العوامل المؤثرة في صنف الطابوق الآجر المصنوع من ترسبات العصر الرباعي في مناطق مختلفة من العراق

Abstract

In this study, the data of chemical analysis, grain size analysis and physical and mechanical properties of 268 clay samples collected and studied thrir suitability for bricks manufacturing, from different parts of Iraq were evaluated. Statistical analyses (correlation coefficient and factor analysis) were applied to correlate between these data to determine the effective variables that affect the bricks grade. The clays of Quaternary sediments, which are the traditional source of clays for bricks manufacturing, are used in most parts of Iraq. Since the studied samples were chosen from assorted parts of Iraq, therefore the results of this study could be applied as a general rules for the bricks manufacturing. The study revealed that the efflorescence and the mineralogical composition plays an important role and affects bricks grade. The relationships between the chemical oxides could explain the mineral content and then its effect on the physical properties of bricks manufactured from them. The positive relationships between CaO, MgO and L.O.I., reflect presence of the carbonate minerals in the raw clay, which affects the longitudinal and volumetric shrinkage and water absorption, which in turn affects the bricks grade. Al2O3 is used to calculate the percentage of the clay minerals, which incorporate K2O in illite, MgO in palygorskite and CaO in montmorillonite. The presence of large quantities of palygorskite reduces the bricks grade and might lead to their failure. Also the presence of CaO and SO3 with positive relationship between them indicates the presence of gypsum, which causes the efflorescence and affects the bricks during firing at high temperatures. Na2O, MgO and Clˉ indicate for the chloride salts and Na2O with SO3 indicate the presence of sodium sulphate salt, which all cause efflorescence of the bricks. Carbonate minerals produces CaO and CO2 during the bricks firing. CaO, when absorbs water turns to Ca(OH)2, which has larger volume, leading to disintegration and breakage of the bricks. While CO2 produces pores, leading to an increase in porosity and water absorption and reduces the compressive strength. The high increase in the sand size percentage will decrease the compressive strength of the bricks and the high increase in the clay size percentage will lead to fracturing of the bricks during the drying process in air.