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Wednesday, July 29, 2020 | History

2 edition of Alkali aggregate reactions, concrete aggregate testing and problem aggregates in Ontario found in the catalog.

Alkali aggregate reactions, concrete aggregate testing and problem aggregates in Ontario

C. A. Rogers

Alkali aggregate reactions, concrete aggregate testing and problem aggregates in Ontario

a review

by C. A. Rogers

  • 297 Want to read
  • 1 Currently reading

Published by Ontario Ministry of Transportation and Communications, Engineering Materials Office in [Toronto] .
Written in English

    Subjects:
  • Alkali-aggregate reactions.,
  • Concrete -- Testing.

  • Edition Notes

    Statementby C.A. Rogers.
    SeriesReport -- EM-31, Report (Ontario. Highway Engineering Division. Engineering Materials Office) -- EM-31.
    ContributionsOntario. Highway Engineering Division. Soils and Aggregates Section., Ontario. Ministry of Transportation and Communications.
    Classifications
    LC ClassificationsTA440
    The Physical Object
    Pagination38 p. :
    Number of Pages38
    ID Numbers
    Open LibraryOL19514243M

    The alkali–silica reaction (ASR), more commonly known as "concrete cancer", is a swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive non-crystalline silica found in many common aggregates, given sufficient moisture. on reactions of aggregates involving alkalies and on methods by which potentially alkali-reactive aggregates or cement-aggregate combinations can be detected. How­ ever, chemical properties and reactions of aggregates not involving alkalies are locally of great significance, especially in architectural quality of concrete, and shouldFile Size: 5MB.

    5. Gogti B.S., An evaluation of some common Indian rocks with special reference to alkali-aggregate reactions. Engineering Geology 7 ((), Amsterdam pp. 6. IS: (Part VII) – , Method of test for aggregate for concrete: Part VII alkali-aggregates reactivity. 7. ACI Committee , Selection and use of aggregates for concrete. Alkali Aggregate Reaction (AAR) When a highly basic fluid which consist of alkali hydroxides ions like (K +, Na + ـــــ OH –) fill the pores in concrete and the aggregate in concrete are chemically unstable in the high pH environment, the concrete encounter with distresses such as cracking, losing serviceability.

    Two forms of alkali aggregate reactions are recognized: Alkali carbonate reactions (ACR) occur with dolomitic limestone aggregate of a specific mineralogy and microstructure. Sources of these aggregates is relatively rare. ACR is typically a more aggressive reaction and File Size: KB. Alkali-reactivity problems with emphasis on Canadian aggregates. Eng. Geol, The "classical" form of alkali-aggregate reaction involves the disordered forms of silica particularly opal, chert and by: 9.


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Alkali aggregate reactions, concrete aggregate testing and problem aggregates in Ontario by C. A. Rogers Download PDF EPUB FB2

Rogers, C.A. () Alkali Aggregate Reactions, Concrete Aggregate Testing and Problem Aggregates in Ontario – A Review.

Ontario Ministry of Transportation and Communications, Engieering Materials Office, Report EM, 5th Revised Edition, : Paddy E.

Grattan-Bellew, Tetsuya Katayama. Certain concrete aggregates react with the alkaline pore solution in concrete, which produces expansion leading to the cracking and deterioration of concrete. These reactions are known as alkali–aggregate reactions (AAR).

The reac-tions found in Ontario can be grouped into two broad types: alkali–carbonate rock reaction and alkali–silica File Size: KB. One particular area of expertise is alkali-aggregate reaction in concrete, a costly and world-wide problem.

He was a member of the international committee for the organisation of a series of major ‘ICAAR conferences’ on alkali-aggregate reaction until and chaired the two held in the UK.

In Ontario, two types of alkali--aggregate reaction exist. Each type is evaluated using different tests. Over the past few years, new tests have been introduced to replace some existing test methods.

Chapter 1: Alkali-aggregate reaction (AAR) and its effects on concrete – an overview AAR and its visible characteristics The chemical characteristics of AAR Guarding against AAR Main types of AAR and the appearance of fractures caused by AAR Chemical mechanisms of AAR Necessary and sufficient requirements for AAR to occur.

The alkali content of the concrete mix A (kg/m3) can be Alkali aggregate reactions calculated from the alkali content of the cement a (%) and the cement content of the concrete C (kg/m3) by the following expression: References American Society for Testing and Materials Constituents of natural mineral aggregates ASTM Designation C Annual Book of ASTM.

[Show full abstract] alkali-aggregate reactivity (AAR) of concrete aggregates, (2) the prevention of AAR in new structures, and (3) the management of existing structures affected by this problem. outlines the strategy to proactively address the problem.

Key words: Instructions, layout, headings, figures and tables, references. INTRODUCTION Alkali-aggregate reaction (ASR) in concrete is one of the least dealt with concrete degradation mechanism in Finland. It was a common belief that Finland does not have ASR. The reasons forFile Size: 7MB.

Alkali-aggregate Reactions in Concrete - A review - Benoit Fournier Fortaleza Concrete Prism Test (CPT) Aggregate potentially reactive in the aggregates Sufficient Alkali Sufficient Moisture. Preventive Measures Against ASR. 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.

concrete bars with silica aggregate and high-alkali con- tent cement, and scale of the expansion of the mortar bars stored in a sodium hydroxide solution at 80 °C. ASTM Book of Standards, 14(C): ASTM, i. Standard method of test for effectiveness of mineral admixtures in preventing excessive expansion of concrete due to the alkali-aggregate reaction.

ASTM Book of Standards, 14(C): Adams, L. D., Determination of minor alkali compounds in cement by: Alkali-silica reaction (ASR) is of more concern because aggregates containing reactive silica materials are more common.

In ASR, aggregates containing certain forms of silica will react with alkali hydroxide in concrete to form a gel that swells as it adsorbs water from the surrounding cement paste or the environment. 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.

A: Issues surrounding alkali-silica reactivity (ASR) of aggregates are occurring in many areas where concrete producers were not historically required to produce such data. ASR is a reaction between the alkalies in the cement and silica in the aggregates.

This reaction causes a gel which expands when water is available. 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).Author: Madeh Izat Hamakareem.

Alkali Aggregate Reaction (AAR) results in deleterious expansive cracking of concrete occurring at later ages after construction. While mostly inert, some concrete aggregates can react in the highly alkaline environment in concrete resulting in internal expansion that causes deleterious cracking.

Alkali-Aggregate Reaction (AAR means a chemical reaction that occurs in concrete between alkalis in) the cement (e.g., sodium and potassium) and minerals in the aggregate. This reaction may cause deleterious expansion and cracking of the concrete. AAR includes alkali-carbonate and alkali-silica Size: KB.

Manual of Aggregate and Concrete Testing1 INTRODUCTION This manual is intended to supplement, not in any way to supersede, the variousASTM test methods for sampling and testing aggregate and freshly mixed and hardened portland-cement concrete. The manual was prepared by Committee C09 on Concrete and ConcreteAggregates and has been accepted.

The alkali-silica reaction forms a gel that swells as it draws water from the surrounding cement on products from ASR have a great affinity for moisture.

In absorbing water, these gels can induce pressure, expansion, and cracking of the aggregate and surrounding reaction can be visualized as a two-step process:†† 1.

M1: Restrict the alkalinity of pore solution, e.g. limit the alkali content of concrete, use of low alkali cement, include PFA, GGBS, etc. M2: Avoid the presence of a critical amount of reactiveFile Size: 2MB.due to an increase in alkali content in the concrete.

Key words: Alkali-silica reaction, aggregate, alkali content, durability. 1. INTRODUCTION. ASR is a complex physical and chemical reaction between water, alkali in the concrete pore solution and reactivesilica minerals in aggregates [1].

The reaction demands an alkaline environment which is Author: Samanta Robuschi, Ignasi Fernandez, Kamyab Zandi, Karin Lundgren.Alkali-Silica Reaction. T.E. Stanton (), working in California, first identified reactions between the alkalis in cement and aggregates as a cause of concrete distress. In the early literature, prior to the discovery of ACR, the reaction was simply called the alkali-aggregate reaction .