Vaterite can be synthesized from solid waste carbide residue through a novel CO2 sequestration process. This 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 the fresh and hardened properties of mortar. The study revealed remarkable performance characteristics of VC3 mortar. With a 50% cement replacement, VC3 mortar achieved compressive strength comparable to OPC at 91 days, substantially outperforming LC3, which reached only 60% and 75% of OPC’s compressive strength at 28 and 91 days, respectively.