Search results for: chemical strength

Authors: Nihal Abdel Hamid Taha

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Crack evaluation of flexure reinforced concrete (RC) member is considered an important step in the design process, since the formation of concrete cracks depends on the possibility of exposure to various conditions(pollution, humidity,..etc.). Because of the disparity between different grades of steel in the service load stresses, this affects the cracking behavior. This paper is concerned with the crack pattern and cracking load for concrete beams with T-section reinforced with two different grades of steel at the service load levels stages up to ultimate load. A practical program has been put up to investigate the difference between reinforced steel bars with yield strength 420 N/mm2 and 500 N/mm2 through six T-section reinforced beams. The beams were tested under static- monotonic two– point service loading up to ultimate failure under flexural stresses. The influence of parameters such as clear concrete cover and concrete compressive strength are considered for each of the two grades of steel used. Cracking load, spacing and width were determined. The experimental results demonstrated that increasing the concrete strength results in both of cracking and ultimate load increase, while no significant difference in yield load for the two steel grades used. It has also become obvious, that the number of cracks was more for the lower steel strength, which is followed by decrease in crack width and spacing.

Keywords: RC beams, cracking behavior, steel stress, crack width, crack spacing

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Authors: Robert K. Hillyard, Jonathan Thomas, Brett A. Story

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Compressed Stabilized Earth Blocks (CSEB) are masonry units that combine soil, sand, stabilizer, and water under pressure to form an earth block. These CSEB’s offer a cost-effective building solution for remote construction, using local resources and labor to minimize transportation and material costs. However, CSEB’s, and earthen construction generally have not been widely adopted as standardized construction materials. One shortcoming is the difficulty in standardizing strength values of CSEB units and systems due to the inherent variations in mix design, including production compression. This research presents findings on compressive strengths of full-scale CSEB’s from 60 different mix designs as a function of the amount of cement, sand, soil, and water added to the mixture. The full-scale results are compared with CSEB cylinder cores.

Keywords: CSEB, compressive strength, earth construction, mix design

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Authors: Zhuo Cheng, Gaohang Cui, Yang Zheng, Zhiqiang-Pan

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To explore the effect of freeze-thaw cycles on saline soil mechanical properties of fly ash, this study examined the influence of different numbers of freezing and thawing cycles, fly ash content, and moisture content of saline soil in unconfined compression tests and triaxial shear tests. With increased fly ash content, the internal friction angle, cohesion, unconfined compressive strength, and shear strength of the improved soil increased at first and then decreased. Using the Desk-Expert 8.0 software and based on significance analysis theory, the number of freeze-thaw cycles, fly ash content, water content, and the interactions between various factors on the mechanical properties of saline soil were studied. The results showed that the number of freeze-thaw cycles had a significant effect on the mechanical properties of saline soil, while the fly ash content had a weakly significant effect. At the same time, interaction between the number of freeze-thaw cycles and the water content had a significant effect on the unconfined compressive strength and the cohesion of saline soil, and the interaction between fly ash content and the number of freeze-thaw cycles only had a significant effect on the unconfined compressive strength.

Keywords: fly ash, saline soil, seasonally frozen area, significance analysis, qualitative analysis

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Authors: Mohammedi Ferhate, Hakim Chadli, Laggoun Chaouki

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The main objectives of work in this area are, first, obtaining the high laser energies in short time durations needed for the feasibility studies of laser induced thermodynamically exothermic chemical reactions , second, investigating the physical principles that can be used to make laser sources capable of delivering high average powers. We note that, in order to reach both objectives, one has to convert electrical or chemical energy into laser energy, using dense gaseous media.. We present results from the early development of an F atom source appropriate for HF and DF chemical laser research. We next explain the very important difficulties encountered in working with dense gases for that purpose, and we shall describe how, especially at Evaluation of downstream-mixing scheme –levels transitions (001) → (100) and (001) → (020) gas dynamic laser The physical phenomena that control the operation of presently existing laser devices are now sufficiently well understood, so that it is possible to predict that new generations of lasers could be designed in the future. The proposed model of excitation and relaxation levels was finally proved by the computational numerical code of Matlab toolboxes of different parameters of nozzle.

Keywords: hydrogen, combust, chemical laser, halogen atom

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Authors: Daniel Y. Abebe, Jaehyouk Choi

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The idea of adding metallic energy dissipaters to a structure to absorb a large part of the seismic energy began four decades ago. There are several types of metal-based devices conceived as dampers for the seismic energy absorber whereby damages to the major structural components could be minimized for both new and existing structures. This paper aimed to develop and evaluate structural performance of both stiffened and non stiffened circular shear panel damper for passive seismic energy protection by inelastic deformation. Structural evaluation was done using commercially available nonlinear FE simulation program. Diameter-to-thickness ratio is employed as main parameter to investigate the hysteresis performance of stiffened and unstiffened circular shear panel. Depending on these parameters three different buckling mode and hysteretic behavior was found: yielding prior to buckling without strength degradation, yielding prior to buckling with strength degradation and yielding with buckling and strength degradation which forms pinching at initial displacement. Hence, the hysteresis behavior is identified, specimens which deform without strength degradation so it will be used as passive energy dissipating device in civil engineering structures.

Keywords: circular shear panel damper, FE analysis, hysteretic behavior, large deformation

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Authors: Md. Jahidul Islam, A. K. M. Rakinul Islam, M. Salamah Meherier

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This study investigates the suitability of using plastic, such as polyethylene terephthalate (PET), as a partial replacement of natural coarse and fine aggregates (for example, brick chips and natural sand) to produce lightweight concrete for load bearing structural members. The plastic coarse aggregate (PCA) and plastic fine aggregate (PFA) were produced from melted polyethylene terephthalate (PET) bottles. Tests were conducted using three different water–cement (w/c) ratios, such as 0.42, 0.48, and 0.57, where PCA and PFA were used as 50% replacement of coarse and fine aggregate respectively. Fresh and hardened properties of concrete have been compared for natural aggregate concrete (NAC), PCA concrete (PCC) and PFA concrete (PFC). The compressive strength of concrete at 28 days varied with the water–cement ratio for both the PCC and PFC. Between PCC and PFC, PFA concrete showed the highest compressive strength (23.7 MPa) at 0.42 w/c ratio and also the lowest compressive strength (13.7 MPa) at 0.57 w/c ratio. Significant reduction in concrete density was mostly observed for PCC samples, ranging between 1977–1924 kg/m³. With the increase in water–cement ratio PCC achieved higher workability compare to both NAC and PFC. It was found that both the PCA and PFA contained concrete achieved the required compressive strength to be used for structural purpose as partial replacement of the natural aggregate; but to obtain the desired lower density as lightweight concrete the PCA is most suited.

Keywords: polyethylene terephthalate, plastic aggregate, concrete, fresh and hardened properties

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Authors: G. Purushotham, Joel Hemanth

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An investigation has been carried out to fabricate and evaluate the strength and soundness of chilled composites consisting of nickel matrix and fused silica particles (size 40–150 μm) in the matrix. The dispersoid added ranged from 3 to 12 wt. % in steps of 3%. The resulting composites cast in moulds containing metallic and non-metallic chill blocks (MS, SiC, and Cu) were tested for their microstructure and mechanical properties. The main objective of the present research is to obtain fine grain Ni/SiO2 chilled sound composite having very good mechanical properties. Results of the investigation reveal the following: (1) Strength of the composite developed is highly dependent on the location of the casting from where the test specimens are taken and also on the dispersoid content of the composite. (2) Chill thickness and chill material, however, does significantly affect the strength and soundness of the composite. (3) Soundness of the composite developed is highly dependent on the chilling rate as well as the dispersoid content. An introduction of chilling and increase in the dispersoid content of the material both result in an increase in the ultimate tensile strength (UTS) of the material. The temperature gradient developed during solidification and volumetric heat capacity (VHC) of the chill used is the important parameters controlling the soundness of the composite. (4) Thermal properties of the end chills are used to determine the magnitude of the temperature gradient developed along the length of the casting solidifying under the influence of chills.

Keywords: metal matrix composite, mechanical properties, corrosion behavior, nickel alloy, fused silica, chills

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Authors: L. Pu, C. Unluer

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MgO cements have the potential to sequester CO2 in construction products, and can be partial or complete replacement of PC in concrete. Construction block is a promising application for reactive MgO cements. Main advantages of blocks are: (i) suitability for sequestering CO2 due to their initially porous structure; (ii) lack of need for in-situ treatment as carbonation can take place during fabrication; and (iii) high potential for commercialization. Both strength gain and carbon sequestration of MgO cements depend on carbonation process. Fly ash and ground granulated blast-furnace slag (GGBS) are pozzolanic material and are proved to improve many of the performance characteristics of the concrete, such as strength, workability, permeability, durability and corrosion resistance. A very limited amount of work has been reported on the production of MgO blocks on a large scale so far. A much more extensive study, wherein blocks with different mix design is needed to verify the feasibility of commercial production. The changes in the performance of the samples were evaluated by compressive strength testing. The properties of the carbonation products were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/ field emission scanning electron microscopy (FESEM), and the degree of carbonation was obtained by thermogravimetric analysis (TGA), XRD and energy dispersive X-ray (EDX). The results of this study enabled the understanding the relationship between lab-scale samples and scale-up blocks based on their mechanical performance and microstructure. Results indicate that for both scaled-up and lab-scale samples, MgO samples always had the highest strength results, followed by MgO-fly ash samples and MgO-GGBS had relatively lowest strength. The lower strength of MgO with fly ash/GGBS samples at early stage is related to the relatively slow hydration process of pozzolanic materials. Lab-scale cubic samples were observed to have higher strength results than scaled-up samples. The large size of the scaled-up samples made it more difficult to let CO2 to reach inner part of the samples and less carbonation products formed. XRD, TGA and FESEM/EDX results indicate the existence of brucite and HMCs in MgO samples, M-S-H, hydrotalcite in the MgO-fly ash samples and C-S-H, hydrotalctie in the MgO-GGBS samples. Formation of hydration products (M-S-H, C-S-H, hydrotalcite) and carbonation products (hydromagnecite, dypingite) increased with curing duration, which is the reason of increasing strength. This study verifies the advantage of large-scale MgO blocks over common PC blocks and the feasibility of commercial production of MgO blocks.

Keywords: reactive MgO, fly ash, ground granulated blast-furnace slag, carbonation, CO₂

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Authors: Muhammad Javed Bhatti, Tariq Ali, Muazz Ali

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Due to growing environmental awareness in Pakistan, the researchers are increasingly turning to assess and analyze properties of industrial waste and finding solutions on using industrial waste as secondary material. Due to industrialization, enormous by-products are produced and to utilize these by-products is the main challenge faced in Pakistan. Induction furnace slag is one of the industrial by-products from the iron and steel making industries. This paper highlights the true utilization of induction furnace slag as partial replacement of fine aggregate. For the experimental investigation, mixes were prepared with fine aggregate replacement using 0 percent, 5 percent, 10 percent, 15 percent, 20 percent, 25 percent, 30 percent, 35 percent and 40 percent induction furnace slag to evaluate the workability, compaction factor, compressive strength, flexural strength, modulus of elasticity.

Keywords: compressive strength, deflection, induction furnace slag, workability

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Authors: Choi Woo-Seok, Kim Eun-Sup, Ha Eun-Ryong

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Converter slag is used as a low-value product like a construction fill material and soil stabilizer unlike electric furnace slag and blast furnace slag. This study is fundamental research for utilizing the converter slag as the cement admixture. Magnetic separation was conducted for quality improvement of the converter slag, and it was classified according to into 3 types; SA: pure slag, SB: separated slag, SC: remained slag after separating. In XRF result, SB slag was Fe₂CO₃ ratio was higher, and CaO ratio was lower than SA. SC slag was Fe₂CO₃ ratio was lower, and CaO ratio was higher than SA. In compressive strength test for soil cement using SA, SB, SC as the cement admixture, SC slag was more effective in terms of 28days compressive strength than SA, SB slag. In this result, it is considered that the remained material (SC) after magnetic separation is available as the cement admixture.

Keywords: converter slag, magnetic separation, cement admixture, compressive strength

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Authors: G. Kim, R. Sterkenburg

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One of the disadvantages of honeycomb sandwich structure is that they are prone to fluid intrusion. The purpose of this study is to determine if the structural properties of honeycomb core are affected by contact with a fluid. The test specimens were manufactured of fiberglass prepreg for the facesheets and Nomex^® honeycomb core for the core material in accordance with ASTM C-365/365M. Test specimens were soaked in several different kinds of fluids, such as aircraft fuel, turbine engine oil, hydraulic fluid, and water for a period of 60 days. A flatwise compressive test was performed, and the test results were analyzed to determine how the contact with aircraft fluids affected the compressive strength of the Nomex^® honeycomb core and how the strength was recovered when the specimens were dry. In addition, the investigation of de-bonding between facesheet and core material after soaking were performed to support the study.

Keywords: sandwich structure, honeycomb, environmental degradation, debonding

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Authors: Jee-Sang Kim, Jong Ho Park

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Geopolymer concretes are a new class of construction materials that have emerged as an alternative to Ordinary Portland cement concrete. Considerable researches have been carried out on material development of geopolymer concrete, however, a few studies have been reported on the structural use of them. This paper presents the bond behaviors of reinforcement embedded in fly ash based geopolymer concrete. The development lengths of reinforcement for various compressive strengths of concrete, 20, 30 and 40 MPa, and reinforcement diameters, 10, 16, and 25 mm are investigated. Total 27 specimens were manufactured and pull-out test according to EN 10080 was applied to measure bond strength and slips between concrete and reinforcements. The average bond strengths decreased from 23.06MPa to 17.26 MPa, as the diameters of reinforcements increased from 10mm to 25mm. The compressive strength levels of geopolymer concrete showed no significant influence on bond strengths in this study. Also, the bond-slip relations between geopolymer concrete and reinforcement are derived using non-linear regression analysis for various experimental conditions.

Keywords: bond-slip relation, bond strength, geopolymer concrete, pull-out test

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Authors: O. Balamane-Zizi, L. M. Rouidi, A. Boukhrissa, N. Daas, H. Ait-amar

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The objective of this study was to test the possibility of a mixed treatment (physical-chemical and biological) of Ouled Fayet leachates which date of 10 years and has a large fraction of hard COD that can be reduced by coagulation-flocculation. Previous batch tests showed the possibility of applying the physical-chemical and biological treatments separately; the removal efficiencies obtained in this case were not interesting. We propose, therefore, to test the possibility of a combined treatment, in order to improve the quality of the leachates. Estimation of the treatment’s effectiveness was done by analysis of some pollution parameters such as COD, suspended solids, and heavy metals (particularly iron and nickel). The main results obtained after the combination of treatments, show reduction rate of about 63% for COD, 73% for suspended solids and 80% for iron and nickel. We also noted an improvement in the turbidity of treated leachates.

Keywords: landfill leachates, COD, physical-chemical treatment, biological treatment

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Authors: S. K. Khosrowshahi, E. Güler

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This study investigates the reinforcement function of geosynthetics on the shear strength and strain profile of sand. Conducting a series of simple shear tests, the shearing behavior of the samples under static and cyclic loads was evaluated. Three different types of geosynthetics including geotextile and geonets were used as the reinforcement materials. An image processing analysis based on the optical flow method was performed to measure the lateral displacements and estimate the shear strains. It is shown that besides improving the shear strength, the geosynthetic reinforcement leads a remarkable reduction on the shear strains. The improved layer reduces the required thickness of the soil layer to resist against shear stresses. Consequently, the geosynthetic reinforcement can be considered as a proper approach for the sustainable designs, especially in the projects with huge amount of geotechnical applications like subgrade of the pavements, roadways, and railways.

Keywords: image processing, soil reinforcement, geosynthetics, simple shear test, shear strain profile

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Authors: Ralph Gruber, Martina Hafner, Theresia Greunz, Christian Reisecker, David Stifter

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The application of dry lubricant on aluminium for automotive industry is indispensable for a high-quality forming behaviour. To provide a short production time those forming aids will not be removed during the joining step. The aim of this study was the characterization of the influence of dry lubricants on the bond strength and the corrosion resistance of an 6xxx aluminium alloy for automotive applications. For this purpose, samples with a well-defined surface were lubricated with 1 g/m² dry lubricant and joined with a commercial thermosetting 1K-epoxy structural adhesive. The bond strength was characterized by means of lap shear test. To evaluate the corrosion resistance of the adhered aluminium samples an immersion test in 5 w% NaCl-solution was used. Based on fracture pattern analysis, the corrosion behaviour could be described. Dissolved corrosion products were examined using ICP-MS and NMR. By means of SEM/EDX the elementary composition of precipitated solids was determined. The results showed a dry lubricant independent bond strength for standard testing conditions. However, a significant effect of the forming aid, regarding the corrosion resistance of adhered aluminium samples against corrosive infiltration of the metal-adhesive-interface, was observed

Keywords: aluminium alloys, dry film lubricants, automotive industry, adhesive bonding, corrosion

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Authors: C. C. Igwe

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Several parts of Neem tree (Azadirachta indica) are used in traditional medicine in many West African countries for the treatment of various human diseases. The leaf, stem - bark and seed were air dried for 8, 5 and 7 days, respectively. The shells were carfully separated from the seeds, each powdered sample obtained with mechanical miller and 250 mm sieve. The neem samples were individually subjected to extraction with acetone, n-hexane for 48hr and 72 hr, respectively. Physico-chemical and antibacterial evaluation were carried out using standard methods. Results of physico - chemical analyses of the extracted oil from the seed shows that it has a brownish colour, with a smell similar to garlic while the moisture content, refractive index are 0.76% and 1.47 respectively. Other vital chemical results obtained from the neem oil such as saponification value (234.62), acid value (10.84 %), free fatty acid (5.84 %) and peroxide value (10.52%) indicated the oil extracted satisfied standard oils parameters for quality soap and cosmetics production. The antibacterial screening by disc diffusion revealed the oil demonstrated high activity against Staphylococcus aureus. Both the physio-chemical and antibacterial of samples have been certified by National Agency for Food and Drugs Administration and Control. The preliminary results of this study may validate the medicinal value of the plant. Further studies are in progress to clarify the in vivo potentials of neem extracts in the management of human communicable diseases and this is a subject of investigation in our group.

Keywords: anti-bacterial, neem extract, physico-chemical analyses, staphylococcus aureus

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Authors: Salwa M. Elmesallamy, Ahmed A. Farag, Magd M. Badr, Dalia S. Fathy, Ahmed Bakry, Mona A. El-Etre

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The term green environment is an international trend. It is become imperative to treat the corrosion of steel with a green coating to protect the environment. From the potential adverse effects of the traditional materials.A series of polybenzoxazine/henna composites (PBZ/henna), with different weight percent (3,5, and 7 wt % (of henna), were prepared for corrosion protection of carbon steel. The structures of the prepared composites were verified using FTIR analysis. The mechanical properties of the resins, such as adhesion, hardness, binding, and tensile strength, were also measured. It was found that the tensile strength increases by henna loading up to 25% higher than the tidy resin. The thermal stability was investigated by thermogravimetric analysis (TGA) the loading of lawsone (henna) molecules into the PBZ matrix increases the thermal stability of the composite. UV stability was tested by the UV weathering accelerator to examine the possibility that henna can also act as an aging UV stabilizer. The effect of henna content on the corrosion resistance of composite coatings was tested using potentiostatic polarization and electrochemical spectroscopy. The presence of henna in the coating matrix enhances the protection efficiency of polybenzoxazine coats. Increasing henna concentration increases the protection efficiency of composites. The quantum chemical calculations for polybenzoxazine/henna composites have resulted that the highest corrosion inhibition efficiency, has the highest EHOMO and lowest ELUMO; which is in good agreement with results obtained from experiments.

Keywords: polybenzoxazine, corrosion, green chemistry, carbon steel

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Authors: Abhishek Khupsare, Ajay Parmar, Ajay Agarwal, Swapnil Wanjari

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The extreme demand for aggregate leads to the exploitation of river-bed for fine aggregates, affecting the environment adversely. Therefore, a suitable alternative to natural river sand is essentially required. This study focuses on preventing environmental impact by developing polymer sand to replace natural river sand (NRS). Development of polymer sand by mixing high volume fly ash, bottom ash, cement, natural river sand, and locally purchased high solid content polycarboxylate ether-based superplasticizer (HS-PCE). All the physical and chemical properties of polymer sand (P-Sand) were observed and satisfied the requirement of the Indian Standard code. P-Sand yields good specific gravity of 2.31 and is classified as zone-I sand with a satisfactory friction angle (37˚) compared to natural river sand (NRS) and Geopolymer fly ash sand (GFS). Though the water absorption (6.83%) and pH (12.18) are slightly more than those of GFS and NRS, the alkali silica reaction and soundness are well within the permissible limit as per Indian Standards. The chemical analysis by X-Ray fluorescence showed the presence of high amounts of SiO2 and Al2O3 with magnitudes of 58.879% 325 and 26.77%, respectively. Finally, the compressive strength of M-25 grade concrete using P-sand and Geopolymer sand (GFS) was observed to be 87.51% and 83.82% with respect to natural river sand (NRS) after 28 days, respectively. The results of this study indicate that P-sand can be a good alternative to NRS for construction work as it not only reduces the environmental effect due to sand mining but also focuses on utilising fly ash and bottom ash.

Keywords: polymer sand, fly ash, bottom ash, HSPCE plasticizer, river sand mining

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Authors: Wei Jun, Liao Hualin, Wang Huajian, Chen Jingkai, Liang Hongjun, Liu Chuanfu

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Kuqa Piedmont is rich in oil and gas resources and has great development potential in Tarim Basin, China. However, there is a huge thick gravel layer developed with high content, wide distribution and variation in size of gravel, leading to the condition of strong heterogeneity. So that, the drill string is in a state of severe vibration and the drill bit is worn seriously while drilling, which greatly reduces the rock-breaking efficiency, and there is a complex load state of impact and three-dimensional in-situ stress acting on the rock in the bottom hole. The dynamic mechanical properties and the influencing factors of conglomerate, the main component of gravel layer, are the basis of engineering design and efficient rock breaking method and theoretical research. Limited by the previously experimental technique, there are few works published yet about conglomerate, especially rare in dynamic load. Based on this, a kind of 3D SHPB system, three-dimensional prestress, can be applied to simulate the in-situ stress characteristics, is adopted for the dynamic test of the conglomerate. The results show that the dynamic strength is higher than its static strength obviously, and while the three-dimensional prestress is 0 and the loading strain rate is 81.25~228.42 s-1, the true triaxial equivalent strength is 167.17~199.87 MPa, and the strong growth factor of dynamic and static is 1.61~1.92. And the higher the impact velocity, the greater the loading strain rate, the higher the dynamic strength and the greater the failure strain, which all increase linearly. There is a critical prestress in the impact direction and its vertical direction. In the impact direction, while the prestress is less than the critical one, the dynamic strength and the loading strain rate increase linearly; otherwise, the strength decreases slightly and the strain rate decreases rapidly. In the vertical direction of impact load, the strength increases and the strain rate decreases linearly before the critical prestress, after that, oppositely. The dynamic strength of the conglomerate can be reduced properly by reducing the amplitude of impact load so that the service life of rock-breaking tools can be prolonged while drilling in the stratum rich in gravel. The research has important reference significance for the speed-increasing technology and theoretical research while drilling in gravel layer.

Keywords: huge thick gravel layer, conglomerate, 3D SHPB, dynamic strength, the deformation characteristics, prestress

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Authors: Fils Olivier Kamanzi

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This research Paper shows that materials CFRP were used to rehabilitate 9 Beams and retrofitting of 9 Beams with size (125x250x2300) mm each for M50 grade of concrete with 20% of Volume of Cement replaced by GGBS as a mineral Admixture. Superplasticizer (ForscoConplast SP430) used to reduce the water-cement ratio and maintaining good workability of fresh concrete (Slump test 57mm). Concrete Mix ratio 1:1.56:2.66 with a water-cement ratio of 0.31(ACI codebooks). A sample of 6cubes sized (150X150X150) mm, 6cylinders sized (150ФX300H) mm and 6Prisms sized (100X100X500) mm were cast, cured, and tested for 7,14&28days by compressive, tensile and flexure test; finally, mix design reaches the compressive strength of 59.84N/mm2. 21 Beams were cast and cured for up to 28 days, 3Beams were tested by a two-point loading machine as Control beams. 9 Beams were distressed in flexure by adopting failure up to final Yielding point under two-point loading conditions by taking 90% off Ultimate load. Three sets, each composed of three distressed beams, were rehabilitated by using CFRP sheets, one, two & three layers, respectively, and after being retested up to failure mode. Another three sets were freshly retrofitted also by using CFRP sheets one, two & three layers, respectively, and being tested by a two-point load method of compression strength testing machine. The aim of this study is to determine the flexural Strength & behaviors of repaired and retrofitted Beams by CFRP sheets for gaining good strength and considering economic aspects. The results show that rehabilitated beams increase its strength 47 %, 78 % & 89 %, respectively, to thickness of CFRP sheets and 41%, 51 %& 68 %, respectively too, for retrofitted Beams. The conclusion is that three layers of CFRP sheets are the best applicable in repairing and retrofitting the bonded beams method.

Keywords: retrofitting, rehabilitation, cfrp, rcc beam, flexural strength and behaviors, ggbs, and epoxy resin

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Authors: K. Khouzami, J. Brassinne, C. Branca, E. Van Ruymbeke, B. Nysten, G. D’Angelo

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The development of hybrid organic-inorganic nanocomposites has recently attracted great interest. Typically, polymer silicates represent an emerging class of polymeric nanocomposites that offer superior material properties compared to each compound alone. Among these materials, complexes based on silicate clay and polysaccharides are one of the most promising nanocomposites. The strong electrostatic interaction between chitosan and montmorillonite can induce what is called physical hydrogel, where the coordination bonds or physical crosslinks may associate and dissociate reversibly and in a short time. These mechanisms could be the main origin of the uniqueness of their rheological behavior. However, owing to their structure intrinsically heterogeneous and/or the lack of dissipated energy, they are usually brittle, possess a poor toughness and may not have sufficient mechanical strength. Consequently, the properties of these nanocomposites cannot respond to some requirements of many applications in several fields. To address the issue of weak mechanical properties, covalent chemical crosslink bonds can be introduced to the physical hydrogel. In this way, quite homogeneous dually crosslinked microstructures with high dissipated energy and enhanced mechanical strength can be engineered. In this work, we have prepared a series of chitosan-montmorillonite nanocomposites chemically crosslinked by addition of poly (ethylene glycol) diglycidyl ether. This study aims to provide a better understanding of the mechanical behavior of dually crosslinked chitosan-based nanocomposites by relating it to their microstructures. In these systems, the variety of microstructures is obtained by modifying the number of cross-links. Subsequently, a superior uniqueness of the rheological properties of chemically crosslinked chitosan-montmorillonite nanocomposites is achieved, especially at the highest percentage of clay. Their rheological behaviors depend on the clay/chitosan ratio and the crosslinking. All specimens exhibit a viscous rheological behavior over the frequency range investigated. The flow curves of the nanocomposites show a Newtonian plateau at very low shear rates accompanied by a quite complicated nonlinear decrease with increasing the shear rate. Crosslinking induces a shear thinning behavior revealing the formation of network-like structures. Fitting shear viscosity curves via Ostward-De Waele equation disclosed that crosslinking and clay addition strongly affect the pseudoplasticity of the nanocomposites for shear rates γ ̇>20.

Keywords: chitosan, crossliking, nanocomposites, rheological properties

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Authors: Filip Stojcevski, Tim Hilditch, Luke Henderson

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Although carbon fibre composites are becoming ever more prominent in the engineering industry, interfacial failure still remains one of the most common limitations to material performance. Carbon fiber surface treatments have played a major role in advancing composite properties however research into the influence of manufacturing variables on a fiber manufacturing line is lacking. This project investigates the impact of altering carbon fiber manufacturing conditions on a production line (specifically electrochemical oxidization and sizing variables) to assess fiber-matrix adhesion. Pristine virgin fibers were manufactured and interfacial adhesion systematically assessed from a microscale (single fiber) to a mesoscale (12k tow), and ultimately a macroscale (laminate). Correlations between interfacial shear strength (IFSS) at each level is explored as a function of known interfacial bonding mechanisms; namely mechanical interlocking, chemical adhesion and fiber wetting. Impact of these bonding mechanisms is assessed through extensive mechanical, topological and chemical characterisation. They are correlated to performance as a function of IFSS. Ultimately this study provides a bottoms up approach to improving composite laminates. By understanding the scaling effects from a singular fiber to a composite laminate and linking this knowledge to specific bonding mechanisms, material scientists can make an informed decision on the manufacturing conditions most beneficial for interfacial adhesion.

Keywords: carbon fibers, interfacial adhesion, surface treatment, sizing

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Authors: Jatindra Lahkar

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The effect of chemical reaction on laminar mixed convection flow and heat and mass transfer along a vertical unsteady stretching sheet is investigated, in the presence of heat generation/absorption with variable viscosity and viscous dissipation. The governing non-linear partial differential equations are reduced to ordinary differential equations using similarity transformation and solved numerically using the fourth order Runge-Kutta method along with shooting technique. The effects of various flow parameters on the velocity, temperature and concentration distributions are analyzed and presented graphically. Skin-friction coefficient, Nusselt number and Sherwood number are derived at the sheet. It is observed that the influence of chemical reaction, the fluid flow along the sheet accelerate with the increase of chemical reaction parameter, on the other hand, temperature of the fluid increases with increase of chemical reaction parameter but concentration of the fluid reduces with it. The boundary layer decreases on the surface of the sheet for all values of unsteadiness parameter, increasing values of the chemical reaction parameter. The increases in the values of Sc cause the species concentration and its boundary layer thickness to decrease resulting in less induced flow and higher fluid temperatures. This is depicted in the decreases in the velocity and species concentration and increases in the fluid temperature as Sc increases.

Keywords: chemical reaction, heat generation/absorption, magnetic number, unsteadiness, variable viscosity

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Authors: Mark Kennedy, E. Bantugon, Noruane A. Daileg

Abstract:

Leaks arising from aircraft fuel tanks is a protracted problem for the aircraft manufacturers, operators, and maintenance crews. It principally arises from stress, structural defects, or degraded sealants as the aircraft age. It can be ignited by different sources, which can result in catastrophic flight and consequences, exhibiting a major drain both on time and budget. In order to mitigate and eliminate this kind of problem, the researcher produced an experimental sealant having a base material of natural tree resin, the Pili Tree Resin. Aside from producing an experimental sealant, the main objective of this research is to analyze its physical, chemical, mechanical, thermal, and rheological properties, which is beneficial and effective for specific aircraft parts, particularly the integral fuel tank. The experimental method of research was utilized in this study since it is a product invention. This study comprises two parts, specifically the Optimization Process and the Characterization Process. In the Optimization Process, the experimental sealant was subjected to the Flammability Test, an important test and consideration according to 14 Code of Federal Regulation Appendix N, Part 25 - Fuel Tank Flammability Exposure and Reliability Analysis, to get the most suitable formulation. Followed by the Characterization Process, where the formulated experimental sealant has undergone thirty-eight (38) different standard testing including Organoleptic, Instrumental Color Measurement Test, Smoothness of Appearance Test, Miscibility Test, Boiling Point Test, Flash Point Test, Curing Time, Adhesive Test, Toxicity Test, Shore A Hardness Test, Compressive Strength, Shear Strength, Static Bending Strength, Tensile Strength, Peel Strength Test, Knife Test, Adhesion by Tape Test, Leakage Test), Drip Test, Thermogravimetry-Differential Thermal Analysis (TG-DTA), Differential Scanning Calorimetry, Calorific Value, Viscosity Test, Creep Test, and Anti-Sag Resistance Test to determine and analyze the five (5) material properties of the sealant. The numerical values of the mentioned tests are determined using product application, testing, and calculation. These values are then used to calculate the efficiency of the experimental sealant. Accordingly, this efficiency is the means of comparison between the experimental and commercial sealant. Based on the results of the different standard testing conducted, the experimental sealant exceeded all the data results of the commercial sealant. This result shows that the physicochemical-mechanical, thermal, and rheological properties of the experimental sealant are far more effective as an aircraft integral fuel tank sealant alternative in comparison to the commercial sealant. Therefore, Pili Tree possesses a new role and function: a source of ingredients in sealant production.

Keywords: Aircraft Integral Fuel Tank, Physicochemi-mechanical, Pili Tree Resin, Properties, Rheological, Sealant, Thermal

Procedia PDF Downloads 293

Authors: Divyanshoo Singh, Hemant Kumar Singh, Kumar Nilankar

Abstract:

Major engineering constructions and foundations (e.g., dams, tunnels, bridges, underground caverns, etc.) in and around the Himalayan region of Uttarakhand are not only confined within hard and crystalline rocks but also stretched within weak and anisotropic rocks. While constructing within such anisotropic rocks, engineers more often encounter geotechnical complications such as structural instability, slope failure, and excessive deformation. These severities/complexities arise mainly due to inherent anisotropy such as layering/foliations, preferred mineral orientations, and geo-mechanical anisotropy present within rocks and vary when measured in different directions. Of all the inherent anisotropy present within the rocks, major geotechnical complexities mainly arise due to the inappropriate orientation of weak planes (bedding/foliation). Thus, Orientations of such weak planes highly affect the fracture patterns, failure mechanism, and strength of rocks. This has led to an improved understanding of the physico-mechanical behavior of anisotropic rocks with different orientations of weak planes. Therefore, in this study, block samples of phyllite belonging to the Chandpur Group of Lesser Himalaya were collected from the Srinagar area of Uttarakhand, India, to investigate the effect of foliation angles on physico-mechanical properties of the rock. Further, collected block samples were core drilled of diameter 50 mm at different foliation angles, β (angle between foliation plane and drilling direction), i.e., 0⁰, 30⁰, 60⁰, and 90⁰, respectively. Before the test, drilled core samples were oven-dried at 110⁰C to achieve uniformity. Physical and mechanical properties such as Seismic wave velocity, density, uniaxial compressive strength (UCS), point load strength (PLS), and Brazilian tensile strength (BTS) test were carried out on prepared core specimens. The results indicate that seismic wave velocities (P-wave and S-wave) decrease with increasing β angle. As the β angle increases, the number of foliation planes that the wave needs to pass through increases and thus causes the dissipation of wave energy with increasing β. Maximum strength for UCS, PLS, and BTS was found to be at β angle of 90⁰. However, minimum strength for UCS and BTS was found to be at β angle of 30⁰, which differs from PLS, where minimum strength was found at 0⁰ β angle. Furthermore, failure modes also correspond to the strength of the rock, showing along foliation and non-central failure as characteristics of low strength values, while multiple fractures and central failure as characteristics of high strength values. Thus, this study will provide a better understanding of the anisotropic features of phyllite for the purpose of major engineering construction and foundations within the Himalayan Region.

Keywords: anisotropic rocks, foliation angle, Physico-mechanical properties, phyllite, Himalayan region

Procedia PDF Downloads 58

Authors: Eyüp S. Akbas, Betul Ayaz, Beyza S. Haksever, Sema Basat

Abstract:

We aimed to evaluate the relationship between insulin resistance, muscle mass and muscle strength in patients with Hepatitis B virus-related cirrhosis. In our study, there were 65 patients with hepatitis B virus-related cirrhosis in Child A and B group and 65 healthy control individual. Control group was chosen between patients who admitted to the internal medicine clinic and had no pathological values in a routine examination. Muscle mass index was calculated with bioimpedance analysis for both groups to determine muscle strength and muscle mass. Handgrip strength, arm, and calf circumference were measured. In both groups, HOMA-IR was calculated to determine insulin resistance. Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) value was detected 3,47±3,80 in the study group and 1,83±1,20 in control group. There were significant differences between the two groups in arm circumference, fasting insulin, fasting glucose, HOMA-IR, High-density lipoprotein (HDL) and total cholesterol parameters. The correlation coefficient between muscle mass and insulin resistance was statistically insignificant, especially in the study group. In healthy individuals group and all the groups, there wasn’t a correlation between muscle mass and insulin resistance. The upper limit for HOMA-IR was determined as 3,2. In control group, %78,9 of individuals were in HOMA-IR ( < 3.2) group and %21,1 of them were in ( ≥ 3,2) group. In study group, %68,3 of individuals were in HOMA-IR ( < 3,2) group and %31.7 were in HOMA-IR ( ≥ 3,2) group. In our study, we did not find a relationship between muscle mass and insulin resistance in patients with liver cirrhosis. In the study group, we detected a positive relationship between muscle mass, handgrip strength, and calf circumference. We did not find a relationship between insulin resistance and handgrip strength in our study.

Keywords: cirrhosis, hepatitis B, Insulin resistance, muscle mass

Procedia PDF Downloads 150

Authors: G. Ravi Kiran, G. Radhakrishnamacharya

Abstract:

In this paper, the dispersion of a solute in the peristaltic flow of a Jeffrey fluid in the presence of both homogeneous and heterogeneous chemical reactions has been discussed. The average effective dispersion coefficient has been found using Taylor's limiting condition under long wavelength approximation. It is observed that the average dispersion coefficient increases with amplitude ratio which implies that dispersion is more in the presence of peristalsis. The average effective dispersion coefficient increases with Jeffrey parameter in the cases of both homogeneous and combined homogeneous and heterogeneous chemical reactions. Further, dispersion decreases with a phase difference, homogeneous reaction rate parameters, and heterogeneous reaction rate parameter.

Keywords: peristalsis, dispersion, chemical reaction, Jeffrey fluid, asymmetric channel

Procedia PDF Downloads 584

Authors: Mustafa Yıldız, Ali Ulvi Uzer, Murat Olgun

Abstract:

In this study, geotechnical and mineralogical properties of gypsum containing clay basis which form the ground of Second Organized Industrial Zone in Konya province have been researched through comprehensive field and laboratory experiments. Although sufficient geotechnical research has not been performed yet, an intensive structuring in the region continues at present. The study area consists of mid-lake sediments formed by gypsum containing soft silt-clay basis which evolves to a large area. To determine the soil profile and geotechnical specifications; 18 drilling holes were opened and disturbed / undisturbed soil samples have been taken through shelby tubes within 1.5m intervals. Tests have been performed on these samples to designate the index and strength properties of soil. Besides, at all drilling holes Standart Penetration Tests have been done within 1.5m intervals. For the purpose of determining the mineralogical characteristics of the soil; all rock and X-RD analysis have been carried out on 6 samples which were taken from various depths through the soil profile. Strength and compressibility characteristics of the soil were defined with correlations using laboratory and field test results. Unconfined compressive strength, undrained cohesion, compression index varies between 16 kN/m2 and 405.4 kN/m2, 6.5 kN/m2 and 72 kN/m2, 0.066 and 0.864, respectively.

Keywords: Konya second organized industrial region, strength, compressibility, soft clay

Procedia PDF Downloads 308

Authors: Ferhat Kadioglu, Hasan Puskul

Abstract:

A composite material with carbon fiber and polymer matrix has been used as adherent for manufacturing adhesive joints. In order to evaluate different fiber orientations on joint performance, the adherents with the 0°, ±15°, ±30°, ±45° fiber orientations were used in the single lap joint configuration. The joints with an overlap length of 25 mm were prepared according to the ASTM 1002 specifications and subjected to tensile loadings. The structural adhesive used was a two-part epoxy to be cured at 70°C for an hour. First, mechanical behaviors of the adherents were measured using three point bending test. In the test, considerations were given to stress to failure and elastic modulus. The results were compared with theoretical ones using rule of mixture. Then, the joints were manufactured in a specially prepared jig, after a proper surface preparation. Experimental results showed that the fiber orientations of the adherents affected the joint performance considerably; the joints with ±45° adherents experienced the worst shear strength, half of those with 0° adherents, and in general, there was a great relationship between the fiber orientations and failure mechanisms. Delamination problems were observed for many joints, which were thought to be due to peel effects at the ends of the overlap. It was proved that the surface preparation applied to the adherent surface was adequate. For further explanation of the results, a numerical work should be carried out using a possible non-linear analysis.

Keywords: composite materials, adhesive bonding, bonding strength, lap joint, tensile strength

Procedia PDF Downloads 369

Authors: Aicha Chaouay, Lahsen Bazzi, Mustapha Hilali

Abstract:

Seawater has chemical and biological characteristics making it particularly aggressive in relation to the corrosion of many materials including copper and steels low or moderate allies. Note that these materials are widely used in the manufacture of port infrastructure in the marine environment. These structures are exposed to two types of corrosion including: general corrosion and localized corrosion caused by the presence of sulfite-reducing micro-organisms. This work contributes to the study of the problematic related to bacterial contamination of the marine environment of large Agadir and evaluating the impact of this pollution on the corrosion resistance of copper. For the realization of this work, we conducted monthly periodic draws between (October 2012 February 2013) of seawater from the Anza area of the Bay of Agadir. Thus, after each sampling, a study of the electro chemical corrosion behavior of copper was carried out. Electro chemical corrosion parameters such as the corrosion potential, the corrosion current density, the charge transfer resistance and the double layer capacity were evaluated. The electro chemical techniques used in this work are: the route potentiodynamic polarization curves and electro chemical impedance.

Keywords: Bay of Agadir, microbial contamination, seawater (Morocco), corrosion, copper

Procedia PDF Downloads 506