The current study dealt with the assessment of red clay deposits of the Injana and Mukdadiyah formations in the Taq taq area, northern Iraq, for some ceramic industries.
The two formations have high thicknesses and good extensions of deposits. Five samples were collected; they represented F1, F2, and F3 in the Injana formation, and B1 and B2 in the Mukdadiyah formation. The samples were analyzed to determine the mineralogical, chemical, and physical properties of clay deposited to assess their suitability for manufacturing clay brick and different types of tiles.
The grain size analysis revealed that the studied samples are mostly sandy mud. The mineralogical analysis reveals the dominance of quartz and calcite as non-clay minerals with minor percentages of feldspar and dolomite in both formations and notes the decreased content of calcite in Mukdadiyah clay compared to Injana clay. The most dominant clay minerals are the mixed layer (montmorillonite) clay, followed by illite, chlorite, and kaolinite. The geochemical analysis of the studied samples showed that the clay raw materials are composed mainly of silica and alumina, which act as refractor materials in the ceramic industry. In addition to that, there are different proportions of calcium, iron oxides, magnesium, potassium, and sodium, which act as flux oxides.
For the assessment of the ceramic industry, 84 rectangular briquettes (8*4*1 cm) were prepared by the semi-dry method and the pressing method (250 kg/cm2) and fired at 800, 900, 1000, and 1080oC. The briquettes were used to evaluate the physical properties such as thermal conductivity, color, linear shrinkage, apparent porosity, water absorption, bulk density, and efflorescence and mineralogical change caused by the different temperatures, as well as mechanical properties such as modulus of rupture, and 20-cylinder briquettes (4 cm high and diameter) were planned for the compressive strength testing process.
The results showed that the color of the briquettes varied from deep red to yellow and that thermal conductivity increased with increasing firing temperature as a function of various mineralogical compositions. Also, linear shrinkage increased as the temperature increased. In addition, increasing in length happened in the Injana Formation in F1 due to the decomposition of calcium carbonate creating pores at 900 and 1000˚C firing temperatures. Due to the rising dry sensitivity index, drying shrinkage, and moisture content percent values of the investigated ceramic briquettes, they must be dried at low temperatures for extended periods by adding between 9.5% and 12.6% water during briquette paste preparation. Bulk density and mechanical strengths increased and decreased apparent porosity and water absorption percentage with increasing firing temperature. The new minerals phase after firing at 1000 and 1080˚C Gehlenite, Diopside, Sublcalic, Hedenburgite, Tridymite, and Anorthite in brick bodies.
compare these test results to the international standard specifications for the ceramic industry: Iraqi Standard No. 25 (1988), 17 (1998), and ASTM C1167 (2003). This study demonstrated that all of the studied samples can be used in the brick industry in Class A except F1 and B1 at 800˚C located in class B, the floor and wall tile industry, which is all of them located in B3 class tile and grade three, except F2 and B2 at 1080˚C located in class two, and so when fired at 1080oC, they can also be used as chemical-resistant tiles except F1 and that do not resist HCL.