A special computer program semquant was applied to eliminate the coincidence of peaks of gold with those of other elements denoted in the specimen, especially sulfur, in the semiquantitative analysis. Deterioration due to the alkalisilica reaction is more common and this paper refers to this aspect. Alkaliaggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and noncrystalline silicon dioxide, which is found in many common aggregates. Scope this test method is intended to determine rapidly the potential alkalireactivity of aggregates through the evaluation of the expansion of mortarbars immersed in. Concrete technology diagnosis and control of alkali. The potential for deleterious alkalisilica reaction was verified using the accelerated mortar bar test. The potential for deleterious alkali silica reaction was verified using the accelerated mortar bar test. I briefly appraise the problems and trends in aar research in the pacific northwest region. Aj,1troet the main objective of this study was to determine the influences of the constituents of portland cement, aggregates, and mineral admixtures on alkali silica reaction. If the aggregate contains soluble silica, however, new. A method to quantify the reaction degree bulteel, d.
Alkalisilica reactivity, alkaliaggregate reaction, reactive aggregates. Alkali aggregate reaction in concrete is the name given to a group of reactions leading to expansion caused by a chemical reaction between the alkalis contained in the cement paste and certain reactive forms of usually silica containing minerals in the aggregates, see figure 4. Factors affecting the alkalisilica reaction and control of these using the aar tri. Incidences of acr are relatively scarce and generally restricted to a few isolated regions. This is a short introduction to asr for more information, see the understanding cement bookebook.
Reclassification of alkali aggregate reaction, in 14th international conference on alkaliaggregate reactions in concrete, 2025 may 2012, austin, texas, usa. Avoid the presence of a critical amount of reactive silica, e. Free lime cao in cement 1 reacts with co2 in the atmosphere to precipitate caco3 around the cement grains. Alkaliaggregate reaction in concrete containing fly ash 16. For the love of physics walter lewin may 16, 2011 duration. The reactionleads to the formation of a gel which absorbs water and expandsleading to damaging expansions and cracking in the concrete. A new constitutive model for alkaliaggregate reaction aar expansion is presented. A deleterious chemical reaction between hydroxyl oh ions associated with alkalis sodium and potassium present in cement or other sources and certain reactive siliceous components that may be. If the aggregate is shown to be potentially reactive by the tests, some mitigation measure must be used to control the expansion and cracking. Two types of alkali reactivity of aggregates are recognized.
Alkaliaggregate reaction aar of concrete structures. An initial survey on the occurrence of alkali aggregate. Alkali aggregate reaction in concrete types, causes, and. Hydropower structure a ected by alkali aggregate reaction. This followup paper first examines how this co mplex and coupled model can be used for the longterm until reaction exhaustion prediction of an aaraffected concrete structure. The observed alkaliaggregate reaction products are presented both in the form of an xray spectrum and a micrograph. Studies relating to the mechanism by which the alkaliaggregate reaction. There are three types of alkali aggregate reactions, namely the alkali silica, alkali silicate and akalicarbonate reactions. One particular area of expertise is alkaliaggregate reaction in concrete, a costly and worldwide problem. Acr is typically a more aggressive reaction and occurs earlier in the life of the structure. Alkali aggregate 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 expansion 3. It is well documented that for alkalisilica reaction to occur, three conditions must be present. Alkali aggregate reaction is the expansive reaction that takes place in pcc between alkali contained in the cement paste and elements within an aggregate.
Potential alkalireactivity of granite aggregates in the. 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. The alkali content of portland cements has increased because of the process changes prompted by energy and environmental constraints. Alkaliaggregate reaction transportation research board. In asr, the reaction is between alkalies and certain siliceous rocks or minerals, such as opaline chert. Alkaliaggregate reaction article about alkaliaggregate. David stark construction technology laboratories, inc. An overview of research richard helmuth construction technology laboratories, inc. Asr is the most common form of alkaliaggregate reaction aar in concrete. From the many different damage mechanisms that can originate the deterioration of concrete, alkalisilica reaction asr is the one that involves the aggregates. In 1992 a first edition entitled the alkalisilica reaction in concrete, edited by professor narayan swamy, was published in a first attempt to cover this concrete. The international conference on alkaliaggregate reaction icaar, which is held every four years since 1974, deals on the study of a harmful chemical reaction alkaliaggregate reaction that affects concrete structures worldwide, causing an important decrease on their durability and service life. Nov 12, 2015 asr is the most common form of alkali aggregate reaction aar in concrete.
Submitted to ctcs09, chemomechanical interaction in concrete session version 3 april 10, 2009. Alkaliaggregate reaction in concrete is the name given to a group of reactions leading to expansion caused by a chemical reaction between the alkalis contained in the cement paste and certain reactive forms of usually silica containing minerals in the aggregates, see figure 4. Lithuanian quarry aggregates concrete effects of alkaline corrosion tests lietuvos karjeru uzpildu poveikio betono sarminei korozijai tyrimai. Then, through a series of parametric studies, sensitivity analyses are performed, and then basic modeling. Total alkali content in concrete gives a better figure. It was a common belief that finland does not have asr. Recent developments in the use of fly ash to reduce alkali. Alkaliaggregate reactions in concrete springerlink. Upper limit for total alkalis when reactive aggregates are used 5lbyd. A deleterious chemical reaction between hydroxyl oh ions associated with alkalis sodium and potassium present in cement or other sources and.
Alkaliaggregate reaction is the expansive reaction that takes place in pcc between alkali contained in the cement paste and elements within an aggregate. Submitted to ctcs09, chemomechanical interaction in concrete. Chapter 2 alkalisilica reaction guidelines for the use of. Free lime cao in cement reacts with co 2 in the atmosphere to precipitate caco 3 around the cement grains. Alkali aggregate reactions can be either alkali carbonate reactions acrs or alkali silica reactions asrs. It will subsequently analyse the efforts thus far in understanding and modelling this reaction, and the experimental methods and tests which have been carried out in pursuit of this goal. It is based on the south african nbri national building research institute accelerated test method. Stress analysis of concrete structures subjected to alkali. The alkalisilica reaction is the most common form of alkaliaggregate reaction. The expansive reactions between alkalis and alkalireactive aggregates within concrete structures are a. Modelling of alkali aggregate reaction effects in reinforced concrete structures ancacristina 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. Alkaliaggregate reaction aar or any other aggregate degradation mechanism is a gradual process and. For alkalisilica reaction to occur, three conditions must be present. The traditional use of fly ash to reduce the expansion from the alkaliaggregate reaction may not be beneficial if the fly ash has a low amorphous silica content and high alkali particularly sodium content.
This report is mainly based on the results of a survey conducted among the finnish laboratories with thin section microscopy analysis capabilities listed in appendix a. Abstract identifying the susceptibility of an aggregate to alkalisilica reaction asr before using it in concrete is one of the most efficient practices for preventing damage and failure. Sand and gravel sources had to be tested using kansas test method ktmr23 1999, wetting and drying test of sand and sandgravel aggregate for concrete. Alkaliaggregate reaction aar is only one of the many factors that might be fully or partly responsible for the deterioration and premature loss in serviceability of concrete infrastructure.
Nonetheless, concrete deterioration caused by each type of alkaliaggregate reaction is similar. Alkaliaggregate reaction asr in concrete is one of the least dealt with concrete degradation mechanism in finland. Apr 07, 2017 for the love of physics walter lewin may 16, 2011 duration. Alkali silica reaction asr can cause serious expansion and cracking in concrete, resulting in major structural problems and sometimes necessitating demolition. This reaction can cause expansion of the altered aggregate, leading to spalling and loss of strength of the concrete more accurate terminology. Standard test method for potential alkali reactivity of. Alkaliaggregate reactions can be either alkalicarbonate reactions acrs or alkalisilica 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. This paper presents theoretical and applied stateoftheart information in the field of alkaliaggregate reactivity aar in concrete.
Modelling of alkaliaggregate reaction effects in reinforced concrete structures ancacristina jurcut master of applied sciences graduate department of civil engineering university of toronto 2015 abstract significant research has been performed worldwide on alkaliaggregate reaction aar since its. A new constitutive model for alkali aggregate reaction aar expansion is presented. Alkaliaggregate reaction aar, which includes alkalisilica reaction asr, is the leading cause of dam concrete deterioration. Concrete problems and repair techniques professor khaled a. Two forms of alkali aggregate reactions are recognized. Deterioration due to the alkali silica reaction is more common and this paper refers to this aspect. The research approach used in this investigation was to conduct a comparative study of the behavior of several mixes made using several aggregate sources in combination with cements with high and low alkali content, and.
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. Distribution, posting, or copying of this pdf is strictly prohibited without written permission of the transportation research board of the national academy of sciences. Alkaliaggregate reaction in concrete containing fly ash. This test method is not suitable as a means to detect alkali silica. There are three types of alkaliaggregate reactions, namely the alkalisilica, alkalisilicate and akalicarbonate reactions. Report on the diagnosis, prognosis, and mitigation of. Progress in the evaluation of alkaliaggregate reaction in. The alkali silica reaction was first recognized as a problem in north american in 1940, in. Topics on alkalisilica reaction development bureau. Chemomechanical interaction in concrete session jfs, april 10, 2009 221. Asr is the most common form of alkali aggregate reaction aar in concrete. The alkalisilica reaction was first recognized as a problem in north american in 1940, in. In 1992 a first edition entitled the alkalisilica reaction in concrete, edited by professor narayan swamy, was published in a. Alkalicarbonate rock reaction alkalisilica reaction.
Report on the diagnosis, prognosis, and mitigation of alkalisilica reaction asr in transportation structures. Pdf appraising structures affected by the alkaliaggregate. 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 expansion 3. It also has one manual pressure relief valve and two pressure indicators. Unless otherwise indicated, all materials in this pdf are ed by the national academy of sciences. The ft dete rioration mechanism occurs when water within the cement. Alkalisilica reaction asr is of more concern because aggregates containing reactive silica materials are more common. The kansas department of transportation kdot has controlled alkalisilica reaction asr for more than 70 years through the use of selected aggregates. In 1992 a first edition entitled the alkalisilica reaction in concrete, edited by professor narayan swamy, was published in a first attempt to cover this. The traditional use of fly ash to reduce the expansion from the alkali aggregate reaction may not be beneficial if the fly ash has a low amorphous silica content and high alkali particularly sodium content. It should be known that no structure has ever collapsed due to alkali aggregate reactions, but there are cases in which structural concrete members demolished due to the effect of alkali aggregate reactions most of the structures severely cracked by aar are exposed to the weather or are in. Control of alkaliaggregate reaction alkalis can come, not only from cement, but also from chemical and mineral admixtures and from the aggregate itself. This thermochemomechanical model is rooted in the chemistry, physics, and mechanics of concrete.
Effects of moisture, temperature, and freezing and thawing on. At the same time a longterm ageing effect caused by dryingout of the cement. Soudki, peng department of civil engineering university of waterloo waterloo, ontario, canada, n2l 3g1 tel. A tc 1062 detection of potential alkalireactivity of. This slowevolving internal concrete damage is causing millions of dollars of damage worldwide, and whereas there is no economically feasible method to stop the reac. Alkalisilica reaction in portland cement concrete 16. The effects of supplementary cementitious materials on. In the following a description of each of these factors concerning finnish practise reality is given.
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