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alkali aggregate reaction crack

Chemical reactions in concrete - Cornell University

Chemical reactions in concrete As you learned in the concrete section, a chemical reaction occurs when concrete is formed from water, cement, and aggregate. There is another chemical reaction that may occur later in the life of the concrete, called alkali-aggregate reaction (#).In this case, the cement reacts with a chemical in the aggregate to produce a gel or some other substance.

CONCRETE TECHNOLOGY Diagnosis and Control of Alkali ...

For alkali-silica reaction to occur, three conditions must be present: • reactive forms of silica in the aggregate • high-alkali (pH) pore solution • sufficient moisture The amount of gel formed in the concrete depends on the amount and type of reactive silica, and the alkali hydroxide concentration in the con-crete pore solution.

MODELLING OF ALKALI-AGGREGATE REACTION EFFECTS IN ...

Modelling of Alkali-Aggregate Reaction Effects in Reinforced Concrete Structures Anca-Cristina Jurcut Master of Applied Sciences Graduate Department of Civil Engineering University of Toronto 2015 Abstract Significant research has been performed worldwide on alkali-aggregate reaction (AAR) since its

Alkali Aggregate Reaction in Concrete - Types, Causes, and ...

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 cracking over a period of many years. This alkali-aggregate reaction has two forms, namely: Alkali-silica reaction (ASR) and Alkali-carbonate reaction (ACR).

Suppressing Alkali Aggregate Reaction (SAAR) Method

reaction (AAR)," which is one of the major causes of early deterioration of concrete structures. This is a repair method that suppresses alkali aggregate reaction using the combination of a crack injection agent, which consists of blast furnace slag powder and an added alkali adsorbent,

Alkali-Aggregate Reaction, Where Are You? | SpringerLink

Abstract. Since American Professor Atanton had firstly found practical project of alkali-aggregate reaction in California in 1920s, reports concerned about discovering project destroyed example of alkali-aggregate reaction all over the world are emerging continuously, especially in the USA.

Home | FHWA

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Aggregate Reaction - an overview | ScienceDirect Topics

Alkali-aggregate reaction (AAR) is a reaction between the alkali hydroxides present in the pore solution of concrete and certain constituents of some aggregates; under certain conditions the reaction may produce deleterious expansion and cracking of the concrete. There are two distinct types of alkali-aggregate reaction in concrete; these are ...

ALKALI AGGREGATE REACTION IN NUCLEAR CONCRETE …

The Alkali-Aggregate Reaction progresses with time in concrete between the alkaline cement paste and reactive amorphous silica. The reaction uses the moisture in the atmosphere and produces a gel that keeps dilating. The dilating gel causes cracks in the concrete mass thus possibly compromising the integrity of concrete.

Alkali-Aggregate Reaction - Portland Cement Association

In most concrete, aggregates are more or less chemically inert. 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).

Stress Analysis of Concrete Structures Subjected to Alkali ...

alkali-aggregate reactions (AAR). This internal reaction causes gel formation inside the aggregate and the matrix and results in swelling of the concrete. This swelling in turn may cause secondary compressive stresses (if the structure is restrained, as most are), localized map cracks, and, ultimately structural cracks.

Alkali Aggregate Reaction Topic - concrete.org

Alkali-aggregate reactions can be either alkali-carbonate reactions (ACRs) or alkali-silica reactions (ASRs). In ACR, the reaction is between the alkalies (sodium and potassium) and certain carbonate rocks, particularly calcitic dolomite and dolomitic limestones, present in some aggregates. In ASR, the reaction is between alkalies and certain siliceous rocks or minerals, such as opaline chert ...

Alkali Silica Reaction (ASR) – Portal on Deterioration of ...

Nov 01, 2018· The phenomenon of aggregates reacting with alkali component of cement is called alkali aggregate reaction (AAR). The predominant form of alkali aggregate reaction is alkali- silica reaction (ASR) in which the silica content of aggregate reacts with sodium and potassium hydroxide of concrete. Other forms of AAR are alkali-carbonate reaction and alkali-silicate reaction.

Influence of alkali-silica reaction and crack orientation ...

Jul 10, 2018· Alkali-Silica reaction (ASR) is a well-known deterioration mechanism in Denmark. In Denmark, most aggregate sources contain reactive silica minerals both in the fine and in the coarse aggregate fraction. Opaline and calcareous opaline flint were found as the main reactive aggregate types in the country .

Alkali-Aggregate Reaction in Concrete: A World Review

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 ...

Alkali-silica reaction in concrete

Mar 14, 2013· 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 ...

Victor E. Saouma | Home

Alkali-Aggregate Reactions. Chloride Diffusion; Nonlinear finite element simulation of reinforced concrete structures, in particular; Dams (gravity, arch) subjected to strong seismic excitation, or alkali-aggregate reactions. Nuclear reactor containers, in particular: ageing, cracking, structural assessment (Such as Crystal River delamination).

Alkali-Aggregate Reaction - Pavement Interactive

Alkali-aggregate reaction is the expansive reaction that takes place in PCC between alkali (contained in the cement paste) and elements within an aggregate. The most common is an alkali-silica reaction. This reaction, which occurs to some extent in most PCC, can result in map or pattern cracking (see Figure 1), surface popouts and spalling if ...

15 Factors Affecting Durability of Concrete

13. Alkali Aggregate Reaction. Alkali-aggregate reaction or alkali-silica reaction, takes place between alkali content of cement and silica content of aggregates is also a major factor effecting durability of concrete. Due to this reaction, Concrete expansion occurs which finally lead to severe cracking and concrete gets deteriorated.

ALKALI AGGREGATE REACTION IN NZ CONCRETE

Alkali aggregate reactions (AAR) are chemical reactions between alkalis in the pore solution of hardened concrete and some types of minerals within concrete aggregates. The product is a gel that expands in the presence of moisture. Its expansion can cause the concrete itself to expand.

Dealing with Alkali-Aggregate Reaction in Hydraulic ...

Jul 01, 2010· Alkali-aggregate reaction (AAR) is a chemical reaction between the alkali in Portland cement and reactive minerals in aggregate and additives that takes place when moisture is present. This reaction results in the formation of a hygroscopic gel that absorbs water and expands, causing significant expansion and characteristic cracking of the ...

Diagnosis and Control of Alkali-Aggregate Reactions in ...

Bérubé, M. A., and Duchesne, J., "Evaluation of Testing Concrete—Importance of Cement Content and Alkali Methods Used for Assessing the Effectiveness of Equivalent," in Concrete Alkali-Aggregate Reactions, Mineral Admixtures in Suppressing Expansion Due to Proceedings of the 7th International Conference, Alkali-Aggregate Reaction ...

(PDF) Alkali–Silica Reactions: An Overview. Part I

The alkali-aggregate reactions of the alkali-silica type, causing concrete fissuration and expansion, result from chemical unstability of siliceous phases in the highly basic concrete pore ...

EFFECTS OF THE CATHODIC CURRENT ON ALKALI-SILICA …

kali-silica aggregate reaction is illu strated in Fig. 3. The main crack propagated along the direction of the rebar, which is different from the map cracks that usually appear when the alkali-silica aggregate reaction occurs. This can be attributed to two reasons: (1) the alkali-silica aggregate reaction for

(PDF) Modeling of alkali-silica reaction in concrete: A review

The alkali-silica reaction in concrete is a chemical reaction that occurs between amorphous or poorly crystalline silica present in reactive aggregate and alkali and hydroxyl ions

Topics on Alkali-Silica Reaction - Development Bureau

Alkali­SilicaReaction (ASR) is a result of reaction between the alkalinepore solution and reactive silica in the aggregate. The reactionleads to the formation of a gel which absorbs water and expandsleading to damaging expansions and cracking in the concrete.