High carbon emissions of cementitious materials are increasingly raising concerns under the grand goal of global carbon neutrality. This presentation will introduce an approach to achieve low-carbon cementitious materials and enhance the mechanical properties while retaining the desired constructability for cast-in-place and precast applications of civil infrastructure. The proposed approach utilizes CO2 to produce a CaCO3 suspension that is uniformly dispersed and used to prepare cement pastes. The mechanical properties were tested, and the results showed that the 28-day compressive strength was increased by up to 16%. Further research was conducted to understand the effects of CaCO3 suspension on cement hydration kinetics and microstructures of cement pastes through isothermal calorimetry, thermal gravimetry analysis, mercury intrusion porosimetry, dynamic light scattering analysis, and scanning electron microscopy. The results revealed that the CaCO3 suspension promoted cement hydration and densified the microstructures because of the nucleation effect caused by the high-level dispersion of CaCO3 particles. The proposed approach provides an alternative solution for CO2 utilization in the concrete industry with minimal modification of the manufacturing facility and offers a promising avenue for achieving low-carbon infrastructure.