A micro-expansion plasticizing material contains bulk powder, a coagulation accelerator and a bonding agent, wherein the bulk powder, the coagulation accelerator and the bonding agent are mixed in a ratio being 90:8:2; the bulk powder is prepared from bauxite clinker, kyanite and andalusite in a ratio being 80:10:10; the coagulation accelerator is composite aluminate; the bonding agent is PA80 glue. The micro-expansion plasticizing material is laid to the top of a dust settling chamber, stability of an arch crown can be effectively improved, and the probability of deformation of the arch crown is reduced, so that the overall service life of the dust settling chamber is prolonged correspondingly.