Effect Of Drying Rate On Shrinkage Of Alkali-Activated Slag Cements,
2014
Pennsylvania State University
Effect Of Drying Rate On Shrinkage Of Alkali-Activated Slag Cements, Hailong Ye, Christopher Cartwright, Farshad Rajabipour, Aleksandra Radlińska
International Conference on Durability of Concrete Structures
The volumetric instability of alkali-activated slag (AAS) binders has raised concerns and impeded the acceptance of this Portland cement-free material. The objective of this article is to characterize the influence of drying rate on drying shrinkage behavior of AAS mortars to better understand the mechanisms responsible for its large shrinkage deformation. A series of four AAS mortar mixtures with varying activator composition, as well as a reference Portland cement mortar, was cast and dried at different relative humidities, that is, 30, 50, 70, and 85% RH. Drying took place inside nitrogen-purged environmental chambers for the purpose of eliminating the contribution …
Influence Of Fly Ash On Surface Chloride Concentration Under Shallow Immersion Condition,
2014
Shenzhen University
Influence Of Fly Ash On Surface Chloride Concentration Under Shallow Immersion Condition, Jun Liu, Xiaodong Wang, Feng Xing, Ningxu Han
International Conference on Durability of Concrete Structures
In this paper, the influence of fly ash content on concrete surface chloride concentration was investigated through periodical tests of surface chloride concentration of concrete by immersing three kinds of concrete specimens in 5.0 wt.% sodium chloride solution. One kind of specimen is common concrete without fly ash, whereas the other two kinds of specimens are mixed with fly ash. The results show that the surface chloride ion concentration ranges from 0.295 to 0.777 wt.% for the immersed concrete samples in this study; in the initial stage of immersion, the concrete surface chloride ion concentration is affected by added fly …
Effects Of Stirrups On Bond Behavior Between Concrete And Corroded Steel Bars,
2014
Zhejiang University
Effects Of Stirrups On Bond Behavior Between Concrete And Corroded Steel Bars, Hongwei Lin, Yuxi Zhao, Ming Sun
International Conference on Durability of Concrete Structures
Steel corrosion leads to the deterioration of bond between concrete and steel bars. The serviceability and ultimate strength of concrete elements within RC structures are hence affected. Many researchers have studied the bond behavior of corroded steel bars. However, very few studies have investigated the effects of confinements on the degradation of bond strength. The present paper proposed a new kind of beam specimen based on which the effects of stirrups on degradation of bond were investigated. The test results proved that stirrups can effectively increase the bond strength between concrete and corroded steel bars.
Saturation Of Air Entrained Voids And Its Implication On The Transport Of Ionic Species In Concrete,
2014
Purdue University
Saturation Of Air Entrained Voids And Its Implication On The Transport Of Ionic Species In Concrete, Yiwen Bu, Jason Weiss
International Conference on Durability of Concrete Structures
Air entrainment is commonly used to improve the durability of concrete materials exposed to freezing and thawing. While the influence of air voids on freeze/thaw damage and salt scaling is frequently studied, the influence of entrained air voids on ionic transport has been studied less frequently. Since ionic transport in concrete materials relies on pore fluid as the medium of conduction, only saturated or partially saturated air voids participate in the transport processes. This paper discusses the conditions under which air voids could become saturated. Specifically, the saturation condition of entrained air voids in laboratory tests and in service is …
Visualization And Quantification Of Solute Diffusivity In Cracked Concrete By X-Ray Ct,
2014
Hokkaido University
Visualization And Quantification Of Solute Diffusivity In Cracked Concrete By X-Ray Ct, Michael Henry, T. Sugiyama, I. S. Darma
International Conference on Durability of Concrete Structures
This paper explores the usage of microfocus X-ray computed tomography (CT) for visualization and quantification of diffusion phenomena in cracked concrete. Mortar specimens of varying shapes (prismatic and cylindrical), crack types (artificial and splitting tensile), and binder compositions (OPC and fly ash) were prepared. Cesium carbonate (Cs2CO3) was used as a tracer in the diffusion test because it has high X-ray absorption due to its high atomic number and thus contrasts with mortar and air voids in the CT images. Image processing and analysis was carried out to visualize and quantify the diffusion behavior in 3D …
Effect Of Blast Furnace Slag Powder And Fly Ash On Durability Of Concrete Mixed With Seawater,
2014
Tokyo Institute of Technology
Effect Of Blast Furnace Slag Powder And Fly Ash On Durability Of Concrete Mixed With Seawater, Nobuaki Otsuki, Takahiro Nishida, Chang Yi, Tomohiro Nagata, Hiroki Ohara
International Conference on Durability of Concrete Structures
According to the report of the United Nations, it is said that two-third of world population would be influenced by water shortage before 2050. To use fresh water effectively, the usage of seawater in concrete industry seems imperative. However, the usage of seawater as concrete material is prohibited in almost all the standards or specifications around the world. In this article, the usage of seawater as a material of concrete based on the results of experimental works and deterioration prediction was discussed. Especially, the effects of by-products such as blast furnace slag or fly ash on the durability of concrete …
Surface Treatment Of Cement-Based Materials With Nanosio2,
2014
University of Jinan
Surface Treatment Of Cement-Based Materials With Nanosio2, Pengkun Hou, Xin Cheng, Jueshi Qian, Surendra P. Shah
International Conference on Durability of Concrete Structures
A dense surface structure of cement-based material is favorable for its resistance to the impacts of environment. In this work, effectiveness and mechanisms of the surface treatment of cement-based materials with nanoSiO2 of different states, that is, colloidal nanoSiO2 (CNS) and the in situ formed nanoSiO2 gel through the hydrolysis of its precursor of tetraethoxysilane (TEOS), by brushing and soaking techniques, were investigated. Results showed that both CNS and TEOS are capable of reducing the liquid and gaseous transport properties of hardened cement-based materials, although at a different extent. It revealed that the pozzolanic reactivity and the …
Research On Embedded Sensors For Concrete Health Monitoring Based On Ultrasonic Testing,
2014
University of Jinan
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 …
Review Of Microbially Induced Corrosion And Comments On Needs Related To Testing Procedures,
2014
Purdue University
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 …
Numerical Simulation Of The Early Age Three-Dimensional Microstructure Development Of Cement Pastes,
2014
Southeast University
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 …
Study On Variable Action Value Standard For Harbor Infrastructures,
2014
Yangzhou University
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 …
Application Of Nanomechanical Methods In Investigation Of C–S–H Gel/Cement Grain Interface,
2014
Tongji University
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 …
Revised Model Of Chloride Diffusion In Concrete Bridge By Considering Complex Action Of Load And Chloride Binding Capacity,
2014
Zhejiang University
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.
Effect Of Aggregate Gradation With Fuller Distribution On Properties Of Sulfoaluminate Cement Concrete,
2014
University of Jinan
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 …
Effect Of Transverse Crack On Chloride Penetration Into Concrete Subjected To Drying–Wetting Cycles,
2014
Jiangsu University
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 …
Surface And Uniaxial Electrical Measurements On Layered Cementitious Composites Having Cylindrical And Prismatic Geometries,
2014
Purdue University
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, …
Experimental Research On Corrosion-Induced Cracking Monitoring Based On Optical Fiber Sensor,
2014
Zhejiang University
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 …
Numerical Simulation Method For Fracture Effect Of Corroded Steel Strand Under Tension,
2014
China University of Mining and Technology
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 …
Nondestructive Integrated Ct-Xrd Method For Research On Hydrated Cement System,
2014
Hokkaido University
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 …
Research On Chloride Penetration Resistance Of Phosphoaluminate Cement Concrete,
2014
Shenzhen University
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 …
