Combining mineral and clay-based wastes to produce porcelain-like ceramics: An exploratory study

摘要

The present work was aimed at producing waste-only ceramics with higher added value, while finding a viable end-use, other than landfilling, for wastes from extraction and beneficiation of mineral resources. Based on their fluxing character and plasticity, four non-hazardous industrial wastes were selected and characterized: one clay mining tail, the sludge from potable water treatment and two sludges from gneiss and varvite cutting processes. Using the phase diagram of the SiO_2-Al_2O_3-K_2O system, four mixtures located within the wastes-defined polygon were formulated, uniaxially pressed and fired for 40 min at 900-1150 ℃ The results obtained for the properties of fired samples show that water absorption values below 10% (ceramic tiles) and 3% (porcelain tiles) were reached upon firing at 1100 and 1150℃ respectively, without firing warpage. Density values were also within the usual range but flexural strength, although adequate for common application, is lower than usual (at least 3 MPa). In terms of industrial production, although process adjustments are still required (green processing, firing cycle) the obtained results demonstrate that porcelain-like ceramic tiles can be manufactured using only the selected wastes as raw materials, suggesting that, for the composition range investigated, firing temperatures should be -1100℃ and a fast-firing type processing might be feasible.