A review of drivers for implementing geopolymers in construction: Codes and constructability. Andrés Martínez, Sabbie A. Miller, in Resources, Conservation and Recycling, 2023. 5.6 Alkali-silica reaction. The alkali-silica reaction is a chemical interaction between the hydroxyl ions of an alkaline system and siliceous constituents in the mixture, generally in the aggregates, that …
Section snippets Reaction mechanisms. ASR damage is a result of a number of sequential reactions, including: (1) dissolution of metastable silica, (2) formation of nano-colloidal silica sol, (3) gelation of the sol, and (4) swelling of the gel: S i O 2 solid → 1 S i O 2 aqueous → 2 S i O 2 sol → 3 S i O 2 gel → 4 swelling of gel. Alternatively, a highly degraded (SiO 2) solid …
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 ...
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 the reaction is in alkali-silica gel composed of Na, K, Ca, and Si The gel forms around and within the aggregate.c The gel imbibes water from the surrounding cement …
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 degradations resulting from this reaction …
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 ...
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.
In 1923, a number of concrete structures in the USA were observed to develop severe cracking, with unidentified cause. In 1940, Stanton recognized for the first time alkalis, Na and K, in the paste combined with silica from the aggregate, in a deleterious reaction dubbed 'alkali–silica reaction' (ASR) (see [27, entry 1008]).Since its original discovery, deleterious …
According to Multon [73], the expansion of the gel includes two phases namely alkali-silica gel hydration and increased volume followed by the gel diffusion in the cement paste.During the hydration of alkali-silica gel the chemical potential difference between the solution within the gel and the concrete pore solution induces higher water adsorption and …
The American Concrete Institute (ACI) is a leading authority and resource worldwide for the development and distribution of consensus-based standards, technical resources, educational programs, certification programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best …
1. Introduction. 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.
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 the host cement …
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 2. It ...
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 the …
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 …
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 reaction (ASR) in concrete, …
Alkali-Silica Reaction: - Less reactive aggregates often expensive or difficult to find ... exerting a force against surrounding concrete. Creation of alkali-silica gel ... | PowerPoint PPT presentation | free to view
ALKALI SILICA REACTION: TOOLS OF MICROSCOPIC CHARACTERIZATION AND DISCUSSION ABOUT ITS TREATMENT IN THE NEW CHILEAN STANDARD NCh170. REACCIÓN ÁLCALI SÍLICE : HERRAMIENTAS DE CARACTERIZACIÓN MICROSCÓPICA Y DISCUSIÓN SOBRE SU TRATAMIENTO EN LA NORMA CHILENA EN CONSULTA NCh170.
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.
This attack, which in wet conditions produces a hygroscopic gel, can cause cracking and disruption of the concrete. The deterioration mechanism is termed alkali aggregate reaction (AAR) or, more specifically, for siliceous …
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.
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 ...
There are a number of ASTM tests used to identify alkali-silica reactive aggregates, and the effects of different alkali-bearing cements and pozzolans in accommodating the ASR reaction. Nevertheless, in many areas of the country, the "good" aggregates have been used up, and "poorer" aggregates, of necessity or for unknown reasons, are ...
Permeability is increased by porosity, microcracks, and dampness/seepage, allowing chemicals to enter. Major agents are chlorides, sulfates, and alkali-silica reaction, which can cause corrosion, cracking, or expansion through carbonation, sulfate attack, or silica gel formation. Read less
Alkali-silica reaction is one of the most recognized deleterious phenomena in concrete. Various types of silica present in aggregates react with the hydroxyl ions present in the pore solution in concrete. The silica, now in solution, reacts with the sodium (Na+) and potassium (K+) alkalis to form a volumetrically unstable alkali silica gel. ...
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 ...
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 this research is to …
The two main types are alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). ASR was first identified in California in the 1930s and has caused damage in structures worldwide. Remediation methods include using low-alkali cement, avoiding reactive aggregates, controlling moisture, and treating affected concrete with lithium compounds ...
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 ...
Alkali-silica reaction (ASR) significantly contributes to the degradation and reduced performance of concrete structures worldwide. This mechanism causes swelling pressure in the aggregate material(s) and cement paste adjacent to it when moisture is absorbed, resulting in microcracking and loss of physical integrity and functionality [1, 2].Various laboratory …
This paper presents a comprehensive review of modeling of alkali-silica reaction (ASR) in concrete. Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material. The concept of ASR and the mechanism of expansion are first outlined, and the state-of-the-art of modeling …
Creation of alkali-silica gel 4. Released SiO- molecules attract alkali cations in pore solution, forming an alkali-silica gel around the aggregate. Si-OH + Na+ + OH- Si-O-Na + H20. Creation of alkali-silica gel 5. Alkali-silica gel takes in water, expanding and exerting an osmotic pressure against the surrounding paste or aggregate.
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 aggregates that cause si…
The alkali–silica reaction is a universally known destructive mechanism in concrete that can lead to the premature loss of serviceability in affected structures.
