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An ettringite formation in hardened concrete does not in every case lead to a direct damage of the concrete structure. At present, there is still controversy whether different types of ettringite exist; whether the damage mechanism can be initiated by coarse- or fine-crystalline ettringite; whether the formation of large ettringite Water is a critical element in the formation of ettringite. The purpose of extending mellowing time before compaction in soils is to force ettringite formation prior to compaction of pavement layers. To achieve this, additional water is normally required during mellowing and must be added to the surface during curing. At ambient temperature curing, ettringite forms as a part of the “normal” hydration process of portland cement.

DEF is a result of high early temperatures (above 70 o C – 80 o C) in the concrete which prevents the normal formation of ettringite. L'ettringite peut provoquer un gonflement si elle se forme après la prise du ciment. C'est ce qu'on appelle l'ettringite secondaire. Elle est présente dans les ouvrages à base de ciment Portland qui subissent des traitements à des températures supérieures à 65 °C [12]. La formation de l'ettringite différée peut schématiquement se résumer comme suit : formation de gypse dit " tardif "qui résulte d'une substitution entre la portlandite Ca(OH)2 et les sulfates solubles ; puis réaction entre le gypse "tardif" et les aluminates de calcium du ciment. 2017-03-16 · The primary ettringite formation in the initial stage of the hydration is seen as a positive effect because it enables the setting regulation, a damaging role is often attributed to delayed ettringite formation in hardened concrete. Damaged concretes often show large amounts of ettringite in structure damages even if they we The formation of ettringite was observed only for the high pH solutions in the experiments, whereas its thermochemical possibility from the air-cooled BF slags was always expected by the calculation.

Work Unit No. (TRAIS) Download Citation | Kinetics of ettringite formation from calcium aluminoferrite hydration | Kinetics of ettringite formation at room temperature from hydration of the mixtures with mole ratio of termed "secondary ettringite forma-tion," but because that phrase has an other meaning to most petrographers, the more definitive term "delayed et tringite formation," or simply DEF, was coined. DEF is the development of ettringite within the cement paste system of concrete after the concrete has hardened. The result is expansion, The term “secondary ettringite formation” will be used to distinguish this reaction from DEF. To keep the risk for secondary ettringite formation at a reasonable level, the current water soluble sulfate limit in coarse recycled aggregates is established at 0.2% by EN 206 [ 29 ], with no specific mention of FRA. Characterization of High-Calcium Fly Ashes and Their Potential Influence on Ettringite Formation in Cementitious Systems.

The kinetics of ettringite formation and dilatation in a blended

PDF | Thaumasite has been synthetized with and without ettringite in the reaction medium. The compositions of solids have been analyzed over time by | Find, read and cite all the research you formation of ettringite in cement-based materials under certain conditions and when these conditions change formation of ettringite can be enabled. Some possible causes of the (re)crystallization and/or new formation of ettringite are: Ostwald ripening, variations in pH, / SO Al O. 3 2 3. Page 2 Ettringite formation is considered to be the cause of most of the expansion and disruption of concrete structures involved in the sulfate attack (1).

Study of hydration processes of Portland cements blended with

(2001) milled their powders for a much longer time. A comparison of the {110}α X-ray diffraction peaks An even distribution of globular pearlite is created in the material that helps with cold-forming. Recrystallization. This intermediate annealing heats steel until its TY - JOUR.

DEF is a result of high early temperatures (above 70 o C – 80 o C) in the concrete which prevents the normal formation 2006-09-01 2021-04-07 2001-05-01 Delayed Ettringite Formation in Concrete Jochen Stark, Katrin Bollmann Bauhaus-University Weimar / Germany 1. Introduction The problem of durability of concrete with cement as binding material comes more and more to the fore with the increased use of concrete, with the changed production and utilization Request PDF | Ettringite formation | The rheology of cementitious system containing superplasticizer is the consequence of a physical process due to the electrostatic repulsion | Find, read and The kinetics of ettringite formation and dilatation in a blended cement with beta-hemihydrate and anhydrite as calcium sulfate. / Evju, C; Hansen, Staffan.. In: Cement and Concrete Research, Vol. 35, No. 12, 2005, p.
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of material properties based on data from existing structures affected by the alkali silica reaction or delayed ettringite formation; identification of critical features reactor vessel, which contains all the fuel elements forming a reactor core and decomposition of ettringite and the loss of water from part of the carboaluminate. testing, failure modes, interfacial transition zone, micro structure, ettringite, set In such a shotcrete material the tensile strength increases after the formation of av L BERNTSSON — 7.

19. Nov. 2019 Main Title: Relating Ettringite formation and rheological changes during the Initial cement hydration. Subtitle: a comparative study applying 14 Jun 2014 Ettringite is formed in hydrated Portland cement system as a result of the reaction of calcium aluminate with calcium sulfate, both present in Keywords: Sulfate Attack, DEF, Secondary Ettringite Formation, Coexisting Materials, C-S-H. 1 Introduction.
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Delayed ettringite formation (DEF) is expansion and cracking of concrete associated with the delayed formation of the mineral ettringite which is a normal product of early cement hydration. DEF is a result of high early temperatures (above 70 o C – 80 o C) in the concrete which prevents the normal formation of ettringite. L'ettringite peut provoquer un gonflement si elle se forme après la prise du ciment.

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The time taken for ettringite formation was determined without admixture and in the presence of admixtures. The results showed that superplasticiser, barium nitrate and stearic acid retard The use of calcium-based stabilizers such as calcium oxide (lime) in sulfate-bearing clay soils has historically led to structural distress because of the formation of a mineral called ettringite a The formation of ettringite was observed only for the high pH solutions in the experiments, whereas its thermochemical possibility from the air-cooled BF slags was always expected by the calculation. The kinetic analysis showed that the dissolution of alumina from the slag may control the whole reaction rate. Ettringite has a high mineral content of sulfate calcium sulfoaluminate. The former name for ettringite is "cement bacillus." It occurs naturally or is formed by sulfate attack on mortar and concrete. Bacillus is generally a bacteria that increases the compression strength of concrete through its biomass.