Avoiding & Mitigating Alkali-Aggregate Reaction (AAR) in Concrete Structures

Avoiding & Mitigating Alkali-Aggregate Reaction (AAR) in Concrete Structures
Author: Diego Jesus De Souza
Publisher:
Total Pages:
Release: 2022
Genre:
ISBN:

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Alkali-Aggregate Reaction (AAR) is one of the most harmful distress mechanisms affecting the serviceability and durability of concrete critical infrastructure worldwide. Over the past decades, several approaches and recommendations have been developed to assess the potential reactivity of aggregates in the laboratory and the efficiency of preventive measures (e.g., supplementary cementing materials - SCMs) to mitigate ASR in the field. Yet, recent findings suggest that the appropriate use of SCMs "only" delayed and does not entirely prevent ASR occurrence. Moreover, once ASR starts in the field, there is no "universal" solution that should be applied in various cases, and each situation should be evaluated as "unique". Nevertheless, artificially triggering healing agents have been studied in the late years, thus presenting an interesting "physical" solution to reduce the ingress of water and recover damaged concrete elements, which could present an interesting solution for durability-related distress due to ASR. This Ph.D. project focuses on detailed laboratory investigations aiming first to understand the self-healing process of concrete (i.e., by the natural or engineered process). Then, its further influence on ASR-induced expansion and deterioration, either applied internally or externally to the concrete. To achieve this goal, concrete mixtures presenting a wide range of binder compositions, using distinct types of chemical admixtures (e.g., crystalline self-healing), and incorporating five different types/nature of highly reactive aggregates (i.e., coarse and fine) were combined to manufactured concrete specimens in the laboratory. Otherwise, in aging specimens, concrete samples were designed only with GU-cement as the binder material but incorporated two different types/nature of highly reactive aggregates. Then, the samples were exposed to ASR-induced development until they reached pre-determined expansion levels, in which a wide range of sealers and coating materials were applied on the surface of the affected specimens. Mechanical (i.e., stiffness damage test, modulus of elasticity, micro indentation, shear and compressive strengths) and microscopic (damage rating index and scanning electron microscopy) tests were performed on samples at different ages (up to two years of accelerated ASR development). The results show that besides changing AAR-kinetics, the different binder compositions or the chemical admixtures could modify the distress mechanism due to AAR. The addition of crystalline healing agents or their combination with SCMs in concrete not only delayed the development of inner damage but significantly lowered the compressive strength loss at equivalent expansion amplitudes than control specimens. Moreover, the combination of different binder materials modified the chemical and mechanical properties of the ASR-gel, changing its swelling properties and the further damage development in concrete. On the other hand, the wide range of surface treatments used were not able to alter ASR distress mechanism; yet, they changed ASR-kinetics. Moreover, their effectiveness to slower the reaction shows to be significantly influenced by the damage degree to which the surface treatment is applied. Finally, a comprehensive framework enabling the optimized selection of raw materials to prevent or mitigate ASR development is proposed.

Alkali-Aggregate Reaction in Concrete

Alkali-Aggregate Reaction in Concrete
Author: Ian Sims
Publisher: CRC Press
Total Pages: 1044
Release: 2017-08-01
Genre: Science
ISBN: 131748441X

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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.

Alkali-aggregate Reaction in Concrete

Alkali-aggregate Reaction in Concrete
Author:
Publisher:
Total Pages: 25
Release: 2000
Genre:
ISBN:

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This paper presents theoretical and applied state-of-the-art information in the field of alkali-aggregate reactivity (AAR) in concrete. The aspects discussed include basic concepts of the reaction and expansion mechnasims, conditions conducive to the development and the sustainability of AAR in concrete, field and laboratory investigation program for evaluating the potential alkali-reactivity of concret aggregates, selection of preventive measures against AAR, and the management of structures affected by AAR. The management section includes the diagnosis of AAR in existing concrete structures, evaluation of potential for future distress due to AAR, and mitigation and repair approaches used on such structures. This is an introductory paper and sets the stage for a special review of the current AAR situation in the various regions of Canada that is presented in seven papers as part of this issue.

RILEM Recommendations for the Prevention of Damage by Alkali-Aggregate Reactions in New Concrete Structures

RILEM Recommendations for the Prevention of Damage by Alkali-Aggregate Reactions in New Concrete Structures
Author: Philip J. Nixon
Publisher: Springer
Total Pages: 181
Release: 2015-09-30
Genre: Technology & Engineering
ISBN: 9401772525

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This book contains the full set of RILEM Recommendations which have been produced to enable engineers, specifiers and testing houses to design and produce concrete which will not suffer damage arising from alkali reactions in the concrete. There are five recommended test methods for aggregates (designated AAR-1 to AAR-5), and an overall recommendation which describes how these should be used to enable a comprehensive aggregate assessment (AAR-0). Additionally, there are two Recommended International Specifications for concrete (AAR-7.1 & 7.2) and a Preliminary International Specification for dams and other hydro structures (AAR-7.3), which describe how the aggregate assessment can be combined with other measures in the design of the concrete to produce a concrete with a minimised risk of developing damage from alkali-aggregate reactions.

The Alkali-Silica Reaction in Concrete

The Alkali-Silica Reaction in Concrete
Author: R N Swamy
Publisher: CRC Press
Total Pages: 288
Release: 1991-09-01
Genre: Architecture
ISBN: 0203036638

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This book reviews the fundamental causes and spectrum effects of ASR. It considers he advances that have been made in our understanding of this problem throughout the world.

Guide to Diagnosis and Appraisal of AAR Damage to Concrete in Structures

Guide to Diagnosis and Appraisal of AAR Damage to Concrete in Structures
Author: Bruno Godart
Publisher: Springer Science & Business Media
Total Pages: 95
Release: 2013-04-08
Genre: Technology & Engineering
ISBN: 9400765673

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This book describes procedures and methodologies used predominantly to obtain a diagnosis of damaged concrete possibly caused by Alkali-Aggregate Reaction (AAR). It has two primary objectives, namely firstly to identify the presence of AAR reaction, and whether or not the reaction is the primary or contributory cause of damage in the concrete; and secondly, to establish its intensity (severity) in various members of a structure. It includes aspects such as field inspection of the structure, sampling, petrographic examination of core samples, and supplementary tests and analyses on cores, such as mechanical tests and chemical analysis. Evaluation of test data for prognosis, consequences and appraisal will be more fully set out in AAR-6.2.