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Author: Ahmad Shayan
Publisher:
ISBN:
Category : Alkali-aggregate reactions
Languages : en
Pages :
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Book Description
Precast prestressed concrete railway sleepers manufactured from somewhat deformed granitic rock and cement of moderate alkali content have shown signs of distress in the form of parallel and map cracking. The dominant form of cracking in the section between the rails is longitudinal and parallel. The cracks extend to the shoulders, but these may also show random (map) cracking depending on the stage of the deterioration. Petrographic examination, scanning electron microscopy and energy-dispersive X-ray analysis indicated that the primary cause of the deterioration was alkali-aggregate reaction (AAR). Although another reaction product (ettringite) was present in the cracks, this was considered to have formed as a consequence of cracking (due to AAR) rather than being the cause of it. Measurement of expansion and water absorption on large prisms (~100 x 100 x 300 mm) cut from the sleepers, have shown that the upper half of the sleepers that were subject to service traffic and loading expanded more than the lower half and also had a higher moisture absorption, indicating more extensive microcracking. This was the case for both the visually cracked and uncracked sleepers from the track. For the unloaded sleepers from a storage area there was no difference between the lower and upper halves. These observations indicate that the traffic may have affected the extent of the deterioration, once expansion and microcracking had been initiated by AAR. Treatment of a large number of sleepers with 100% isobutyltriethoxy-silane has shown that the silane is able to reduce the rate of deterioration, as evident from monitoring the progress of cracking, but cannot prevent it. Evaluation of concrete mix compositions for the manufacture of sleepers for a new railway track has shown that incorporation of 10% of a low-alkali silica fume in the mixes is effective in suppressing the expansions that may be caused by AAR, and at the same time inhibits the delayed formation of ettringite.
Author: Ahmad Shayan
Publisher:
ISBN:
Category : Alkali-aggregate reactions
Languages : en
Pages :
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Book Description
Precast prestressed concrete railway sleepers manufactured from somewhat deformed granitic rock and cement of moderate alkali content have shown signs of distress in the form of parallel and map cracking. The dominant form of cracking in the section between the rails is longitudinal and parallel. The cracks extend to the shoulders, but these may also show random (map) cracking depending on the stage of the deterioration. Petrographic examination, scanning electron microscopy and energy-dispersive X-ray analysis indicated that the primary cause of the deterioration was alkali-aggregate reaction (AAR). Although another reaction product (ettringite) was present in the cracks, this was considered to have formed as a consequence of cracking (due to AAR) rather than being the cause of it. Measurement of expansion and water absorption on large prisms (~100 x 100 x 300 mm) cut from the sleepers, have shown that the upper half of the sleepers that were subject to service traffic and loading expanded more than the lower half and also had a higher moisture absorption, indicating more extensive microcracking. This was the case for both the visually cracked and uncracked sleepers from the track. For the unloaded sleepers from a storage area there was no difference between the lower and upper halves. These observations indicate that the traffic may have affected the extent of the deterioration, once expansion and microcracking had been initiated by AAR. Treatment of a large number of sleepers with 100% isobutyltriethoxy-silane has shown that the silane is able to reduce the rate of deterioration, as evident from monitoring the progress of cracking, but cannot prevent it. Evaluation of concrete mix compositions for the manufacture of sleepers for a new railway track has shown that incorporation of 10% of a low-alkali silica fume in the mixes is effective in suppressing the expansions that may be caused by AAR, and at the same time inhibits the delayed formation of ettringite.
Author: Ian Sims
Publisher: CRC Press
ISBN: 131748441X
Category : Science
Languages : en
Pages : 1044
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Book Description
Alkali-Aggregate Reaction in Concrete: A World Review is unique in providing authoritative and up to date expert information on the causes and effects of Alkali-Aggregate Reaction (AAR) in concrete structures worldwide. In 1992 a first edition entitled The Alkali-Silica Reaction in Concrete, edited by Professor Narayan Swamy, was published in a first attempt to cover this concrete problem from a global perspective, but the coverage was incomplete. This completely new edition offers a fully updated and more universal coverage of the world situation concerning AAR and includes a wealth of new evidence and research information that has accumulated in the intervening years. Although there are various textbooks offering readers sections that deal with AAR deterioration and damage to concrete, no other single book brings together the views of recognised international experts in the field, and the wealth of scattered research information that is available. It provides a ‘state of the art’ review and deals authoritatively with the mechanisms of AAR, its diagnosis and how to treat concrete affected by AAR. It is illustrated by numerous actual examples from around the world, and comprises specialist contributions provided by senior engineers and scientists from many parts of the world. The book is divided into two distinct but complementary parts. The first five chapters deal with the most recent findings concerning the mechanisms involved in the reaction, methods concerning its diagnosis, testing and evaluation, together with an appraisal of current methods used in its avoidance and in the remediation of affected concrete structures. The second part is divided into eleven chapters covering each region of the world in turn. These chapters have been written by experts with specialist knowledge of AAR in the countries involved and include an authoritative appraisal of the problem and its solution as it affects concrete structures in the region. Such an authoritative compilation of information on AAR has not been attempted previously on this scale and this work is therefore an essential source for practising and research civil engineers, consultant engineers and materials scientists, as well as aggregate and cement producers, designers and concrete suppliers, especially regarding projects outside their own region.
Author: Odd E. Gjorv
Publisher: CRC Press
ISBN: 9780419250609
Category : Architecture
Languages : en
Pages : 400
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Book Description
Concrete technology for a sustainable development in the 21st century focuses on the problems and challenges for the concrete industry today and in the future with particular emphasis on environmental consiousness. Primary topics include: the improvement of concretes service life to ease technical and economical problems and the waste of natural resources; environmentally friendly concrete production including new production methods and recycling materials; and actually using concrete to solve environmental problems, for example through the containment of hazardous waste. The book is the result of the international workshop held in Lofoton, Norway. With very select contributions from the most distinguished international professional experts, this book provides a basic framework and guidelines for national and international bodies.
Author:
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 1266
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Book Description
Author: V. M. Malhotra
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 816
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Book Description
Author: Jan P. Skalny
Publisher: Wiley-American Ceramic Society
ISBN:
Category : Science
Languages : en
Pages : 600
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Book Description
This volume contains papers on phase composition and quantitative x-ray powder diffraction analysis of Portland cement and clinker; neutron diffraction and neutron scattering studies of cement; scanning probe microscopy: a new view of the mineral surface; the stereological and statistical properties of entrained air voids in concrete: a mathematical basis for air void system characterization; fresh concrete rheology: recent developments; early age behavior of cement-based materials; transport mechanisms and damage: current issues in permeation characteristics of concrete; the use of silica fume to control expansion due to alkali-aggregate reactivity in concrete: a review; delayed ettringite formation in concrete: recent developments and future directions; use of durability indexes to achieve durable cover concrete in reinforced concrete structures; and microfiller partial substitution for cement.
Author:
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 816
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Book Description
Author:
Publisher: Transportation Research Board
ISBN: 0309258243
Category : Technology & Engineering
Languages : en
Pages : 695
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Book Description
TCRP report 155 provides guidelines and descriptions for the design of various common types of light rail transit (LRT) track. The track structure types include ballasted track, direct fixation ("ballastless") track, and embedded track. The report considers the characteristics and interfaces of vehicle wheels and rail, tracks and wheel gauges, rail sections, alignments, speeds, and track moduli. The report includes chapters on vehicles, alignment, track structures, track components, special track work, aerial structures/bridges, corrosion control, noise and vibration, signals, traction power, and the integration of LRT track into urban streets.
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 9782883940772
Category : Technology & Engineering
Languages : en
Pages : 44
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Book Description
In 1986, the FIP Commission on Prefabrication issued the state-of-art report "Concrete Railway Sleepers", which included design considerations, manufacturing methods, rail fastening systems and field performance. During the two decades since that report, precast concrete has gained importance in the field of railway track systems for plain track, switches and crossings, tunnels and other applications. Developments in production methods for concrete sleepers in switch and crossing layouts to cope with the complex geometry and the industry's confidence in their performance have contributed to the huge increase in the use of this type of sleeper. The use of slab track for high-speed track has also grown, particularly where either new track is built or where existing track is renewed and long periods of track possession are possible. There has also been progress in the development of plant and equipment for the installation, renewal and maintenance of concrete sleepered track. With machines now able to replace existing track at a rate of 5000 sleepers (over 3 km track) per day, choosing concrete sleepers can reduce the time on site, meaning tracks can be reopened quickly whilst reducing labour requirements and costs. Today, precast concrete is considered to be the best performing and preferred material for railway sleepers, due to the following factors: long-term durability; improved geometric retention of track and greater weight vital for high-speed and heavy freight lines; improved elasticity of track; improved ride quality; low first cost; minimum life cycle cost; low cost of maintenance; environmental friendliness - no chemical treatment required and can be recycled. As all aspects of precast concrete railway track systems, from design through manufacture to installation and maintenance, have progressed since the publication of the FIP report, an update was considered timely, in order to provide a synthesis of currently available information. This new edition covers quality, design, production, durability, maintenance and environmental considerations, and includes survey on the use of precast concrete track systems in over 30 countries.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 0727703617
Category : Technology & Engineering
Languages : en
Pages : 30
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Book Description
The use of concrete sleepers in railways started in the 1940s. They are currently used in many countries thoughout the world at a rate of over 12 million per year. This report discusses the various types of sleeper which have been developed - monoblock, two-block, reinforced and prestressed concrete. Separate sections deal with design, rail fastening systems, manufacture, quality control and testing, installation and performance, and research and development.
