Emma Qingnan Zhang - Senior Development Scientist - Delta

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Minor amounts of secondary ettringite are often encountered in air voids of hardened concretes, regardless of the type of cement used. In concrete chemistry ettringite is a hexacalcium aluminate trisulfate hydrate, of general formula: (CaO) 6 (Al 2 O 3)(SO 3) 3 ·32H 2 O. or (CaO) 3 (Al 2 O 3)(CaSO 4) 3 ·32H 2 O. Ettringite is formed in hydrated Portland cement system as a result of the reaction of calcium aluminate with calcium sulfate, both present in Portland cement. 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 crystals in hardened concrete, which also occur without heat treatment, is the primary cause Ettringite is normally one of the earliest phases formed during cement hydration. However, when the concrete temperature is higher than approximately 65 °C (150 °F), ettringite is unstable and the formation of the primary ettringite is halted. The constituents of ettringite are dispersed as monosulfate and calcium silicate hydrates.

in Figure 17 a large number of needle-like crystals of ettringite in VS0LF15 can be seen. ASR-problematik i. Sverige och arbete på. CBI Betonginstitutet.

What is meant by ettringite in concrete?

THESIS IN MICRO STRUCTURE OF CONCRETE - Dissertations.se

Ettringite causes concrete decaying only in case Understanding the mechanisms by which concrete structures can be adversely of gypsum (calcium sulfate) and calcium mono-sulfoaluminate (ettringite). Ettringite is formed in hydrated Portland cement system as a result of the reaction of calcium aluminate with calcium sulfate, Gypsum and other sulfate compounds react with calcium aluminate in the cement to form ettringite within the first few hours after mixing with water. Most of the sulfate in the cement is normally consumed to form ettringite at early ages. The formation of ettringite in the fresh, plastic concrete is the mechanism that controls stiffening.

Gilles Plusquellec - Scientific Researcher - RISE Research

Two different types of DEF are examined depending on the sulfate source: DEF caused by external sulfate attack (EM) or internal sulfate attack (ISA).

Ettringite is a primary constituent of hydration of Portland cement concrete. Its formation plays an important role in the control of setting. Minor amounts of secondary ettringite are often encountered in air voids of hardened concretes, regardless of the type of cement used. Cracks form either in the early (plastic stage) or at a later stage (fully hardened stage) in the life of the concrete .
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Contrary to normal carbonation, bi-carbonation results in an increase in porosity making the concrete soft and friable. Purpose and goalThis project intends to solve the bottleneck problem in the new technology for wastewater treatment by experimentally investigate the feasibilities for utilizing its by-product ettringite in cementitious concrete as a value-adding mineral addition.

2020-1-14 · Hobbs, D.W.: Expansion and cracking in concrete attributed to delayed ettriugite formation. In: Erlin, B. (ed.) Program on Ettringite-The Sometimes Host of Destruction, AC1 SP-177, 1999, pp.
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DEF is a gradual reformation of ettringite (3CaO・ Al 2 O 3・3CaSO 4・32H 2 O, Fig. 1), following their original formation in concrete and subsequent decomposition in high temperatures. Ettringite is a normal product of early Ettringite Group.

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‪Nicola Cefis‬ - ‪Google Scholar‬

If both ettringite formation and concrete deterioration are simultaneously reduced, then the case for ettringite induced expansion/cracking is strengthened. Our experiments used four commercial inhibitors – two phosphonates, a polyacrylic acid, 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 … DEF is believed to be a result of improper heat curing of the concrete where the normal ettringite formation is suppressed.

Emma Qingnan Zhang - Senior Development Scientist - Delta

The AFt phase ettringite forms rapidly in cements containing natural pozzolanas 197 Chemical degradation of concrete. J. 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. Ettringite is a primary constituent of hydration of Portland cement concrete. Its formation plays an important role in the control of setting. Minor amounts of secondary ettringite are often encountered in air voids of hardened concretes, regardless of the type of cement used. effects since the concrete in a fresh state is highly deformable.

Reactive Powder Concrete – SESBE. Seminarium Cement blandat med finmaterial producerar murbruk för murverk, eller med sand och grus , producerar betong. Similalry, innehållet i ettringite ökar i ITZ. Gypsum and other sulfate compounds react with calcium aluminate in the cement to form ettringite within the first few hours after mixing with water. Most of the sulfate in the cement is normally consumed to form ettringite at early ages. The formation of ettringite in the fresh, plastic concrete is the mechanism that controls stiffening.