Influence of different calcined clays to the water transport performance of concretes

This study compares the pozzolanic activity of kaolinitic and illite clays after calcination as they are the most abundant types of clays worldwide. The impact of calcined clays on microstructure development is tested by determining the porosity of cement paste as well as by phase and optical analysis of cement matrix and interfacial transition zone of concrete. As water transportation with damaging carbonate or chloride ions is the main reason for reduced durability of reinforced concrete, the results are complemented with water absorption tests on blended concretes. At 28 days, system with calcined kaolinitic clay reveal a higher densification of its microstructure with lower water absorption rate compared to plain concrete and concrete with calcined illite clay, which is related to its higher pozzolanic reactivity. Nonetheless calcined illite clays can be considered as low-cost clinker replacement as a significant pozzolanic contribution is detectable and after 90 days, the water absorption behaviour is comparable with those of the other systems investigated.

Analysis of Effects of Foreign Clay and Local Clay Additives on Viscosity of Water Based Drilling Mud

This research compared the viscosity and other allied rheological properties of formulated water based drilling mud using local clay (that is modified with cheap and available additives) and foreign clay. These additives (such as xanthum gum, high viscosity polyanionic cellulose (PAC-R), modified natural polyanionic cellulose (PAC-L), potassium hydroxide (KOH), sodium carbonate (Na2CO3), and barite) are added to enhance/control the rheological properties (such as density, viscosity, yield point and gel strength) of the drilling mud. In this work, the viscosity and other allied rheological properties of water based mud were improved by the use of locally sourced clay from Awgu in Enugu State. The local clay was beneficiated/treated with hydrochloric acid (HCl) and characterized using x-ray fluorescence (XRF) spectrometer. The results of the characterization revealed that the local clay is more of silica which is typical of a kaolinitic clay. Local clay was examined as a possible replacement for foreign bentonite by comparing the rheological properties of water based mud (WBM) with bentonite and WBM with clay. Plastic viscosities (PV) of WBM with bentonite and WBM with clay were found to be 11.7 and 12.3 cP respectively. Other allied properties such as yield point, gel strength, pH and mud weight of WBM with bentonite and WBM with clay adequately compared closely. Laboratory analyses on the effects of three process variables (such as temperature, aging time and dosage of clay/bentonite) on the viscosity of the formulated muds were investigated. The laboratory results show that the readily available additives added to the local clay improved its viscosity and other allied rheological properties for effective drilling of oil and gas well when compared with foreign bentonite.

Thermal behaviour of ceramics obtained from the kaolinitic clays of Terra Alta, Catalonia, Spain

The thermal properties and evolution of mineralogy and colour of kaolinitic clay from the Terra Alta region were studied. The mineralogy of these materials consists mainly of kaolinite (13–27 mass%) and quartz (48–86 mass%). Minor illite, hematite, K-feldspar and calcite also occur. The linear expansion and absorption curves were used to predict the optimal firing temperature of the raw clays. During firing, from 1100 °C the water absorption decreases steeply, due to an increase in liquid phase, which penetrates into the pores and close the porosity. At this temperature, the firing shrinkage increases progressively. The fired clays are mainly composed of quartz, cristobalite and mullite, with minor hematite and rutile. Mullite starts to appear at 1050–1100 °C. SEM observations show that porosity decreases with the firing temperature. The colour properties were measured in the raw clays and in the fired bricks at different temperatures. The lightness, L*, is lower in the fired test pieces respect to the natural clays. This colour varies according to the hematite content, being from white to reddish in the fired samples.

A Mottled, Non-Lithified Paleosol in Brazil: Diagnosis by Morphological and Mineralogical Features

The identification of paleosols is difficult when no buried horizons or lithification occur. Here, we described the identification of a possible paleosol, its characterization, and which features supported its positive diagnosis. In a construction site, a vertical cut exposed an unusual red–yellow mottling with massive structure and channels (probably faunal), in contrast with the overlying homogeneous red Oxisol with fine granular structure. A similar but more deferrified section with white–yellow mottling also occurred nearby, and both were sampled as large clods. In thin sections, many oriented clay coatings occur along channel voids, suggesting illuviation, as well as dissolving Fe nodules and Mn coatings along planar and channel voids. X-ray diffraction showed a clay dominated by kaolinite, traces of illite, and absence of gibbsite, again contrasting with the gibsitic-kaolinitic clay of the Oxisol. We confirmed the diagnosis of a Paleoultisol due to the following incompatibilities with the overlying Oxisol: (1) massive, apedal structure, and higher bulk density; (2) clay coatings indicative of illuviation as key soil-forming process; (3) low clay contents in particle-size analysis due to cementation; (4) very low organic carbon consistent with long-term inhumation; and (5) kaolinitic–illitic clay. The unusual granular microstructure of the B horizon of the Oxisol is partly derived from disintegration and desilication of the Paleoultisol.

Fabricación de crisoles con caolinita de Combita - Boyacá para la caracterización de minerales de oro

La región boyacense cuenta con grandes riquezas minerales y una de ellas es la roca sedimentaria de arcilla caolinitica, con excelentes propiedades para la industria cerámica tradicional. Al realizar pruebas de caracterización a este material se encontró en el análisis propiedades plásticas, de alta refractariedad, bajo punto de fusión, resistencia a los choques térmicos y resistencia a la rotura. A partir de estos resultados se crearon crisoles resistentes a altas temperaturas, por diferentes tipos de fabricación, obteniéndose crisoles aptos para utilizarlos en ensayos de fusión a temperaturas de 1200°C. The Boyacá region has great mineral wealth and one of them is the sedimentary rock of kaolinitic clay, with excellent properties for the traditional ceramic industry. When performing characterization tests on this material, its plastic properties, high refractoriness, low melting point, resistance to thermal shocks and resistance to breakage were defined. These properties are due to its kaolinitic composition, aluminum silicate and the presence of magnesium in the clay. From these results, crucibles resistant to high temperatures were created by different types of manufacture, suitable for use in fusion tests at temperatures of 1200 ° C, and especially in fire tests for the characterization of gold ore.