1. Shi Ying is an important barren raw material in ceramic tiles. Its introduction can reduce the shrinkage and deformation defects of product blanks, help accelerate the drying process and save process time.

 2. Shi Ying undergoes polymorph transformation and volume expansion at high temperature, which can partially reduce shrinkage during green body firing and reduce stress caused by excessive firing shrinkage, thus improving product firing performance.

 3. During the firing process, Shi Ying partially dissolves in feldspar glass liquid, which can increase the viscosity of the glass liquid, while the excess Shi Ying forms the skeleton of the green body.  This not only enables the green body to resist deformation at high temperature, but also increases the physical strength of the product.

 Clinker as barren raw material

 Clinker series pre-calcining some natural mineral raw materials at high temperature to reduce shrinkage, increase strength, partially change their physical and chemical properties, and improve and improve process performance.  For example, kaolin series raw materials can be calcined at high temperature to produce mullite crystals.  Calcining talc raw materials can form cordierite crystal substances.  After some clay raw materials are calcined into mature materials, a large amount of gas is removed due to excessive organic impurities in the sintering process, eliminating hidden dangers, thus effectively ensuring the speed of speeding up the new low-temperature rapid sintering process and having important significance for improving product quality and high sintering efficiency.  After the clay raw materials are processed into mature materials, the crystal water and organic matter contained in the clay raw materials are removed, thus losing plasticity and generating volume shrinkage. When calculating the formula, its chemical composition is equivalent to removing burning loss from the original composition.

 At present, many ceramic enterprises can also achieve barren effect by grinding the burnt ceramic tile waste and adding it into the blank according to a certain proportion.  This method does not affect the chemical composition of the product, but is also an economical and reasonable method.  However, the addition amount should be determined according to the specific conditions of each enterprise's technological process, and the proportion of waste blanks added and the requirements of blanks on plasticity must be considered.  In enterprises producing colored glaze tiles, glaze on waste products will cause unstable sintering performance of green body due to special chemical composition in liquid phase, so attention should be paid to it when batching.  At present, the introduction amount of biscuit firing waste in ceramic tile ingredients can be controlled in the range of 5 % - 15 %.  In short, barren raw materials occupy a very important position in the ceramic tile production process and should not be ignored.

 Research Status of Foreign Clinker At present, for the purpose of environmental protection and saving the earth's high-quality raw materials, some ceramic enterprises in Europe and Japan have incorporated the full development and utilization of geological inferior raw materials and the comprehensive utilization of municipal waste and construction waste into the production field of ceramic products. Many inferior raw materials and wastes have been calcined at high temperature to remove organic substances and harmful impurities to become usable clinker and then added to the blank formula as barren materials.  At present, with the continuous improvement of technology content in high-temperature rapid firing process, the firing temperature has been greatly reduced, so the range of barren raw materials that can be selected has a tendency to expand.  It is against this background that developed countries have accelerated the development and utilization of new barren materials and have achieved great results.