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Article
Publication date: 1 March 1991

P.L. Pratt

Discusses the use of high alumina cement concrete (HAC) in theconstruction industry, highlighting both its advantages anddisadvantages. Outlines its strengths and uses…

Abstract

Discusses the use of high alumina cement concrete (HAC) in the construction industry, highlighting both its advantages and disadvantages. Outlines its strengths and uses, and analyses the materials science of HAC concentrating on composition, hydration and attempts to avoid conversion. Examines the Imperial College experience with HAC and its implications for surveyors.

Details

Structural Survey, vol. 9 no. 3
Type: Research Article
ISSN: 0263-080X

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Article
Publication date: 1 September 1998

R.V. Balendran, H.W. Pang and H.X. Wen

This paper offers a brief review of the present use of scanning electron microscopy (SEM) in concrete studies, from the perspective of how research in materials science is…

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Abstract

This paper offers a brief review of the present use of scanning electron microscopy (SEM) in concrete studies, from the perspective of how research in materials science is translated into applications in construction engineering. It describes the scope of present use of the method, and attempts a prospective for the near future in areas where more work could make productive use of the technology. Selected case studies have also been discussed. The electron microscope has been used as a research tool in understanding the root cause of the differing performance of various types of concrete under various conditions, a development tool in making better concrete, and a diagnosis tool on problems like cracking of concrete. The paper also explains how sample preparation affects the type and quality of information which the SEM can produce.

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Structural Survey, vol. 16 no. 3
Type: Research Article
ISSN: 0263-080X

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Article
Publication date: 12 July 2013

Giovanna Xotta, Valentina A. Salomoni and Carmelo E. Majorana

Knowledge of the behavior of concrete at mesoscale level requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal properties if fire…

Abstract

Purpose

Knowledge of the behavior of concrete at mesoscale level requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal properties if fire hazards (e.g. spalling) are accounted for. The assessment of aggregates performance (and, correspondingly, concrete materials made of aggregates, cement paste and ITZ – interfacial transition zone) is crucial for defining a realistic structural response as well as damage scenarios.

Design/methodology/approach

It is here assumed that concrete creep is associated to cement paste only and that creep obeys to the B3 model proposed by Bažant and Baweja since it shows good compatibility with experimental results and it is properly justified theoretically.

Findings

First, the three‐dimensionality of the geometric description of concrete at the meso‐level can be appreciated; then, creep of cement paste and ITZ allows to incorporate in the model the complex reality of creep, which is not only a matter of fluid flow and pressure dissipation but also the result of chemical‐physical reactions; again, the description of concrete as a composite material, in connection with porous media analysis, allows for understanding the hygro‐thermal and mechanical response of concrete, e.g. hygral barriers due to the presence of aggregates can be seen only at this modelling level. Finally, from the mechanical viewpoint, the remarkable damage peak effect arising from the inclusion of ITZ, if compared with the less pronounced peak when ITZ is disregarded from the analysis, is reported.

Originality/value

The fully coupled 3D F.E. code NEWCON3D has been adopted to perform fully coupled thermo‐hygro‐mechanical meso‐scale analyses of concrete characterized by aggregates of various types and various thermal properties. The 3D approach allows for differentiating each constituent (cement paste, aggregate and ITZ), even from the point of view of their rheologic behaviour. Additionally, model B3 has been upgraded by the calculation of the effective humidity state when evaluating drying creep, instead than using approximate expressions. Damage maps allows for defining an appropriate concrete mixture to withstand spalling and to characterize the coupled behaviour of ITZ as well.

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Article
Publication date: 9 January 2009

Tuan Anh Nguyen and Xianming Shi

This research aims to unravel the role of salt contamination and corrosion inhibiting admixtures in the processes of cement hydration and rebar corrosion.

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2129

Abstract

Purpose

This research aims to unravel the role of salt contamination and corrosion inhibiting admixtures in the processes of cement hydration and rebar corrosion.

Design/methodology/approach

Mortar samples were prepared with NaCl and one of three corrosion inhibitors, sodium nitrite, disodium β‐glycerophosphate, or N,N′‐dimethylethanolamine, admixed. After 28 days curing, all steel‐mortar samples were ponded with 3 percent NaCl solution and electrochemical impedance spectroscopy (EIS) measurements were conducted periodically during the first 48 days. After 60 days of ponding by 3 percent NaCl solution, field‐emission scanning electron microscopy (FESEM) analyses were conducted on the fracture surface of the steel‐mortar sample.

Findings

The FESEM results revealed that admixing chlorides and inhibitors in fresh mortar changed the morphology and cement hydration product of hardener mortar at the steel‐mortar interface. The EIS data indicated that all inhibitors increased the polarization resistance of steel, implying reduced corrosion rate of the steel over 48‐day exposures to salt ponding. 0.05 M N,N′‐dimethylethanolamine was the most effective corrosion inhibitor, followed by 0.5 M sodium nitrite; whereas 0.05 M disodium β‐glycerophosphate was a slower and less capable corrosion inhibitor. The admixing of inhibitors in fresh mortar consistently increased the capacitance and decreased the electrical resistance of hardened mortar. The effect of sodium nitrite inhibitor on the resistance of steel mortar interfacial film compensated that of corrosive NaCl by participating to the formation of a protective ferric oxide film.

Originality/value

The results reported shed light on the complex role of admixed salt and corrosion inhibitors in cement hydration and their implications on the durability of steel‐reinforced concrete.

Details

Anti-Corrosion Methods and Materials, vol. 56 no. 1
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 February 2021

Nurizaty Zuhan, Mariyana Aida Ab Kadir, Muhammad Najmi Mohamad Ali Mastor, Shek Poi Ngian and Abdul Rahman Mohd. Sam

Concrete-filled steel hollow (CFHS) column is an innovation to improve the performance of concrete or steel column. It is believed to have high compressive strength, good…

Abstract

Purpose

Concrete-filled steel hollow (CFHS) column is an innovation to improve the performance of concrete or steel column. It is believed to have high compressive strength, good plasticity and is excellent for seismic and fire performance as compared to hollow steel column without a filler.

Design/methodology/approach

Experimental and numerical investigation has been carried out to study the performance of CFHS having different concrete in-fill and shape of steel tube.

Findings

In this paper, an extensive review of experiment performed on CFHS columns at elevated temperature is presented in different types of concrete as filling material. There are three different types of concrete filling used by the researchers, such as normal concrete (NC), reinforced concrete and pozzolanic-fly ash concrete (FC). A number of studies have conducted experimental investigation on the performance of NC casted using recycled aggregate at elevated temperature. The research gap and the recommendations are also proposed. This review will provide basic information on an innovation on steel column by application of in-filled materials.

Research limitations/implications

Design guideline is not considered in this paper.

Practical implications

Fire resistance is an important issue in the structural fire design. This can be a guideline to define the performance of the CFHS with different type of concrete filler at various exposures.

Social implications

Utilization of waste fly ash reduces usage of conventional cement (ordinary Portland cement) in concrete production and enhances its performance at elevated temperature. The new innovation in CFHS columns with FC can reduce the cost of concrete production and at the same time mitigate the environmental issue caused by waste material by minimizing the disposal area.

Originality/value

Review on the different types of concrete filler in the CFHS column. The research gap and the recommendations are also proposed.

Details

Journal of Structural Fire Engineering, vol. 12 no. 2
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 21 June 2013

Jeroen Staring

The purpose of this paper is to explore the political, toy manufacturing, and educational activities of Caroline Louise Pratt (1867‐1954), founder of the Play School…

Abstract

Purpose

The purpose of this paper is to explore the political, toy manufacturing, and educational activities of Caroline Louise Pratt (1867‐1954), founder of the Play School (later renamed City and Country School), New York City.

Design/methodology/approach

The paper reviews previously unreported biographical material and draws on a number of Caroline Pratt's own writings, combining results of archival text research and digital searches.

Findings

Newly available data sources on Caroline Pratt's 1896‐1921 life show her to be more of a social reconstructionist than previously concluded. This research demonstrates that it was Pratt's feminist, socialist and trade unionist ideals, transformed into educational aims, that formed the core of her educational work.

Research limitations/implications

This investigation is limited to Pratt's activities during the years 1896 to 1921.

Originality/value

The internet has provided ready access to a wealth of newspaper and journal documents. The ease of access has no precedent, and the volume of newly available data sources has brought opportunities for reinterpretation and rewriting of the history of education. Yet even more new data will inevitably become accessible. This paper provides insights into how previously unresearched documents, now easily found through digital research, can enhance understanding of the contributions of Caroline Pratt.

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Article
Publication date: 14 January 2014

Shyam Barua, Frank Liou, Joseph Newkirk and Todd Sparks

Laser metal deposition (LMD) is a type of additive manufacturing process in which the laser is used to create a melt pool on a substrate to which metal powder is added…

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1870

Abstract

Purpose

Laser metal deposition (LMD) is a type of additive manufacturing process in which the laser is used to create a melt pool on a substrate to which metal powder is added. The powder is melted within the melt pool and solidified to form a deposited track. These deposited tracks may contain porosities or cracks which affect the functionality of the part. When these defects go undetected, they may cause failure of the part or below par performance in their applications. An on demand vision system is required to detect defects in the track as and when they are formed. This is especially crucial in LMD applications as the part being repaired is typically expensive. Using a defect detection system, it is possible to complete the LMD process in one run, thus minimizing cost. The purpose of this paper is to summarize the research on a low-cost vision system to study the deposition process and detect any thermal abnormalities which might signify the presence of a defect.

Design/methodology/approach

During the LMD process, the track of deposited material behind the laser is incandescent due to heating by the laser; also, there is radiant heat distribution and flow on the surfaces of the track. An SLR camera is used to obtain images of the deposited track behind the melt pool. Using calibrated RGB values and radiant surface temperature, it is possible to approximate the temperature of each pixel in the image. The deposited track loses heat gradually through conduction, convection and radiation. A defect-free deposit should show a gradual decrease in temperature which enables the authors to obtain a reference cooling curve using standard deposition parameters. A defect, such as a crack or porosity, leads to an increase in temperature around the defective region due to interruption of heat flow. This leads to deviation from the reference cooling curve which alerts the authors to the presence of a defect.

Findings

The temperature gradient was obtained across the deposited track during LMD. Linear least squares curve fitting was performed and residual values were calculated between experimental temperature values and line of best fit. Porosity defects and cracks were simulated on the substrate during LMD and irregularities in the temperature gradients were used to develop a defect detection model.

Originality/value

Previous approaches to defect detection in LMD typically concentrate on the melt pool temperature and dimensions. Due to the dynamic and violent nature of the melt pool, consistent and reliable defect detection is difficult. An alternative method of defect detection is discussed which does not involve the melt pool and therefore presents a novel method of detecting a defect in LMD.

Details

Rapid Prototyping Journal, vol. 20 no. 1
Type: Research Article
ISSN: 1355-2546

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Book part
Publication date: 16 September 2019

Lorien Pratt

Abstract

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Link
Type: Book
ISBN: 978-1-78769-654-9

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Book part
Publication date: 16 April 2014

Gary R. Weaver and Jason M. Stansbury

Religious institutions can affect organizational practices when employees bring their religious commitments and practices into the workplace. But those religious…

Abstract

Religious institutions can affect organizational practices when employees bring their religious commitments and practices into the workplace. But those religious commitments function in the midst of other organizational factors that influence the working out of employees’ religious commitments. This process can generate varying outcomes in organizational contexts, ranging from a heightened effect of religious commitment on employee behavior to a negligible or nonexistent influence of religion on employee behavior. Relying on social identity theory and schematic social cognition as unifying frameworks for the study of religious behavior, we develop a theoretically informed approach to understanding how and why the religious beliefs, commitments and practices employees bring to work have varying behavioral impacts.

Details

Religion and Organization Theory
Type: Book
ISBN: 978-1-78190-693-4

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Book part
Publication date: 13 August 2018

Robert L. Dipboye

Abstract

Details

The Emerald Review of Industrial and Organizational Psychology
Type: Book
ISBN: 978-1-78743-786-9

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