The Effect of Flux on a Waste-Derived Foamed Ceramic: Analysis of Microstructure and Properties

Foamed ceramics with high closed porosity were prepared using granite scrap as the raw material and silicon carbide as a foaming agent, and the effects of Na2O, K2O, and MgO on the pore structure and properties of the foamed ceramics were investigated. The results show that both Na2O and K2O could reduce the viscosity of the melt and promote the formation of the liquid phase, and the increase in content could enhance the foaming ability of the blank. When the dosage of Na2O was 4-6 wt% and the dosage of K2O was 6-8 wt%, the homogeneity of the pore structure of the foamed ceramics could be effectively improved, and the samples exhibited an optimal performance, including a bulk density of 510.36-593.33 kg/m3, a closed porosity of 68.24-78.04%, a compressive strength of 1.33-2.66 MPa, and a water absorption capacity of 0.57-1.31%. A further increase in the Na2O and K2O dosages destroyed the uniformity of the pore structure, resulting in a large number of irregular macropores. MgO had a slight effect on regulating the pore structure of the foamed ceramics, and the increase in dosage promoted the precipitation of forsterite crystals, creating conditions suitable for the preparation of foamed ceramics with small pores.