Previous studies had shown that a promising material could be obtained by mixing aluminium-rich sludge with slate powder (with Al2O3:SiO2 molar proportion of 2:1), shaping by uniaxial pressing and sintering at 1300 degrees C, in order both to detoxify the sludge by fixing the metals in a leach-resistant ceramic matrix and to yield a new material from the reactions of the above compounds at high temperature. In view of potential applications, since this material was also found to be inert after leaching tests, a further systematic study, reported in the present paper, was carried out, in order to determine its mechanical properties and discuss them in function of the microstructure. The average values of Vickers hardness HV3 (683), bend strength (126 Mpa),Young's modulus (161 Gpa) and fracture toughness (3.35 Mpa.m(1/2)) are significantly higher than Young's modulus (161GPa) and fracture toughness (3.35 MPa.m(1/2)) are significantly higher than those found for the as sintered slate powders, which is attributed to the increased fraction of alumina and reduced content of glassy phase in the microstructure of the material with sludge addition.