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Alkali-Silica Reaction (ASR) is considered one of the most significant critical internal deterioration mechanisms for concrete. ASR produces internal stresses that causes expansion and extended cracks threatening the country's wealth of existing infrastructure. Since ASR recognition in 1940 by Stanton, many studies had been conducted to evaluate the degree of reactivity for different types of gravel. However, limited research has focused on studying the effect of specimens' shape and size, and casting direction on the accuracy of measured ASR expansion and find a correlation between cylindrical and standard prismatic specimens. Moreover, few studies have attempted to evaluate the optimum expansion level for controlling ASR expansion by strengthening ASR-damaged concrete. An experimental work divided into three phases was conducted to evaluate; (1) The effect of these new approaches on ASR expansion using fused silica (FS) as a fast-acting material, (2) The selection of a suitable jacketing materials based on target performance rather than focusing only on the achieved strength investigating concrete mixtures incorporating four types of fibre and fine crumb rubber aggregates (FCRA) with and without silica fume, (3) The effectiveness of six different strengthening materials as CFRP, BFRP, mortar with GG mesh, mortar with BFRP mesh, FRC, and CRC with BFRP to suppress ASR expansion, and evaluate sensitivity of strengthening time and testing time vs. the strengthening types on the concrete mechanical properties. The results exhibited addition of FS caused a drastic increase in the expansion, and plays a crucial role to adversely affect concrete mechanical properties and durability index until age 180 day, then the effectiveness decreased until 548 days. Specimen geometry and size, and casting direction had a significant effect on the rate of expansion. Cylindrical specimens expanded at a higher rate than the prisms until 56 days in the range from 43% to 37%, and from 9% to 15% at 90 days until test termination at 548 days. Specimens cast vertically exhibited an increase in expansion over the others cast horizontally in the range from 2.63% to 8.41%. Specimens Ø100×200mm reveal lower expansion in the range from 5.89% to 9.52% than specimens Ø75×285mm. Concrete mixtures incorporating steel, macro, and micro polypropylene, micro nylon fibres, and FCRA with and without SF were examined. Based on balancing between mechanical properties, durability indices, and electrical resistivity, FRC incorporating micro polypropylene with SF, and CRC contained FCRA with silica were selected as FRC and CRC jacketing. Strengthening type, strengthening time, and testing time after applying strengthening materials showed a significant effect to control ASR expansion and enhanced the damaged concrete properties. For instance, CFRP exhibited a significant reduction in expansion compared to that with control specimens and followed by BFRP, CRC with BFRP, Mortar with GG, Mortar with BFRP, and FRC, respectively. Moreover, strengthening at early ages revealed decreases mechanical properties as a result of high residual expansion. However, testing at early ages showed higher results proved the exposure conditions had an adverse effect on the strengthening materials.
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.
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.
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.
Alkali Silica Reaction (ASR) is recognized as a major distress in concrete for over a century. In United States, ASR is a major cause in deterioration of highway concrete structures (i.e., bridges and pavements). Current methods such as the 14-day Accelerated Mortar Bar Test (AMBT) and 1-year Concrete Prism Test (CPT) used to evaluate ASR potential have limitations. Limited research was conducted on new proposed methods such as the 56-day Miniature Concrete Prism Test (MCPT) and 6-month Accelerated Concrete Prism Test (ACPT) proposed to overcome the limitations of existing methods. In addition, there is a need to reduce or mitigate ASR especially in Idaho where 80% of aggregates are reported reactive. This study conducted comprehensive laboratory evaluation of ASR susceptibility of various aggregates using different test methods. There were strong correlations between the 56-day MCPT method and both the 14-day AMBT and the 1-year CPT methods. Also, the expansion results of the 14-day AMBT method correlated well with the 1-year CPT method. Furthermore, the 6-month ACPT method provided comparable results to the 1-year CPT. these results show the validity of various test methods to evaluate ASR potential. Recommendations were provided to revise the expansion threshold of MCPT to identify reactive aggregates. The use of Supplementary Cementitious Materials (SCMs) along with glass powder was found to reduce ASR expansion substantially. Binary or ternary blends of 20% replacement of slag, glass powder or silica fume can be used for ASR mitigation without compromising other concrete properties. These results were also supported by the findings of the microstructure and chemical analysis where SCMs were found to reduce the cracks formed in concrete due to ASR expansion.
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.
Recycled concrete is among the rising eco-friendly construction materials which helps to reduce waste and the need for new natural resources. However, such concrete may present previous deterioration due to, for instance, alkali-silica reaction (ASR), which is an ongoing distress mechanism that may keep being developed in the recycled material. This work aims to evaluate the potential of further distress and crack development (i.e. initiation and propagation) of AAR-affected RCA concrete in recycled mixtures displaying distinct past damage degrees and reactive aggregate types. Therefore, concrete specimens incorporating two highly reactive aggregates (Springhill coarse aggregate and Texas sand) were manufactured in the laboratory and stored in conditions enabling ASR development. The specimens were continuously monitored over time and once they reached marginal (0.05%) and very high (0.30%) expansion levels, they were crushed into RCA particles and re-used to fabricate RCA concrete. The RCA specimens were then placed in the same previous conditions and the "secondary" ASR-induced development monitored over time. Results show that the overall damage in ASR-affected RCA concrete is quite different from affected conventional concrete, especially with regards to the severely damaged RCA particles, where ASR is induced by a reactive coarse aggregate, as the RCA particle itself may present several levels of damage simultaneously caused by past/ongoing ASR and newly formed ASR. Moreover, the influence of the original damage extent in such RCA concrete was captured by the slightly damaged RCA mixture eventually reaching the same damage level as the severely damaged mixture. Furthermore, the original extent of deterioration influence the "secondary" induced expansion and damage of RCA concrete since the higher the original damage level, the higher the cracks numbers and lengths observed in the RCA concrete for the same expansion level whereas wider cracks are generated by RCA having previously been subjected to slight damage thus indicating the difference in the distress mechanism as a function of original extent of damage. In addition, it has been found that distress on RCA containing a reactive sand generates and propagates from the residual mortar (RM) into the new mortar (NM) as opposed to RCA containing a reactive coarse aggregate, being generated and propagated from the original coarse aggregate (i.e. original virgin aggregate - OVA) into the NM. Likewise, RCA containing a reactive sand caused longer and higher number of cracks for the same "secondary" induced expansion than the RCA made of reactive coarse aggregate. Finally, novel qualitative and descriptive models are proposed in this research to explain ASR-induced distress generation and propagation on RCA mixtures made of reactive fine and coarse aggregates.
As critical concrete infrastructure deteriorates, engineers need efficient and reliable techniques to appraise the causes and the extent of deterioration, to evaluate the structural consequences and to select effective management protocols and rehabilitation strategies. This book looks at deterioration caused by internal swelling reaction (ISR) mechanisms in concrete, such as alkali-aggregate reaction, delayed ettringite formation and freeze-thaw cycles. The book provides accessible and comprehensive coverage of recent work and developments on the most common ISR mechanisms leading to induced expansion and deterioration. It addresses the implications of ISR on different scales (micro, meso and macro), outlines qualitative and quantitative techniques to assess the condition of affected concrete and introduces the multi-level assessment protocol, using advanced microscopic and mechanical techniques, particularly the stiffness damage test and damage rating index, as a reliable approach to appraise ISR-affected infrastructure. Also included is a detailed case study of the Robert-Bourassa Charest Overpass in Quebec. Internal Swelling Reactions in Concrete: Mechanisms and Condition Assessment is primarily intended for undergraduate and graduate students, as well as academics interested in the field of concrete durability and condition assessment of concrete. It will also be of interest to engineers and infrastructure owners dealing with ISR-related problems.