Incinerator Bottom Ash and Ladle Slag for Geopolymers Preparation

Ladle slag (LS) and urban incineration bottom ash (BA) are two types of non hazardous inorganic wastes which do not contain significant amounts of pollutants such as heavy metals and organics. Nowadays they are necessarily disposed of with little attention placed for re-use or recycling. Considering their chemical composition, rich in silica and alumina with substantial levels of lime and iron oxides, these residues can be suitable for generating new alkali activated materials. A safe reuse of these residues in high percentages (60–70 wt%) is presented in this study for mortar production. The final room-temperature consolidated materials, also known as geopolymers, have been characterized in terms of thermogravimetric analysis, morphology, porosity, and crystalline phases evolution. When incinerator BA is used, the morphology of the resulting geopolymer is very close to that of pure metakaolinic pastes, whereas for LS based geopolymers calcium presence promotes the formation of calcium–aluminate– silicate–hydrate phase. This investigation also demonstrated that the content of reactive fraction of BA is of primary importance to assess its possible use in alkaline activation process.