Red mud and fly ash-based ceramic foams using starch and manganese dioxide as foaming agent

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.