The alkaline solution reacts with amorphous silica to produce a viscous alkali silicate gel. As the reaction proceeds Ca 2+ ions are dissolved into the pore water. These react with the gel to form solid calcium silicate hydrate whereas the alkaline solution converts the remaining siliceous minerals into bulky alkali silicate gel.
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Several degradation mechanisms can affect concrete, and the alkali-silica reaction (ASR) is considered one of the most worrying. ... Rock samples collected from the quarry were subjected to petrographic analysis as per the Brazilian standard NBR 15577–3 using the RILEM ASR Petrographic Atlas as reference.
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Alkali-silica reaction (ASR) is the most common form of alkali-aggregate reaction. It occurs when the alkaline pore fluid and siliceous minerals in some aggregates react to form a calcium alkali silicate gel. This gel absorbs water, producing a volume expansion which can disrupt the concrete.
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alkali-silica reactivity. Alkali-silica reaction gels are composed of two-component mixtures of alkali-calcium-silicate hydrate and alkali-silica sols of nearly fixed compositions. Cracking may be initiated by swelling of aggregate particles before copious production of gel and large expansions of cracks caused by swelling of gel occurs.
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This chapter provides an historical review of the alkali-aggregate reactions (AAR) in concrete which reduce service life of concrete, first recognized in 1940, and the …
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However, in aggregates or mineral addition SCMs such as dredged sediments, two phenomena may take place due to its sand-lime nature: alkali-silica reaction or the alkali carbonates reaction ...
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ASR is a durability problem that causes expansion, cracking, and degradation of concrete. Learn about the mechanisms, effects, and evaluation methods of ASR, …
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The alkali-silica-reaction (ASR) is a physio-chemical reaction causing severe deterioration of concrete structures worldwide [[1], [2], [3]]. ASR was first identified and described in detail in 1942 [4]. Despite being in the focus of concrete research since decades, the underlying mechanisms leading to stress and cracking are still under debate.
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Thus, this study recommends utilization of quarry dust to replace fine silica sand in the ECC at amounts ranging from 0% to in order to establish a green, sustainable and cost-effective ECC. The flowability and mechanical demeanor of the ECC mixtures in terms of the tensile, compressive and flexural properties were evaluated.
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study was Spratt siliceous limestone from a quarry in Ottawa, Ontario. At an age in solution of 14 days, the mean expansion was found to be 0.364% (coefficient of ... Alkali-silica reactions between silica from aggregates and alkalies from cement can cause damaging expansion and cracking of concrete. These reactions need three things
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DOI: 10.1016/J.MEASUREMENT.2015.12.022 Corpus ID: 110481243; Potential alkali silica reactivity of various rock types in an aggregate granite quarry @article{Murlidhar2016PotentialAS, title={Potential alkali silica reactivity of various rock types in an aggregate granite quarry}, author={Bhatawdekar Ramesh Murlidhar and Edy …
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The alkali-silica reaction in cementitious composites occurs through the chemical association of the solution contained in the matrix pores, which is strongly basic and rich in alkalis, and the reactive phases of some aggregates. For the process to begin, high relative humidity and a high concentration of total alkalis are required. The …
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The influence of low CaO steel slag, calcined clay and granite dust on the alkali-silica reaction was investigated over a period of 35 days under accelerated curing conditions.
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Alkali-Silica Reactivity (ASR) is a chemical reaction between alkalis in the cement fraction of concrete mortar and certain types of siliceous aggregates. Resulting in the expansion and cracking of the concrete. There are at least two types of interactions between cement components and …
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The following small dictionary describes some of the terms used in concrete examination and description. Agglomerate: 3 or more air voids in close contact Aggregate: Component of the concrete consisting of a coarse aggregate fraction (more than 4 mm) and a fine aggregate fraction (less than 4 mm). Alite: Tricalciumsilicate, C3S (3CaO-SiO2), a …
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Identification of alkali-silica reaction. Gel may be present in cracks and within aggregate particles. The best technique for the identification of ASR is the examination of concrete in thin section, using a petrographic …
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5.2 Types of Reaction (AAR = ACR + ASR) 5.2.2 Alkali Silica Reaction (ASR) In the presence of a high concentration of hydroxyl ions (OH-) silica tends towards dissolution (modified from Dent Glasser & Kataoka, 1981): first by neutralization of the silanol groups and then by attack on the siloxane groups
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The alkali–silica reaction can shorten concrete life due to expansive pressure build-up caused by reaction by-products, resulting in cracking. Understanding the role of the aggregate, as the main reactive component, is essential for understanding the underlying mechanisms of the alkali–silica reaction and thereby reducing, or even …
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Learn about the types, causes, and effects of alkali-aggregate reaction (AAR) in concrete, including alkali silica reaction (ASR). See how to evaluate aggregates, prevent AAR, …
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Generally, alkali-silica reaction (ASR) is considered as an internal chemical reaction between the alkaline components in the cement and active silica-silicate based mineral constituents of some aggregates. The use of aggregates susceptible of ASR in concrete can cause a severe degradation of the concrete structures because of several reasons …
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Damage due to alkali-silica reaction (ASR) in concrete is a phenomenon that was first recognized in the U. S. since 1940 and has since been observed in many countries. …
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Two types of alkali reactivity of aggregates are recognized: (1) an alkali–silica reactive involving certain siliceous rocks, minerals, such as quartz, opal, tridymite, …
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Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its …
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This experience embraces alkali-silica/silicate reaction (ASR) and alkali-carbonate reactivity (ACR) and extends to over thirty countries and more recently, has included the assessment of AAR risk and development in secondary and recycled aggregate materials. It covers both pre-construction AAR risk assessment of concrete constituents, its ...
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Application of crushed recycled glass in concrete materials can offer significant economical and environmental benefits provided that the alkali-silica reaction (ASR) of glass in concrete is properly controlled. Previous work on the use of …
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The alkali–silica reaction is a universally known destructive mechanism in concrete that can lead to the premature loss of serviceability in affected structures. Quite an enormous number of research studies have been carried out focusing on the mechanisms involved as well as the mitigation and prevention of the reaction. A few in-depth …
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The Alkali-Silica Reaction (ASR) causes expansion and cracking in concrete. This can result in structural problems in concrete infrastructure that can limit the infrastructure's service life and also generate high maintenance costs. CSHub research seeks to better understand the reaction and its mechanisms, which is key to determining ...
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Damage due to alkali-silica reaction (ASR) in concrete is a phenomenon that was first recognized in 1940 by Stanton [1,2] in North America and has since been observed in many other countries. Many studies [3,4,5] were published since Stanton's first paper, but
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The alkali-silica reaction (ASR) is a well-known phenomenon, causing premature distress in concrete structures and pavements, shortening their service life. ... This can be based on the proven service record of concrete incorporating the aggregate from the known quarry or river-run materials. If a service record is not available or not ...
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