Subsequent work by swenson 1957, swenson and gillott 1960, and gillott. Pdf investigating the alkali silica reaction of recycled. Typical values substance specific gravity density lbft3 water 1. 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. This protects them from weathering and also gives an alkalinity level ph higher than 7 which helps to protect steel from corrosion. The staining of concrete by an alkali aggregate reaction sidney mindess department of civil engineering university of british columbia vancouver 8, british columbia james c.
The alkali aggregate reaction can be controlled by the following methods. 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 problem from. In absorbing water, these gels can induce pressure, expansion, and cracking of the aggregate and surrounding paste. I briefly appraise the problems and trends in aar research in the pacific northwest region. 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 first deleterious effects on concrete. 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.
Based on the results of astm c1260 test, jin et al. Gilley consulting engineer vancouver, british columbia refereed abstract certain 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. I of the alkaliaggregate reaction in highalkali cements, 11 reactive and nonreactive experimental aggregates were examined by several procedures. This alkaliaggregate reactivity aar has two forms alkalisilica reaction asr and alkalicarbonate reaction. Reaction products from asr have a great affinity for moisture. The effect of concrete industries have contributed to this first edition of temperature and humidity on expansion, and the diagnosis and control of alkaliaggregate reactions in significance of. The concrete prism test is considered to be a better test that correlates with the field performance of an aggregate in concrete. The alkalisilica reaction forms a gel that swells as it draws water from the surrounding cement paste.
Microscopic and chemical methods of diagnosis of alkali. Alkali aggregate reaction topic american concrete institute. Alkaliaggregate reaction aar of concrete structures. 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. If the aggregate contains soluble silica, however, new. Petrographic examination is the rock a quarried carbonate. Request pdf on may 1, 2020, ziyi peng and others published alkali aggregate reaction in recycled aggregate concrete find, read and cite all the research you need on researchgate. However, it is not known exactly what percentage of the aggregate sources in the u. Effects of alkaliaggregate reaction on concrete and. Concrete technology diagnosis and control of alkali. As part of a research project to develop draft specifications for glass in concrete, a major asr testing programme was undertaken to establish appropriate use of glass in concrete which avoided harmful asr. Astm c1778 19b standard guide for reducing the risk of. Free lime cao in cement reacts with co 2 in the atmosphere to precipitate caco 3 around the cement grains.
In 1992 a first edition entitled the alkalisilica reaction in concrete, edited by professor narayan swamy, was published in a. The use of surplus waste glass in concrete has been avoided on the grounds that it is known to undergo harmful alkalisilica reaction asr. Concrete affected by the variety of alkaliaggregate reaction known as alkalisilica reaction often shows exudations of a watery gel which dries to a white deposit. Concrete prism test, astm c 1293 is 1year expansion concrete. Nonetheless, concrete deterioration caused by each type of alkaliaggregate reaction is similar. The most alarming effects from the engineering standpoint, however, are the expansion and deterioration in strength of the concrete. Asr involves reactions between alkali pore solution in the concrete and certain forms of alkalireactive silica. This alkali aggregate reactivity aar has two forms alkali silica reaction asr and alkali carbonate reaction acr, sometimes called alkali carbonate. Asr is a chemical reaction taking place in concrete between reactive forms of silica in the aggregate and the alkalis in the cement pore solution stanton 1940. Progress in the evaluation of alkaliaggregate reaction in. Three main types of alkali aggregate reaction aar have been identified depending on the aggregates. The reactivity is potentially harmful only when it produces significant expansion.
This reaction can cause expansion of the altered aggregate, leading to spalling and loss of strength of the concrete more accurate terminology. Aggregates containing certain constituents can react with alkali hydroxides in concrete. Diagnosis and control of alkaliaggregate reactions in. If it is assumed that 50 percent of all aggregate sources fail the concrete prism test. Alkalisilica reaction in portland cement concrete 16. Alkali aggregate reaction in concrete types, causes, and.
Alkaliaggregate reactions can be either alkali carbonate reactions acrs or alkali silica reactions asrs. Alkali silica reaction asr is of more concern because aggregates containing reactive silica materials are more common. Additionally, there are two recommended international specifications for concrete aar7. For the love of physics walter lewin may 16, 2011 duration. Alkali aggregate reaction aar occurs when the alkali in concrete reacts with some deleterious minerals in the aggregate when there is sufficient moisture, causing expansion and cracking of the concrete. This causes a gel to form within the cement paste matrix. This guide addresses the process of identifying both potentially alkalisilica reactive asr and alkalicarbonate reactive acr aggregates through standardized testing procedures and the selection of mitigation options to minimize the risk of expansion. Alkaliaggregate reaction portland cement association. It is a common belief that it does not occur due to the exceptional quality of finlands granitic rock. Alkaliaggregate reactions in concrete springerlink. Alkaliaggregate reaction in concrete containing fly ash 16.
Alkaliaggregate reaction in concrete ian sims, alan b. 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. Alkalisilica reaction alkalisilica reaction asr in concrete is a reaction between certain silicious constituents in the aggregate and the alkalisodium and potassium hydroxide which are released during the hydration of portland cement. The effects of alkaliaggregate reaction aar on concrete and structures start at the microstructural level, that is, at molecular and microscopic levels, such as the formation of reaction products in concrete and associated microcracking, which ultimately leads to macrolevel effects such as visual cracking, differential movements, displacement and so on. D 583 addition of lightweight aggregate reduces expansion in concrete containing a highly reactive normal weight aggregate boyd, s. Alkaliaggregate reaction in concrete containing fly ash. The effect of lithium nitrate on the course of alkalisilica.
Since a prolonged exposure to nuclear reactor radiation may increase the risk of asr damage in concrete, pomaro et al. Chemical analysis of these exudations or deposits shows them to be composed mainly of silica and alkali often with varying amounts of lime. In asr, the reaction is between alkalies and certain siliceous rocks or minerals, such as opaline chert. Alkaliaggregate reactions can be either alkalicarbonate reactions acrs or alkalisilica 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.
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. Alkalisilica reaction in concrete containing glass. Alkali aggregate reaction asr in concrete is one of the least dealt with concrete degradation mechanism in finland. If the aggregate is shown to be potentially reactive by the tests, some mitigation measure must be used to control the expansion and cracking. A 593 evaluation of different measures to reduce the risk of alkalisilica reaction in recycled aggregate concrete. 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. He found that an alkalisensitive reaction had developed in concrete containing argillaceous calcitic dolomite aggregate that appeared to be different than the alkalisilica reaction. 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. Star 219acs rilem recommendations for the prevention of.
Asr is based on the dissolution of silicarich aggregates in highly alkaline solutions in concrete constructions e. Avoid the presence of a critical amount of reactive silica, e. Alkaliaggregate reaction in recycled aggregate concrete. Evidences of cementaggregate reaction become manifest through several phenomena. Alkali aggregate reactions aar are chemical reactions between alkalis in the pore solution of hardened concrete and some types of minerals within concrete aggregates. Avoid the presence of a critical amount of reactive. Alkaliaggregate reactions in concrete sciencedirect. Its expansion can cause the concrete itself to expand.
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