Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Fe and Fe-P Foam for Biodegradable Bone Replacement Material: Morphology, Corrosion Behaviour, and Mechanical Properties Mon, 24 Oct 2016 13:30:43 +0000 Iron and iron-phosphorus open-cell foams were manufactured by a replica method based on a powder metallurgical approach to serve as a temporary biodegradable bone replacement material. Iron foams alloyed with phosphorus were prepared with the aim of enhancing the mechanical properties and manipulating the corrosion rate. Two different types of Fe-P foams containing 0.5 wt.% of P were prepared: Fe-P(I) foams from a phosphated carbonyl iron powder and Fe-P(II) foams from a mixture of carbonyl iron and commercial Fe3P. The microstructure of foams was analyzed using scanning electron microscopy. The mechanical properties and the corrosion behaviour were studied by compression tests and potentiodynamic polarization in Hank’s solution and a physiological saline solution. The results showed that the manufactured foams exhibited an open, interconnected, microstructure similar to that of a cancellous bone. The presence of phosphorus improved the mechanical properties of the foams and decreased the corrosion rate as compared to pure iron foams. Monika Hrubovčáková, Miriam Kupková, and Miroslav Džupon Copyright © 2016 Monika Hrubovčáková et al. All rights reserved. Synergism Analysis of Bedding Slope with Piles and Anchor Cable Support under Sine Wave Vehicle Load Sun, 23 Oct 2016 12:11:44 +0000 Slope instability under dynamic load is the technical difficulty in the engineering; the evaluation of slope stability under dynamic load and the control of dynamic load is particularly important. In this paper, taking the right side slope of K27+140 m~380 m typical section (K27 slope for short) in Chongqing Fuling-Fengdu-Shizhu expresses highway as an example to calculate and analyze. The K27 slope is under sinusoidal vehicle load and supported by anchor cable and antislide pile to resist downslide strength; at the same time, the combined effect of them is studied. Three-dimensional finite element methodology (FEM) is used to simulate the bedding slope with piles and anchor cable support; furthermore, the eigenvalue can be obtained. In order to reduce error of the elastic boundary conditions caused by the reflection effect of wavelengths, the combination of Lysmer surface viscous boundary and traditional ground support boundaries is utilized to analyze and calculate the time-histories during bedding slope under dynamic load. The dynamic response of pile anchor support to resist sliding force is obtained. The concept of the pile anchor supporting coordinate interval is put forward. Furthermore, it is verified that the pile anchor supporting coordinate interval can be used to evaluate the stability of the slope under dynamic load and provide a new method for the control of the dynamic load. Li Dan-Feng and Wang Lian-Jun Copyright © 2016 Li Dan-Feng and Wang Lian-Jun. All rights reserved. Improvement of Saemangeum Dredged Soils Using Coffee Sludge for Vegetation Soil Thu, 20 Oct 2016 14:37:09 +0000 In Korea, a large scale national project (Saemangeum Project) has been underway that requires a huge amount of dredged soils and their reclamation. Although a lot of dredged soil is needed for reclamation, only about 10% of the dredged soil is used. For this reason, much effort should be made to extensively use the dredged soil. The objective of the study is to find reasonable ways of improving the dredged soils in the Saemangeum area so that they can be used for vegetation of land plants. In order to develop ameliorating methods, we treated silty sand samples, the representative dredged soil of Saemangeum, with mountain soil (0% and 30%), sawdust fertilizer (0% and 6%), bioameliorant (0% and 6%), and coffee sludge (3%, 6%, and 9%), measured the germination rate of bent grass, and applied the lab experiment results to the field for validation. As a result, it was verified that when a mixture of coffee sludge and sawdust fertilizer was used, the chemical and physical properties of dredged soil were significantly improved. This implies that the beneficial use of the dredged soil can be facilitated. Daehyeon Kim, Minseok Kim, Munchae Kim, and Kyungho Park Copyright © 2016 Daehyeon Kim et al. All rights reserved. Electromagnetic Stirring versus ECAP: Morphological Comparison of Al-Si-Cu Alloys to Make the Microstructural Refinement for Use in SSM Processing Thu, 20 Oct 2016 14:14:10 +0000 This work evaluates the morphological evolution at the semisolid state of the Al-4.0wt%Si-2.5wt%Cu alloy produced by direct chill casting under electromagnetic stirring (EMS) and by one equal channel angular pressing (ECAP) pass. The ECAP emerged as a promising technique capable of reduction and homogeneous metals microstructure imposing large deformations occurs in a matrix that contains two channels of the same cross-sectional area and forms an angle of 120°. The materials were submitted to reheating treatment in condition of 60% solid fraction at treatment times of 0, 30, and 90 s. Comparing the two cases, we have the presented ECAP process that had an excellent response to the recovery and recrystallization mechanisms, and refined microstructures ideal for thixoforming were produced. Primary particle sizes of about 45 μm and grain sizes of about 75 μm and a circularity shape factor of more than 0.60 were obtained. The low silicon alloy, Al-4.0wt%Si-2.5wt%Cu, presented excellent refinement when processed via equal channel angular pressing, presenting good morphological stability at the semisolid state, without significant changes in size or shape of the solid particles. This fully globular structure is favourable for thixoforming processes. Luis Vanderlei Torres, Luis Fernando Torres, and Eugênio José Zoqui Copyright © 2016 Luis Vanderlei Torres et al. All rights reserved. Development of Shear Capacity Prediction Model for FRP-RC Beam without Web Reinforcement Thu, 20 Oct 2016 13:49:28 +0000 Available codes and models generally use partially modified shear design equation, developed earlier for steel reinforced concrete, for predicting the shear capacity of FRP-RC members. Consequently, calculated shear capacity shows under- or overestimation. Furthermore, in most models some affecting parameters of shear strength are overlooked. In this study, a new and simplified shear capacity prediction model is proposed considering all the parameters. A large database containing 157 experimental results of FRP-RC beams without shear reinforcement is assembled from the published literature. A parametric study is then performed to verify the accuracy of the proposed model. Again, a comprehensive review of 9 codes and 12 available models is done, published back from 1997 to date for comparison with the proposed model. Hence, it is observed that the proposed equation shows overall optimized performance compared to all the codes and models within the range of used experimental dataset. Md. Arman Chowdhury, Zubayer Ibna Zahid, and Md. Mashfiqul Islam Copyright © 2016 Md. Arman Chowdhury et al. All rights reserved. Influences by Air Voids on the Low-Temperature Cracking Property of Dense-Graded Asphalt Concrete Based on Micromechanical Modeling Thu, 20 Oct 2016 06:07:39 +0000 This study characterized the impacts of air voids on the low-temperature cracking behavior of dense-graded asphalt concrete. Virtual low-temperature bending beam test for dense-graded asphalt concrete was built and executed by discrete element method and PFC3D (particle flow code in three dimensions). Virtual tests were applied to analyze the impacts by content, distribution, and size of air voids on the low-temperature properties of dense-graded asphalt concrete. The results revealed that higher air void content results in worse low-temperature property of dense-graded asphalt concrete, especially when the air void content exceeds the designed air content; even with the same designed air void content, different distributing condition of air voids within asphalt concrete leads to different low-temperature properties of asphalt concrete, especially when the air void content in the central-lower part of testing sample varies. Bigger size of single air void which tends to form interconnected air voids within asphalt concrete has more harmful impacts on the low-temperature properties of asphalt concrete. Thus, to achieve satisfied low-temperature properties of dense-graded asphalt concrete, it is critical to ensure the designed air void content, improve the distribution of air voids, and reduce the interconnected air voids for dense-graded asphalt concrete. Tao Ma, Yao Zhang, Hao Wang, Xiaoming Huang, and Yongli Zhao Copyright © 2016 Tao Ma et al. All rights reserved. Effect of Casting Conditions on the Fracture Strength of Al-5 Mg Alloy Castings Wed, 19 Oct 2016 08:37:09 +0000 During the transient phase of filling a casting running system, surface turbulence can cause the entrainment of oxide films into the bulk liquid. Previous research has suggested that the entrained oxide film would have a deleterious effect on the reproducibility of the mechanical properties of Al cast alloys. In this work, the Weibull moduli for the ultimate tensile strength (UTS) and % elongation of sand cast bars produced under different casting conditions were compared as indicators of casting reliability which was expected to be a function of the oxide film content. The results showed that the use of a thin runner along with the use of filters can significantly eliminate the surface turbulence of the melt during mould filling which would lead to the avoidance of the generation and entrainment of surface oxide films and in turn produce castings with more reliable and reproducible mechanical properties compared to the castings produced using conventional running systems. Fawzia Hamed Basuny, Mootaz Ghazy, Abdel-Razik Y. Kandeil, and Mahmoud Ahmed El-Sayed Copyright © 2016 Fawzia Hamed Basuny et al. All rights reserved. Experimental Study on the Performance and Microstructure of Cementitious Materials Made with Dune Sand Tue, 18 Oct 2016 11:18:38 +0000 This paper presents the results of an investigation on the utilization of dune sand from waterway regulation engineering as the main raw materials to produce cementitious materials. The mechanical and durability properties of the cementitious materials were studied. Furthermore, a scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP) were used to identify the microstructure of the specimens. The results show that the compressive and splitting tensile strength of cementitious materials can be improved due to the addition of ground granulated blast-furnace slag (GGBS) which mainly attributes to a better grain size distribution and pozzolanic effect compared to the specimen added cement alone. The specimen with the addition of suitable cement, GGBS, and gypsum shows low dry shrinkage and excellent abrasion resistance. Correspondingly the specimens present a lower porosity and total volume of pores at different curing ages. The SEM observation indicates that there are quite a lot of hydrate products such as calcium silicate hydrate gel in the matrix which verifies the formation of cementitious compounds. The results obtained suggest that there is potential in manufacturing cementitious material with dune sand in substitution of ordinary concrete to use in hydraulic engineering. Chaohua Jiang, Xiaobin Zhou, Guilan Tao, and Da Chen Copyright © 2016 Chaohua Jiang et al. All rights reserved. Synthesis of Cubic Phase-Co Microspheres by Mechanical Solid-State Reaction-Thermal Decomposition and Research on Its Growth Kinetics Tue, 18 Oct 2016 06:09:35 +0000 Cubic phase cobalt (Co), which can be used as a key component for composite materials given its excellent ductility and internal structure, is not easy to obtain at room temperature. In this study, oxalic acid and cobalt nitrate are used as raw materials to synthesize the cobalt oxalate precursor, which has a stable structure with a five-membered chelate ring. Cobalt oxalate microspheres, having a high internal energy content, were prepared by using mechanical solid-state reaction in the presence of a surfactant, which can produce spherical micelles. The thermal decomposition of the precursor was carried out by maintaining it in a nitrogen atmosphere at 450°C for 3 h. At the end of the procedure, 100 nm cubic phase-Co microspheres, stable at room temperature, were obtained. Isothermal and nonisothermal kinetic mechanisms of cobalt grain growth were investigated. The cubic-Co grain growth activation energy, , was calculated in this study to be 71.47 kJ/mol. The required reaction temperature was low, making the production process simple and suitable for industrial applications. Ying Deng, Yanhua Zhang, Lingling Peng, Xiaolong Jing, and Hui Chen Copyright © 2016 Ying Deng et al. All rights reserved. Investigation of Thermostressed State of Coating Formation at Electric Contact Surfacing of “Shaft” Type Parts Mon, 17 Oct 2016 12:29:52 +0000 The forming of coating at electric contact surfacing is considered. The mathematical model of the coating formation is developed. The method of numerical recurrent solution of the finite-difference form of static equilibrium conditions of the selected elementary volume of coating is used. This model considers distribution of thermal properties and geometric parameters along the thermal deformation zone during the process of electric contact surfacing by compact material. It is found that the change of value of speed asymmetry factor leads to increasing of the friction coefficient in zone of surfacing. This provides the forming of the coating of higher quality. The limitation of the technological capabilities of equipment for electric contact surfacing is related to the size of recoverable parts and application of high electromechanical powers. The regulation of the speed asymmetry factor allows for expanding the technological capabilities of equipment for electric contact surfacing. The nomograms for determination of the stress on the roller electrode and the finite thickness of the coating as the function of the initial thickness of the compact material and the deformation degree are shown. Olena V. Berezshnaya, Eduard P. Gribkov, and Valeriy D. Kuznetsov Copyright © 2016 Olena V. Berezshnaya et al. All rights reserved. Numerical Simulation of Recycled Concrete Using Convex Aggregate Model and Base Force Element Method Mon, 17 Oct 2016 12:14:30 +0000 By using the Base Force Element Method (BFEM) on potential energy principle, a new numerical concrete model, random convex aggregate model, is presented in this paper to simulate the experiment under uniaxial compression for recycled aggregate concrete (RAC) which can also be referred to as recycled concrete. This model is considered as a heterogeneous composite which is composed of five mediums, including natural coarse aggregate, old mortar, new mortar, new interfacial transition zone (ITZ), and old ITZ. In order to simulate the damage processes of RAC, a curve damage model was adopted as the damage constitutive model and the strength theory of maximum tensile strain was used as the failure criterion in the BFEM on mesomechanics. The numerical results obtained in this paper which contained the uniaxial compressive strengths, size effects on strength, and damage processes of RAC are in agreement with experimental observations. The research works show that the random convex aggregate model and the BFEM with the curve damage model can be used for simulating the relationship between microstructure and mechanical properties of RAC. Yijiang Peng, Hao Chu, and Jiwei Pu Copyright © 2016 Yijiang Peng et al. All rights reserved. A Bridge Deflection Monitoring System Based on CCD Mon, 17 Oct 2016 06:47:57 +0000 For long-term monitoring of the midspan deflection of Songjiazhuang cloverleaf junction on 309 national roads in Zibo city, this paper proposes Zhang’s calibration-based DIC deflection monitoring method. CCD cameras are used to track the change of targets’ position, Zhang’s calibration algorithm is introduced to acquire the intrinsic and extrinsic parameters of CCD cameras, and the DIC method is combined with Zhang’s calibration algorithm to measure bridge deflection. The comparative test between Zhang’s calibration and scale calibration is conducted in lab, and experimental results indicate that the proposed method has higher precision. According to the deflection monitoring scheme, the deflection monitoring software for Songjiazhuang cloverleaf junction is developed by MATLAB, and a 4-channel CCD deflection monitoring system for Songjiazhuang cloverleaf junction is integrated in this paper. This deflection monitoring system includes functions such as image preview, simultaneous collection, camera calibration, deflection display, and data storage. In situ deflection curves show a consistent trend; this suggests that the proposed method is reliable and is suitable for the long-term monitoring of bridge deflection. Baohua Shan, Lei Wang, Xiaoyang Huo, Wenting Yuan, and Zhilin Xue Copyright © 2016 Baohua Shan et al. All rights reserved. Experimental Investigation of Tension Stiffening in RC Ties Sun, 16 Oct 2016 16:21:39 +0000 The increasing application of high-performance materials in civil engineering led to the development of reinforced concrete (RC) structures with reduced cross sections and increased spans. In such structures serviceability limit state often becomes the governing condition of the design. Present study investigates the deformation behaviour of high-strength RC ties reinforced with high-grade bars. Experimental investigation was carried out measuring the postcracking stiffness of the specimens at high strain levels. It was found that, despite the reduction in stiffness, a considerable part of the average tensile stresses were carried by the concrete at the advanced loading stages, thus effectively stiffening the RC member. Aleksandr Sokolov, Gintaris Kaklauskas, Ronaldas Jakubovskis, Mantas Juknys, Romualdas Kliukas, Pui Lam Ng, and Viktor Gribniak Copyright © 2016 Aleksandr Sokolov et al. All rights reserved. Experimental Research on Quick Structural Health Monitoring Technique for Bridges Using Smartphone Sun, 16 Oct 2016 14:21:45 +0000 In the recent years, with the development and popularization of smartphone, the utilization of smartphone in the Structural Health Monitoring (SHM) has attracted increasing attention owing to its unique feature. Since bridges are of great importance to society and economy, bridge health monitoring has very practical significance during its service life. Furthermore, rapid damage assessment of bridge after an extreme event such as earthquake is very important in the recovery work. Smartphone-based bridge health monitoring and postevent damage evaluation have advantages over the conventional monitoring techniques, such as low cost, ease of installation, and convenience. Therefore, this study investigates the implementation feasibility of the quick bridge health monitoring technique using smartphone. A novel vision-based cable force measurement method using smartphone camera is proposed, and, then, its feasibility and practicality is initially validated through cable model test. An experiment regarding multiple parameters monitoring of one bridge scale model is carried out. Parameters, such as acceleration, displacement, and angle, are monitored using smartphone. The experiment results show that there is a good agreement between the reference sensor and smartphone measurements in both time and frequency domains. Xuefeng Zhao, Kwang Ri, Ruicong Han, Yan Yu, Mingchu Li, and Jinping Ou Copyright © 2016 Xuefeng Zhao et al. All rights reserved. Finite Element Analysis of Synergy Effect on Concrete Beams Incorporated with Coated Reinforcement and Alternate Aggregates Sun, 16 Oct 2016 09:50:58 +0000 The purpose of this study is to compare the ultimate load carrying capacity of conventional reinforced concrete beams with that of investigation specimen incorporated with coated reinforcement and partially with recycled aggregate and quarry dust. A novel technique of coated reinforcement delays the onset of corrosion with enhanced durability of structures. Results show that not even a film of corrosion (white rust) can be seen in the investigation specimen. There is a progressive increase in stiffness from the state of the first crack to ultimate stage and a negligible difference in ultimate load carrying capacity of the investigation specimen, when compared with the controlled specimen. Incorporation of galvanization, recycled aggregate, and quarry dust seemed to be compatible with the existing conservative concreting procedures. Experimental results are compared with the numerical solutions aided by finite element analysis (FEA by using ABAQUS). Sakthivel Pandiaraj, Rathinasamy Velkennedy, and Soundarapandian Nagan Copyright © 2016 Sakthivel Pandiaraj et al. All rights reserved. Effects of Heat-Treatment on the Microstructure and Wear Resistance of a High-Chromium Cast Iron for Rolls Sun, 16 Oct 2016 09:09:02 +0000 The variations of microstructure and mechanical properties of a high-chromium cast iron for rolls were studied from as-cast to the final heat treatments. Results show that the as-cast microstructure of the HCCI consists of M7C3 carbide, M23C6 carbide, martensite matrix, and retained austenite. The large dendritic M7C3 carbide surrounds the matrix, and the M23C6 carbide is mainly distributed in the matrix. Part of M23C6 carbide transforms to M7C3 carbide and is dissolved in austenite during austenization at 1020°C. Thus, the amount of M23C6 carbide decreases, whereas that of M7C3 carbide increases after quenching; the highest hardness is also obtained. After tempering, the martensite transforms to a tempered martensite, and some carbide precipitates in the martensite matrix. The hardness also changes from HRC62.1, which corresponds to quenching, to HRC55.2 and HRC56.3, which correspond to once and twice tempering, respectively. However, tempering could improve the impact toughness and wear resistance of the HCCI. Zhi-hong Guo, Fu-ren Xiao, Su-ling Lu, Han-yun Li, and Bo Liao Copyright © 2016 Zhi-hong Guo et al. All rights reserved. Development and Physicochemical Characterization of Desonide-Loaded Nanocapsule Suspensions Sun, 16 Oct 2016 08:33:01 +0000 Desonide is a topical corticosteroid that has been used for more than 30 years; however, its prolonged use can induce several side effects, affecting dermis and epidermis. The present work consists of development desonide-loaded nanocapsule suspensions (D-NC) using different polymers (Eudragit S100® or Eudragit L100®) and desonide-loaded lipid-core nanocapsules (D-LNC). They were formulated by interfacial deposition using the preformed polymer method and all formulations showed negative zeta potential and adequate nanotechnological characteristics (particle size 161–202 nm, polydispersity index < 0.20). Simple and sensitive methods using high-performance liquid chromatography (HPLC) were developed to quantify desonide in LNC and to study its release kinetics. The method was linear, specific, precise, and exact and therefore can be applied in quantification of D-NC and D-LNC. We evaluated in vitro methods for drug release (dissolution, Franz diffusion cells, and dialysis sac) and we use mathematical models (monoexponential, biexponential, and Korsmeyer-Peppas) to show release kinetics from this system. M. B. Antonow, R. Lorenzoni, G. M. Barbosa, A. F. Ourique, P. Gomes, and R. P. Raffin Copyright © 2016 M. B. Antonow et al. All rights reserved. Brittle or Quasi-Brittle Fracture of Engineering Materials 2016 Sun, 16 Oct 2016 07:55:33 +0000 Filippo Berto, Liviu Marsavina, Majid R. Ayatollahi, Sergei V. Panin, and Konstantinos I. Tserpes Copyright © 2016 Filippo Berto et al. All rights reserved. Metallurgical and Mechanical Research on Dissimilar Electron Beam Welding of AISI 316L and AISI 4340 Sun, 16 Oct 2016 06:55:53 +0000 Dissimilar electron beam welding of 316L austenitic stainless steel and AISI 4340 low alloy high strength steel has been studied. Studies are focused on effect of beam current on weld geometry, optical and scanning electron microscopy, X-ray diffraction of the weld microstructures, and heat affected zone. The results showed that the increase of beam current led to increasing depths and widths of the welds. The optimum beam current was 2.8 mA which shows full penetration with minimum width. The cooling rates were calculated for optimum sample by measuring secondary dendrite arm space and the results show that high cooling rates lead to austenitic microstructure. Moreover, the metallography result shows the columnar and equiaxed austenitic microstructures in weld zone. A comparison of HAZ widths depicts the wider HAZ in the 316L side. The tensile tests results showed that the optimum sample fractured from base metal in AISI 316L side with the UTS values is much greater than the other samples. Moreover, the fractography study presents the weld cross sections with dimples resembling ductile fracture. The hardness results showed that the increase of the beam current led to the formation of a wide softening zone as HAZ in AISI 4340 side. A. R. Sufizadeh and S. A. A. Akbari Mousavi Copyright © 2016 A. R. Sufizadeh and S. A. A. Akbari Mousavi. All rights reserved. Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature Thu, 13 Oct 2016 14:30:08 +0000 Scanning Electron Microscopy (SEM) test on 30 pieces of fractured granite has been researched by using S250MK III SEM under triaxial compression of different temperature (25~1000°C) and confining pressure (0~40 MPa). Research results show that () the change of fractal dimension (FD) of rock fracture with temperature is closely related to confining pressure, which can be divided into two categories. In the first category, when confining pressure is in 0~30 MPa, FD fits cubic polynomial fitting curve with temperature, reaching the maximum at 600°C. In the second category, when confining pressure is in 30~40 MPa, FD has volatility with temperature. () The FD of rock fracture varies with confining pressure and is also closely related to the temperature, which can be divided into three categories. In the first category, FD has volatility with confining pressure at 25°C, 400°C, and 800°C. In the second category, it increases exponentially at 200°C and 1000°C. In the third category, it decreases exponentially at 600°C. () It is found that 600°C is the critical temperature and 30 MPa is the critical confining pressure of granite. The rock transfers from brittle to plastic phase transition when temperature exceeds 600°C and confining pressure exceeds 30 MPa. X. L. Xu and Z. Z. Zhang Copyright © 2016 X. L. Xu and Z. Z. Zhang. All rights reserved. Performance and Behaviour of Ground Granulated Blast Furnace Slag Imparted to Geopolymer Concrete Structural Elements and Analyzed with ANSYS Thu, 13 Oct 2016 12:07:55 +0000 This paper deals with the behaviour of geopolymer concrete using ground granulated blast furnace slag and steel fibre to compare with M40 grade cement concrete. The cast GPC specimens were placed in a hot curing chamber at 60∘C temperature for 24 hours and tested after 1, 7, 14, and 28 days of ambient curing to find the strength and durability of hardened concrete. The optimum value of compressive strength was attained at 12 Molarities. Fly ash was replaced by GGBS in GPC with different proportions such as 0% to 60% at 5% interval; the optimum strength value was obtained on 40% replacement. From the test results, the compressive, split-tensile, and flexural strength of GPC specimens were 20%, 43%, and 53% higher than those of the control specimens. Based on the optimum strength mix proportion, the structural elements were cast to investigate the stress-strain relations. The GPC beam and L-section showed 33% and 16% higher value. From the results of acid and sulphate resistance tests, it was found that the strength and weight ratio of GPC were higher than the control specimens. From the simulations, it was found that the experimental test results were approximately equal to the ANSYS. Maria Rajesh Antonyamaladhas, Selvamony Chachithanantham, and Anandakumar Ramaswamy Copyright © 2016 Maria Rajesh Antonyamaladhas et al. All rights reserved. Analysis on the Mechanical Characteristics and Energy Conversion of Sandstone Constituents under Natural and Saturated States Thu, 13 Oct 2016 11:29:20 +0000 Given that apparent differences exist between physical and mechanical properties of sandstone constituents under natural and saturated states, uniaxial and triaxial tests of sandstone specimens taken from a deep tunnel in Chongqing under the two states were, respectively, conducted in the laboratory. Analysis on the energy conversion of sandstone constituents under natural and saturated states reveals the varying strain energy conversion mechanisms under the two different conditions. It shows that water saturation has significant effects on the strength and deformation characteristics of sandstone constituents. The load bearing capacity and nondeformability decrease once the sandstone constituents are saturated. The strength weakening due to water in saturated specimens mainly takes place after the dilatancy stress and reaches its maximum at the peak stress . Strain energies of sandstone constituents under the saturated state are lower than those under the natural state, which indicates that water reduces the strain energy absorption. The strain energy of specimens at the peak stress point under the two states has a good linear positive correlation with the confining pressure. Moreover, the fitting curve of the case under the natural state has a higher slope, which means that the strain energy under such state is more sensitive to the confining pressure than that under the saturated state. Xinrong Liu and Jun Liu Copyright © 2016 Xinrong Liu and Jun Liu. All rights reserved. Effect of Concrete Age and Creep on the Behavior of Concrete-Filled Steel Tube Columns Thu, 13 Oct 2016 11:24:59 +0000 The influence of concrete age and creep on the ultimate axial loading capacity of concrete-filled steel tube (CFST) columns is experimentally and numerically investigated. After validation of numerical models, a parametric study is conducted and the results are used to formulate empirical formulas for predicting the ultimate axial load-bearing capacity of the columns. Formulas are also proposed for predicting both the composite creep and aging coefficients of the CFST columns, which consider the confinement action of steel tubes on concrete. Then, the proposed formulas are validated independently by comparing their predictions with existing test results performed by other researchers. The comparisons show that the empirical formulas have the potential to be used in the practical design of CFST columns. HaiYang Wang, XiaoXiong Zha, and Wei Feng Copyright © 2016 HaiYang Wang et al. All rights reserved. Retracted: Enhancing Microstructure and Mechanical Properties of AZ31-MWCNT Nanocomposites through Mechanical Alloying Wed, 12 Oct 2016 07:01:00 +0000 Advances in Materials Science and Engineering Copyright © 2016 Advances in Materials Science and Engineering. All rights reserved. A Simulation Study of Effect of Mn-Ce/γ-Al2O3 on NOx Storage and Reduction over Pt-Ce-Ba/γ-Al2O3 Catalysts Mon, 10 Oct 2016 06:04:21 +0000 A series of Pt-Ce-Ba/γ-Al2O3 and Mn-Ce/γ-Al2O3 catalysts were synthesized by a sol-gel method and the samples were characterized by XRD, SEM, and EDS. The effect of Mn-Ce/γ-Al2O3 on the storage and reduction of NOx over Pt-Ce-Ba/γ-Al2O3 catalysts was studied in a fix-bed reactor with simulation gases NO, O2, and N2. The results indicated that NO oxidation to NO2 was reduced with the increase of inlet NO concentration, which was up to 83% when the concentration of NO was 500 ppm but reduced to 76% with the concentration of NO increasing to 1000 ppm. Comparing with the Pt-Ce-Ba/γ-Al2O3 catalysts, the rate of NOx storage and reduction was remarkably increased over Pt-Ce-Ba/γ-Al2O3 combined with Mn-Ce/γ-Al2O3 catalysts. However, the reductant used for NOx reduction reaction over Pt-Ce-Ba/γ-Al2O3 catalysts was consumed under the treatment of Mn-Ce/γ-Al2O3 catalyst, which caused the NOx conversion to obviously drop, but the rate of NOx absorption declined slightly. Lili Lei, Chuan Sun, Bo Zhang, and Wenye Gu Copyright © 2016 Lili Lei et al. All rights reserved. An Image-Based Finite Element Approach for Simulating Viscoelastic Response of Asphalt Mixture Sun, 09 Oct 2016 14:35:40 +0000 This paper presents an image-based micromechanical modeling approach to predict the viscoelastic behavior of asphalt mixture. An improved image analysis technique based on the OTSU thresholding operation was employed to reduce the beam hardening effect in X-ray CT images. We developed a voxel-based 3D digital reconstruction model of asphalt mixture with the CT images after being processed. In this 3D model, the aggregate phase and air void were considered as elastic materials while the asphalt mastic phase was considered as linear viscoelastic material. The viscoelastic constitutive model of asphalt mastic was implemented in a finite element code using the ABAQUS user material subroutine (UMAT). An experimental procedure for determining the parameters of the viscoelastic constitutive model at a given temperature was proposed. To examine the capability of the model and the accuracy of the parameter, comparisons between the numerical predictions and the observed laboratory results of bending and compression tests were conducted. Finally, the verified digital sample of asphalt mixture was used to predict the asphalt mixture viscoelastic behavior under dynamic loading and creep-recovery loading. Simulation results showed that the presented image-based digital sample may be appropriate for predicting the mechanical behavior of asphalt mixture when all the mechanical properties for different phases became available. Wenke Huang, Xiaoning Zhang, and Yingmei Yin Copyright © 2016 Wenke Huang et al. All rights reserved. Effect of Nanosilica on the Fresh Properties of Cement-Based Grouting Material in the Portland-Sulphoaluminate Composite System Wed, 05 Oct 2016 16:13:04 +0000 The effect of NS particle size and content on the fresh properties of the grouting material based on the portland-sulphoaluminate composite system was analyzed. The experimental results indicated that air content increased and apparent density decreased, with increased NS content, but the NS particle sizes have minimal effect on the air content and apparent density. The setting time of mortar was significantly shortened, with increased NS content; however, NS particle sizes had little influence on the setting time. The effect of fluidity on the mortars adding NS with particle size of 30 nm is larger than NS with particle sizes of 15 and 50 nm and the fluidity decreased with increased NS content, but the fluidity of mortars with the particle sizes of 15 and 50 nm is almost not affected by the NS content. XRD analysis shows that the formation of ettringite was promoted and the process of hydration reaction of cement was accelerated with the addition of NS. At the microscopic level, the interfacial transition zone (ITZ) of the grouting material became denser and the formation of C-S-H gel was promoted after adding NS. Shengli Li and Tingting Xu Copyright © 2016 Shengli Li and Tingting Xu. All rights reserved. Mechanical Performance and Chloride Diffusivity of Cracked RC Specimens Exposed to Freeze-Thaw Cycles and Intermittent Immersion in Seawater Wed, 05 Oct 2016 14:36:22 +0000 The effects of crack width on chloride ingress and mechanical behavior of reinforced concrete (RC) specimens were experimentally studied after exposure to 300 cycles of freeze-thaw and seawater immersion (75 times). Cracks were induced prior to exposure by an eccentric compression load which was sustained until the end of the exposure period. The maximum cracks widths induced in the four column specimens were 0, 0.06, 0.11, and 0.15 mm, respectively. Results show that when the crack width was less than 0.06 mm, the effect of cracks on chloride ingress could be neglected. However, when the crack width was more than 0.11 mm, chloride ingress was accelerated. Results of static loading tests show that both yield load and ultimate load of RC columns decreased as crack width increased. When the crack width was 0.15 mm, yield load and ultimate load of RC column specimen decreased by 17.0% and 18.9%, respectively, compared to a specimen without cracks. It was concluded that crack width significantly promoted local chloride ingress and mechanical performance degradation of RC structures in cold coastal regions or exposed to deicing salts. Bei Shen, Yinghua Ye, Bo Diao, and Xiaoning Zheng Copyright © 2016 Bei Shen et al. All rights reserved. Experimental Investigation on Strength and Water Permeability of Mortar Incorporate with Rice Straw Ash Wed, 05 Oct 2016 13:15:23 +0000 The utilization of various agricultural residue ash as a pozzolanic material has the potential to reduce both the environmental impact and cost associated with building materials. In this paper, the authors studied the strength and permeability of mortar using different percentages of rice straw ash (RSA) as cement replacement and the possibilities of using RSA as a pozzolanic material. Locally available rice straws were burnt at a temperature of 600°C and ground to make RSA. The chemical and physical properties of RSA were studied and the outcome shows that the ash contains about 76% of silica in it. This investigation further focused the strength and water permeability of mortar using RSA, which demonstrates that up to 10% replacement both the strength and permeability have a better result than that of control specimen. Surajit Munshi and Richi Prasad Sharma Copyright © 2016 Surajit Munshi and Richi Prasad Sharma. All rights reserved. Solidification/Stabilization of Fly Ash from a Municipal Solid Waste Incineration Facility Using Portland Cement Tue, 04 Oct 2016 07:08:17 +0000 This study investigated the solidification/stabilization of fly ash containing heavy metals using the Portland cement as a binder. It is found that both the cement/fly ash ratio and curing time have significant effects on the mechanical (i.e., compressive strength) and leaching behaviors of the stabilized fly ash mixtures. When the cement/fly ash ratio increases from 4 : 6 to 8 : 2, the increase of compressive strength ratio raises from 42.24% to 80.36%; meanwhile, the leaching amount of heavy metals decreases by 2.33% to 85.23%. When the curing time increases from 3 days to 56 days, the compressive strength ratio of mixtures raises from 240.00% to 414.29%; meanwhile, the leaching amount of heavy metals decreases by 16.49% to 88.70%. The decrease of compressive strength with the lower cement/fly ash ratios and less curing time can be attributed to the increase of fly ash loading, which hinders the formation of ettringite and destroys the structure of hydration products, thereby resulting in the pozzolanic reaction and fixation of water molecules. Furthermore, the presence of cement causes the decrease of leaching, which results from the formation of ettringite and the restriction of heavy metal ion migration in many forms, such as C-S-H gel and adsorption. Qiang Tang, Yang Liu, Fan Gu, and Ting Zhou Copyright © 2016 Qiang Tang et al. All rights reserved.