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UNIT II | PPT

• Control of Alkali-Aggregate Reaction From the foregoing discussion it is apparent that alkali-aggregate reaction can be controlled by the following methods: (i ) Selection of non-reactive aggregates; (ii ) By the use of low alkali cement (iii ) By the use of corrective admixtures such as pozzolanas; (iv ) By controlling the void space in ...

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Alkali-Aggregate Reactivity

Chapter 5 Alkali-Aggregate Reaction 5.1 Introduction 5.2 Types of Reactions 5.3 Evaluating Aggregates 5.4 Preventive Measures 5.5 Tests for Evaluating Preventive Measures 5.6 Protocols for Minimizing the Risk of AAR. 5.1 Introduction History of ASR (Thomas Stanton, 1940) History of ACR

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Effect of glass powder on alkali-silica reaction mitigation for …

Alkali-Aggregate Reaction (AAR) refers to the chemical reaction between alkali in concrete and alkali-reactive aggregates, leading to volume expansion and cracking in the concrete [1], [2], [3].AAR is difficult to halt and causes irreversible damage to the durability of concrete, which is known as "concrete cancer" [4].Among the types of AAR, …

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Aggregate Reaction

The durability of concrete for marine construction. M. Thomas, in Marine Concrete Structures, 2016 6.2.6 Alkali–aggregate reaction. Alkali– aggregate reaction (AAR) is a reaction between the alkali hydroxides in the pore solution of the concrete (supplied predominantly by the PC) and certain aggregates; alkali–silica reaction (ASR) involves …

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100+ Subject alkali aggregate reactivity PowerPoint (PPT) …

Lectures No. 09 & 10. Subject: Alkali-Aggregate Reactivity. Certain constituents in aggregates can react harmfully with alkali hydroxides in concrete and cause significant expansion. There are two forms of this reaction: Alkali silica reaction (ASR) ★ ★ ★ ★ ★

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Classification, properties and extraction of Aggregates | PPT

Alkali-Reaction: One of the most important examples of reactive aggregates is the Alkali-aggregate reaction in which alkali hydroxides react with the reactive silicates to form alkali silica gels which subsequently absorb water from their surroundings. This leads to internal stresses in hardened concrete until its tensile strength is reached ...

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Alkali Aggregate Reaction in Concrete

Alkali Aggregate Reaction in Concrete - Types, Causes, and Effects - Free download as PDF File (.pdf), Text File (.txt) or read online for free.

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Alkali Aggregate Reaction | PDF | Materials

Alkali Aggregate Reaction - Free download as Powerpoint Presentation (.ppt / .pptx), PDF File (.pdf), Text File (.txt) or view presentation slides online. Alkali aggregate reaction is a chemical reaction between highly …

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alkali-aggregatereaction-5.pdf

alkali-aggregatereaction-5.pdf - Download as a PDF or view online for free. Submit Search. Upload. alkali-aggregatereaction-5.pdf ...

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Alkali-carbonate reaction – Knowledge and References – …

Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017. Paddy E. Grattan-Bellew, Tetsuya Katayama. The term 'alkali-carbonate reaction' (ACR) would appear to apply to a reaction between the alkaline pore solution in concrete and any aggregate made from carbonate rocks such as limestones or …

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Alkali-Silica Reaction: "The Cancer of Concrete"

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. Creation of alkali-silica gel 6. …

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Overall assessment of Alkali-Aggregate Reaction (AAR) in …

1. Introduction. Alkali-Aggregate Reaction (AAR), a chemical reaction between certain mineral phases from the aggregates and the alkali hydroxides from the …

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Alkali-aggregate reaction in alkali-activated cement …

Testing methods for alkali-aggregate reaction in alkaline-activated cement concrete16.2.1. Pore solution extraction tests. Pore solution is a critical element in analyzing the ASR and ACR reactions in AAC, AAS, or AAF systems, since variation of concentration of calcium in pole solution indicates the degree of occurred ASR or ACR.

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ICAAR Proceedings | Concrete & Alkali-Aggregate …

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 …

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Cement & Concrete FAQ

Alkali-silica reactivity (ASR) is the result of alkalies in concrete (most commonly from the cementitious materials) chemically interacting with reactive silica in certain susceptible …

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Aggregate

• Extensive expansion and complete disruption and disintegration of the concrete is known as alkali aggregate reaction or concrete cancer. • The trouble is due to reaction between silica in aggregate and alkalis in cement. • A reactive aggregate, if in finely ground state will inhibit the action. • Reaction between cement and aggregate ...

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alkali aggregate reaction powerpoint

alkali aggregate reaction powerpoint - berkol.co.za. alkali aggregate reaction powerpoint, Alkali aggregate reaction 01/01/2018 AlkaliAggregate Reaction Is the reaction between the active mineral constituents of some aggregates and the sodium and potassium alkali hydroxide in the concrete Harmful only when it produes significant …

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Alkali-carbonate reaction in concrete and its implications …

According to Katayama [10], the alkali-aggregate reaction of carbonate rocks can be subdivided into three categories: (1) the ACR of dolomitic limestone that results in dedolomitisation, (2) the ACR of non-dolomitic limestone that produces reaction rims and (3) ... B_H2O_60C_1y, PPT. (b) B_H2O_60C_1y, XPT.

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Chemical attack in concrete | PPT

Alkali-Aggregate Reaction • Chemical reactions between aggregate containing certain reactive constituents and alkalis (sodium and potassium salts) and hydroxyl ions released by the hydration of cement …

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Overall assessment of Alkali-Aggregate Reaction (AAR) in …

1. Introduction. Alkali-Aggregate Reaction (AAR), a chemical reaction between certain mineral phases from the aggregates and the alkali hydroxides from the concrete pore solution is one of the most harmful distress mechanisms affecting the durability of concrete infrastructure worldwide [1].Normally, AAR is divided in two …

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Corrosion in reinforcement | PPT

The document discusses corrosion in steel reinforcement in concrete. It describes the mechanism of corrosion as an electrochemical process where rust forms. The main causes of corrosion are cracks in concrete, moisture, permeability of concrete, carbonation, chlorides, sulphate attack, and alkali-aggregate reaction.

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Properties of aggregates- Physical properties, Chemical …

Alkali- aggregate reaction; Alkali aggregate reaction or AAR is a reaction that starts with the attack on reactive siliceous minerals or other minerals in aggregate by the alkaline hydroxides formed from alkaline oxides (K2O, Na2O) present in the cement, forming alkali silicate gel having unlimited swelling ability in presence of water. ...

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Mineral admixtures | PPT

Effect of silica fume • Particle packing and pozzolanic reaction – high compressive strength • resistant to alkali aggregate reaction • More reactive than fly ash and other natural pozzolana 15. Rice Husk Ash • Produced by control burning of rice husk • High amount SiO2 ...

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Chemical attack on concrete 2017 | PPT

Because of alkali aggregate reaction manufactures are more careful about alkali content (K2O and Na2O) . Alkali content = [Na2O + (0.658)K2O ] < (0.6% by mass of cement) Alkali aggregate reaction takes place at higher concentration of OH-, that is at high pH value. High alkali cement pH(13.5 to 13.9) unsafe against AAR Low alkali …

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IS 2386-7 (1963): Methods of Test for Aggregates for …

Concrete, Part VII: Alkali Aggregate Reactivity [CED 2: Cement and Concrete] ls:2sss (Putv'5)-196s Indian Standard METHODS OF TEST FOR AGGREGATES FOR CONCRETE PART WI ALKALI AGGREGATE REACTIVITY Cement and ConcreteSictional Committee,BDC 2 R#prumtiq SHU K. K. N-m The Oancrete Association of Indis, Bombav

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CON 121 Session 4

CON 121 Session 4 - Aggregate Testing - Download as a PDF or view online for free. ... Observe the alkali-silica reaction rim around the reactive aggregate and the crack formation. Influencing Factors Reactive forms of silica in the aggregate, High-alkali (pH) pore solution Sufficient moisture If one of these conditions is absent ― ASR …

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Alkali aggregate reaction | PDF

3. 9/12/2015 3 Most common reaction of ASR is that between the active silica constituents of the aggregate and the alkalis in cement It results in the formation of an alkali-silicate gel, either in planes of weakness or pores in the aggregate (where reactive silica is present) or on the surface of the aggregate particles. In the latter case, a characteristic altered …

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Alkali silica reaction in concrete-RRS | PPT

However, some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. This alkali-aggregate reaction has two forms— alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). ASR is the most common form of alkali-aggregate reaction (AAR) in concrete.

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Durability of concrete | PPT

2. Alkali - Aggregate Reaction2. Alkali - Aggregate Reaction • Alkali from cement, reacts with reactive silica (of aggregates) to form alkali-silica gel of unlimited swelling type. • The continuous growth of silica gel exerts osmotic pressure within the concrete. • This manifests into cracking and bulging of concrete Occurrence is due to : 1.