Preparation of reactive seedings by in-situ precarbonation under power ultrasound-assisted mixing: Enhancing the hydration and mechanical properties of OPC

In this study, a precarbonation process of cement paste was developed using a power ultrasound-assisted mixing method to prepare a highly reactive seedings admixture, which was subsequently added to the remaining cement paste for secondary mixing. The results revealed that power ultrasound greatly facilitated the release of ions from the cement into the pore solution, promoting the formation of calcium carbonate, aluminum hydroxide and C–S–H gels. After the 20 min ultrasound treatment, a substantial quantity of very fine seedings was observed, capturing 7.09 wt% CO₂ of the total cement used. These seedings also acted as nucleation sites to accelerate further cement hydration, which shortened the hydration induction period and ultimately formed a more homogenous, denser cement microstructure.