Alkali-aggregate reaction in reinforced concrete structures pdf

Alkaliaggregate reactions in concrete springerlink. Alkalisilica reaction asr is a reaction between alkali, hydroxyl ions from concrete pore solution and amorphous siliceous minerals present in reactive aggregates mehta and monteiro, 2006. Alkaliaggregate reactions can be either alkalicarbonate reactions acrs or alkalisilica reactions asrs. Diagnosis of concrete structures distress due to alkaliaggregate reaction cement with equivalent na2o content of 0.

Aggregate reaction an overview sciencedirect topics. Alkaliaggregate reaction asr in concrete is one of the least dealt with concrete degradation mechanism in finland. Durability of reinforced concrete structures alkaliaggregate reaction of concrete structures ir steven chak public works laboratories, standards and testing division, geotechnical engineering office, civil engineering and development department. The specific uses of these results will be in managing structures affected by alkali reactions, also in specifying, designing and proving concrete mixes for new structures on a projectspecific basis. The book discusses methods that can be used for laboratory destructive and in situ nondestructive testing to. Deterioration of concrete structures because of alkali reactions is an increasing problem worldwide. Alkalisilica reaction asr is of more concern because aggregates containing reactive silica materials are more common. Alkali aggregate reaction in concrete types, causes, and. Three main types of alkali aggregate reaction aar have been identified depending on the aggregates. However, concrete made with lowalkali cementand extremelyreactive aggregate is still susceptible to deleterious asr if moisture movement. Such modeling is essential for investigating the chemical expansion mechanism and the subsequent influence on the mechanical aspects of the material.

These reactions form an alkaline hygroscopic gel that absorbs water and expands causing internal stresses with cracking 1. Alkaliaggregate reaction aar is one of the most harmful distress mechanisms affecting the performance of aging reinforced concrete structures worldwide. Diagnosis of concrete structures distress due to alkali. Deterioration due to the alkalisilica reaction is more common and this paper refers to this aspect. Providing information on the symptoms and signs of concrete affected by aar, how to identify aar and distinguish it from other mechanisms of deterioration in concrete, and how to assess the severity and extent of aar in concrete. Introduction alkaliaggregate reaction aar problem is common in many structures such as bridges, roadways, airport runways, and nuclear power plants.

Alkaliaggregate reaction is the expansive reaction that takes place in pcc between alkali contained in the cement paste and elements within an aggregate. In most concretes, aggregates are more or less chemically inert. The reasons for this are that the aggregate commonly used originates from very high quality granitic rock. 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. The alkalisilica reaction was first recognized as a problem in north american in 1940, in. N 257 evaluation of the potential alkalireactivity of concrete aggregates. Concrete nuclear structures have been identified as suffering from alkali aggregate reaction aar in both canada and the united states. 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. There are three types of alkaliaggregate reactions, namely the alkalisilica, alkalisilicate and akalicarbonate reactions. They wrote a regular column for cc for many years, collected into the book, the concrete intrigue, available through the world of concrete bookstore.

Alkaliaggregate reaction portland cement association. It is a common belief that it does not occur due to the exceptional quality of finlands granitic rock. Sensitivity and uncertainty analysis of aar affected. Diagnosis and control of alkaliaggregate reactions in. Asr involves reactions between alkali pore solution in the concrete and certain forms of alkalireactive silica. Prognosis, and mitigation of alkalisilica reaction asr in transportation structures fournier et al. Mappattern cracking resulting from an alkaliaggregate reaction.

Blight, mark g alexander since aar was first identified in 1940, it has been a subject dominated by studies of the mineralogy of aarsusceptible aggregates, the chemistry of the aar and related reactions and laboratory tests. Rilem recommendations for the prevention of damage by alkaliaggregate reactions in new concrete structures stateoftheart report of the rilem technical committee 219acs. Alkaliaggregate reaction and structural damage to concrete engineering assessment, repair and management. The alkalisilica 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 noncrystalline silica found in many common aggregates, given sufficient moisture. Concrete technology diagnosis and control of alkali. Although much research effort has been directed toward understanding its effect on reinforced concrete structures, unresolved issues still remain. Material, structural and modelling aspects of alkali. Asr is a slow chemical process in which alkalis, usually predominantly from the cement, react with certain reactive types of silica e. Abstract alkali aggregate reaction aar occurs when the alkali in concrete reacts with. Canadian experts on the diagnosis and treatment of concrete structures affected by alkaliaggregate reaction aar have written this guide.

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. Alkalicarbonate reaction in concrete was not documented until 1957. Alkaliaggregate reactions aar occur in concrete as a result of chemical reactions between the. Asr is one type of alkaliaggregate reaction that can degrade concrete structures. The alkaliaggregate reaction aar in concrete is a group of chemical reactions that involves the reaction of certain minerals present in the aggregates with alkali and hydroxyl ions in the interstitial solution of cement paste in concrete. The vector suite of nonlinear finite element programs, developed at the university of toronto for the analysis of reinforced concrete structures, can be developed into such a tool. Progress in the evaluation of alkaliaggregate reaction in. A 247 alkaliaggregate reaction assessment in kansas clowers, k. Rilem recommendations for the prevention of damage by.

Single and multihazard capacity functions for concrete dams. Analysis of concrete structures deteriorated by alkali. Testing of australian concrete mixtures for alkalisilica reaction potential and calibration with field performance of structures carse. Premature failure of concrete structures economic costs.

Significant research has been performed worldwide on alkaliaggregate reaction aar since its first deleterious effects on concrete structures were identified 75 years ago. I briefly appraise the problems and trends in aar research in the pacific northwest region. 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. 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. On the basis of systematic study since these failures now it has been established beyond doubt that certain type of reactive aggregates are responsible for promoting alkali. Diagnosis and control of alkaliaggregate reactions in concrete. Although several prediction models have been developed to assess the chemical reaction, a thorough and comprehensive. Founded in 1904 and headquartered in farmington hills, michigan, usa, the american concrete institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensusbased standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design. Choosing a backup generator plus 3 legal house connection options transfer switch and more duration. Modelling of the effects of alkaliaggregate reaction in. This research aims to analyze the alkaliaggregate reaction with the case study of a waterfront structure pier, a reinforced concrete structure located in a marine environment in brazil. Microp ores in concrete are highly basic with ph value generally greater than 12. Although acr is much less common, this report also briefly. In most concrete, aggregates are more or less chemically inert.

Modelling of the effects of alkaliaggregate reaction in reinforced concrete structures article in computers and concrete 125 november 20 with 101 reads how we measure reads. 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. The cause of this type of reaction can be related to sand and aggregates, such as opal, chert, flint, and volcanic ash that have a high concentration of high silica. The lower the watercement ratio, the less permeable the concrete. The walls were tested under lateral displacement excursions while simultaneously subjected to axial load simulating seismic loads. However, some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. Alkali aggregate reaction topic american concrete institute. In 1992 a first edition entitled the alkalisilica reaction in concrete, edited. 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. Performance of testing methods and a producers point. According to the csa a86400, conventional methods become invalid for the structural assessment of aaraffected. This paper deals with application of a nonlinear continuum model for reinforced concrete affected by alkaliaggregate reaction aar to analysis of some nuclear structures. As such, there is a need for proper analysis tools to investigate the behaviour of an aaraffected structure, and assist in identifying possible rehabilitation actions.

Effects of alkaliaggregate reaction on concrete and. Engineering assessment, repair and management geoffrey e. Alkaliaggregate reaction and structural damage to concrete. It was a common belief that finland does not have asr.