Waterglass Waste as an Additive to a Ceramic Floor Tile Mixture

Waterglass is the commercial name of an important Egyptian product whose chemical composition is mainly sodium silicate. The industrial waste of its production is a large quantity of a heavy grey sludge that comes out as a viscous slurry, then solidifies quickly causing a major environmental problem. In the work described in the present article, the dried sludge was finely ground to form a powder that can be utilized as additive to a mixture of Egyptian raw materials used in the manufacture of ceramic floor tiles. The main targets were to recycle an industrial polluting waste and to make use of its fluxing components. The experimental program included both chemical and mineralogical assessment of both mixture and sludge. The waste was then added in various proportions from 5 % to 20 % of the mixture by weight. Samples were dry pressed and fired at950°C, 1000 °C 1050 °C, 1100 °C, 1150 °C and 1160°C with 5 minutes soaking time and a heating rate of 999 °C/h. Fining shrinkage, weight loss, compressive strength, water absorption, bulk density, and apparent porosity were measured and compared to both ISO and Egyptian Standards. Fired samples of a basic mixture, 5 % waste and 20 % waste were subjected to XRD and SEM in order to investigate both expected and unexpected behaviour.