english OUADAH NOUREDINE, ABDESSEMED MOULOUD, KECHOUANE FOUAD
Rezumat
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.
Cuvinte cheie
beton, armare, compozit, adeziv, nanotub, desfacere, frecvență, analiză, structură
A nondestructive testing technique for high strength concrete：explosive-loaded nail penetration test
CHAORAN DUAN , SUHANG YANG
Rezumat
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.
Cuvinte cheie
rezistență la compresiune, încercare in-situ, beton de înaltă rezistență, încercare nedistructivă (NDT), încercare (ENPT)
SELÇUK MEMİŞ , ALİ ALSHAAB RAMROOM
Rezumat
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.
Cuvinte cheie
beton ultra performant (UHPC), ciment, fibre de oțel, superplastifianți bazați pe eter policarboxilat (PCEs), rezistență la compresiune, metoda Taguchi, rezistența la foc
D. VAIČIUKYNIENĖ , A. KANTAUTAS, A. A. NAVICKAS, V. VAIČIUKYNAS, E. IVANAUSKAS, A. AUGONIS, THIYAGARAJU LOGANATHAN
Rezumat
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.
Cuvinte cheie
deșeu zeolitic, pastă întărită de ciment, hidratare ciment portland, material suplimentar cimentos, accelerator CaCl2
MARINELA BARBUȚĂ, PETRU MIHAI , ALINA-MIHAELA NICUȚĂ PRECUL, LILIANA BEJAN, NICOLAE ȚĂRANU, OANA-MIHAELA BANU
Rezumat
Articolul prezintă rezultatele experimentale și numerice obținute pe blocuri din beton preparate folosind deșeuri ca înlocuitor pentru agregatele naturale. Au fost folosite două tipuri de deșeuri, recipiente din PET tocate și rumeguș pentru înlocuirea nisipului într-un dozaj de 40%. De asemenea, 10% din cantitatea de ciment aferentă rețetei betonului obișnuit a fost înlocuit cu cenușă zburătoare. Au fost determinate experimental densitatea, rezistența la compresiune, modulul de elasticitate și diagrama forță de compresiune-deformație. Blocurile din beton cu goluri construite au fost testate la compresiune fiind evidențiate sarcina limită ultimă la compresiune și modurile de cedare. S-a efectuat și o analiză numerică a comportării la compresiune a blocurilor din beton cu goluri, utilizând programul de modelare cu element finit ATENA. S-a remarcat faptul că cedarea blocurilor supuse la compresiune a fost una de tip progresiv, în trepte, distribuția fisurilor fiind aferentă zonelor în care tensiunile de întindere depășesc rezistențele materialelor analizate. Rezultatele studiilor efectuate au relevat o bună corelare a datelor numerice cu cele experimentale.
Cuvinte cheie
cenușă zburătoare, sticle de plastic tocate, deșeu de rumeguș, dezvoltare sustenabilă, rezistență la compresiune, analiza numerică
MARIAM FAROUK GHAZY, METWALLY ABD ALLAH ABD ELATY, MOHAMED FATTOUH ABD EL HAMEED
Rezumat
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.
Cuvinte cheie
mortar geopolimeric, metodologia suprafeței de răspuns, TOPSIS, optimizarea roiului de particule, proprietăți mecanice, temperaturi crescute
ZENO GHIZDĂVEȚ, OVIDIU DUMITRESCU, MIHAI EFTIMIE, ADRIANA MOANȚĂ, IONELA PETRE, NICOLETA CÎRSTEA
Rezumat
Două clase de deșeuri de sticlă, colorate (C) și transparente (A), vor fi utilizate pentru substituția parțială a amestecurilor brute, în special a nisipului, în obținerea clincherului de ciment. Metode statistice avansate vor ajuta la identificarea și extragerea corelațiilor compoziție–măcinare amestec brut–clincherizare–măcinare ciment–proprietăți. Se urmăreste dacă și cum înlocuirea parțială a materiilor prime cu sticlă ar putea influența unele proprietăți ale cimentului. Se investighează dacă diversele amestecuri de materii prime și deșeuri de sticlă vor prezenta un comportament diferit la măcinare. Substituția totală a nisipului cu sticlă implică un aport mai mare de alcalii, care poate influența compoziția și calitatea clincherului dar și funcționarea instalației de clincherizare. Aptitudinea la măcinare afectează direct costurile operaționale, deci va fi și ea evaluată și corelată; printre alți factori, aptitudinea la măcinare este legată de cantitatea de alcalii din clincher.
Cuvinte cheie
deșeuri de sticlă, clincher, substituție parțială, corelații
LEONID DVORKIN, VADIM ZHITKOVSKY , VITALIY MARCHUK, YURI RIBAKOV
Rezumat
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.
Cuvinte cheie
mortar, cenușă zburătoare, cimenturi compozite, superplastifiant, măcinare, modele experimentale - statistice, optimizare
V. VOLCHUK, S. KROVIAKOV, V. KRYZHANOVSKYI
Rezumat
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.
Cuvinte cheie
beton, structură, rezistență, dimensiune fractal, discrepanță metrică, echivalent topologic, model
ANIL NIŞ, TAHA SALAH WAHHAB AL-ANTAKI
Rezumat
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.
Cuvinte cheie
agregat de piatră ponce vulcanică, beton ușor, factorul de eficiență al cimentului, durabilitate, rezistență la acid sulfuric
DENG CHEN, LI-WU MO, KAI-WEI LIU, AI-GUO WANG, SHI-PING ZHANG, QIN-FENG DI, JUN YAN
Rezumat
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.
Cuvinte cheie
1H câmp jos de rezonanță magnetică nucleară, hidratare, structura porilor, ciment alb
CONSTANTIN DORINEL VOINIȚCHI , DAN CARAGHEORGHEOPOL, FĂNICA CĂPĂȚÂNĂ, ANDREEA MATEI
Rezumat
Obiectivul acestei lucrări este o estimare a numă rului de fibre care traversează o secțiune.
Au fost utilizate două metode, considerînd o distribuție uniformă numărul mediu de fibre dintr-o secțiune oarecare a unei prisme cu lățime și grosime considerate infinite.
Metoda probabilistică a fost utilizată pentru zona centrală a prismei, în care nu se ține cont de efectul de perete.
A doua metodă a implicat o simulare Monte Carlo; rezultatele obținute prin cele două metode au fost apropiate.
Validarea experimentală a implicat utilizarea a două dozaje diferite, unul uzual (25kg/m3) și unul mult mai mare (125kg/m3), încercându-se evidențierea unui posibil efect de interinfluențare a fibrelor.
A fost studiat de asemenea și efectul granulelor mari care ar putea modifica distribuția fibrelor, prin realizarea unor probe de beton doar cu agregat mic 0/4mm și a unuia cu agregate mai mari 0/16mm. Rezultatele experimentale, apropiate de cele prevăzute prin cele două metode, au arătat o influență minoră a dozajului de fibre precum și a dimensiunii granulelor de agregat.
Cuvinte cheie
simulare Monte Carlo, fibra, distribuție, beton
CICI JENNIFER RAJ J , VINOD KUMAR M , SHABARISH S
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
KRISHNA KUMAR P , CHINNARAJU K
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
QUN GUO, XIAOZHEN LI, JUNZHE LIU
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
MURAT OZOCAK, CAN BURAK SİSMAN
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
SEYED VAHID RAZAVI TOSEE , IMAN FARIDMEHR
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
B.RANJITH BABU, R.THENMOZHI
Rezumat
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.
Cuvinte cheie
beton ușor
SREENATH SREEKUMARAN , SARAVANA RAJA MOHAN KALIYAPERUMAL
Rezumat
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.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
CORINA ANCA SIMION , IULIANA MĂDĂLINA STANCIU, TIBERIU BOGDAN SAVA, DORU GHEORGHE PACESILA
Rezumat
Acest articol prezintǎ rezultatele datǎrii cu radiocarbon prin metoda AMS pentru un eşantion de mortar hidraulic prelevat din fundaţiile vǎmii romane Porolissum - Moigrad, România. Datarea cu radiocarbon dă încredere în eșantionul care urmează a fi prelevat, și anume că acesta aparține perioadei istorice în cauză, și nu ca urmare a unor intervenții tardive sau recente. Studiul de caz oferă o descriere detaliată a metodei de pretratare a probei, stadiului de obținere a fracției de calcit provenit din momentul întăririi mortarului în zidărie, stadiului de separare și purificare a dioxidului de carbon rezultat în urma digestiei chimice a analitului final. Unele aspecte originale au fost dezvoltate la Laboratorul RoAMS, Mǎgurele. Reducerea dioxidului de carbon la carbon depus intim pe catalizatorul de fier (grafitizare), precum și etapa de măsurare AMS, calcule și calibrare sunt de asemenea descrise pe scurt. Rezultatul calibrat și interpretarea acestuia în context istoric și arheologic recomandă utilizarea acestui eșantion de mortar în viitoare analize multidisciplinare privind rețeta originală și posibilele surse de materii prime implicate.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
ANA J. MOMČILOVIĆ-PETRONIJEVIĆ , GORDANA A.TOPLIČIĆ-ĆURČIĆ, DUŠAN Z. GRDIĆ, DRAGAN M. ĐORĐEVIĆ, NENAD S. RISTIĆ ,ZORAN J. GRDIĆ
Rezumat
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.
Cuvinte cheie
Caričin Grad, microscopie electronică B, mortare antice, microscopie optică B, mortare de reparație, metode de raze X
SASIKUMAR P, MANJU R
Rezumat
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.
Cuvinte cheie
coloană din oțel compozit, deformare axială, încărcare axială, ductilitate, beton de inaltă performanță, rigiditate
KARTHICK PALANISAMY , REVATHI VAIYAPURI
Rezumat
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.
Cuvinte cheie
silice de alumină, cenușă, GGBS, beton geopolimer auto compactant, EFNARC
BENGİ AYKAÇ , ALTAN YAVUZCAN
Rezumat
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.
Cuvinte cheie
reparație, lățime fisurare, armare la încovoiere, modernizare seismică, structuri beton
GANESH NAIDU GOPU, A. SOFI
Rezumat
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.
Cuvinte cheie
atac clorurat, forța de legătură, coroziune indusă, testul de extragere, viteza de coroziune
SASIKUMAR P, MANJU R
Rezumat
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.
Cuvinte cheie
beton de înaltă performanță, încărcare axială, deformare axială, rigiditate, ductilitate bare GFRP
KHAWAJA ADEEL TARIQ, HADHI HASSAN KHAN, FARHAN ASIF, NOMAN JABBAR
Rezumat
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.
Cuvinte cheie
sub-bază, var, cenușă zburătoare, valori CBR, covor din fibră