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properties of the mixture [ 3 ]. For a determination of the effect of additive on the course of hydration, various methods based on calorimetry proved to be useful for their fastness, simplicity of analysis and high informative value [ 5 ]. From the
Introduction The kinetics and mechanism of hydration in various cementitious systems can be investigated by use of calorimetry [ 1 – 5 ]. The heat evolution curve reflects the rate of reactions occurring in the hydrating system
Abstract
Water, magnesium acetate, magnesium chloride, acetic acid and hydrochloric acid were used as hydrating agents for an industrially obtained MgO sample. The influence of these different hydrating agents on the pH of the hydrating solution, degree of hydration to Mg(OH)2, and product surface area was studied as a function of the temperature of hydration. When compared to the hydration in water, all hydrating agents improved the degree of hydration between 5 and 50% at all temperatures. MgCl2 and a mixture of HCl and Mg(CH3COO)2 seemed to be the most effective hydrating agents below 60C, while at temperatures above 60C Mg(CH3COO)2 formed the largest percentage Mg(OH)2. Mg(CH3COO)2 was the hydrating agent that showed the strongest temperature dependence. The mechanism of the hydration reaction seems to be dependent of the availability of Mg2+ ions and the increased formation of Mg(OH)2 as temperature increases.
technique seeks the immobilization of hazardous wastes, using the properties of cement hydration [ 5 ]. The mechanism used for S/E and the evaluation of its effectiveness has been widely studied and discussed [ 6 , 7 ]. The cement hydration process
Quantitative study of hydration of C3S and C2S by thermal analysis
Evolution and composition of C–S–H gels formed
–70 wt% of alite (C 3 S) and 5–30 wt% of belite. The characterization of anhydrous constituents and the hydrated products together with the calculation of hydration degree of each component over time clearly constitute a solid experimental basis for
Introduction Clathrate hydrates are crystalline structures in which water molecules associated via hydrogen bonds form cavities of various shapes. Small hydrophobic molecules, mostly light hydrocarbons (C1–C8), acid gases (CO 2
this way one may obtain a new binder of improved and/or changed properties. It is the effect of action of active additives that influence physical and chemical processes and arising products of hydration. The main products of hydration of
Abstract
Modulated DSC has been applied to the study of methane, ethane and propane hydrates at different hydrate and ice concentrations. The reversing component of the TMDSC curves, makes it possible to characterize such hydrates. Methane and ethane hydrates show the melting-decomposition peak at a temperatures higher than the ice contained in the sample, while propane hydrate melts and decomposes at lower temperature than the ice present in the sample. The hydrate peaks tend to disappear if the hydrate is stored at atmospheric pressure. Guest size and cavity occupation fix the heat of dissociation and stability of the hydrates, as confirmed by parallel tests on tetrahydrofurane hydrates.
Abstract
Some new hydrazinium lanthanide sulphite hydrates of the formula N2H5Ln(SO3)2(H2O)2 where Ln=La, Pr, Nd and Sm and N2H5Ce(SO3)2 have been prepared and characterized by chemical analyses, magnetic studies and electronic and infrared spectroscopy. Thermal degradation of these complexes has been investigated by simultaneous TG-DTA techniques. These complexes decompose in air after dehydration to give the respective lanthanide sulphate as the final residue. However, cerium complex gives a mixture of cerium sulphate and ceric oxide as the end products. Cerium and neodymium complexes have also been subjected to thermal degradation in nitrogen atmosphere and the dehydration of neodymium complex was observed at a higher temperature than in air. The anhydrous neodymium and cerium complexes decompose in one step to give the respective sulphate in nitrogen atmosphere.
the perovskite layers weaker than Nd 3+ and have a substantial mobility that results in high ionic conductivity and ion-exchange activity of NaLnTiO 4 [ 12 , 13 ]. The protonated and hydrated Ruddlesden–Popper phases H x Na 1− x LaTiO 4 · y H 2 O
