Brick clay analysis

In the drying of materials such as wood or clay, the moisture concentration at the end of the constant rate period is not uniform, and is more nearly parabolic. Sherwood has presented an analysis for this case, and has given experimental values for the drying of brick clay. 

Fortunately this description covers most of the commonly-used British clays—ball clays, fireclays, china clays and some brick-clays. For clays containing a montmorillonite or a chlorite, rational analysis presents a much more difficult problem, requiring special analytical methods. 

The principal minerals in brick-clays are kaolinite and chlorite, with illite, quartz, and organic matter many brick-clays contain considerable amounts of iron oxide and calcium carbonate. Because the composition of the minerals, particularly chlorite, is uncertain, it is difficult to calculate a rational analysis for brick-clays, as has been done for ball clays. 

The thermal techniques are routinely used for quality control purposes. A typical TG/DTA analysis is shown in Fig. 13 for a Thessalian brick clay.t None of these clays contains kaolin and the characteristic mullite peak is absent. The endothermic peak between lOOand 160°Cisdue to the removal of adsorbed water, and its size is dependent on the surface area and crystallinity of the clay. The peak (400-700°C) is attributed to the dehydration of the combined water (dehydroxylation of the silicate lattice) and decomposition of the clay. The third peak (800°C) indicates decomposition of the carbonates and other salts present in the clays. 

The fire clay for making the bricks which line the furnace, and which is generally found in the same mine with the ironstone, varies very considerably in composition in different localities, having properties more or less suitable for the purpose, according to the absence of oxides, and the quantity of silica and alumina. Tav-lok, in his analysis of the rocks of the coal-measures at the Hartley pit, gives the following... 

These bricks may therefore be called nlicecus oj etone bricks, and will no doubt prove admirably adapted for the construction of many kinds of chemical furnaces. A red fire-brick is likewise manufactured at Windsor, the analysis of the clay from which it is prepared being... 

Figure 5. Principal component analysis showing relationships between Chapel bricks and local clays. Ellipses indicate 95% confidence limits.

Mineralogical and chemical information is essential for determining the brick making characteristics of a mudrock. Differential thermal analysis and thermogravimetric analysis can identify clay minerals in mudrocks, but provide only very general data on relative abundance. X-ray diffraction methods are used to determine the relative proportions of clay and other... 

The thermal analysis of different archaeological samples of bricks, terra-cotta, and local clays provides useful information on the chemical composition of historical samples and can provide confirmation of specific sites of originJ ] The thermal characterization of local clays is valuable to assist the restoration of historical pottery materials. 

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