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2014

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Articles 1921 - 1950 of 7240

Full-Text Articles in Engineering

Research On Embedded Sensors For Concrete Health Monitoring Based On Ultrasonic Testing, Shifeng Huang, Mimi Li, Yuesheng Xu, Dongyu Xu, Xinchun Xie, Xin Cheng Jul 2014

Research On Embedded Sensors For Concrete Health Monitoring Based On Ultrasonic Testing, Shifeng Huang, Mimi Li, Yuesheng Xu, Dongyu Xu, Xinchun Xie, Xin Cheng

International Conference on Durability of Concrete Structures

In this article, embedded ultrasonic sensors were prepared using 1–3-type piezoelectric composite and piezoelectric ceramic as the piezoelectric elements, respectively. The frequency bandwidth of the novel embedded ultrasonic sensors was investigated. To obtain the relationship between the receiving ultrasonic velocity and compressive strength, as well as their response signals to crack damage, the sensors were fabricated and embedded into the cement mortar before testing. The results demonstrated that the piezoelectric composite sensor had wider frequency bandwidth than the piezoelectric ceramic sensor. The compressive strength and ultrasonic velocity had a positive linear relationship, with a correlation coefficient of 0.9216. The head …

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Finite Volume Numerical Analysis Of The Thermal Property Of Cellular Concrete Based On Two And Three Dimensional X-Ray Computerized Tomography Images, She Wei, Yang Yonggan, Xie Deqing, Zhang Yunsheng Jul 2014

Finite Volume Numerical Analysis Of The Thermal Property Of Cellular Concrete Based On Two And Three Dimensional X-Ray Computerized Tomography Images, She Wei, Yang Yonggan, Xie Deqing, Zhang Yunsheng

International Conference on Durability of Concrete Structures

Cellular concrete is one kind of lightweight concrete, which are widely used in thermal insulation engineering project. In this study, a three dimensional (2D and 3D) finite-volume-based models was developed for analyzing the heat transfer mechanisms through the porous structures of cellular concretes under steady-state heat transfer condition and also for investigating the differences between 2D and 3D modeling results. 2D and 3D reconstructed pore networks were generated from the microstructural information measured by a 3D image captured by X-ray computerized tomography (X-CT). In addition, the 3D-computed value of the effective thermal conductivity was found to be in better agreement …

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Review Of Microbially Induced Corrosion And Comments On Needs Related To Testing Procedures, Mitchell House, W. J. Weiss Jul 2014

Review Of Microbially Induced Corrosion And Comments On Needs Related To Testing Procedures, Mitchell House, W. J. Weiss

International Conference on Durability of Concrete Structures

Concrete is the most widely used material for the construction of the wastewater collection, storage, and treatment infrastructure. The chemical and physical characteristics of hydrated Portland cement may make it susceptible to degradation under highly acidic conditions. As a result, some concrete wastewater infrastructure may be susceptible to a multistage degradation process known as microbially induced corrosion (MIC). MIC begins with the production of aqueous hydrogen sulfide (H2S(aq)) by anaerobic sulfate-reducing bacteria present below the waterline. H2S(aq) partitions to the gas phase where it is oxidized to sulfuric acid by the aerobic sulfur-oxidizing bacteria Thiobacillus that resides on concrete surfaces …

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Behavior Of Steel–Concrete Composite Beams With Corroded Shear Studs Under Negative Bending Moment, Ju Chen, A. Jiang, W. Jin Jul 2014

Behavior Of Steel–Concrete Composite Beams With Corroded Shear Studs Under Negative Bending Moment, Ju Chen, A. Jiang, W. Jin

International Conference on Durability of Concrete Structures

The behavior of corroded steel–concrete composite beams under hogging moment was studied by experimental investigation and theoretical analysis. A total of eight specimens, six of which had corroded shear studs, were tested. The corrosion rate of studs ranged from 0 to approximately 50%. The constant-current accelerated corrosion method was adopted to accelerate the corrosion process. The loading test results indicated that the bending capacity of the corroded beams decreased slightly with increasing corrosion ratio of the studs. The corroded beams also exhibited an obvious decrease in bending rigid stiffness and increase in the slip between the steel beam and the …

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Experimental Study On Water Absorption By Concrete Damaged By Uniaxial Loading, Licheng C. Wang Jul 2014

Experimental Study On Water Absorption By Concrete Damaged By Uniaxial Loading, Licheng C. Wang

International Conference on Durability of Concrete Structures

Cracking of concrete, which may be induced by several mechanisms, such as shrinkage, thermal effect, and loading, plays an important role in the deterioration of reinforced concrete structures because they provide additional pathways for water and aggressive agents, for example, chlorides, to penetrate into concrete. To well understand the transport properties of cracked/damaged concrete is essential for predicting its long-term durability. In general, water acts as the medium for agents to move into concrete, and water penetration by capillary absorption is more common for the real concrete structures since concrete is rarely saturated. As a result, absorption of water is …

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Numerical Simulation Of The Early Age Three-Dimensional Microstructure Development Of Cement Pastes, Yunsheng Zhang, Zhiyong Liu, Wei Sun Jul 2014

Numerical Simulation Of The Early Age Three-Dimensional Microstructure Development Of Cement Pastes, Yunsheng Zhang, Zhiyong Liu, Wei Sun

International Conference on Durability of Concrete Structures

The formation process of microstructure in cement pastes was first simulated with a numerical model CEMHYD3D. The influence of water-to-cement ratio and particles size on heat release and degree of hydration were then investigated. In addition, the mass of CH and C–S–H phases simulated have been verified by measuring values by thermogravimetry–differential scanning calorimetry (TG-DSC) and X-ray diffraction (XRD)-Rietveld analysis. The evolutions of solids phase percolation and capillary pores de-percolation were also identified by means of a three-dimensional (3D) numerical model. The results show that the simulated values are in good agreement with the available experimental data, indicating a good …

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Study On Variable Action Value Standard For Harbor Infrastructures, Xiaoping Zhong, Qianyi Zhao, Weiliang Jin Jul 2014

Study On Variable Action Value Standard For Harbor Infrastructures, Xiaoping Zhong, Qianyi Zhao, Weiliang Jin

International Conference on Durability of Concrete Structures

To meet with different levels of requirements from proprietors and users and to offer a basis for variable action value to the designers, associated with the standards, this dissertation studied the value standard of load effect and environmental effect. For load effect, on the foundation of analyzing variable load effect model, we used equal exceeding probability principle to calculate the load adjustment coefficient for the cargo loading in harbor and river port under different designing service life. For environmental effect, according to the ranks of marine chloride environment in standards GB/T 50476-2008, after analyzing and comparing the research achievements on …

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Application Of Nanomechanical Methods In Investigation Of C–S–H Gel/Cement Grain Interface, Jing Xu, David J. Corr, Surendra P. Shah Jul 2014

Application Of Nanomechanical Methods In Investigation Of C–S–H Gel/Cement Grain Interface, Jing Xu, David J. Corr, Surendra P. Shah

International Conference on Durability of Concrete Structures

Investigation on the mechanical properties of cement-based materials at micron and submicron scales is important for understanding the overall performance, particularly of high-performance concrete (HPC). Due to low water-tocement ratio of HPC, a large amount of unhydrated cement grains remain in matrix, and a significant impact of the interface between C–S–H gel and cement grains on concrete behavior could be expected. Recent progress in experimental nanomechanics opens new access to nanoengineering of cement-based composites. In this paper, nanoindentation and viscoelastic modulus mapping were used to study the interfacial properties. The interface width measured by modulus mapping was around 200 nm …

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On Utilization Of Elliptical Rings In Assessing Cracking Tendency Of Concrete, Xiangming Zhou, Olayinka G. Oladiran, Wei Dong Jul 2014

On Utilization Of Elliptical Rings In Assessing Cracking Tendency Of Concrete, Xiangming Zhou, Olayinka G. Oladiran, Wei Dong

International Conference on Durability of Concrete Structures

A new experimental method by utilizing elliptical rings to replace circular rings recommended by ASTM and AASHTO was explored for assessing cracking potential of concrete and other cement-based materials under restrained condition. A series of thin and thick elliptical concrete rings were tested alongside circular ones until cracking. Cracking age, position, and propagation were carefully examined. It is found that thin elliptical rings with appropriate geometry can initiate cracks quicker than circular ones, which is desirable for accelerating the ring test. However, thick elliptical rings seem not to exhibit a desirable geometry effect of accelerating ring test compared with circular …

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Revised Model Of Chloride Diffusion In Concrete Bridge By Considering Complex Action Of Load And Chloride Binding Capacity, Yiqiang Xiang, Dongmei Guo Jul 2014

Revised Model Of Chloride Diffusion In Concrete Bridge By Considering Complex Action Of Load And Chloride Binding Capacity, Yiqiang Xiang, Dongmei Guo

International Conference on Durability of Concrete Structures

Coastal concrete bridges will suffer from deterioration of RC structural performance and resistance attenuation because of the chloride penetration and other environment factors. This article discusses current different chloride diffusion models and puts forward the revised model of chloride diffusion in concrete bridge by considering the complex action of load influence and chloride-binding capacity. Comparison of numerical predicted values and relative experimental tests show the presented chloride diffusion model to be more accurate. It provides a theoretical basis for the performance assessment and accurate prediction of the remaining life of highway concrete bridges.

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Effect Of Aggregate Gradation With Fuller Distribution On Properties Of Sulfoaluminate Cement Concrete, Chenchen Gong, Jie Zhang, Shoude Wang, Wen Zong, Lingchao Lu Jul 2014

Effect Of Aggregate Gradation With Fuller Distribution On Properties Of Sulfoaluminate Cement Concrete, Chenchen Gong, Jie Zhang, Shoude Wang, Wen Zong, Lingchao Lu

International Conference on Durability of Concrete Structures

Aggregate, the main ingredient of concrete, has a great effect on mechanical property and durability of concrete. Sulfoaluminate cement has lots of special properties such as high early-age compressive strength, fast hydration and setting rate, and hydration with slight swelling. But effect of aggregate gradation with Fuller distribution on properties of sulfoaluminate cement concrete was seldom studied. Hence, in this paper, experimental investigations on mechanical property and durability of sulfoaluminate cement concrete with aggregate gradations according to Fuller distribution were presented. Fuller distribution of aggregates was beneficial to the close packing of aggregates, and the packing density was changed by …

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Effect Of Transverse Crack On Chloride Penetration Into Concrete Subjected To Drying–Wetting Cycles, Chunhua Lu, Y. Gao, R. G. Liu Jul 2014

Effect Of Transverse Crack On Chloride Penetration Into Concrete Subjected To Drying–Wetting Cycles, Chunhua Lu, Y. Gao, R. G. Liu

International Conference on Durability of Concrete Structures

In this paper, several transversely cracked RC beams, self-anchored in a three-point bending mode, were prepared and subjected to NaCl solution drying–wetting cycles. Based on two experimental results obtained after 15 and 30 cycles, respectively, the profiles of free chloride concentration at different sections of sound and cracked concretes were presented and analyzed. The depth of surface convection zone in cracked concretes subject to chloride drying–wetting cycles is about 10–20 mm, which may increase gradually with the increasing of crack width. Then, it can be found that the speed of chloride penetration in concrete will be increased by cracks. Based …

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Preparation And Properties Of Alkali-Activated Ground-Granulated Blast Furnace Slag Thermal Storage Concrete, Linnu Lu, Bing Ping, Yongjia He, Qingjun Ding, Fazhou Wang, Hang Zhu Jul 2014

Preparation And Properties Of Alkali-Activated Ground-Granulated Blast Furnace Slag Thermal Storage Concrete, Linnu Lu, Bing Ping, Yongjia He, Qingjun Ding, Fazhou Wang, Hang Zhu

International Conference on Durability of Concrete Structures

Thermal storage concrete is prepared by using alkali-activated ground-granulated blast furnace slag as cementitious material. To improve thermal conductivity, graphite aggregate is used to replace part of the coarse aggregate, and, furthermore, polypropylene fiber is added to improve the heat resistance performance of the concrete. The compressive strength of concrete specimens before and after heating (up to 450 °C) was tested, and, furthermore, scanning electron microscopy was used to investigate the structure alteration due to heating. Results showed that the partial replacement of coarse aggregate by graphite block could obviously improve the thermal conductivity of the thermal storage concrete. At …

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Surface And Uniaxial Electrical Measurements On Layered Cementitious Composites Having Cylindrical And Prismatic Geometries, Robert Spragg, Scott Z. Jones, Chiara Villani, Kenneth A. Snyder, Dale P. Bentz, Amire Poursaee, Jason Weiss Jul 2014

Surface And Uniaxial Electrical Measurements On Layered Cementitious Composites Having Cylindrical And Prismatic Geometries, Robert Spragg, Scott Z. Jones, Chiara Villani, Kenneth A. Snyder, Dale P. Bentz, Amire Poursaee, Jason Weiss

International Conference on Durability of Concrete Structures

Electrical measurements are becoming a common method to assess the transport properties of concrete. For a saturated homogenous system, the surface resistance and the uniaxial resistance measurements provide equivalent measures of resistivity once geometry is appropriately taken into account. However, cementitious systems are not always homogenous. This article compares bulk and surface resistance measurements in cementitious materials intentionally composed of layered materials (i.e., layers with different resistivities). For this study, layered systems were composed of paste and mortar layers, representing the heterogeneity that can exist in the surface layers of field applications as a result of differences in moisture content, …

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Experimental Research On Corrosion-Induced Cracking Monitoring Based On Optical Fiber Sensor, Mao Jianghong, Jin Weiliang, Xiong Yanjun, Wang Qi, Yong He, Zhang Jun Jul 2014

Experimental Research On Corrosion-Induced Cracking Monitoring Based On Optical Fiber Sensor, Mao Jianghong, Jin Weiliang, Xiong Yanjun, Wang Qi, Yong He, Zhang Jun

International Conference on Durability of Concrete Structures

Corrosion-induced cracking is a widely existent issue for coastal infrastructure, which leads to its advanced failure. The monitoring of corrosion-induced cracking is an important means of evaluating its influence on structure normal use and safe operation. However, traditional sensors such as strain gage are unsuitable to embed into concrete and to record long-term strain of concrete caused by steel bar corrosion. The optical fiber sensor, Brillouin Optical Time Domain Analysis (BOTDA) can effectively avoid the undetected phenomenon existing in point-wise test method, and it has the characteristic of automated monitoring. The optical fiber sensor is also electrical insulation and anti-electromagnetic …

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Probabilistic Estimation Of Corrosion Propagation Period For Prestressed Concrete Structures Exposed To Chlorides, Radhakrishna G. Pillai, Jayachandran Karuppanasamy Jul 2014

Probabilistic Estimation Of Corrosion Propagation Period For Prestressed Concrete Structures Exposed To Chlorides, Radhakrishna G. Pillai, Jayachandran Karuppanasamy

International Conference on Durability of Concrete Structures

The overall service life of concrete structures can be divided into corrosion initiation and corrosion propagation phases. The durations of these two phases depend on the chloride threshold (Clth) and corrosion rate (icorr), respectively, of the embedded steel reinforcement. Quantitative information on Clth and icorr of conventional steel reinforcement are available in literature. Now‑a‑days, the use of prestressed concrete elements are rapidly increasing and there is a dire need for estimating their service life. Quantitative information on the Clth and icorr of prestressing steel are required for this estimation. However, very limited …

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Numerical Simulation Method For Fracture Effect Of Corroded Steel Strand Under Tension, Fumin Li, Yaxu Qu, Yu Zhao, Rong Lu Jul 2014

Numerical Simulation Method For Fracture Effect Of Corroded Steel Strand Under Tension, Fumin Li, Yaxu Qu, Yu Zhao, Rong Lu

International Conference on Durability of Concrete Structures

Steel strand presents characteristic pitting corrosion in chloride environment, which leads PC structures to a serious structural failure even with light presentational corrosion. So it is necessary to analyze the fracture effect of steel strand caused by pitting corrosion. The theoretical analyses are difficult for the presence of complicated threedimension pits, so numerical method becomes a feasible choice. A numerical simulation method for fracture effect of corroded steel strand under tension by the ANSYS software is introduced in this paper, which contains mainly four issues such as fracture criterion, constitutive relation, geometrical models, and simplified mechanical models. The Mises strain …

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Nondestructive Integrated Ct-Xrd Method For Research On Hydrated Cement System, Takafumi Sugiyama, T. Hitomi, K. Kajiwara Jul 2014

Nondestructive Integrated Ct-Xrd Method For Research On Hydrated Cement System, Takafumi Sugiyama, T. Hitomi, K. Kajiwara

International Conference on Durability of Concrete Structures

A nondestructive integrated CT-XRD method has been developed and used to study hydrated cement system. In this research, a beam line (BL) at the third-generation synchrotron radiation facility, SPring-8, in Japan, was used. First, X-ray computed tomography (CT) was employed to obtain three-dimensional (3D) images and select a region of interest (ROI) in a given plane section of the hardened cement paste. Then, X-ray diffraction analysis (XRD) was conducted on the specified region. These operations were implemented in situ without the removal of specimen from the stage inside the BL. The hardened cement paste was precracked and then leached by …

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Prediction Of Corrosion-Induced Crack Width Of Corroded Reinforced Concrete Structures, Jin Xia, Wei-Liang Jin Jul 2014

Prediction Of Corrosion-Induced Crack Width Of Corroded Reinforced Concrete Structures, Jin Xia, Wei-Liang Jin

International Conference on Durability of Concrete Structures

This paper presents an experimental investigation on the crack width induced by the corrosion of reinforcing steel bars in concrete. Reinforcing steel bars with different diameters were corroded using an accelerated test in three types of concrete members, including 24 beams with corroded stirrup and 20 beams with corroded longitudinal reinforcing steel bars. The corrosion patterns and rusts characteristics of the corroded steel bars were examined and compared with those observed in real RC structures. According to the experimental result, the corrosioninduced crack width were analyzed and showed a linear relationship with the corrosion loss of reinforcing steel bar. Finally, …

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Study On Deterioration Mechanism And Prevention And Curing Techniques Of An Rc Bunker, Henglin Lv, Haijian Xie, Shuchun Zhou, Sun Lei Jul 2014

Study On Deterioration Mechanism And Prevention And Curing Techniques Of An Rc Bunker, Henglin Lv, Haijian Xie, Shuchun Zhou, Sun Lei

International Conference on Durability of Concrete Structures

In the coal mining industrial environment, the materials of RC bunkers suffer from serious aging problems. The cracking and deterioration of concrete and the corrosion of steel reinforcement lead to a degeneration of structural performance and a decline of structural reliability. In this paper, based on on-site detection and coal mining ground industrial environment, the deterioration characteristics of RC bunkers were tested. The investigation involved the apparent characteristics, carbonized depth, compression strength of concrete, reinforcement distribution and cover thickness, corrosion rate and mechanical properties of reinforcement, decline degree of bunkers, and so on. Then a design review check was done. …

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Influence Of Controlled Permeability Formwork On The Permeability Of Concrete, Wei Lin, Q. Jiang, J. Liu, J. Liu Jul 2014

Influence Of Controlled Permeability Formwork On The Permeability Of Concrete, Wei Lin, Q. Jiang, J. Liu, J. Liu

International Conference on Durability of Concrete Structures

Corrosion of steel reinforcement related to the intrusion of chloride ion is still the main threats to the durability of concrete structure, especially in marine environment. For the purpose of delaying the Cl− concentration at the surface of steel reinforcement reaching the critical value leading to initial corrosion, the permeability of concrete is usually improved by optimizing the concrete mixture to achieve high compatibility as well as optimized pore structure. In recent years, controlled permeability formwork (CPF) which was originally developed to obtain much smoother surface of the concrete proves to promote the service performance of the concrete by …

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The Correlation Of Chloride Diffusion Coefficient And Concrete Maturity Value And Its Application In Hong Kong–Zhuhai–Macao Bridge Engineering, Pengping Li, Shengnian Wang, Jianbo Xiong, Rui Chai, Yu Yan Jul 2014

The Correlation Of Chloride Diffusion Coefficient And Concrete Maturity Value And Its Application In Hong Kong–Zhuhai–Macao Bridge Engineering, Pengping Li, Shengnian Wang, Jianbo Xiong, Rui Chai, Yu Yan

International Conference on Durability of Concrete Structures

The correlation of chloride diffusion coefficient and concrete maturity value within 56 days of curing was investigated by the chemically combined water content method, rapid chloride migration (RCM) test, and concrete maturity test. The experimental results showed that chloride diffusion coefficient of concretes decreased not only with increasing curing ages but also with increasing curing temperature, which can promote the hydration degree of cementitous materials. There is a significant correlation between the chloride diffusion coefficient of indoor cured specimens and the concrete maturity value when expressed as a power function (R2 = 0.976). In addition, the calculated values of …

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Research On Chloride Penetration Resistance Of Phosphoaluminate Cement Concrete, Wu-Jian Long, Ning Xu Han, Da Wang Li, Feng Xing, Ya-Man Zhao Jul 2014

Research On Chloride Penetration Resistance Of Phosphoaluminate Cement Concrete, Wu-Jian Long, Ning Xu Han, Da Wang Li, Feng Xing, Ya-Man Zhao

International Conference on Durability of Concrete Structures

The chloride penetration resistance of phosphoaluminate cement (PAC) concrete was investigated in this study. The effects of mixture proportioning parameters, including cement content, water–cement ratio (w/c), and superplasticizer content on chloride ion penetration resistance of PAC concrete were investigated by the rapid chloride migration test (RCM). The result shows that the increase of cement content and the decrease of w/c can reduce the coefficient of chloride ion penetration of PAC concrete at a certain range. Moreover, the penetration of chloride ion can be declined effectively when polycarboxylate superplasticizer is employed. The PAC concrete exhibited better chloride penetration resistance compared with …

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Tensile Bond Between Substrate Concrete And Normal Repairing Mortar Under Freeze–Thaw Cycles, Ye Qian, Dawei Zhang, Tamon Ueda Jul 2014

Tensile Bond Between Substrate Concrete And Normal Repairing Mortar Under Freeze–Thaw Cycles, Ye Qian, Dawei Zhang, Tamon Ueda

International Conference on Durability of Concrete Structures

Concrete patch repair has long been used to repair the damaged concrete structures. In cold regions, freeze– thaw cycle is one of the major damage factors. Not only the material itself is damaged by freeze–thaw cycles, but also the adhesive interface, which is regarded as the weakest part of composite system, degrades under freeze–thaw cycles. Air entraining agent has long been used to increase the freeze–thaw resistance of concrete materials. However, the effect of air entraining agent on the adhesive interface under freeze–thaw cycles has not been explored. The degradation mechanism and failure mode of concrete repair system have not …

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Flexural Behavior Of Rc Beams Under Combined Effects Of Acid–Salt Mist And Carbon Dioxide, Wu Yuan-Zhou, Lv Heng-Lin, Fang Zhong-Nian Jul 2014

Flexural Behavior Of Rc Beams Under Combined Effects Of Acid–Salt Mist And Carbon Dioxide, Wu Yuan-Zhou, Lv Heng-Lin, Fang Zhong-Nian

International Conference on Durability of Concrete Structures

The coupling effects of hydrochloric acid mist, carbon dioxide, and salt mist rich in Cl– and SO42– on the degradation of reinforcement concrete (RC) beams were researched with the simulation of colliery ground environment (CGE) and experimental investigation. The results indicated that carbonation of concrete and corrosion of rebar increased slowly as the maximum width of crack became <0.5 mm. Meanwhile, the flexural carrying capacity of the deteriorated beam decreased slightly, while the concrete strength got a small increase first and a large decrease of more than 20% quickly. As the width of crack exceeded 0.5 mm, each target changed rapidly except the carbonation depth. Because of the interaction of deteriorated concrete and corroded rebar, the crack width, and flexural behavior of the beams have discrete correlation with the corrosion of rebar. The failure mode of beams changed from the crushing of compression concrete to the yielding of rebar.

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Growth Of Graphene Films And Graphene Patterns, Yongfeng Lu, Wei Xiong, Yunshen Zhou Jul 2014

Growth Of Graphene Films And Graphene Patterns, Yongfeng Lu, Wei Xiong, Yunshen Zhou

Department of Electrical and Computer Engineering: Faculty Publications

Large area graphene can be fabricated by depositing carbon and catalytic metal thin film(s) on a substrate, heating the carbon and the catalytic metal, and forming graphene on the substrate. The catalytic metal is evaporated during the heating process. The catalytic metal can be, for example, nickel, cobalt, or iron.

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Influence Of Micro And Macro Cracks Due To Sustained Loading On Chloride-Induced Corrosion Of Reinforced Concrete Beams, Junjie Wang, Sreejith V. Nanukuttan, P. A. Muhammed Basheer, Yun Bai Jul 2014

Influence Of Micro And Macro Cracks Due To Sustained Loading On Chloride-Induced Corrosion Of Reinforced Concrete Beams, Junjie Wang, Sreejith V. Nanukuttan, P. A. Muhammed Basheer, Yun Bai

International Conference on Durability of Concrete Structures

Chloride-induced corrosion of steel is one of the most commonly found problems affecting the durability of reinforced concrete structures in both marine environment and where de-icing salt is used in winter. As the significance of micro-cracks on chloride induced corrosion is not well documented, 24 reinforced concrete beams (4 different mixes - one containing Portland cement and another containing 35% ground granulated blastfurnace slag at 0.45 and 0.65 water-binder ratios) were subjected to three levels of sustained lateral loading (0%, 50% and 100% of the load that can induce 0.1 mm wide cracks on the tension surface of beam - …

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Reinterpretation Of Velocity-Dependent Atomic Friction: Influence Of The Inherent Instrumental Noise In Friction Force Microscopes, Yalin Dong, Hongyu Gao, Ashlie Martini, Philip Egberts Jul 2014

Reinterpretation Of Velocity-Dependent Atomic Friction: Influence Of The Inherent Instrumental Noise In Friction Force Microscopes, Yalin Dong, Hongyu Gao, Ashlie Martini, Philip Egberts

Mechanical Engineering Faculty Research

We have applied both the master equation method and harmonic transition state theory to interpret the velocity-dependent friction behavior observed in atomic friction experiments. To understand the discrepancy between attempt frequencies measured in atomic force microscopy experiments and those estimated by theoretical models, both thermal noise and instrumental noise are introduced into the model. It is found that the experimentally observed low attempt frequency and the transition point at low velocity regimes can be interpreted in terms of the instrumental noise inherent in atomic force microscopy. In contrast to previous models, this model also predicts (1) the existence of a …

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The Effect Of Platelet-Rich Plasma (Prp) On Muscle Contusion Healing In A Rat Model., Demetris Delos, Matthew J. Leineweber, Salma Chaudhury, Saif Alzoobaee, Yingxin Gao, Scott Alan Rodeo Jul 2014

The Effect Of Platelet-Rich Plasma (Prp) On Muscle Contusion Healing In A Rat Model., Demetris Delos, Matthew J. Leineweber, Salma Chaudhury, Saif Alzoobaee, Yingxin Gao, Scott Alan Rodeo

Faculty Publications

Background: Current therapy for muscle contusions is usually limited to nonsteroidal anti-inflammatory drugs and/or use of the RICE principle (rest, ice, compression, elevation); thus, other forms of treatment that can potentially accelerate the rate of healing are desirable. Hypotheses: A local injection of platelet-rich plasma (PRP) would lead to accelerated healing rates compared with controls; also, delayed administration of PRP would lead to a blunted response compared with immediate treatment. Study Design: Controlled laboratory study. Methods: Forty-six male Lewis rats each underwent a single blunt, nonpenetrating impact to the gastrocnemius muscle via a drop-mass technique and subsequently received either a …

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Comparative Study Of Alkali-Activated Fly Ash Manufactured Under Pulsed Microwave Curing And Thermal Oven Curing, Shi Shi, Yun Bai, H. Li, D. L. Xu, P. A. Muhammed Basheer Jul 2014

Comparative Study Of Alkali-Activated Fly Ash Manufactured Under Pulsed Microwave Curing And Thermal Oven Curing, Shi Shi, Yun Bai, H. Li, D. L. Xu, P. A. Muhammed Basheer

International Conference on Durability of Concrete Structures

This paper compares the alkali-activated fly ash (AAFA) manufactured with thermal oven curing and pulsed microwave curing methods. Fly ash activated by 8M NaOH solution at a liquid to solid ratio of 0.3 was cured by thermal oven at 85°C and domestic microwave oven, respectively. Apart from compressive strength test, the temperature profiles of AAFA samples were captured by thermal camera. Reaction products of AAFA were characterised with XRD, FTIR and TG/DTG, while the microstructure of AAFA was analysed by MIP and SEM. The results showed that with much shorter curing duration, the compressive strength of AAFA samples under microwave …

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