Potentiality for using paper sludge waste in the manufacture of red wall tiles

Paper sludge waste is produced on a large scale by the paper industry and causes significant environmental impacts. This work investigates the potential of paper sludge waste incorporation as an alternative raw material into a red wall tile formulation, replacing traditional limestone material by up to 5 wt%. Red wall tile pieces containing paper sludge waste were produced by uniaxial dry pressing and fired at 1170°C using a fast-firing cycle. Technical properties of the fired wall tile pieces have been determined. The development of the fired microstructure was determined by scanning electron microscopy. It was found that water absorption was 17.15–18.31%, flexural strength was 15.77–16.17 MPa, linear shrinkage was 2.88–3.22% and apparent density was 1.76–1.81 g/cm³. Therefore, the results indicated that the paper sludge waste, in the range of up to 5 wt%, can produce red wall tiles (group BIII in the ISO 13006 standard). At the same time, this application helps minimise the environmental impacts caused by the paper industry.