Alkali Aggregate Reaction
— Alkali aggregate reaction (AAR), also known as alkali silica reaction (ASR), is a major form of concrete deterioration for older structures. AAR will eventually weaken the concrete, induce cracking, and can jeopardize the integrity of dams and nuclear structures to the point of having them decommissioned.
Alkali-Silica Reaction: "The Cancer of Concrete"
1 Alkali-Silica Reaction: "The Cancer of Concrete" Courtney Collins . Jason Ideker . Gayle Willis . Jessica Hurst. 2 Outline What is ASR and why is it important? How does ASR …
Investigating the Effect of Alkali Silica Reaction in concrete …
However, the main worry with using RCA as a sustainable construction material is its potential for Alkali-Silica Reaction(ASR), shrinkage, freezing-thawing. The objective of …
Alkali-Silica Reaction (ASR)
Alkali-Silica Reaction (ASR) Conditions leading to ASR. ASR Mechanism. Nationwide Impacts. ASR Definition: A Process in which silica (found in aggregate) in the presence …
Alkali–aggregate reaction
— Concentrating mainly on alkali–silica reaction (ASR), the mechanisms are elucidated, and the necessary requirements for ASR to occur are described. Assessing potential aggregates for use in concrete in terms of their alkali-reactivity is always crucial, and this aspect receives considerable attention. Lastly, practical measures to avoid or ...
What is Alkali-Aggregate Reaction in Concrete.pptx
— 3. TYPES OF ALKALI-AGGREGATE REACTION IN CONCRETE • Alkali-Silica Reaction (ASR) Alkali-Silica Reaction (ASR) is a prevalent form of alkali-aggregate that occurs when certain reactive forms of silica minerals present in aggregates, such as opal, chert, and strained quartz, react with the alkalis, namely sodium and potassium, in …
Alkali-silica reaction in concrete: Mechanisms, mitigation …
— In the last few decades, the alkali–silica reaction (ASR) has been reported as one of the major concrete concerns regarding durability, leading to hig…
Alkali-Silica Reactivity Mitigation | SpringerLink
— Alkali-silica reaction (ASR) is a chemical reaction between the alkali hydroxide in Portland cement and certain siliceous rocks and minerals present in aggregates, such as opal, chert, chalcedony, trimite, cristobalite, strained quartz, etc. The resulting alkali-silica gel then absorbs water and expands, which results in cracking of …
A Multiscale and Multimethod Approach to Assess …
— Alkali–silica reaction (ASR) is a chemical reaction within concrete which can lead over time to cracking and spalling. Due to the complexity of the problem, it still causes damage to concrete …
Alkali-Silica Reaction: "The Cancer of Concrete"
— Creation of alkali-silica gel 4. Released SiO- molecules attract alkali cations in pore solution, forming a gel around the aggregate. Creation of alkali-silica gel 5. Alkali-silica gel takes in water, expanding and exerting a force against surrounding concrete. Creation of alkali-silica gel 6. When the expansionary pressure exceeds the tensile ...
Alkali-Aggregate Reaction
The mechanism for this alkali-silica reaction proposed by Diamond is as follows (Mindess and Young, 1981 [1]): Initial alkaline depolymerization and dissolution of reactive silica. Cement (a high-alkali substance) can increase the solubility of non-crystalline silica and the rate at which it dissolves. Additionally, the cement will raise the pH ...
Alkali Silica Reaction
Alkali-silica reaction (ASR) is the chemical reaction that occurs between alkali cations and hydroxyl ions in the pore solution of hydrated cement paste and certain reactive silica phases present in the aggregates used in concrete. The product of that reaction, called ASR gel, can expand by imbibing water and thus lead to the expansion and ...
Alkali-Silicate Reaction in Cement | PDF | Silicon …
Alkali-silicate reaction in cement - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. The document provides an overview of alkali silica …
Alkali–silica reactions (ASR): Literature review on …
— At later ages the alkali–silica gel reacts with calcium, and alkalis will be released into the pore solution and increase the alkalinity of the pore solution after 28 days up to 2 or 3 years [111]. Alkali recycling starts after a fixation phase, at least part of the alkalis eventually become available for alkali–silica reaction.
Alkali-Aggregate Reactivity
Alkali aggregate reactions (AAR) occur when aggregates in concrete react with the alkali hydroxides in concrete producing a hygroscopic gel which, in the presence of moisture, absorbs water and causes expansion and …
Alkali-Silica Reaction and High Performance Concrete
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
Alkali–silica reaction: Current understanding of the reaction
— Alkali–silica reaction (ASR) is a deleterious reaction between the alkaline pore solution of concrete and various metastable forms of silica contained in many natural and synthetic aggregates [1], [2].The silica structure is dissolved by the nucleophilic attack of OH − ions, and the highly degraded silica structure behaves as a hygroscopic silica gel.
Alkali–Silica Reaction in Concrete
— Keywords: recycled rubber waste; alkali–silica reaction; ASR environment; expansion 1. Introduction The Alkali–silica reaction (ASR) is the main deleterious process responsible for prema-ture deterioration in concrete structures. It is a chemical reaction between alkalis present in the cement matrix and reactive siliceous phases in the ...
Alkali-silica reaction in concrete: Mechanisms, mitigation …
— Especially prone to alkali-silica reaction (ASR), the expansion of the paste leads to the appearance of cracks and a decrease in porosity. This provides pathways for harmful ions such as chloride ions and sulfate radicals to enter the environment, thereby compromising durability. This review provides better theoretical guidance for improving ...
Alkali–Silica Reactions: An Overview. Part I
the deterioration of concrete, alkali–silica reaction (ASR) is the one that involves the aggregates. Aggregates con-stitute about three-quarter of the volume of concrete, and therefore their physical and chemical properties need to be correctly assessed before their use in concrete. Since the 1940s, considerable research has been developed to
Alkali-Aggregate Reactions in Concrete
— a Concrete pore solution is dominated by Na, K, and OH (with minor amounts of Ca). If the silica in the aggregate is reactive — the OH and then the Na and K will react with the SiO 2.. b The product of …
Alkali-Silica Reaction In Concrete
Alkali-silica reaction (ASR) in concrete is a reaction between certain silicious constituents in the aggregate and the alkali-sodium and potassium hydroxide which are released during …
Alkali-Silica Reaction
— 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.
An overview of a twofold effect of crystalline admixtures …
— Ferrara et al. [7] also suggested the processing of pozzolanic reactions promoted by CAs, based on the identification of C–S–H by SEM/EDS. Likewise, Esgandani et al. [16] attributed the refinement of the concrete pore to the replacement of CH by C–S–H based on the presence of active silica in CAs by the FTIR spectrum.
Alkali-Silicate Reaction in Cement | PDF | Silicon …
The document provides an overview of alkali silica reaction (ASR) in concrete, including its mechanism, effects, symptoms, factors that influence it, diagnosis, testing, and mitigation techniques. It describes how a …
ICAAR Proceedings | Concrete & Alkali-Aggregate Reaction
International Conference on Alkali-Aggregate Reaction Proceedings Alkali-Aggregate reaction is a an umbrella term for two types of premature concrete deterioration: alkali-silica reaction (most common) and alkali-carbonate reaction (less common). These forms of deterioration encompass a chemical reaction between CERTAIN aggregate types and …
Alkali-Silica Reaction In Concrete
alkali-aggregate reaction. There are three types of alkali-aggregate reactions, namely the alkali-silica, alkali-silicate and akali-carbonate reactions. Deterioration due to the alkali-silica reaction is more common and this paper refers to this aspect. The alkali-silica reaction was first recognized as a problem in North American in 1940, in
Alkali-silica Reaction Consulting
Alkali-silica reaction (ASR) can lead to premature failure of concrete elements and structures including pavements, bridges, tunnels, power plants, dams, and others. ASR is a chemophysical reaction within the concrete's microstructure occurring between certain alkalis, typically from the cement, and specific aggregates. ...
Alkali silica reactivity | PPT
— Alkali-silica reaction (ASR) is a reaction between alkali hydroxide and silica particles from aggregate in concrete that causes expansion and cracking. The reaction forms a gel product that absorbs …
(PDF) Alkali-Aggregate Reactions in Concrete
— In Portugal, the alkali-silica reaction (ASR) was recognized for the first time in concrete structures in the beginning of the 1990's. Since then, a lot of work has been carried out in order to ...
Assessing Alkali Silica Reaction in Low-Alkali Concrete …
— Among the many concrete distress mechanisms, alkali-silica reaction (ASR) is one of the most harmful which affects the durability and serviceability of concrete infrastructure worldwide [7, 8]. This shortens the service life of concrete, resulting in an inefficient use of the non-renewable resources and material that previously emitted CO …
Alkali-silica reaction (ASR) in concrete structures: …
— Alkali-silica reaction (ASR) and its associated deformation are major durability problems in concrete structures and was reported as far back as the 1940s by Stanton (2008) [1]. This deleterious reaction causes excessive expansion and cracks that can lead to severe degradation of the concrete structures. Despite the age-long discovery and ...