Balancing cost and eco-friendliness are the major challenges of the refractory industry. Aiming at reducing greenhouse emissions, zero-carbon bricks were recently introduced in the market. The latter refractories have some advantages such as lower thermal conductivity and no direct CO₂ emissions during operation, reducing thermal losses and environmental impacts related to their use. One way to enhance their thermomechanical properties is by adding spinel-like inducers (such as MgO and ZnO) to in-situ react with alumina forming MgAl₂O₄ and ZnAl₂O₄, respectively. However, if the reactants content were not precisely adjusted, a detrimental porosity can be generated during the in-situ spinalization due to the Kirkendall effect. Aiming at circumventing this issue, the addition of preformed MgAl₂O₄ has already been extensively reported in the literature, resulting in a brick with suitable thermal shock damage resistance, good dimensional stability, and high corrosion resistance. Nevertheless, using preformed magnesium aluminate has some disadvantages such as the hydration likelihood and high linear thermal expansion coefficient, the former, specially for MgO-rich spinels. In this work, the effects of adding preformed ZnAl₂O₄ or a complex spinel comprised of a specific Al₂O₃-MgO-ZnO composition, selected with the help of thermodynamic calculations (CALPHAD method), in alumina-based refractory bricks were carried out and compared to a reference composition containing preformed MgAl₂O₄. For a fair analysis with some works in the literature, 23.1 vol.% of each preformed spinel-like synthetic raw material, was added to all compositions. The distinct bricks had their physical, thermomechanical, and mineralogical phases evaluated after firing at different thermal treatments (after 200, 800, 1000, 1200, 1400, and 1600 ºC in oxidizing atmosphere conditions). As suspected, all the evaluated compositions showed suitable dimensional stability and constant apparent porosity values after firing at temperatures in the range of 800 ºC and 1600 °C. These features provided suitable thermomechanical properties for a refractory brick composition when compared with the in-situ reacted counterpart. Moreover, pre-formed ZnAl₂O₄ was effective to induce higher thermal shock damage resistance. Nevertheless, an additional significant result of this study is the potential use of preformed synthetic triple oxide-complex spinels for applications in refractory materials, opening up vast venues for engineered microstructures with superior physical, chemical, and thermomechanical properties. Therefore, this work addressed the role played by the preformed spinel additions on alumina-based refractory bricks, highlighting their sintering effect on the physical and thermomechanical properties.