Engineering Commons^™

Investigation Of Microstructure Of Cementitious Materials Exposed To High Temperature By Non-Destructive Integrated Ct-Xrd Method, Takuya Mikami, H Takahashi, T Sugiyama

International Conference on Durability of Concrete Structures

Severe accident occurred in 2011 at the Fukushima Daiichi nuclear power plant and it can be assumed that the concrete building was exposed to high temperatures environment for a long time due to loss of the cooling function of the nuclear reactor. In order to prepare for the best scenario in the decommission plan, it should be first needed to clarify and evaluate the level of damage and deterioration of the contaminated concrete. To solve this problem, experiments were conducted for cementitious materials with the maximum temperature of 400 or 1000 degrees Celsius with durations of up to 2 hours. …

Influence Of Pore Structure On Relative Chloride Diffusion Coefficient In Unsaturated Cementitious Materials, Yong Zhang, Guang Ye

International Conference on Durability of Concrete Structures

Chloride-induced corrosion of reinforcement in concrete structures is a serious issue in engineering practice. This paper investigates the influence of pore structure on the relative chloride diffusion coefficient Drc in unsaturated cementitious materials. The effects of various pore features, including porosity, pore size, and pore connectivity, on the continuity of water-filled pores in unsaturated porous systems are analyzed based on the Kelvin law and water desorption process. In the experimental program, different cementitious materials (OPC, slag, fly ash, and limestone powder) were used to prepare paste and mortar samples. The Drc of the mortar samples (one year old) at various …

Development Of Engineered Cementitious Composites With Conductive Inclusions For Use In Self-Sensing Applications, Benny Suryanto Dr, Danah Saraireh Ms, Steven Walls Mr, Jaehwan Kim Dr, W John Mccarter Prof

International Conference on Durability of Concrete Structures

The mechanical and a.c. electrical properties of a new varietal of engineered cementitious composite (ECC) incorporating conductive inclusions are presented. Electrical measurements were undertaken over a wide frequency range while curing and when under uniaxial tensile loading to study the influence of ongoing hydration and multiple microcrack formation on the composite electrical impedance. When presented in Nyquist format, the work shows that conductive inclusions reduce the bulk resistance of the composite while enhancing its polarizability, transforming the classic, single-arc bulk response of typical cement-based materials to a two-arc response. The bulk resistance was shown to increase with time and damage, …

Diagnosis On Expansion Of Heat-Cured Precast Concrete Blocks Due To Delayed Ettringite Formation In Japan, Yuichiro Kawabata

International Conference on Durability of Concrete Structures

Delayed ettringite formation (DEF) in concrete causes internal swelling, which reduces the mechanical properties of concrete and can lead to issues with concrete structures due to potentially large expansive deformation. In order to address the issues of DEF-affected structures, proper assessment of the structures affected is important. However, petrographic diagnosis of concrete affected by DEF remains a controversial issue. In this paper, as case studies, diagnosis on precast concrete blocks suspected of experiencing DEF was carried out. The concrete blocks were made of white Portland cement, limestone gravel, and limestone sand mixed with copper slag. The blocks were excessively heat-cured …

Rehabilitation Of Low Rise Rcc Structure Along 9m High Retaining Wall, Aniruddha Nakhawa Er, Vivek Deshmukh Dr

International Conference on Durability of Concrete Structures

Mumbai is the financial, commercial and entertainment capital of India, facing bigger challenges in accommodating its over growing population day by day. The Mumbai City has population of 18.4 million over its 634 km2 area, ie. Almost 350 ft2/person. This enormous rise in population density has restricted the development to expand vertically. This also, results in growth of major slums, which is almost 62% of the population dwelling in slums. Subsequently, the authorities is in need of a large scaled Slum Sanitation Program, which utilize the scarcely available land for construction of Community Toilet Blocks with involvement of NGO’s and …

A “Double-Multi” Model For Electromigration Of Lithiums And Chlorides In Asr Affected Concrete, Qing-Feng Liu, Li-Xuan Mao, Zhi Hu, Jin Xia, Gan-Lin Feng, Long-Yuan Li

International Conference on Durability of Concrete Structures

Existing reinforced concrete structures experience severe durability degradation when subjected to alkali– silica reaction (ASR) and chloride attack. A special electrochemical rehabilitation treatment, containing lithium compound anolyte, has been developed to drive lithium ions into concrete as well as remove chlorides simultaneously, for mitigating both the ASR-induced cracks and the chloride-induced corrosion. Good performance of introduced lithiums in controlling ASR-induced expansion has already been proved. Unfortunately, the migration mechanism of lithium in concrete under an external electric field is seldom investigated in existing literature. In this study, with help of the “double-multi” model, the efficiency of impregnation of lithium ions …

Distribution Of Lithium Nitrite Injected Into Concrete And Its Asr Suppression Effect, Koichi Kobayashi, K Rokugo, Y Takagi, T Otani

International Conference on Durability of Concrete Structures

In this research, lithium nitrite was injected into ASR-deteriorated concrete specimens made with reactive aggregates in order to suppress further deterioration. The amount of injected lithium nitrite was set to three different levels, and the subsequent expansion behavior and area of lithium permeation were investigated. The area of permeation was checked using the coloring reagent TDI. It was found that the prescribed amount of lithium cannot be injected fully into the non-deteriorated specimens. When the lithium was injected at an early stage of deterioration, the area of permeation was small and the ASR suppression effect was small regardless of the …

Mortar Quality Assessment For An Iconic Building Repair In Sydney Australia, Ion Dumitru, Tony Song, John Sury, Tom Wenzel

International Conference on Durability of Concrete Structures

Remedial work for an iconic building in Sydney, Australia is currently being carried out. Two façade mortars, capable of matching the current exposed quartz aggregate finish and achieving a 40 years design life, are required. In order to ensure the quality of the imported quartz aggregates for this project, test have been carried out for particle size distribution, density, wet/dry strength variation, sodium sulphate soundness and Los Angeles Abrasion value. The two mortar mixes employed for repair work (Form & Pour and Hand Applied mixes) were comprehensively assessed for mix workability, compressive strength in warm and cold conditions, drying shrinkage, …

Efficiency Of Electrochemical Chloride Removal From Concrete At Different Environmental Temperatures, Shijie Jin, Jin Xia, Weiliang Jin, Zhi-Yong Yu, Jia-Yuan Hu, Qingfang Lyu, Xiaoping Zhong

International Conference on Durability of Concrete Structures

Electrochemical chloride removal (ECR) is an effective and curative method to treat existed reinforced concrete structures about to suffer or already suffering from chloride attack, however, its application is still limited due to its side effect and efficiency, including the velocity and maximum capacity of chloride removal. This paper presents a temperature related numerical transport model to study the effect of temperature on efficiency of electrochemical chloride removal from concrete. Based on Fick’s law and Nernst-Planck equation with Gauss’ Law, temperature effect, chloride binding, multi-species coupling, electrochemical reactions were taken into account in this model. Temperature effect was considered on …

Comparison Data Between Hybrid And Galvanic Anode Installation In The Arousa Island Bridge, José Antonio Becerra Mosquera, Diego Carro López, José Enrique Pardo Landrove, José Manuel Millán Pérez

International Conference on Durability of Concrete Structures

The Arousa Island Bridge, with its 1980 m is the only road access to the Arousa Island. Built in 1985, this single-cell box girder divided in 40 spans runs entirely on the sea. The deck is between 2 to 12 m above sea level, so after 25 years in a marine environment, the structure showed reinforcement corrosion, especially in piles and deck bottom. Attending to the corrosion damages, caused simply from a chloride attack, the local government decided to intervene with an ambitious repair project. This decision has been taken only after an exhaustive cost analysis to determine the feasibility …

Monitoring Historic Concrete And Associated Cementitious Repair- A Case Study Of Boathouse 4, Portsmouth Historic Dockyard, Uk, Ahmed Alwaal, Stepanie Barnett, Robert Inkpen, Linley Hastewell

International Conference on Durability of Concrete Structures

This study presents a method of monitoring historic concrete and associated repairs. A case study of Boathouse 4, Portsmouth Historic Dockyard, UK is presented. Boathouse 4 is an iconic building within Portsmouth Historic Dockyard which was constructed during the 1930’s rearmament period. It was used during World War ll to construct the three-man midget X-Craft submarine. The building was restored and converted into a Boatbuilding Skills Training Centre in 2015. A field investigation was conducted to analyse the concrete damage and to monitor microscale changes to the surface of the original concrete and repairs over a period of three years. …

Improvements Of The Carbonation Resistance Of Concrete After Steam Autoclave Curing, Guo Li, Jiang Yue, Feng Yao

International Conference on Durability of Concrete Structures

Incorporation of mineral admixtures, secondary water curing, and surface treatments were performed to improve the carbonation resistance of concrete after steam autoclave curing. The mineral admixtures used were fly ash, slag, and a mixture of both, and the surface treatments applied were those of organic silicone (OS) water repellent and epoxy resin (ER) coating. Accelerated carbonation experiments were performed on specimens at 28, 90, 180, and 360 d. Experimental results indicated that steam autoclave curing significantly reduces concrete carbonation resistance compared with standard curing. Secondary water curing for one week can replenish water in concrete and further hydrate …

Transport Properties Of Steam Curing Concrete Using Mineral Admixtures, Kenji Sasaki, Tetsuo Harada, Tsuyoshi Katayama

International Conference on Durability of Concrete Structures

Steam curing has been used widely in the precast concrete industry. However, investigations on steam curing concrete focused mainly on their strength development. Research on durability of steam curing concrete, particularly on mixes using mineral admixtures, is somewhat limited.

In this study, transport properties and mechanical properties of concretes using mineral admixtures under different steam curing conditions were measured. Normal Portland cement, high early strength Portland cement, ground granulated blast-furnace slag and fly ash were used. Steam curing conditions were varied by changing the preliminary curing time, temperature drop rate and curing method after steam curing. Transport properties, such as …

Characterization Of Vibration Effects On The Internal Structure And Strength Of Regular And High Strength Recycled Concrete, Jovanca Smith, Rekha Rampit, R. Parey

International Conference on Durability of Concrete Structures

There is a need for more in depth understanding of the consolidation effect of concrete on its durability, especially in tropical climates. During placement of fresh concrete in molds vibration is required to prevent quality problems such as honeycombs and desegregation. Nevertheless, precise monitoring of concrete vibration time has been avoided by construction professionals. This results in concrete durability reduction of appropriately designed concrete due to variation in aggregate settlement, air void content and change in water to cement ratio. In this study, the effects of vibration time on concrete strength, aggregate segregation, and physical properties were experimentally investigated on …

A Novel Methodology Of Powder-Based Cementitious Materials In 3d Inkjet Printing For Construction Applications, Pshtiwan Shakor, Shami Nejadi, Gavin Paul, Jay Sanjayan

International Conference on Durability of Concrete Structures

Recently, additive manufacturing techniques such as 3D printing are becoming increasingly popular and widely used in a variety of applications. Inkjet 3D printing (i.e. powder-based printing) is one of the most reliable frequently-implemented techniques in 3D printers. This paper discusses a novel methodology to replace the currently used typical powders in 3D printing to make it possible to use the printed specimens in construction applications. The printed cubic (20Í20Í20mm) and prism (60Í5Í5mm) specimens with different saturation levels are printed to investigate the relative strength of the 3D printed specimens. Curing in different …

Improving The Spacer-Concrete Interface For Bond Strength And Durability, Fadhilah Muslim, H. S. Wong, N. R. Buenfeld

International Conference on Durability of Concrete Structures

Spacers are important devices in reinforced concrete that are used to support reinforcing steel during concreting in order to achieve the required concrete cover. They are placed at every meter length or less of steel reinforcement and left permanently in the structure. However, it has been shown that the weak interface between spacer and concrete is highly porous and microcracked. This lowers the resistance of the concrete cover to ingress of aggressive agents causing degradation. This study aims to address this problem by improving spacer design to enhance bond strength and durability of the spacer-concrete interface. Cementitious spacers with a …

Performance Oriented Functionalisation Of Concrete: An Integrated Approach For Prevention In Construction, Andreas Gerdes, Matthias Schwotzer, Julia Süßmuth

International Conference on Durability of Concrete Structures

The long-term preservation and the future-oriented development of the infrastructure are of utmost importance for every country in the world. An increasing failure of infrastructure underpins a tremendous need for action. The reasons for this unsatisfactory situation are various, but certainly among them is often an insufficient performance of the building materials. This holds particularly true for reinforced concrete and its additives, which are nowadays commonly developed by empirical research. Almost all shortcomings of concrete durability are related to the transport of detrimental substances into the pore system. In this regard, a promising approach to prevent chemical deterioration processes is …

Development Of A New Method To Reduce Drying Shrinkage Of Concrete By Applying Urea, Kosuke Shirayama, H. Fujiwara, M. Maruoka, L Lingling

International Conference on Durability of Concrete Structures

Cracking of concrete caused by drying shrinkage adversely affects the durability of the structure. In the past research results, it is effective to add urea to concrete as a way to reduce drying shrinkage. However, in ready mixed concrete factory in Japan, adding various admixture materials to concrete will increase equipment costs and labor costs because of the increase in the number of input items, the management problem and putting problem when mixing.

In this research, in consideration of the above problems, we attempted to develop a cheaper and simpler method to apply or infiltrate the urea solution on the …

Surface Treatments For Concrete Under Physical Salt Attack, Mohamed Sakr, Mohamed T. Bassuoni

International Conference on Durability of Concrete Structures

Physical salt attack (PSA) is a key deterioration mechanism for concrete structures in contact with salt-rich media. Yet, procedures and techniques for protecting and repairing concrete affected by PSA are not adequately addressed in the technical literature. Therefore, in this study, three surface coatings of concrete were tested to determine their ability to withstand conditions stimulating to PSA. The treatments were selected to achieve either a single function such as acting as a membrane layer or hydrophobic agent, or combined pore blocking and water repelling functions. Coatings were applied on a concrete mixture typically used for residential foundations in Canada. …

Social Dimensions In Sustainability Evaluation Of Deteriorating Reinforced Concrete Bridges, Zhujun Wang, Weiliang Jin, Wu Kexian, Dan M. Frangopol

International Conference on Durability of Concrete Structures

Structural sustainability requires that structural engineering activities should find ways to design and maintain structures that perform as required during their life-cycle considering intergenerational needs. Massive attention has been paid to the economic and environmental evaluation of structures. However, being a completely different discipline from structural engineering, the social dimensions associated with structures were rarely considered in previous studies due to the difficulty in determination and quantification, unavoidable subjectivity and controversy, as well as the lack of historical data. This paper identifies the social impacts induced by engineering activities associated with the deterioration of reinforced concrete structures, and proposes corresponding …

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, 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, 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, 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, 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, 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, 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, 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, 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, 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 …