Abstract:Ceramic foams were prepared using red mud and fly ash as raw materials with sodium borate as sintering aid agent, starch and MnO₂ as foaming agent, respectively. The influence of the amount of starch or MnO₂ on the crystalline phase, pore morphology and physical–chemical porosities was studied. The results showed that the main crystal phases of samples with starch addition and MnO₂ addition were sodalite phase Na₆ (AlSiO₄)₆ and Na₈(SiAlO₄)₆MnO₄, respectively. The SEM images showed that the variation of porous structure was mainly dominated by the addition of foaming agent. With the increase of foaming agent, the samples exhibited better comprehensive properties: bulk density of 0.59-0.96 g/cm³, porosity of 41.82%-63.51%, water absorption of 3.16%-9.17%, compressive strength of 4.22-8.38 MPa, flexural strength of 2.44-5.82 MPa, acid resistance of 95.59%-99.60%, alkali resistance of 99.82%-99.99%. Based on these properties, the ceramic foams can be used in building field.

Key words: red mud; fly ash; starch; manganese dioxide; ceramic foam