Self-levelling underlayments (SLUs) based on Portland cement (PC) are susceptible to cracking due to drying shrinkage. The present study evaluated the influence of binder contents on systems consisting of calcium aluminate cement (CAC), PC, and a source of calcium sulfate (C$), derived from the flue gas desulfurization process (FGD), on the mechanical (flexural and compressive) properties and drying shrinkage of SLUs. The main objective was to analyze the influence of replacing limestone filler (LF) by bottom ash (BA) and red mud (RM) wastes on the properties of SLUs based on the CAC/FGD/PC (56/24/20) binder system. For this purpose, mini-slump flow, setting times, water absorption, mechanical (flexural and compressive) strength, linear shrinkage, and X-ray diffraction essays were performed. The replacement at a level of 0.2 filler with wastes reduced linear shrinkage while replacing 0.3 filler level provided greater initial (1 day) compressive strength.