română ALEXANDRA GABRIELA PALADE, MIHAELA IVANCIA, DIANA FELICIA LOGHIN, ANCA MIHAELA MOCANU
Abstract
The paper aims to obtain prosthetic devices made of two different dental ceramics and characterized by infrared absorption spectroscopy (FITR), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and thermal analysis (TG- DTG-DTA). The two types of dental ceramics (VITA VM13 and IPS Style) were analyzed both in powder form, in the form before the firing process, and in the one resulting after this stage, sintered mass. The TG, DTG and DTA thermal analysis study identified the temperature range in which the ceramics are thermally stable and can be used in dental technique, with IPS Style ceramics showing a lower degree of decomposition.
Keywords
ceramic mass kits, layering technique, absorption spectroscopy, scanning electron microscopy, X-ray spectroscopy, thermal analysis.
MEDDOUR BELKACEM, BREK SAMIR, SAOUDI ABDELHAK, BAKHOUCHE HIBAT ERRAHMANE
Abstract
The choice of material for an implant is considered one of the best for successful arthroplasty. The prosthesis implants for knee joints are usually made of metallic biocompatible materials and polymers. However, this work proposes the replacement of stainless steel with zirconia. Zirconia is known for its weak cracking strength; therefore, this paper aims to predict the cracking of the femoral implant made of zirconia. To do so, a pre-crack was created while performing a numerical simulation to determine the stress intensity factor. This procedure is repeated for the incremented length of the pre-crack until the stress intensity factor reaches the fracture toughness value. To extend the investigation, three areas of the femoral implant where the stress concentration could be expected were considered. In all cases, the simulation results showed good zirconia behavior against cracking, and no crack propagation was expected.
Keywords
crack, toughness fracture; zirconia; knee
NOUR-DJIHANE MAZOUZI, KHALIDA BOUTEMAK, AHMAD HADDAD
Abstract
Films based on hydroxypropylmethylcellulose (HPMC) find applications in for various applications due to their environmental nature, low cost, flexibility and transparency. However, the mechanical properties and moisture content need to be improved. The point of this study was to examine the impact of the magnesium oxide (MgO) addition on the physicochemical, mechanical and rheological properties of hydroxymethylcellulose films. HPMC/MgO composite films showed a four-fold increase in mechanical properties compared to unreinforced HPMC films. In addition, the addition of MgO nanoparticles reduced the moisture content to 2%. The latter was influenced by the difference in water solubility of various composite films, the incorporation of MgO into HPMC films improved the water barrier properties despite the increased water resistance value. Steam wettability was obtained for the HPMC/MgO composite film.
Keywords
hydroxypropyl methylcellulose HPMC, magnesium oxide MgO, nanoparticles, rheological properties
HAO LI, WEI ZHOU, KSENIIA RUDENKO
Abstract
High-performance fiber-reinforced cement composites (HPFRCCs) are attractive in applied in life-cycle structures. Hybrid properties of HPFRCCs with various fibers was experimentally investigated in this study. Three fibers contains the long and short smooth steel fibers and PE fibers, were blended into paste and mortar reinforced with 1.5% vol. fibers, respectively. Enhancements in mechanical properties including compressive strength and flexural strength, and workability were various for different types of fibers. The results show that for FRCCs with available amount of PE and steel fiber was achieved satisfactory workability. The better compressive strength was obtained at 28 day is 100.5MPa and 95.0MPa for the paste and the mortar, respectively. Incorporation of PE fiber in cement paste led to improvement in flexural strength. Microstructure has indicated effectively dense cementitious composites strong bond between the fibers and the cement paste for both of the mixes.
Keywords
high-performance fiber-reinforced cement composites (HPFRCCs), compressive strength, flexural strength, workability
GONZÁLEZ-FÉLIX JULIO CESAR, MENDOZA-RANGEL JOSÉ MANUEL, DIAZ-PEÑA ISMAEL, FÉLIX-MEDINA JENNIFER VIANEY
Abstract
The addition of Polypropylene Microfibers (PM) to an Ordinary Portland Cement (PC) based mortar with a substitution by weight of ground Fly Ash (FA) promotes a decrement of the angle of internal friction (Φ) in a cementitious matrix of the repair mortar and an increment of the cohesion (c) value in the interface between the substrate and the repair mortar zone. Mixtures samples were prepared by replacing cement by fly ash at 0% and 20% by weight, additions of polypropylene microfibers at 0% and 5% and compared with a reference mixture. The characterization of raw materials was carried out by Scanning Electron Microscopy (SEM) with Secondary Electrons (SE) for morphology, Backscattering Electrons (BE) for chemical composition and Energy Dispersive X-Ray Spectroscopy (EDS) for elemental analysis. Substrate and repair mortars were tested for compressive strength, indirect tensile strength, Young’s Modulus, Poisson Coefficient to study the mechanical behavior of the specimens. Electrical resistivity and carbonatation depth (concentration 4%, relative humidity 60 +/- 5%) were analyzed to study the durability of the samples. Samples with FA show a slightly decrement of the cohesion of the interface but samples with PM show an increment of this value, resulting in a higher cohesion with only PM. The use separately of FA and PM promote a lower angle of internal friction than reference samples. The results obtained under the experimental conditions used in this work, show that there is a synergistic effect between the use of polypropylene fibers and the pozzolanic material to reduce the carbonation depth caused using only the microfibers in the mixture.
Keywords
Fly Ash, Repair Mortar, Mechanical Properties, Polypropylene Microfibers, Durability, Cement Base Materials
SANG-SOON PARK
Abstract
Concrete sewer pipe line is one of the important civil infrastructures. Since the concrete sewer pipe is buried underground, the deterioration could be serious problem in maintenance and the repair and replacement cost is very high. The main aggressive factor affecting the durability of concrete sewer pipe is chemical attack by chloride and sulfate, so the sulfate resistant concrete should be used for the construction of sewer pipe line. In this study, the feasibility for the application of ferronickel slag powder (FSP) as a supplementary cementing material (SCM) used to improve the performance of concrete sewer pipe was investigated and the experimental tests were performed with different replacement ratio and fineness to determine the optimum level of replacement securing the improved chemical resistance and durability. The improvement of durability and chemical resistance of FSP contained mortar was verified through accelerated chloride ion penetration test, chemical resistance test and microstructural analysis. The optimum replacement rate of FSP can be considered as 40 % to assure the durability of concrete sewer pipe.
Keywords
concrete sewer pipe; ferronickel slag powder; durability; chemical resistance
SAFIA KHENGAOUI, MOULOUD ABDESSEMED, SAID KENAI, NOUREDDINE OUADAH
Abstract
In many countries, linear infrastructures (roads, railways or airports) are the most efficient and advantageous means of transport for citizens. Some of these infrastructures, such as roads or runways, are made of concrete, and as they are exposed to repeated loads and weather conditions, cracks are forming and spreading throughout the pavement. Several repair techniques have been applied to ensure their continued use under various types of traffic. The repair technique of adding lightweight welded mesh or geosynthetic layers seems to be a suitable solution, given their mechanical and aesthetic performance. This paper presents an experimental study on the effect of wire mesh and geogrids on the reinforcement of rigid concrete pavements. Twenty-four (24) specimens of concrete slabs, unreinforced and reinforced with a combination of geogrid sheets and wire mesh, were fabricated and tested in four-point bending. Validation of the experimental results was obtained by applying the finite element method, using a commercial software. Non-destructive in situ tests with a heavy deflectometer (HWD) were carried out on the central part of a rigid runway located in southern Algeria (arid zone), before and after its reinforcement with geogrids. It was found that geogrids are more effective than wire mesh in terms of tensile strength, stress and displacement reduction and downward crack propagation, with percentages ranging from 15 to 30%.
Keywords
Pavement, rigid, geogrid, wire mesh, reinforcement, experimentation, HWD, numerical
RASIM CEM SAKA, HALIT YAZICI
Abstract
In this study, LC30 structural lightweight concrete and LC60 high performance structural lightweight concrete were produced by using completely pumice aggregate. A total of 6 mixture designs were created by substituting 40% fly ash (FA) by weight into cement and adding 5.5 kg/m3 polypropylene fiber (PPF) to two different lightweight concrete designs. Flexural strength, compressive strength, total water absorption, electrical resistivity, rapid chloride ion penetrability tests were carried out on the produced concretes, and SEM-EDS analyzes were performed. As a result, lightweight structural concretes with a unit weight below 2000 kg/m3 could be produced by using 100% pumice aggregate, and LC60 high-performance lightweight concrete exhibited superior performance in all mechanical and physical tests compared to LC30 lightweight concrete. Since pumice has a porous structure, it has been confirmed by SEM images that there is a good interface between the aggregate and the matrix.
Keywords
Pumice, Fly ash, Synthetic fiber, Structural lightweight concrete, Lightweight aggregate