tailieunhanh - Applied Clay Mineralogy Phần 9

Đất sét thông thường xảy ra trong nhiều môi trường và trong các loại đá khác nhau trên tất cả các khoảng thời gian của hồ sơ địa chất. Các vật liệu đất sét nguồn có thể được băng đất sét, đất, phù sa, hoàng thổ, đá phiến sét, thời tiết và phiến thạch tươi, đá, argillate, và underclays hoặc đất chỗ ngồi. | 144 Applied Clay Mineralogy goethite the firing temperature and degree of vitrification the proportion of alumina lime and magnesia in the clay material and the composition of the fire-gases during burning Butterworth 1953 . The best white firing clays contain less than 1 Fe2O3. B tan-burning clays contain between 1 and 5 Fe2O3 and red-firing clays contain 5 or more Fe2O3. Common clays occur in a variety of environments and in many different rocks across all time periods of the geologic record. The source clay material can be glacial clay soils alluvium loess shale weathered and fresh schist slate argillate and underclays or seat earths. 2. LIGHTWEIGHT AGGREGATE Certain common clays are used to produce lightweight aggregate. The American Society for Testing Materials has published a standard specification governing lightweight aggregates for concrete Code No. C33053 T 1955 . The unit weight of fine lightweight aggregate cannot exceed 70lb ft3 and the unit weight of coarse lightweight aggregate cannot exceed 55 lb ft3. Clay and or shale which is a common clay is used as the raw material to make lightweight aggregate. The raw material is crushed and fed into a rotary kiln or sintering machine. The raw material is heated rapidly up to the range between incipient and complete fusion. The bloating and vesiculation require the presence of substances that release gas after fusion has developed a molten jacket around the particles to prevent the escape of the gas. The molten jacket must be viscous enough to prevent the escape of the expanding gas. Conley et al. 1948 and Riley 1951 have investigated the causes of bloating. Several factors are important most of which are based on chemical and mineralogical composition. Shales and clays containing illites chlorite some montmorillonite and mixed-layer clays are the most promising sources to make lightweight aggregate. A close relationship exists between the chemical composition and the bloating characteristics of clay and .