement of QP with RHA lead to better strength results. Further, EE and EC of mixes were considerably reduced due to the incorporation of GGBS and RHA.
Keywords
Reactive Powder Concrete, Rice Husk Ash, Response Surface Design, Embodied Energy, Embodied Carbon
HARIDASA ANAYAK, N KRISHNAMURTHY, SHAILESH RAO A
Abstract
In recent years, the coating of different materials inside the cylinder liner has emerged as a prime focus of research among the scientists as it improves the efficiency of the engine. In this paper, the coating material, YSZ + Al2O3 with equal proportion were coated on the cast iron substrate using two bonding materials (Iron Nickel Aluminium composite powder (Metco 452) and Nickel Aluminium cermet (Metco 410 NS)) with the three-coating thickness of 100µm, 200µm and 300µm. Initially, the wear characteristics were carried out and properties like the coefficient of friction (CoF), wear rate for different load conditions were determined. The analyses of the worn sample were studied in details with the aid of SEM images. Further, the scratch studies for the worn samples were also carried out.
Keywords
plasma spraying, wear, microhardness, coating thickness, the coefficient of friction
MD INSIAT ISLAM RABBY , SITI UJILA MASURI, N.M.S. HASSAN, SK MAHAFUJUR RAHMAN, TAZEEN AFRIN MUMU, MAHFUZ ALAM
Abstract
A triangular corrugated pipe was studied numerically along with Al2O3-water, CuO-water, and SiC-water nanofluids, to identify the thermal capacity for laminar flow. Ansys fluent software and steady-state control volume method were applied for simulation purposes. Hence, different volume fractions (1% - 5%) of CuO, Al2O3, and SiC nanoparticles were considered to mix with water to suspend nanofluids. 400 to 1200 Reynolds number with a constant wall heat flux of 1000 W/m2 were considered to calculate the heat transfer rate. In addition, the required pumping power for such enhancements was determined as well. The simulation results highlighted that corrugated pipe provided highest improvement in heat transfer with increase in Reynolds number compared to straight pipe. Consequently, the mixing of nanoparticles in the working fluid showed more enhancement. For the corrugated pipe, at Re =1200, CuO-water, Al2O3-water, and SiC-water nanofluids showed a maximum 11.94%, 8.96%, and 9.15% enhancement respectively of Nusselt number compared to water. Furthermore, CuO-water, Al2O3-water, and SiC-water nanofluids showed enhancement in pumping power compared to water. Additionally, a correlation to predict the Nusselt number for nanofluid and triangular corrugated pipe was also developed by using Buckingham π Theorem, which showed good agreement with numerical results. However, it can be concluded that corrugated pipe, along with nanofluids, provide enhancement in heat transfer for the laminar developed region of a pipe.
Keywords
Nusselt number; nanofluids, volume concentration, Buckingham π Theorem, pumping power
CORINA ANCA SIMION , IULIANA MĂDĂLINA STANCIU, TIBERIU BOGDAN SAVA, DORU GHEORGHE PACESILA
Abstract
This paper presents the results of AMS radiocarbon dating for a sample of hydraulic mortar taken from foundations of the Roman customs Porolissum - Moigrad, Romania. We test the feasibility of the radiocarbon dating, namely that it delivers an age for the analyzed fraction which belongs to the historical period in question, and is not a result of late or recent interventions. The present case study provides a detailed description of the pre-treatment method of the sample, the stage of obtaining the calcite fraction originating from the moment of mortar hardening in the masonry, the stage of separation and purification of carbon dioxide resulting from the chemical digestion of the final analyte. Some original aspects were developed at RoAMS Laboratory in Magurele. The reduction of carbon dioxide to carbon in the presence of iron catalyst (graphitization), as well as the spectrometric measurement, calculations and calibration are also briefly described. Calibrated result and its interpretation in historical and archeological context recommend the use of this mortar sample in future multidisciplinary analyzes regarding the original recipe and possible sources of raw materials involved in the construction.
Keywords
CUVINTE CHEIE (ENGLEZĂ)
ANA J. MOMČILOVIĆ-PETRONIJEVIĆ , GORDANA A.TOPLIČIĆ-ĆURČIĆ, DUŠAN Z. GRDIĆ, DRAGAN M. ĐORĐEVIĆ, NENAD S. RISTIĆ ,ZORAN J. GRDIĆ
Abstract
Caričin Grad is an archeological site dating back to VI century, located in the vicinity of present day Leskovac, Serbia. The city is the legacy of the famous early Byzantine Emperor Justinian I. The city, in the town planning terms, is divided into three large units. Acropolis, Middle town and Lower town, connected by the suburban area. The grandeur and importance of the city are witnessed by the remenants of several lines of city walls, planned street network, cisterns, thermae, aqueduct and sewage, numerous sacral buildings, administrative structures and housing architecture. Considering the complexity of the city, in town planning and architectonic terms, and diversity of building types in it, the mortars taken for analyses were collected from various types of buildings: from housing, public buildings, fortifications and from the aqueduct structure. In the paper, basic physical properties, as well as mineralogic, morphologic and chemical features of the sampled mortars were examined. The testing was performed using optical and scanning electron microscopy, XRF semi-quantitative analysis and XRD (x-ray diffraction). Based on the mentioned analyses, it was concluded that the main binder in the mortar was pulverized brick, which activated its pozzolanic activity. In addition, as an auxiliary binder, there was limestone powder, considering that the mortar contained the crushed limestone aggregates as well. The detected aggregate grains are the river aggregate, pieces of bricks and fine crushed limestone aggregate. These results would be further used for making the mix designs of repair mortars.
Keywords
Caričin Grad; electron microscopy B; historical mortars; optical microscopy B; repair mortars, X-ray methods
SATISHKUMAR SENGOTTAIYAN, SURESH PARAMASIVAM
Abstract
The health risks connected with the use of asbestos-based brake linings have sparked research into the use of environmentally benign agro-based biomaterials as reinforcing agents in composite materials used in the manufacturing of brake pad linings. The purpose of this research is to determine the feasibility of employing coconut shell (CS) powder in the manufacturing of asbestos-free brake lining materials. The powders, in conjunction with the appropriate fillers, were utilised in the manufacture of the brake lining. The compositions of the reinforcing powders were varied between 20% and 35%, those of the resin binder were varied between 58 and 43%, and those of the filler metal and curing agents were maintained constant. Weighed, prepared, mixed, cured, and moulded these materials. Water and oil absorption, compressive strength, hardness, and wear tests were performed on the created composite materials. The research indicated that increasing the amount of reinforcing elements leads in an increase in the samples water and oil absorption. Compressive strength of the composite rose proportionately with the addition of up to 35% composition. The coefficient of friction tested was determined to be within an acceptable range. Additionally, when combined with other fillers and confined, CS powder shown great potential for brake lining manufacturing.
Keywords
Coconut shell (CS), Brake linings, Compressive strength, Hardness, wear
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Year
2022
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Issue
52 (4)
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Pages
368-373
SASIKUMAR P, MANJU R
Abstract
This research investigated the axial compression behaviour of high strength concrete Encased Steel Composite (ESC) columns. Six high strength concrete ESC columns were made with M70 grade concrete, including with and without Alkaline Resistant Glass Fibre (AR-GF), all the specimens were tested after curing periods. A study of structural performance was conducted, which included axial load-deformation, ultimate load-carrying capacity, failure mode, ductility, and stiffness. As a result of the experiments, the failure mode of ESC columns without AR-GF are sudden failures once the peak load is reached, and with AR-GF at 1.20% volume prevented concrete covers from spalling and increased the load-carrying capacity. In the whole experimental study, the reinforcement ratio was maintained at a constant. In conclusion, the results of the experimental study were compared with the Finite Element (FE) model results, the FE model is help to prediction of axial compression behaviour of ESC columns.
Keywords
Encased steel composite column, axial deformation, axial load, ductility, high strength concrete, stiffness
KARTHICK PALANISAMY , REVATHI VAIYAPURI
Abstract
Professor Davidovits fathered the idea that geopolymer binder is a viable alternative to Portland cement. Geopolymer can be synthesized by alkali activation of alumina silica rich inorganic materials of industrial by products and natural materials. An exhaustive study carried out on geopolymer concrete by the researchers establishes a strong pathway in the construction field. Furthermore, Self-Compacting Geopolymer Concrete (SCGPC) has been promoted using fly ash, GGBS, rice husk ash, silica fume, etc. In this respect, the present study proposes to carry out experimental studies on self-compacting geopolymer concrete, incorporating bottom ash and GGBS, under ambient curing condition. Bottom ash and GGBS were added in the proportion of 100:0, 75:25, 50:50, 25:75, 0:100. The fresh and hardened properties of the SCGPC were analysed for all the mixes. The test result of fresh concrete properties indicates that it satisfies the limits specified by EFNARC standards. The maximum compressive strength of self-compacting geopolymer concrete was ascribed as 38.5MPa and 54.8 MPa at 3 and 28 days by the mix containing only GGBS. An excellent strength achieved at early age is observed in the GGBS mix. Also, the strength results reveal that increase in the content of GGBS achieved greater strength.
Keywords
Alumina silica, Bottom ash, GGBS, self-compacting geopolymer concrete, EFNARC
BENGİ AYKAÇ , ALTAN YAVUZCAN
Abstract
The presented study investigates the efficiency of repairing damaged reinforced concrete beams by a novel technique, which is the injection of epoxy resin to the cracks. The two main test parameters were the amount of flexural reinforcement (low, medium, and high) and the level of seismic damage before repair (light, moderate, and heavy). Nine cantilever beams were tested under reversed cyclic transverse loading in the undamaged (original) and repaired (after damaging) states. The test results were examined and discussed in terms of the initial flexural rigidity and ultimate load capacity. The technique was shown to be the most effective in damaged beams with mid-sized cracks. The minor cracks particularly in lightly-reinforced beams were not suitable for proper injection of resin, while the major cracks resulted in the epoxy to govern the flexural behavior of the beam after repair. The experimental load capacities were shown to be in close agreement with the analytical flexural capacities of the respective beams. The sizes of the cracks before repair and the longitudinal reinforcement did not affect the repaired beam to reach the load capacity of the original counterpart but affected the extent of deformations before reaching this load level.
Keywords
Repair; Crack width; Flexural reinforcement; Seismic retrofit; Concrete structures
GANESH NAIDU GOPU, A. SOFI
Abstract
The chloride attack on the reinforced concrete structure resulted in a substantial loss of bond strength due to reinforcing bar corrosion. E-glass, Steel and E-waste copper fibers were used in concrete to investigate corrosion-induced bonding behaviour. It was determined to perform pull-out tests in order to evaluate the bond behavior in relation to test variables such as the ratio of concrete cube clear cover (C) to rebar diameter (Ø) and the type of fiber. The bond stress-slip curves produced in this work adequately represented the bond behavior of corroded and uncorroded concrete specimens (with and without fibers). According to the findings, adding fibers to concrete appears to strengthen the connection and reduce corrosion. The bond strength of steel fiber reinforced concrete was found to be higher than that of concrete mixes including E-glass and E-copper wire fibers.
Keywords
Chloride attack; Bond strength; Corrosion-induced; pull out test; corrosion rate; chloride attack
SASIKUMAR P, MANJU R
Abstract
The present study carried out the axial compressive behaviour of High Strength Concrete (HSC) columns reinforced with GFRP bars under axial compression. Only a limited number of research works only done with GFRP Reinforced (RC) Concrete Columns. Twelve columns of 150x150mm cross-section and 1000mm height made with M70 grade of HSC, including 1.20% of Alkaline Resistant Glass Fibre (AR-GF), were tested under axial loading. The main parameters were studied in this research, including the Axial Load (AL) carrying capacity, axial deformation, failure pattern, ductility, and stiffness. GRFP RC columns are 90% axial load only carried compared to steel RC columns. The analytical study helped to predict the ultimate AL carrying capacity of HSC columns.
Keywords
High strength concrete, Axial load, Axial deformation, Stiffness, Ductility, GFRP bars
KHAWAJA ADEEL TARIQ, HADHI HASSAN KHAN, FARHAN ASIF, NOMAN JABBAR
Abstract
The efficient pavement performance depends on the stability of the supporting layers. Road failures mostly occur due to poor selection of material and insufficient drainage arrangements. Subbase layer is an essential component of the pavement along with base, subgrade and surface wearing course. This research work is related to investigating the effect of Lime, Fly ash and Mat fiber on the strength and permeability characteristics of Subbase material. Results show that the maximum dry density and soaked California bearing ratios (CBR) values are increasing with the increase of lime and fly ash ratio in subbase. Whereas, maximum dry density and soaked California bearing ratios (CBR) values are decreasing with the increase of Mat fiber in the subbase. The increase in content of Mat fibers also resulted in increase in permeability of subbase material. It is also observed that higher content of fly ash results in swelling of the subbase material as compared with lime content.
Keywords
subbase; lime; fly ash; CBR; mat fiber