Advanced Materials Research Vol. 1174

Abstract: Fired bricks have shown tremendous potential as a construction material due to their properties. However, their use required some specifications in terms of quality, resistance, and durability. In developing countries, the lack of tools to make test specimens leads to many defects in these brick specimens responsible for low durability and weak precision during mechanical tests and shrinkage. In this study, a simple and traditional method of making test bricks is presented. This simple method allows the production of bricks with the required properties. This method is especially efficient for semi-soft consistency pastes. The elaborated handmade pastes present a very different particle-size distribution < 2 mm (clay: 18-66%; silt: 12-53%; sand: 5-65%). The pastes do not stick to the walls of the mould like in the case of steel moulds, and it gives specimens with standard shape, smooth surface, and sharp edges. The resulting fired bricks exhibit high mechanical strength (up to 102 MPa for the compressive strength, and up to 28 MPa for the flexural strength) comparable to and even better than those of conventional methods. The elaborated bricks allowed also the measurement of very important parameters such as drying and firing shrinkage, drying, and firing weight loss, and porosity.

Abstract: One of the most important processes of physical deterioration in concrete is the exposure to high temperatures that influences their durability and stability during life service. In addition, if self-compacting concrete is formed by lightweight aggregates, such as EPS, it is necessary to analyze its behaviour after it has been exposed to high temperature conditions. This research shows research that evaluates the effect EPS on the mechanical properties of self-compacting concrete at high temperatures. This study evaluated physical-mechanical properties, including residual compressive strength and thermal conductivity after exposure at 22oC, 150oC, 350oC, 500oC and ISO834. Experimental results showed that the loss of residual compressive strength of the specimens up to 350oC is almost insignificance, but it will be reduced by 49% and 70% when temperatures increase up to 500oC and 700oC respectively. EPS contributes to lightness, thermal insulation, and commitment to the environment in lightweight SCC.

Abstract: The main objective of this study was to investigate the influence of using magnetized water on the mechanical properties and durability behavior in terms of freeze-thaw resistance of recycled aggregate concrete. In addition to the effect of different numbers of water rounds in the magnetic field, other variables including steel fibers, super-plasticizers and silica-fume were considered in the concrete production in order to achieve the ideal possible performance for recycled aggregate concrete made with 100% coarse aggregates replacements. For this purpose, a total of 11 concrete mixes were prepared and tested. At the first step, the effects of the mentioned variables on the basic properties, including workability, water absorption, compressive strength, splitting tensile strength, flexural strength and freeze-thaw durability test were investigated. Additionally, flexural toughness was evaluated in accordance with the post-crack strength (PCS) method and the microstructure of concrete specimens was also observed by using scanning electron microscope (SEM). The results of most experiments indicated that magnetized water, although highly effective on the mechanical properties of concrete, should not be solely utilized as a compensating factor for the defects caused by recycled coarse aggregates. The optimum toughness and durability results regarding the fiber-reinforced concrete mixes produced with recycled coarse aggregates, were related to samples containing silica-fume and 10-rounds magnetized water. Furthermore, the existence of cement replaced by 10% of silica-fume and 10-rounds magnetized water in the concrete mix MW-SF2, increased the durability of the recycled aggregate concrete by an average of approximately 63%.

Abstract: The present study aims to carry out a parametric investigation on a pile made of different materials, and subjected to static and dynamic loading resulting from the weight of the structure and the shear force acting on the head of the pile. It is worth specifying that the pile is anchored in the ground on a Winkler-Pasternak elastic foundation that is made up of five different layers. In this study, the equilibrium equations were treated using the high-order theory with a new shear deformation shape function of a cylindrical pile made of an isotropic material and a sandwich functionally graded material.The results obtained with a numerical study based on the minimization of energies by the Rayleigh-Ritz method was carried out in order to highlight the influence of the geometric ratio, the volume fraction of the functionally graded material, and the type of loading on the vibration frequencies and the admissible stresses in order to determine the most appropriate material for the pile so that extreme stresses can be absorbed. The precision and the applicability of the method with new solution of the transverse shear deformation are demonstrated through this study with modeling of the layered property of the soil, were then compared with those reported in previous work available in the literature. It turned out that these results are in good agreement with each other, for the different materials of pile and for all boundary conditions considered. The results of pile with sandwich functionally graded material, it is revealed that the role of this material has an influence on the type of loading, especially, in the case statique of a pile subjected to a compound bending weight and the shear effect, in case dynamique the pile with vibration flexible or rigid .

Abstract: The self-compacting concrete (SCC) workability is usually ensured by the addition of superplasticizers in the mixture. The effect of some properties of superplasticizers was investigated by many researchers. However, in the literature, there is no study related to the effect of dry extract of superplasticizer admixture on the rheological and mechanical properties of self-compacting concrete.The objective of this work is to characterize the effects of six types of superplasticizers with various solids on the rheological properties as well as the compressive strength and elastic modulus of SCC.This experimental study shows that the dry extract of superplasticizer affects the various properties of concrete both in the fresh and hardened state: first, the dry extract allows controlling the flow properties (the lower its value, the more the concrete is self-compacting), and second, the dry extract allows the reduction of the water to cement ratio (the greater its value, the stronger the concrete). The statistical coefficients, analyzed in this work, indicate a high-level relationship between the dry extract and the rheological and mechanical behavior of SCC.

Abstract: This study employs 2D finite element modeling using Plaxis to investigate the behavior of the railway embankment constructed on the active Ganges-Bramhaputra floodplain. The parametric study considers three different train speeds, 100, 120, and 170 km/hr, and two different soil profiles along different chainages, chainage 82 km+183 m (Ch1) and 84 km+102 m (Ch2) of Padma Bridge Rail Link. Pseudo-static trainloads have been applied and the settlement of the ballast bottom (BB) and embankment bottom (EB) have been determined and compared along with the factor of safety (FS). From the obtained results, the maximum settlement of EB in Ch1 ranged between 27.45 cm to 29.2 cm which is lower by 9.2 cm from Ch2 on average. For BB, greater settlements have been observed as they varied between 33.25 cm to 36.20 cm for Ch1 and 42.80 cm to 45.31 cm for Ch2. Thus in both cases, Ch2 shows greater settlements. Also in both chainages, the settlements exceed the allowable range. As the train speed increases from 100 to 170 km/hr, the increase in the settlement is noticeable for the ballast bottom but not for the embankment bottom. Considering the FS, the embankments are assessed to be safe in all considered cases with an FS> 1.2, without any significant effect of train speeds.

Abstract: Plastic waste disposal is among the most challenging problems of the current era. Therefore, new methods and applications for the utilization of waste plastics are increasingly needed. To find them, it is essential to research and develop the material properties of recycled plastics. The effect of different ultraviolet light (UV) stabilizers on the color stability, melt properties and tensile properties of mixed waste plastics blends was studied in this paper. The mixed waste plastics collected from two different waste sources were prepared as specimens by injection molding, and studied with two different types and loading amounts of UV stabilizers. UV absorbers (UVAs) and hindered amine light stabilizers (HALS) were used as UV stabilizers. A specimen produced without the addition of a UV stabilizer was used as a reference specimen of both the blends. After the accelerated weathering, the addition of a UVA provided an improved, smaller change in color than the addition of HALS. Among the tensile properties, the addition of UV stabilizers clearly improved the tensile strength and tensile modulus for almost all the studied specimens. Additionally, the melt properties of both the studied plastic blends were found to be increased by the addition of UV stabilizers.

Abstract: In this work, the adhesion and corrosion resistance of TiN coating by magnetron sputtering on stainless steel substrates under different bias voltages conditions (-50 V and-100 V) was investigated. AFM was used for surface roughness and grain size analysis, XRD for phase identification, Rockwell C for adhesion and nanoindentation for hardness and elastic modulus. According to AFM the coating deposited at-100V bias had decreased surface roughness, the value decreased from 2.7 nm (for-50V sample) to 1.8 nm, this was due to an etching like process which occurs when ions with higher energies start hitting the surface. The coated samples came under HF1 adhesion parameter which is the highest class of adhesion in the model on the basis of Rockwell C adhesion test. nanoindentation hardness and elastic modulus results of-50 V and-100V were found to be 224 GPa and 182 GPa, respectively and the value of hardness, 16 GPa and 22 GPa, respectively. The corrosion behavior of TiN coatings were studied in 3.5wt. % NaCl solutions using Tafel Extrapolation, Cyclic Polarization and Open Circuit Potential. It was noted on the basis of these corrosion tests that, as bias voltage is increased, it leads to the formation of more densely packed, fine grained columnar structures with less pores, which decreases the chances of corrosion. .

Abstract: The elastic and structural properties of Aluminum-doped Gallium Arsenide at different pressure have been investigated by using the first-principles density functional theory. In order to calculate the exchange correlation potentials, the exchange and correlation potential is determined by the generalized gradient approximation parameterized by Perdew Burke Ernzerhof and local density approximation. The results showed the decrease of the lattice constants with increasing pressure and the bulk modulus increase from increasing pressure of binary Gallium Arsenide and their ternary alloy by both the approximations mentioned above. This results show a good agreement is found between the theoretical and the experimental available data. The elastic constants, Young modulus, Bulk modulus, Shear modulus, Poisson’s ratio and Debye temperatures of Gallium Arsenide binary and their ternary alloy as function of pressure have been calculated for the first time. The results provide a theoretical reference for doping of Gallium Arsenide with Aluminum atom at different pressures.