Authors:Nabila Guindy, S. El Enien, F. El Hosiny, and S. El Gamal
The hydration of two calcium hydroxide— silica fume mixtures was studied at 25°C, these are Mix I and Mix II with molar lime/silica
ratios of 1 and 1.7, respectively. The free lime, free silica and chemically combined water contents were determined at various
time of hydration from which the molar CaO/SiO2 ratios of the formed calcium silicate hydrate, C−S−H, were calculated. The results indicated that hydration takes place in
six steps where C−S−H (I) is formed at early stages of hydration, for Mix I, While for Mix II formation of C−S−H (I) and C−S−H
(II) were detected by X-ray diffraction analysis and differential thermal analysis.
Authors:R. Lawrence, T. Mays, P. Walker, and D. D’Ayala
A high speed method of thermal
analysis was developed to allow the carbonation profile of lime mortars to
be followed within a convenient time-frame. The loss in mass on heating, up
to 700C, of lime/sand mixtures of different proportions was related to
the known quantity of lime in each mixture. It was shown that a heating rate
of 50C min–1 produced data which had
a very high correlation with known quantities of Ca(OH)2.
Thismethod can be used to measure the extent of carbonation at varying depths
through a limemortar. This can be repeated at intervals to give an insight
into the shape and extent of the carbonation front as it develops over time.
A thermogravimetric method has been developed and is suggested for both the qualitative and quantitative phase analyses of
high-calcium lime and calcium speciation as well. Two complementary TG measurements are proved to be satisfactory for the
determination of moisture, calcium oxide, calcium hydroxide and calcium carbonate contents as well as total mineral impurities
in high-calcium limes: quicklime, hydrated lime and limestone.
The effects of the presence of a Pt catalyst on the limestone/lime sulphation process were investigated by thermal analysis methods to provide a better understanding of the factors limiting gas desulphurization when Ca-based sorbents are used. It was found that for the Pt-catalysed sulphation of precalcined limestone the weight increase is above 100% higher under isothermal and dynamic conditions (up to 830°C). These results are direct evidence that Pt catalyses the CaO-SO2-O2 reaction. It can be presumed that the process proceeds through a gaseous intermediate, SO3, a highly reactive gas, which explains the increased rate of sulphation. SO3 then reacts with CaO to form CaSO4 directly, in contrast with the non-catalysed oxidation of SO2 to SO3, where CaSO3 formation is the most probable early stage of sulphation. The proposed mechanisms were supported by the phase identification of the products.
Fly ash is the ash precipitated from the exhaust fumes of coal-fired power stations. It consists mainly of active silica and
alumina, with large amounts of glass. The aim of this work was to study the pozzolanic activity of fly ash with lime by means
of DTA as a function of the lime content and the curing time. The curves revealed that the rate of hydration, as indicated
by the residual lime and hydrated compounds, increases with increasing lime content and curing time. It is concluded that
fly ash can be used as a blending material in pozzolanic cement.
The popular areca nuts were sampled and their stuffed white and red lime were collected simultaneously from four marketplaces in Taiwan in different growing seasons. Samples of areca nut were treated via homogenizer prior to freeze drying, about 100–150 mg each of the areca nut and lime were packed into PE bag. Samples were irradiated with neutron flux about 1012 n·cm–2·s–1. A total of 17, 18, and 13 elements was analyzed with INAA for white lime, red lime, and areca nut, respectively. The results indicated that Ca have the highest concentration in both limes. Most elements in collected samples have wide range of concentrations among different seasons and marketplaces. It is suggested that the elemental concentration of areca nut and limes exists in divergence originated from various farms in Taiwan. In addition, four elements of Ca, Fe, Mg, and Sc are probably overtaken by persons having chewing habit of areca nut and their effects on oral cancer are discussed.
Authors:Zdenko Lončarić, Brigita Popović, Krunoslav Karalić, Domagoj Rastija, and Meri Engler
Bowszys T. — Ruszkowski K. — Bobrzecka D. — Wierzbowska J.: 2005. The effects of liming and complete fertilizers application on soil pH and content of some heavy metals in soil — Journal of Elementology vol. 10
The kinetics of the pozzolanic reactions of illite clay from the ‘Mirkovo’ deposit with lime is studied using X-ray, DTA/TG,
optical and electron microscopy methods. In parallel, the compressive strength properties of the specimens, stored under appropriate
conditions for up to 6 months, are measured. Illite reacts almost completely with lime for about 3 to 4 months. The reaction
of kaolinite takes place slowly and only about 2/3 of its quantity transform for the 6 months storage period.
The hardened amorphous hydrosilicates and hydroaluminate are formed through the pozzolanic reactions and contribute to the
mechanical properties of the stabilized clay specimens. The maximal compressive strength obtained at the experiments reaches
about 5-6 MPa. At the end of the storage period, the formation of fibrous or prismatic crystallites is observed on the surface
of the particles.