Effect of microporous aggregates and spinel powder on fracture behavior of magnesia-based refractories

The influences of microporous aggregates and spinel powder on the properties and fracture behavior of magnesia-based refractories were investigated by the three-point bending test and wedge splitting test with the digital image correlation method. With microporous aggregates instead of dense ones, lower thermal conduc-tivity, higher cold modulus of rupture and compressive strength were observed for lightweight magnesia-based refractories. Besides, the results indicate that the strengthened interlocking interface between microporous ag-gregates and matrix in lightweight magnesia refractories decreased the proportion of crack propagation along the aggregate/matrix interface (PAM). This reduced the tortuosity of crack propagation as well as increased the brittleness. With the addition of spinel powder in the matrix, the pregenerated microcracks by thermal mismatch increased the PAM, which increased the tortuosity of crack propagation, improved fracture energy and reduced the brittleness. Lightweight magnesia spinel refractories merely showed a slightly higher brittleness than dense ones.