EVALUATION OF FEDHAT CLAYS IN AL-SALMAN AREA, SOUTHERN IRAQ, FOR THE MANUFACTURE OF CLAY BRICKS

Clay sediments were evaluated in playa lake called (Fedhat) in the south of Al-Samawa city within Al-Muthanna Governorate as a raw material for the bricks industry. These sediments are distributed in the specific area belonging to the Al-Salman district. Six samples were carefully selected from these sediments. These deposits are considered as a layer of fine-grained dark brown silt, interspersed with sandy lenses of various sizes. The chemical analysis showed that the major oxides are within the acceptable limits of the brick industry. The X-ray diffraction results of the samples showed two types of minerals; the clay minerals included (montmorillonite, palygorskite, kaolinite, chlorite, and illite), while the non-clay minerals are quartz, calcite, dolomite, and feldspar and gypsum. The clay samples were ground to obtain fine sizes for each sample. Then, the sample was divided, squared, and sieved by a dry sieve device. The materials were mixed well by the continuous stirring of the sample and an amount of 600 grams was taken from each of the studied samples, and fermentation by adding an appropriate amount of water estimated at 18% to the sample for 72 hours for the bricks formed by extrusion method. As for the bricks manufactured by the semi-dry pressing method, water is an addition at a rate of 8% to the sample, which is equivalent to 48 milliliters, and then the samples were kept in sealed plastic bags for fermentation for 24 hours. Sixty samples were formed by extrusion method with a laboratory size (2.5 x 3.85 x 7.5) cm, and 60 samples by semi-dry pressing method with dimensions 5.12 cm2 in diameter and height, the samples were squeezed under a pressure of 250 kg/cm2. The drying process of the samples was carried out in two stages at room temperature for 48 hours, and in a binder oven, at a temperature of 100 °C (±5)° for 24 hours. These samples were burned according to a specific firing program at different temperatures (750, 950, and 1100 °C). When the prepared brick samples were fired under temperatures of 1100 °C, the fired samples have good results in terms of compressive strength, water absorption, gradual increase in bulk density, and the absence of cracks, in general, the external appearance of the bricks remained unbroken. It is important that a very large reduction of calcite was observed when temperatures rose to 1100 °C, as the mineral calcite does not decrease with increasing temperatures, calcite can react with other compounds and form new phases accompanied by glass phases resulting from the presence of molten materials. The reactions that occur during burning at a temperature of (1100 °C) lead to the formation of the mineral mullite in a crystalline form