A Novel Multiscale Modelling Approach For Evaluation Of The Asr In Concrete Structures,
2019
Texas A & M University - College Station
A Novel Multiscale Modelling Approach For Evaluation Of The Asr In Concrete Structures, Mostafa Jalal, M Mirsayar, Anol Mukhopadhyay
International Conference on Durability of Concrete Structures
This paper presents a new multiscale approach for evaluation of the volume change in concrete structures due to the alkali-silica reaction (ASR). A practical step by step approach that can be applied to the real structures is developed based on combined experimental and numerical assessment by considering the most influential ASR parameters at different scales. In the first step, the ASR expansion is measured using accelerated concrete cylinder test (ACCT) for different concrete mixtures covering different variables of important factors such as mix design (e.g., w/cm, fly ash type and replacement percentages), aggregate reactivity, alkali loadings, temperature, and relative humidity …
Fem Analysis Of Structural Behaviour Of Reinforced Concrete Beam Under The Effect Of Frost Damage,
2019
Hokkaido University
Fem Analysis Of Structural Behaviour Of Reinforced Concrete Beam Under The Effect Of Frost Damage, Zhao Wang, Tamon Ueda, Hiroshi Hayashida, Dawei Zhang
International Conference on Durability of Concrete Structures
Minimizing frost damage is one of the important durability issues for concrete structures in cold and wet areas. This paper performed a Finite Element Model (FEM) analysis on the structural behavior of reinforced concrete beam under the effect of frost damage. The frost damage was considered as degradations in two constituents: concrete material and bond between concrete and reinforcement. The constitutive models of deteriorated concrete material were proposed using a mesoscale simulation approach (Rigid Body Spring Model). DIANA FEA program was adopted for the structural analysis and experiments were also conducted for the verification. It was clarified that the structural …
Establishment Of A Numerical Model For Sulfate Attacked Concrete Considering Multi-Factors,
2019
Shenzhen Graduate School, Harbin Institute of Technology
Establishment Of A Numerical Model For Sulfate Attacked Concrete Considering Multi-Factors, Shanshan Qin, Dujian Zou, Jun Jiang, Tiejun Liu
International Conference on Durability of Concrete Structures
Sulfate attack is one of the major durability problems of concrete structures, which is manifested by expansive cracks and deterioration of cement paste. In this study, a numerical model is proposed to predict the process of ionic diffusion into concrete under external sulfate attack. The chemical reaction and diffusion processes are considered in this model. Furthermore, the influence of calcium leaching, chemical activity of multi-ions, temperature and changes in porosity are also taken into account. The initial porosity and tortuosity are assumed to be homogeneous in concrete, and the chemical potential gradient is regarded as the driving force for ions …
Meso-Scale Fracture Modelling Of Concrete Cover Induced By Non-Uniform Corrosion Of Reinforcing Bar,
2019
University of Strathclyde
Meso-Scale Fracture Modelling Of Concrete Cover Induced By Non-Uniform Corrosion Of Reinforcing Bar, Xun Xi, Shangtong Yang, Chun-Qing Li
International Conference on Durability of Concrete Structures
Corrosion-induced concrete cracking is a significant durability problem for reinforced concrete structures. In practice, critical corrosion degree to surface cracking and crack width evolution are of significance in regards to the assessment of serviceability of reinforced concrete structures. Literature review suggests that, although considerable research has been undertaken on corrosion-induced concrete cracking, little has been focused on non-uniform corrosion of reinforcing bar, especially by considering concrete as a three-phase materials. In this paper, a meso-scale fracture model, consisting of aggregates, cement paste/mortar and ITZ, is established. To simulate arbitrary cracking in concrete, cohesive elements are inserted in the fine meshes …
A New Model For Corrosion-Induced Concrete Cracking,
2019
University of Strathclyde
A New Model For Corrosion-Induced Concrete Cracking, Xun Xi, Shangtong Yang, Chun-Qing Li
International Conference on Durability of Concrete Structures
Corrosion of reinforced concrete is one of the major deterioration mechanisms which result in premature failure of the reinforced concrete structures. Due to the actual diffusion of chloride ingress, the corrosion products distribution is seldom uniform along the reinforcing bar. Recently, some non-uniform corrosion models have been proposed to investigate the corrosion-induced cracking mechanism of concrete. In this paper, a new corrosion model based on von Mises distribution is formulated and validated against experimental data. The developed model is then compared with the existing non-uniform models and the advantages are discussed. To demonstrate the application of the developed corrosion model, …
An Image-Based Local Homogenization Method To Model Mass Transport At The Steel-Concrete Interface,
2019
ETH Zurich
An Image-Based Local Homogenization Method To Model Mass Transport At The Steel-Concrete Interface, Zhidong Zhang Dr, Ueli Angst Prof, Alexander Michel Prof, Mads Jensen Dr
International Conference on Durability of Concrete Structures
Mass transport (moisture and ions) at the steel-concrete interface is closely related to corrosion of rebar in reinforced concrete structures. Thus, in the model simulating mass transport, the structure of the steel-concrete interface must be well represented. In this study, an image-based local homogenization method is proposed based on images taken in the scanning electron microscope (SEM) under the backscattered electron (BSE) detector. According to the gray level of the image, porosity can be calculated and then proposed equations are used to associate the transport properties (sorption isotherms, diffusion coefficients and permeability) with porosity. Experimental data of chloride concentration taken …
Residual Service Life Estimation And Its Importance For Pretensioned Concrete (Ptc) Bridges In Coastal Cities,
2019
Indian Institute of Technology Madras
Residual Service Life Estimation And Its Importance For Pretensioned Concrete (Ptc) Bridges In Coastal Cities, Dyana Joseline, Deepak K. Kamde, Sripriya Rengaraju, Radhakrishna G. Pillai
International Conference on Durability of Concrete Structures
Many pre-tensioned concrete (PTC) bridges are experiencing premature chloride-induced corrosion. Hence, it is crucial to estimate their residual service life and update it with newer data on a periodic basis - to plan for corrosionpreventionorcontrolmeasuresandensuresafetyofexistingbridges.Criticalchloridethreshold(Cl th) is one of the parameters necessary to estimate the corrosion initiation period. However, quantitative estimates on Clth for prestressing (PS) steel are not well-reported in literature. This paper presents experimental data on the Clth of PS steel, the chloride diffusion coefficient (Dcl), and surface chloride concentration (Cs) of concrete samples obtained from a PTC bridge girder in a coastal city in India. For estimation …
Estimating Fractal Dimension Of Cement Matrix For Predicting Chloride Ingress Into Cement-Based Materials,
2019
Purdue University
Estimating Fractal Dimension Of Cement Matrix For Predicting Chloride Ingress Into Cement-Based Materials, Elakneswaran Yogarajah, Satoshi Yoshida, Akira Hatanaka, Toyoharu Nawa
International Conference on Durability of Concrete Structures
The durability performance of cement-based materials in service environments is affected by numerous factors, many of which involve attacks due to ionic transport, leading to reduced service life. The durability must be ensured in both an economically and environmentally responsible manner. Chloride-induced steel corrosion is a serious threat to the durability of reinforced concrete structures in marine environments, and the diffusion is the dominant transport mechanism of chloride ingress into concrete. Therefore, clear understanding of chloride transport mechanism, particular the diffusion path, is important for designing the durability performance of reinforced concrete structures. The purpose of this study is to …
Effect Of Time-Dependent Chloride Profile And Temperature Variation On Chloride Diffusion In Concrete,
2019
McMaster University
Effect Of Time-Dependent Chloride Profile And Temperature Variation On Chloride Diffusion In Concrete, Feras Alsheet, A. Ghani Razaqpur
International Conference on Durability of Concrete Structures
Reinforcement corrosion due to chlorides diffusion is one of the main problems in reinforced concrete structures exposed to certain environments. The diffusion rate is function of chloride surface concentration, concrete temperature, humidity, composition and microstructure. The intruded chlorides are partially chemically bound by the concrete and it is the unbound or free chloride which upon exceeding a defined threshold initiates corrosion. The time to corrosion initiation depends on the above variables; therefore, it is important to model their spatial and temporal variations in a manner that will yield a realistic estimate of the actual initiation period. In this study, the …
Modelling Of Capillary Pore Structure Evolution In Portland Cement Pastes Based On Irregular-Shaped Cement Particles,
2019
University College London
Modelling Of Capillary Pore Structure Evolution In Portland Cement Pastes Based On Irregular-Shaped Cement Particles, Cheng Liu, Mingzhong Zhang, G Fang, Yun Bai, Y Zhang
International Conference on Durability of Concrete Structures
The pore structure plays a crucial role in durability performance of cement-based materials. However, the pore structure in cement pastes is highly dependent on the initial packing of cement particles and cement hydration process, which seems to be related to the shapes of cement particles. This paper proposed a numerical method to investigate the effect of cement particle shapes on capillary pore structures in cement pastes. In this study, irregular-shaped cement particles with various shapes are generated using a novel central growth model, and then incorporated into CEMHYD3D model to simulate Portland cement hydration. Some home-made programs of determining pore …
First Principles-Based Design Of Economical Ultra-High Performance Concrete,
2019
Arizona State University
First Principles-Based Design Of Economical Ultra-High Performance Concrete, Aashay Arora, Matthew Aguayo, Farrokh Kianmofrad, Yiming Yao, Barzin Mobasher, Narayanan Neithalath
International Conference on Durability of Concrete Structures
This paper presents a novel strategy to design the binder phase of ultra-high performance concrete (UHPC) from commonly available cement replacement (fly ash, slag, microsilica, metakaolin) and fine filler (limestone) materials. A packing algorithm is used to extract the number density, mean centroidal distance, and coordination number of the microstructure. Similarly, rheological studies on the pastes provide yield stress, plastic viscosity, and mini-slump spread. The selection criteria involves using the three microstructural and three rheological parameters individually or in combination to define packing and flow coefficients. The selection criteria is flexible enough to allow users modify the constraints depending on …
Durability Design Of Segmental Linings For Intended Service Life Of Tunnels,
2019
AECOM
Durability Design Of Segmental Linings For Intended Service Life Of Tunnels, Mehdi Bakhshi, Verya Nasri
International Conference on Durability of Concrete Structures
In one-pass lining systems, the durability of tunnel structure is directly related to durability of concrete segments acting as both the initial support and the tunnel final lining. In this paper, most-frequent degradation mechanisms of concrete linings are discussed including chloride- and carbonation- induced corrosions, sulfate, acid and freeze-and-thaw attacks, and alkali-aggregate reactions. Mitigation method for each specific degradation mechanism is explained. A durability factor specific to railway and subway tunnel known as stray current corrosion is presented. Mitigation methods for this specific corrosion together with coupling effects with other conventional damage mechanisms are explained. Prescriptive approaches for durability design …
Durability Design Based On Serviceability Stage For Corroded Reinforced Concrete Structures,
2019
Yangzhou University
Durability Design Based On Serviceability Stage For Corroded Reinforced Concrete Structures, Zhongxiaoping Zhongxiaoping, J Zhu, Cb Yuan, Wl Jin, J Xia
International Conference on Durability of Concrete Structures
After analyzing such factors as the structural durability failure state, environmental load and resistance, the durability limit state equation considering steel corrosion initiation, concrete cover cracking and maximum corrosion-induced damage value is established to meet its durability service life requirements under chloride environment. For three different durability limit states, the design theory of reliability, the partial factors of variables for load and resistance are introduced to reflect the target reliability requirements of structural durability, and subsequently the partial factors expression form of structural durability design is established. According to the principle of the same reliability level for partial factors design …
Evaluation Of The Rheological Behaviors And Molecular Composition Properties Of Crumb Rubber Modified Emulsion For Chip Seal,
2019
Louisiana State University and Agricultural and Mechanical College
Evaluation Of The Rheological Behaviors And Molecular Composition Properties Of Crumb Rubber Modified Emulsion For Chip Seal, Md Tanvir Ahmed Sarkar
LSU Master's Theses
An experimental study was conducted to characterize the chemical, molecular, and rheological properties of different asphalt emulsions including a newly introduced tire rubber modified asphalt emulsion. One tire rubber modified asphalt emulsion (CRS-2TR), two conventional emulsions (CRS-2 and CRS-2P), and one asphalt rubber binder (AC20-5TR) were evaluated. The differences in functional groups, chemical composition, and molecular weight distribution of the asphalt binder and emulsions under different aging conditions (Original, RTFO-aged, and PAV-aged) were evaluated by the Saturates, Aromatics, Resins and Asphaltenes (SARA) fractionation test, High-Pressure Gel Permeation Chromatography (HP-GPC), and Fourier Transform Infrared Spectroscopy (FTIR) test, respectively. Superpave Performance Grade …
Durability Of Cement-Based Materials In Drinking Water Storage,
2019
Karlsruhe Institute of Technology (KIT)
Durability Of Cement-Based Materials In Drinking Water Storage, Matthias Schwotzer, Andreas Gerdes
International Conference on Durability of Concrete Structures
In order to provide a hygienic storage drinking water reservoirs have been coated with mineral mortar linings in all epochs of European history. However, modern cement-based materials often show in this special operational environment an inadequate durability. Even though drinking water is commonly not considered particularly harmful to cementitious systems, the chemical degradation of mortar linings in drinking water storage systems can occur very fast compared to other common deterioration reactions. This results in cost intensive repair measures and thus high life-cycle costs as well associated with an ecological burden. Furthermore, an insufficient understanding of degradation mechanisms and their underlying …
Experimental And Numerical Study Of Macro-Cell Corrosion Between Crossed Steel Bars,
2019
Tongji University
Experimental And Numerical Study Of Macro-Cell Corrosion Between Crossed Steel Bars, Zheng Dong, Xianglin Gu, Zhihao Jin
International Conference on Durability of Concrete Structures
Reinforcing steel bars embedded in concrete are always intersected with each other to form rebar mesh or three-dimensional steel cage. The present study aims to investigate the phenomenon of severe corrosion observed at stirrups or some intersections of steel rebar mesh, which has not been well studied before. Macro-cell corrosion between crossed steel bars was considered to be the major cause for this phenomenon. In this regard, crossed steel bars were divided into intersected zone (IZ) and non-intersected zone (NIZ). The macro-cell current at the face-to-face IZ was calculated by Ohm’s law. A one-dimensional model based on transmission line method …
Effect Of Multi- Steel Bolt Anchorages On Composite Beams,
2019
Institute of Structural Engineering, Zhejiang University
Effect Of Multi- Steel Bolt Anchorages On Composite Beams, Dawei Zhang, H. F. Shi, W. L. Jin, Tamon Ueda
International Conference on Durability of Concrete Structures
Using fiber-reinforced polymer (FRP) to retrofit or strengthen the concrete structures is an attractive option in construction areas nowadays. However, premature debonding failures limit the efficacy of fiber utilization. It is presently accepted that anchorage system is an attractive option to solve this problem. Much efforts has been made through experimental testing and numerical modeling to investigate the anchorage systems, meanwhile various systems were created and developed. However, researches on the mechanism of the anchorage systems are still too rare to build a countable and union design guideline with respect to different premature debonding failure modes. The present paper focused …
Effect Of Corrosion On The Shear Transfer Behavior Of Stud Shear Connectors,
2019
Zhejiang University of Science and Technology
Effect Of Corrosion On The Shear Transfer Behavior Of Stud Shear Connectors, Wen Xue, Ju Chen, Ao-Yu Jiang, Wei-Liang Jin
International Conference on Durability of Concrete Structures
The effect of corrosion on the shear transfer behavior of stud shear connectors was investigated in this study. Experimental investigation was performed using an innovative test setup for single stud shear connector. Two series of specimens having different stud diameters were fabricated and tested. The test specimens were firstly corroded to different corrosion rates by electronic accelerating method. Loading test were then performed to obtain the load-slip curves and ultimate strengths of corroded test specimens. Corrosion rates were measured from the studs obtained from the failure test specimens. Test results were compared with standard push out test specimens having the …
Drying Shrinkage Of Hardened Cement Paste And Its Relationship To The Microstructure,
2019
Purdue University
Drying Shrinkage Of Hardened Cement Paste And Its Relationship To The Microstructure, Xin Wang, Chaojun Wan, Xiaojing Zhang, Heng Chen
International Conference on Durability of Concrete Structures
The aim of the present study is to relate microstructure to the drying shrinkage of hardened cement paste. Three microstructural features, calcium silicate hydrate(C-S-H), calcium hydroxide(CH) and pore structure were studied. A new method to determine the C-S-H content of hardened cement paste is presented. Drying shrinkage behavior of cement pastes were investigated by drying specimens through successive steps of RH 100% to 7% RH and re-saturating the specimens. The total shrinkage of cement paste after drying to 7% RH and irreversible shrinkage were decreased with the increasing amount of C-S-H and CH. Prolonged curing resulted in a paste with …
Effect Of External Loading On Durability Properties Of Pre-Stressed Concrete Girders With Microcracking,
2019
The University of Texas at Austin
Effect Of External Loading On Durability Properties Of Pre-Stressed Concrete Girders With Microcracking, Savitha Sagari Srinivasan, Raissa Douglas Ferron, Michael Rung
International Conference on Durability of Concrete Structures
Over the last fourteen years, very early in the service life of pre-stressed concrete girders, unexplained microcracks have been observed. Their presence led to concerns about the future integrity of the girders, with one of the major concerns being corrosion of pre-stressing strands. As such, a comprehensive study aimed at understanding the effects these microcracks have on the service life of the girders was initiated. Eight in-service girders, under external loads, and five rejected girders, not under external loads, were selected for the study. In this paper, we present work on the temporal evolution of the cracks during a one-year …
