Kaolin Sand Research Articles

Geochemical evolution of the Capim River kaolin, Northern Brazil

The Capim River kaolin, located in the eastern Brazilian Amazon, constitutes one of the most important kaolin deposits in the world. Known for its high whiteness, its noble application is in the paper industry. Studies were carried out on samples from the six facies of the deposit (sand kaolin, soft kaolin, lower transition facies, ferruginous crust, upper transition facies and flint kaolin) in order to trace its geochemical evolution. The kaolin developed at the expense of Cretaceous sandy–clayey sediments of the Ipixuna Formation. Intense lateritic processes characterized by ferruginization and deferruginization mechanisms led to the distinction of the different facies.

Mechanical behavior of compacted composite clays

Composite clay is a mixture of clay, as the main body, and aggregates, which are floating within the clayey matrix. The undrained behavior of composite clay in its natural or compacted state, e.g., core material of embankment dams, has great importance for geotechnical engineers. An extensive test program was conducted on kaolin–gravel and kaolin–sand mixtures to investigate various effects of aggregates on the mechanical behavior of the mixtures during strain-controlled monotonic and cyclic loadings. Monotonic test results reveal that increasing the aggregate content leads to a gradual increase in shear strength. Meanwhile, when the aggregate content is raised, the pore pressure increases for both monotonic and cyclic loading. It is also found that the presence of aggregates within a cohesive matrix leads to formation of a heterogeneous matrix in the clayey part of composite clays. This heterogeneity in turn causes pore pressure to be increased with an increase in the aggregate content during both monotonic and cyclic loading. In addition, test results show that aggregate size does not influence mechanical behavior appreciably. The results of this experimental research program are presented and discussed in this paper.Key words: composite clay, aggregate, shear strength, pore pressure, heterogeneous matrix, embankment dam.

Effect of sodium adsorption ratio and electrolyte concentrations on the saturated hydraulic conductivity of clay–sand mixtures

SummaryWe did flow experiments under saturated conditions on homoionic (Na+) kaolin–sand and illite–sand systems, containing 5, 10, and 15% clay, to validate a drainage model, and evaluate the effect of the different chemical composition of the percolating solutions on the hydraulic properties of the systems. Column drainage experiments, under a constant hydraulic head, were carried out using solutions with two sodium adsorption ratios (SAR 0 and ∞) and three electrolyte concentrations (10−2, 10−3, and 10−4 m). We calculated the saturated hydraulic conductivity, Ksat, of the systems using Darcy's law when these showed linear relationships between effluent volume and time. The drainage model was applied to characterize the flow of non‐steady‐state drainage of solutions through the porous systems. This model describes and characterizes quantitatively the drainage of solutions from soil columns that vary in intrinsic permeability, k, because of structural modifications that occur within the solid matrix of the systems. For both the systems investigated we always observed a decrease in the flow rate as electrolyte concentration decreased, or clay percentage increased. Under the same conditions the flow was faster for the kaolin system than the illite system, even though kaolin dispersed more than illite. Non‐linear relations were also observed at the smallest electrolyte concentration (10−4 m). In all cases, the equations proposed correlated well with the experimental data, confirming the soundness of the model. The flow rates observed in the experiments at SAR ∞ were unexpectedly greater than those observed at SAR 0, for the two systems, when leaching with solutions at 10−3 and 10−4 m. The values of pH and electrical conductivity of the eluates support the idea that the clay hydrolysis occurred during the saturation and, to a lesser extent, during the leaching phase of the flow.

Performance of TDR calibration models as affected by soil texture

Time domain reflectometry (TDR) is widely used to measure the soil water contents. The effect of soil composition on TDR calibration has to be quantified to diminish the need in re-calibration of TDR. Our objectives were: (a) to evaluate the ability of published models to fit TDR calibration data for the soils of different texture, and (b) to explore using a piecewise-constant distribution to approximate the continuous dependence of the dielectric constant on the position of water within soil pore space. We calibrated TDR in sand–kaolin mixtures, dernovo-podzolic soil, gray forest soil, and leached chernozem. Distinct changes in slopes of the calibration curves were observed for the fine-textured samples in the range of volumetric water contents from 0.13 to 0.27. The ratio of the lack-of-fit mean square error and the mean square pure error was used as a statistic for the error comparison to conclude whether a model provided a satisfactory fit of data. Published models that did not have parameters to adjust fitted well data for coarse-textured mixtures and soils but failed to fit data for fine textured mixtures and soils. The piecewise-constant distribution model with three adjustable parameters fitted well all data. Parameters of this model were related to clay content in the samples.

Experimental study of a heterogeneous plasma flow in a reactor with a multijet mixing chamber

Results of opticospectroscopic measurements of a plasma flow containing particles of different materials (Al2O33, SiO2, kaolin, phosphorite, and chamotte sand) at the outlet of the mixing chamber of a plasma reactor are reported.

The effect of china clay on the fish of St Austell and Mevagissey Bays

INTRODUCTIONDuring the production of china clay, a waste of fine quartz, sand kaolin and mica flakes in suspension is produced. Until recently, only a small proportion of this fine material was retained and settled in lagoons and consequently most of the effluent was discharged. Waste produced in the St Austell area was carried by the Par and White Rivers into Mevagissey Bay (see Fig. 1). In 1968 the china clay industry considered a proposal to combine all its wastes arising in the area and to discharge them into the sea via the White River or if necessary further out to sea by a pipeline. The precise location of the pipeline was not denned at that time but, irrespective of position, deterioration of conditions in St Austell and Mevagissey Bays seemed inevitable.