Search results for "Gypsum"

Mechanisms and parameters controlling the tricalcium aluminate reactivity in the presence of gypsum.

2007

International audience; To understand the mechanisms and the parameters controlling the reactivity of tricalcium aluminate in the presence of gypsum at an early age, a study of the hydration of the “C3A–sulphate” system by isothermal microcalorimetry, conductimetry and a monitoring of the ionic concentrations of diluted system suspensions have been carried out with various gypsum quantities. The role of C3A source and its fineness were also studied. This work shows the fast initial formation of AFm phase followed by ettringite formation during the period when the sulphate is consumed. It has been highlighted that the time necessary to consume all the gypsum varies with the type of C3A and i…

Early C3A hydration in the presence of different kinds of calcium sulfate.

2009

International audience; Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A-CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A-gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to.higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. More…

Sulfuric Acid Caves of Italy: An Overview

2016

First study of gypsum karst in Sicily. The contribution of Olinto Marinelli and Mariano Gemmellaro

2006

Does the Structural Water within Gypsum Remain Crystalline at the Aqueous Interface?

2021

Numerical simulation of heat transfer problem for layered gypsum products exposed to fire

2018

Opportunistic Germination Behaviour of Gypsophila (Caryophyllaceae) in Two Priority Habitats from Semi-arid Mediterranean Steppes

2011

Gypsophila tomentosa and G. struthium are closely related species, characteristic of two European priority habitats, salt and gypsum inland steppes, respectively. Germination strategies of the two taxa were investigated in plants from two nearby populations, growing under the same climatic conditions but on different types of soil, and belonging to different plant communities. Their germination patterns were studied at five constant temperatures in darkness: 5oC, 10oC, 15oC, 20oC and 25oC, and the base temperature and the thermal time requirement were calculated. As the distribution area of both species is subjected to a Mediterranean continental climate with significant differences between…

Pedogenic carbonates and carbon pools in gypsiferous soils of a semiarid Mediterranean environment in south Italy

2013

Abstract Soil carbonates are key features in soils of arid and semiarid environment, playing an important role from pedogenetic, landscape history, paleoclimatic and environmental points of view. The objectives of this work were (i) to study pathways of pedogenic carbonate (PC) formation, (ii) to distinguish between lithogenic and pedogenic inorganic C by using the natural C isotope abundance, and (iii) to estimate the soil C pools in a gypsiferous semiarid Mediterranean environment (Sicily, Italy). Five soil pedons developed on calcareous and non-calcareous parent materials from Holocene (10,000 years BP) to Upper Tortonian (7.2–5.3 Ma BP) in age were surveyed. During field soil descriptio…

Accuracy of fit of implant-supported bars fabricated on definitive casts made by different dental stones

2018

Background The purpose of this study was to evaluate the accuracy of fitting of an implant supported screw-retained bar made on definitive casts produced by 4 different dental stone products. Material and Methods The dental stones tested were QuickRock (Protechno), FujiRock (GC), Jade Stone (Whip Mix) and Moldasynt (Heraeus). Three external hexagon implants were placed in a polyoxymethylene block. Definitive impressions were made using monophase high viscosity polyvinylsiloxane in combination with custom trays. Then, definitive models from the different types of dental stones were fabricated. Three castable cylinders with a machined non-enganging base were cast and connected with a very sma…

Shallow structures at the outer Calabrian accretionary wedge (NW Ionian Sea): new insights from recently migrated reflection data

2010

Terra Nova, 00, 000–000, 2010 Abstract Post-stack time migration of a set of seismic reflection profiles reveals details of the stratigraphic–structural setting of the outermost Calabrian accretionary wedge, in the NW sector of the Ionian Sea, with particular emphasis on the Messinian stratigraphy and the deformation style of the thin frontal portion of this wedge. A structural style and seismic facies analysis, calibrated by refraction data, images a general bipartition of the Messinian evaporite deposits: the `lower subunit', consisting mainly of salt, appears to have undergone ductile-flow deformation, and the `upper subunit', consisting mainly of gypsum and marls, appears to be characte…