Abstract

Limestone clays are used in the ceramic segment in the manufacture of bricks, ceramic tiles, and in the production of cement, among others. Limestone can be present in soils in pure form or as a contaminant, but always from marine environments. The limestone after burning can present a high loss of mass (35–45%), which can cause serious problems with the sintering of ceramic products such as bricks, tiles. The calcium or magnesium carbonate once dissociated forms calcium oxide (CaO) and releases carbon dioxide (CO2). CaO in contact with water subsequently experiences very high expansions that can cause cracks in the materials. Researchers have studied procedures to inhibit limestone action on clays as well as to set the correct temperature for firing. In this chapter, examples of clays with different percentages of calcium carbonate (CaCO3) that are used in the ceramic segment and their characteristics will be given.

Highlights

  • IntroductionNatural, earthy, and fine-grained materials that acquire plasticity when mixed with water [1]

  • Clays are inorganic, natural, earthy, and fine-grained materials that acquire plasticity when mixed with water [1]

  • Masses for ceramic coating: as a source of calcium oxide (CaO) up to the limit of 3%, CaCO3 assists in the formation of the vitreous phase

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Summary

Introduction

Natural, earthy, and fine-grained materials that acquire plasticity when mixed with water [1]. Calcite and dolomite are the most important representatives of carbonates in the ceramic industry They are used as main components in the manufacture of ceramic tiles with high water absorption. According to Amorós [6], properties of parts of a ceramic product are registered by crystalline phases formed based on calcium and magnesium as ghelenite (SiO2ÁAl2O3Á2CaO) and anortite (2SiO2ÁAl2O3ÁCaO) To achieve these phases, use the dolomite calcium oxide and/or magnesium reaction with a remaining clay structure proven by its thermal decomposition. Clays are hydrated aluminum silicates with crystalline structure arranged in layers, consisting of continuous sheets of SiO4 tetrahedrons, ordered in a hexagonal shape, condensed with octahedral sheets of di and trivalent metal hydroxides, usually below 2 μm They are materials that in contact with water become plastic, a fundamental characteristic for conformation of ceramic products because it provides mechanical resistance in the pressing, extrusion, or gluing process. Clays are mixtures of various clay minerals such as kaolinite, illite, and montmorillonite, which may or may not contain impurities [3, 8]

Montmorillonite
Clays used in the ceramic manufacturing process
Heat action on clays
Use of calcite in the ceramic and chemical industry
Specifications of raw materials for ceramic tiles
Chemical analysis
X-ray diffractometry The X-ray diffraction patterns of the clays are shown in
Dilatometric tests
Findings
Conclusions and perspectives

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