2 edition of investigation into delayed ettringite formation. found in the catalog.
investigation into delayed ettringite formation.
Sarah Elizabeth Turner
Dissertation submitted for the M.Sc. degree in Geomaterials.
|Contributions||Queen Mary and Westfield College.|
Then, a stoichiometric amount of water was added directly into the grinding jar and the grinding was continued for the next 30 min. As a result, the formation of a fluffy white powder containing ettringite and a remaining low amount of gypsum was observed (Figure Figure2 2, right). From the Rietveld refinement, 94% of ettringite and 6% of. Results from the petrography analyses of the expanded mortar specimens revealed delayed ettringite formation (DEF) without detecting alkali-silica reaction (ASR). The results also show that deleterious expansions caused by DEF prevails in exposure conditions with high potential leaching of alkali hydroxide to the storage solution.
Although many papers have been written on case studies of incidences of delayed ettringite formation (DEF), few demonstrate a careful study of the methods of analyses for the presence and concentration of the ettringite that has formed. In addition, possibly only one suggests a method to determine potential future development of destructive. Keywords: Delayed ettringite formation (DEF), Scanning electron microscopy (SEM), Fly ash, Metakaolin, Blast-furnace slag, Silica fume, Limestone filler. Abstract. The degradation of concrete structures caused by delayed ettringite formation (DEF) is a problem that affects many concrete structures worldwide . This pathology is due to the.
DURABILITY AND POTENTIAL OF DELAYED ETTRINGITE FORMATION IN MASS CONCRETE STRUCTURES By LUCY ACQUAYE A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL dissertation. Dr. Chini admitted me into this distinguished university and program where all my academic and professional goals were met and exceeded. He was the . Secondary Ettringite this is present in hardened, moist concrete. If concrete is exposed to water for a long period of time, the primary ettringite will dissolve and recrystallize in voids. Secondary Ettringite Formation (SEF) is non-destructive. Delayed Ettringite because Primary Ettringite is unstable above F, it won’t form if curing.
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Investigation of Delayed Ettringite Formation in Precast Members Conference Paper (PDF Available) December with Reads How we measure 'reads'. Heat Curing and Delayed Ettringite Formation - Volume - M.C. Lewis, Karen L. Scrivener, S. KelhamCited by: Massive secondary ettringite (delayed ettringite formation, DEF) Ettringite is a primary constituent of hydration of Portland cement concrete.
Its formation plays an important role in the control of setting. investigation into delayed ettringite formation. book Minor amounts of secondary ettringite are often encountered in air voids of hardened concretes, regardless of the type of cement used. Delayed ettringite formation (DEF) in concrete has been identified in recent as a significant cause of deterioration in some of the reinforced concrete infrastructure in Texas.
This report is part of a research project, TxDOT projectto investigate the possible long-term structural and durability related effects of DEF in such structures.
The. Effect of type of aggregate on delayed ettringite formation Authors: R. Yang, C. Lawrence, J. Sharp Source: Advances in Cement Research, Vol Cited by: structure with delayed ettringite formation. Arrows indicate microcracks that are filled with a clear, gel-like material (red), a void filled with ettringite (green), and the outer surface of the core (blue).
Figure 3. Backscatter electron micrograph at higher magnification showing microcracks (green arrows) from part of the area shown in Fig. into this formation of new phases, known as late ettringite formation, which takes place under normal ambient conditions in concretes which have not been heat-treated.
After carrying out extensive investigations different hypothesis were developed by many authors on how ettringite formation in hardened concrete and therefore a damage mechanism. delayed ettringite reaction CivilDigital > Civil Engineering Articles > Civil Engineering Articles for Mobile > Significance of Delayed Ettringite Formation and Damage Mechanisms > delayed ettringite reaction.
Reducing expansion due to Delayed Ettringite Formation (DEF) is becoming an important issue that must be taken into account, when producing heat-cured concrete. Mineral additives used as partial cement replacement should help in achieving the desired aspect. Based on an ongoing experimental program, this research emphasizes on the effect of Blast Furnace Slag (BFS) on.
In literature heat induced attack is called Secondary Ettringite Formation  or Delayed Ettringite Formation . Some  under the term Delayed Ettringite Formation covers both internal and external sulfate attack.
Sinc in the petrology term “secondary” implies only recrystallization  here will be use the term delayed. What is delayed ettringite formation (DEF). DEF is expansion and cracking of concrete associated with the delayed formation of the mineral ettringite (a hydrated calcium sulfoaluminate) which is a normal product of early cement hydration.
oDEF is a result of high early temperatures (above 70oC – 80 C) in the. Abstract. Delayed ettringite formation (DEF) is a rare problem of concrete, whose reaction mechanisms have been investigated by a large number of studies. In order to develop a performance test, the authors have conducted a feasibility study and an optimization study followed by this validation study.
A performance test was previously developed to. 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.
Delayed ettringite formation (DEF) can damage concrete that has experienced a temperature above about 70°C. Claims that slow release of sulfate from the clinker can have a similar effect in concrete not thus heated are unsupported.
Chemical and. Delayed ettnngite formation (DEF) is an endogenous reaction which can cause deterioration in concrete. At the present time, there is no selective and predictive test for DEF This paper describes the results of a study aimed at developing a test based on drying and wetting cycles.
Its gradual formation in the cooled, set concrete can lead to expansion and cracking in a process known as ’delayed ettringite formation’ (DEF). It can take up to 20 years for cracking to become Information Paper, which is mainly concerned with in-situ concrete, identifies circumstances in which DEF may cause problems.
8 pages. Chapter 1 – Introduction. Recently in Texas, there has been significant damage of field structures resulting from concrete durability problems. Alkali-silica reaction (ASR) and delayed ettringite formation (DEF), or combinations of the two, have been found to be the main causes of these problems.
Abstract Delayed ettringite formation (DEF) is a relatively rare but potentially severe form of internal sulphate attack of concrete. In the worst cases it has caused loss of serviceability of the affected concrete structure. A board-commissioned investigation into fraud-hit CG Power and Industrial Solutions has been delayed by several months due to a severe fund crunch, officials said.
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NDOU DZIVHULUWANI NORMAN. STUDENT NO: Mini-dissertation submitted in partial fulfilment of the degree of Magister Technologiae: Business Administration. DEPARTMENT OF BUSINESS. The presence of ettringite in the concrete sleeper suggests delayed ettringite formation since it’s likely to exist only either in fresh concrete, or at a very early age then ettringite quickly.Crack formation due to secondary ettringite formation.Moreover ettringite formation cam be advantageously used without any sulfate attack on concrete.
The purpose of this review is to present critical analysis of the relationship between ettringite formation and sulfate attack including some special cases of this attack such as those related to thaumasite formation or "delayed ettringite formation.