Determination of consistency limits of clay by means of extrusion tests

The liquid limit of clay is commonly determined through the Casagrande test or the fall-cone test, while the plastic limit is determined through the hand rolling method. The greatest issue with some of these techniques is their low repeatability and operator dependency. In order to minimize those issues, an indirect-extrusion based technique was evaluated as an alternative method to determine both consistency limits. The experimental work was carried out on mixtures of kaolin and bentonite to cover a wide range of plasticity. The results suggested that there is a specific extrusion pressure linked to each consistency limit and that the results are repeatable. The liquid limit obtained through the extrusion method closely matches the results of the fall-cone test. Similarly, the plastic limit out of extrusion closely matches the results of the hand rolling method

Hydraulic conductivity and swelling pressure of GCLs using polymer treated clays to high concentration CaCl(2) solutions

A Geosynthetic Clay Liner (GCL) is a frequently used h ydraulic barrier system designed to impede the flow of contaminated leachate into the environment. The main objective of this barrier system is to maintain a low hydraulic conductivity that is determined by the bentonite fraction. In this study, calcium bentonite, natural sodium bentonites, and sodium activated bentonite were treated with the HYPER clay technique. This involves the adsorption of an anionic polymer, Sodium CarboxyMethylCellulose (Na-CMC) onto the surface of the clay material. The purpose of this research was to show the beneficial effect of the HYPER clay treatment on the swelling and hydraulic performance, while the bentonite is permeated with high concentration CaCl2 solutions. The test results showed that swelling and hydraulic performance increased with Na-CMC treatment, regardless of the type of bentonite that was used. Additionally, a powdered Na CMC configuration provided higher swelling and hydraulic performance compared to a granular configuration

Asociación Nacional Científica de Estudiantes de Odontología del Perú – ANACEOP.

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La R.S.B.A.P., W. Humboldt y José María Murga. Una aproximación de la psicología a la historiografía política

El encuentro del ilustrado vasco Murga con Humboldt a principios del siglo XIX dio lugar a una relación epistolar, breve pero interesante, que sirve de motivo al autor del artículo para hacer una comparación entre ambas personalidades y ensayar una tipología psicológica aplicada a las ideas políticasThe meeting of the Basque Murga with Humboldt at the beginning of the XIXth century originated an epistolary relationship, short but interesting, which is used by the author of the article to compare both personalities and try a psychological typology applied to the political idea

Preliminary test on modified clays for seawater resistant drilling fluids

The quality of a drilling fluid declines in salt water conditions. An engineered clay (HYPER clay) was developed for geosynthetic clay liners with enhanced resistance to aggressive conditions. This study investigates the potential of this superior clay for drilling fluids applied in salt water conditions. A sodium bentonite was treated with a carboxymethyl cellulose (CMC) polymer following the HYPER clay process method. Preliminary tests were performed to investigate suitability of HYPER clay for seawater resistant drilling fluids. Fluid performance was characterized by its thixotropic behavior, rheological properties (gel strength, yield point and viscosity), swell and bleeding behavior. Drilling fluid performance was analyzed at various polymer dosages and electrolyte concentrations. Polymer treatment improved the gel strength and swelling ability of the fluid, especially in electrolyte solutions. Moreover, filter press tests (API 13B-1, 76% seawater) showed that filtrate loss decreased due to polymer treatment

Premiminary tests on modified clays for electrolyte contaminated drilling fluids

The quality of a bentonite suspension declines in aggressive systems like brackish or saline pore water. An engineered clay (HYPER clay) was developed for sealing materials with enhanced resistance to aggressive conditions. The modified clay is produced by treating a sodium activated bentonite with a cellulose polymer following the HYPER clay process method. This study investigates the suitability of the modified clay for electrolyte contaminated drilling fluids. Drilling fluids become contaminated with saline pore water, e.g. pick up an electrolyte contamination, while drilling a formation at for example an estuary or near the coast. Preliminary laboratory tests were performed to study drilling fluid resistance to electrolytes. Therefore the drilling fluids were contaminated with sea water. Subsequently drilling fluid functionality was characterized by its filtration performance, thixotropic behavior, rheology (gel strength, yield point and viscosity) and bleeding behavior. Drilling fluid performance was analyzed at various electrolyte concentrations (7.6, 14 and 28 volume percentage sea water by total volume). Filter press tests (API, 13B-I) showed that the filtration performance improved significantly due to polymer treatment. Moreover, results showed that the rheology properties can be controlled using Xanthan Gum as an additiv

Wet and dry effect on the hydraulic conductivity of polymer treated GCL prototype

Geosynthetic clay liners (GCLs) are widely used to isolate pollutants because of their low hydraulic conductivity to water. However, the performance of clay barriers may be impaired by prolonged exposure to electrolytic liquids which may lead to the compression of the diffuse double layer. The consequences are the increase of permeability and the loss of self-healing capacity. Moreover, the efficiency of the liners can further deteriorate by repeated wet and dry cycles, which may lead to desiccation of the bentonite and associated cracking. Modified bentonites have been introduced to improve the resistance of clay barriers to aggressive solutions. This study deals with a polymer-amended clay, HYPER clay. HYPER clay is treated with an anionic polymer and dehydrated and it shows enhanced performance in presence of electrolyte solutions. The effect of wet and dry cycles on the hydraulic conductivity to seawater of needle-punched GCLs prototypes of treated and untreated bentonite was investigated. The prototype samples containing HYPER clay 8% showed lower permeability compared to those containing untreated bentonite. However, the temperature suggested from the standard used in this study is extremely high and it does not represent the temperature in the field