où n est le degré d ' hydratation du sulfate de calcium. Le PG est produit en grande quantité selon le procédé de fabrication soit sous forme de dihydrate (CaSO

For anhydrite dissolution, r = 2 and k e ~ (0.39–3.9) × 10 –6 mM/(cm 2 /s) (Serafeimidis and Anagnostou, 2013). The dissolution rate of rocks that consist exclusively of gypsum and anhydrite (i.e., gypso anhydrites) have not been studied. The most frequent results are from studies of the dissolution rates for mixed suspensions of varying ...

Anhydrite carbonation progresses at a much slower rate than the carbonation of gypsum. The different carbonation kinetics of these two calcium sulfate phases can be explain as arising from (1) the slower dissolution kinetics of anhydrite compared to gypsum and (2) the much higher volume change and, thus, microporosity generated in gypsum ...

This means that a typical anhydrite screed dries in about 49 days – compared to around 21 days for Ordinary Portland Cement. The speed of drying can be improved by a) increasing the ventilation in the room, b) application of external heat e.g. space heater combined with the use of industrial dehumidifiers in order to remove water vapour, and ...

Re : Calculs en Analyse Thermogravimétrique (ATG) On va prendre un exemple numérique. Je vais utiliser deux indices : l'indice 1 se rapporte au produit initial hydraté, et l'indice 2 au produit anhydre. Imagine que tu partes de m1 g de produit hydraté, et que tu constates une perte de 40% par calcination. Il te restera une masse de produit ...

Hydrogen sulfide (H 2 S) is toxic and corrosive and lowers gas and oil value. Many studies have demonstrated that thermochemical sulfate reduction (TSR) is one of the most important mechanisms responsible for the substantial quantities of H 2 S observed in many petroleum reservoirs deeply buried (Nöth, 1997; Machel 2001; Cross et al., …

A possible working mechanism for SCS on cement hydration reaction and its products can be proposed, as shown in Figure 7.14.When SCS was added to the cement paste, it could strongly adhere to the cement surface because of the interactions of the multiple functional groups of SCS (–COO −, –CH 2 SO 3 −, –OH, –NH 2, and –NHSO 3 −) and cement …

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly …

Anhydrite, an important rock-forming mineral, anhydrous calcium sulfate (CaSO4). It differs chemically from gypsum (to which it alters in humid …

anhydrite until the all of the anhydrite is dissolved. Van't Hoff et al. (1903) were the first ones to investigate the conditions under which anhydrite and gypsum occur in salt deposits. Since then, the system CaSO 4–H 2O (with or without other salts) has been examined by several authors both experimentally and theoretically, based on the ...

Investigation experimentale de l'hydratation de ce materiau anhydre (CaSO::(4)), pouvant se transformer en agregats de gypse (CaSO::(4), 2H::(2)O), pour donner un beton a resistance mecanique elevee ; mise au point d'un accelerateur de prise original, mettant en jeu simultanement les ions nitrates et sulfates

8.2. Hydration of C 3 A. As C 3A is the most reactive phase in cement, its role in (very) early hydration is important and concerns both mechanical properties as well as rheological performances. In the absence of sulfates, C3 A reacts quickly with water and leads to a rapid and unintended setting called "flash set.".

A paper entitled "the gypsum-anhydrite paradox revisited" appeared in year 2014 (Ossorio et al., 2014). In this work kinetic experiments and arguments are discussed for finding primary anhydrite ...

During the hydration process, crystallization of hydrate sulfate exerts influence on hydration of sulfate calcium instead of the z/r ratio of excitation agent. Hydration of anhydrite in fact ...

The Diels–Alder cycloaddition of furan and maleic anhydride has been investigated by several groups. 21–25 The reactions were usually run in diethyl ether, 21,22,26,27 acetonitrile, 23,24 or tetrahydrofuran 28 with yields of only 35% after 24 h of reaction at room temperature. 26 To control the temperature of solvent free Diels–Alder …

The key temperature during the transformation of anhydrite into gypsum is 42 ° C, which is characteristic for a depth of approx. 900-1200 m (Mossop and Shearman 1973). However, this depth is not a factor in maintaining such a temperature, and the occurrence of anhydrite on the earth's surface, despite the temperature drop, still occurs ...

PDF | On Apr 1, 2016, Boushaba Abdellah published Exposé 4 Cycle des roches sédimentaires (S2_STU_SVI_M10) | Find, read and cite all the research you need on ResearchGate

Le système n'évolue quasiment plus après 1 an d'hydratation (la variation du degré d'hydratation déterminé par la mesure d'eau liée est de 0,5 % entre 1 an et 2 ans).

This study focuses on the use of anhydrite ( SC ) as calcium sulfate source. The influence of CAC to CS ratio on the hydration at water to binder ratio (w/b) 0.4 and 0.7 has been investigated. The ...

Moreover, a higher anhydrite content mitigates the drying shrinkage and hinders the strength development. Finally, considering the properties of both the fresh and hardened binder, the ternary blends with 5% anhydrite and OPC/CSA ratios ranging from 3/7 to 2/8 were identified as most suitable for applications that require a high early …

Anhydrite (CaSO 4) and gypsum (CaSO 4 ·2H 2 O) are the two most abundant minerals of ancient marine evaporite deposits and are also common in non-marine evaporite deposits. Sedimentary gypsum forms by direct precipitation out of evaporating seawater under arid climatic conditions in hydrologically restricted marine and marginal …

The gypsum contained some anhydrite (3.3%) and the anhydrite some SiO 2 (1.1%). To determine the amount of alkali sulphates in the OPC and in the CSA clinker (K 2 SO 4 and Na 2 SO 4 in Table 1 ), 5 g of cement or clinker were stirred in 50 ml of deionised water for 5 min. Solution was then filtered and Na and K concentrations in solution were ...

This paper reported a successful preparation of CaCO 3 /anhydrite composites of anhydrite coated with nanosized CaCO 3 by chemical precipitation route using the Ca(OH) 2 –H 2 O–CO 2 reaction system. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron …

The hydration of calcium sulphate hemihydrate (CaSO 4 ·0.5H 2 O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO 4 ·2H 2 O) has been the subject of several investigations over a long period and a vast amount of data is widely distributed throughout in the literature. In this review article an overall picture of the …

Abstract. Mineral transformations of the gypsum–anhydrite system under microwave heating have been studied using in situ dielectric thermal analysis (MW-DETA) and Raman spectroscopy simultaneously. The dielectric properties of samples that were measured under microwave heating provided thorough information about the dynamics …

Vol. 12, No. 6 739 CALCINATION, TEMPERATURE, ANHYDRITE, PROPERTIES, DISSOLUTION KINETICS cuisson conduit ~ un frittage des grains, mais, vers 800°C, il se produit une fragilisation des cristaux par cr%ation de fissu- res, ce qui provoque une discontinuit# dans la courbe finesse- temp#rature. ... Les mesures de cha- …

The Upper Jurassic Arab Formation in central and western offshore Abu Dhabi (study area) contains prolific hydrocarbon-bearing zones, designated as the Arab A to D reservoirs (Figures 1 and 2).The reservoir zones consist of carbonates which are separated by anhydrite layers with the Hith Anhydrite Formation forming the uppermost regional …

105 mixture of polycrystalline anhydrite and gypsum produc ed 3 % more gypsum after 83 days (Hardie, 1967). Evolution of strength, stress -strain behaviour, permeability, and the role of grain size and fabric without any hydration or dehydration reaction in gypsum and anhydrite has been studied by Bell (1994), and De Paola et al. (2009).

Request PDF | Influence des ions monohydrogénophosphates et fluorophosphates sur les propriétés des phosphogypses et la réactivité des phosphoplâtres. | Le phosphogypse est un sous-produit ...