Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates.
Alkali-silica reaction (ASR) is a chemical reaction between the alkalis in portland cement and certain types of silica minerals present in some aggregates. The reaction product is a hygroscopic gel, which absorbs moisture and swells.
The most common damage-causing interaction between cement paste and aggregate is 'alkalisilica reaction' (ASR), the name reflecting the essential interaction between the alkali-rich pore fluid of the concrete and aggregate containing the mineral silica (SiO2).
*Alkali in concrete = Alkali in cement + alkali from other sources(e.g. admixtures,PFA, GGBS, water, etc.) Calculation of equivalent sodium oxide content in the concrete; GS, Section 16 (9) The equivalent sodium oxide (Na. 2. ... B. Alkali-silica reaction (ASR)
Concrete Experts International has extensive, world-wide experience with alkali silica reactions (ASR) in concrete structures and with research regarding the nature and effects of ASR. Diagnosing ASR is an integrated part of our petrographic analysis of concrete.
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.
Alkali-Silica Reaction in concrete – numerical modelling: an engineering approach *Andrzej Winnicki1) and Szymon Seręga2) 1), 2) Faculty of Civil Engineering, Cracow University of Technology, ul. ... Alkali-silica reaction (ASR) in concrete is nowadays a recognized cause of the
"The Alkali-Silica Reaction in Concrete" by R. N. Swamy, published 1992 Design and Control of Concrete Mixtures, 16th edition, 2016, Portland Cement Association "Evaluation of Alkali Silica Reactivity (ASR) Mortar Bar Testing (ASTM C1260 and C1567) at 14 days and 28 days," Portland Cement Durability Subcommittee, PCA …
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.
The term alkali-silica reaction is somewhat misleading- the reaction itself is actually between the OH-ions in the pore solution and certain siliceous components of the aggregates. The alkalies, specifically sodium and potassium, do not actually attack the reactive silica.
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 …
Types of Reaction. There are two types of alkali-aggregate reaction: Alkali-Silica Reaction This is the most common form of alkaliaggregate reaction and results from the presence of certain siliceous aggregates in the concrete found in some granites, gneisses, volcanic rocks, greywackes, argillites, phyllites, hornfels, tuffs, and …
In the case of alkali-silica reaction, the reaction usually occurs much later, possibly years after the concrete was placed. Large aggregate particles (large, that is, compared with cement-sized pozzolan) generate a significant volume of gel which then takes up water and expands within the hardened, mature concrete.
Alkali-Silica Reaction in Concrete Rationale for the AASHTO PP65 Prescriptive Approach . October 2012. Notice. This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of ... Alkali-Silica Reaction. ...
Alkali-Silica Reaction (ASR), the reaction between alkalies in portland cement and certain siliceous rocks or minerals. Diagnosis: An expansive cracking condition with discoloration. Cause: A chemical reaction between the naturally occurring sodium and potassium in Portland cement and certain silicaceous minerals. This reaction causes …
Alkali-Silica Reactivity Test Services. Evaluation, Mitigation and Monitoring. CTLGroup is at the forefront of managing alkali-silica reaction in concrete structures. Alkali-silica reaction (ASR) is a physico-chemical reaction that can lead to premature deterioration and shortened service life.
Alkali Silica Reaction. Alkali-silica reaction (ASR) is the chemical reaction that occurs between alkali cations and hydroxyl ions in the pore solution of hydrated cement paste and certain reactive silica phases present in the aggregates used in concrete.
Jul 26, 2014· Alkali-Silica Reaction (ASR), the reaction between alkalies in portland cement and certain siliceous rocks or minerals Diagnosis: An expansive cracking condition with discoloration. Cause: A chemical reaction between the naturally occurring sodium and potassium in Portland cement and certain silicaceous minerals.
Alkali-silica reaction - overview Barrage damaged due to an alkali-silica reaction In an alkali-silica reaction (ASR) alkali-sensitive SiO 2 constituents in the aggregates react with the alkali and hydroxide ions (K +, Na + and OH - ) in the pore solution of the concrete to form an alkali silica gel with a tendency to absorb water.
Alkali-silica reactivity, better known as ASR, has openly been with us since the early1940s when it was discovered in California and publicized by T.E. Stanton. Over seven decades later, occurrences of this reaction may actually be increasing, despite our vast knowledge about ASR gained over these ...
The use of surplus waste glass in concrete has been avoided on the grounds that it is known to undergo harmful alkali-silica reaction (ASR). 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 ...
What is ASR? Alkali-silica reaction takes place between reactive siliceous minerals in certain aggregates and OH- ions in the cement paste. Alkalis (Na+ and K+) from the cement, mixing water, or environment increase the concentration of OH- ions in the concrete.
Alkali silica reaction is a heterogeneous chemical reaction which takes place in aggregate particles between the alkaline pore solution of the cement paste and silica in the aggregate particles. Hydroxyl ions penetrate the surface regions of the aggregate and break the silicon-oxygen bonds.
Factors Affecting ASR 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