The development of low-carbon binders and the reduction of Ordinary Portland Cement (OPC) content in concrete are pivotal strategies in cement decarbonization, addressing the significant environmental impact of cement production. Limestone Calcined Clay (LC3) binders have garnered considerable attention in recent years due to their ability to replace a large amount of OPC while keeping satisfactory performance. The use of Vaterite (a calcium carbonate polymorph), can be considered as an alternative to limestone in the LC3 binders, producing Vaterite Calcined Clay Cement (VC3) systems. In this research Vaterite was synthesized by employing a lab-scale precipitation method using K2CO3 and CaCl2, together with NH4Cl to ensure purity and reproducibility for systematic evaluation of its cementitious properties. While in large scale production Vaterite can be synthesized from solid waste carbide residue through a novel CO2 sequestration process, using glycine as a regulator. The process not only offers a promising CO2-negative waste management solution but also enhances the potential for sustainable construction. This research investigates VC3’s potential as a low-carbon binder, analyzing the impact of Vaterite on reducing OPC content and examining its influence on both fresh and hardened properties of mortar. This study revealed remarkable performance characteristics of VC3 mortar. With a 50% cement replacement, VC3 mortar achieved compressive strength comparable to OPC at 91 days, outperforming LC3, which reached only 60% and 75% of OPC’s compressive strength at 28 and 91 days, respectively. Moreover, VC3 mixes with 55 and 60% cement replacement still showed outstanding results, attaining 95 and 90% of the reference OPC compressive strength at 91 days. The findings also revealed a direct correlation between Vaterite content and workability, attributed to this calcium carbonate polymorph’s unique spherical morphology and larger particle size than calcite particles. Advanced analytical techniques, such as Scanning Electron Microscope (SEM) and Isothermal calorimetry analysis, were employed to further investigate Vaterite particles and hydration process of mortars, offering valuable insights into their properties.