Characterisation of calcined paper sludge as an environmentally friendly source of metakaolin for manufacture of cementitious materials

The correct assessment of industrial by-products and waste materials requires an in-depth knowledge of their characteristics. In thermally activated products, the calcining conditions have an important influence on the properties and later behaviour of cementitious matrices. The present study was carried out to determine the effect of calcining conditions (2–5 h at 700–800°C) on the properties of treated paper sludge. Various chemical, physical, morphological, mineralogical and pozzolanic characteristics were evaluated in order to provide a complete understanding of the properties of the calcined sludge and the possibility of using them in the manufacture of blended cements. The results showed that the thermal conditions have a major influence on the properties of the calcined sludge, primarily the mineralogical and morphological properties, as well as the pozzolanic behaviour.