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Etude de la réactivité de six variétés de fines de silice en solution aqueuse basique et au cours de l'hydratation des constituants des ciments Portland

Abstract : The alkali-reaction is a phenomenon which can bring the destruction of a work, and which occurs between the more or less reactive aggregates of a concrete and the basic interstitial solution. The aim of this work is to include/understand the chemical mechanisms which intervene in the dissolution of silica, and to find a formulation of concrete for the use of six varieties of silica fines; they are different by their command from crystallinity; of an amorphous silica to a quartz, their granulometry is lower than 50 [micro]mi (order of magnitude of the hair). The fust part relates to the study of the dissolution of silicas in a sodo-potassic solution 0,7N, with or without addition of 10% weight lime. In the liquid phase, silica is all the more dissolved since its amorphous character is large, the pessimum effect, as well as a reduction in pH are observOO. In the presence of lime, the silica concentration strongly decreases, whatever the type of silica In the solid phase, it is formed a gel all the more rich in silica which silica is soluble, moreover gel grows rich in the course of time in alkaline ions, particularly K+. In the presence of lime, this gel is of CSH type. The second part relates to the study of the behavior of these silicas during the hydration of the principal components of a Portland cement The hydration was followed by X-ray diffraction, thermic analyses, electronic microscopy and nuclear magnetic resonance of the [exponent 29]Si. The results obtained show that the hydration of C3S is accelerated by the presence of soluble silica. The hydration of doped C3A with 2 or 4% sodium led to the formation of hydrated gehlenite when silica is soluble, and C3AH6 when silica is little or not soluble. In the system C3S-C3A-gypsum-silica, the late formation of ettringite is observed and explained. The system more complex cement -silica is studied; consultings for the use of these fines are then given in conclusion.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2000_0189_LUCOT.pdf
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https://hal.univ-lorraine.fr/tel-01746516
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Submitted on : Thursday, March 29, 2018 - 10:39:28 AM
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Dominique Lucot. Etude de la réactivité de six variétés de fines de silice en solution aqueuse basique et au cours de l'hydratation des constituants des ciments Portland. Autre. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10189⟩. ⟨tel-01746516⟩

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