A sintered concrete having the following mean chemical composition, as mass percentages on the basis of the oxides and for a total of 100%; ZrO2: 55 to 70%, SiO2: 25 to 40%, P2O5: 0.2 to 9.0%, Al2O3: 0.5 to 7.0%, CaO: >0.2%, CaO+MgO+B2O3+Fe2O3: 0.2 to 10.0%, MgO+B2O3+Fe2O3; ≤7.5%, B2O3+MgO: ≤4.5%, ZrO2+SiO2+P2O5+Al2O3+CaO+MgO+B2O3+Fe2O3: ≥95.0%, and containing more than 70% of zircon, as a mass percentage on the basis of the mass of the crystalline phases.