Efficacy and mechanisms of power ultrasound in regulating the dissolution and precipitation kinetics of super sulfated cement

The sluggish dissolution of slag limits the early hydration and strength development of super sulfated cement (SSC). Promoting slag dissolution and hydrate precipitation is critical for the application of SSC. In this study, the in-situ cavitation effect of power ultrasound (PUS) was employed to regulate the dissolution-precipitation kinetics of SSC, thereby enhancing its hydration and hardening performance. Mechanistically, PUS effectively exfoliates surface attachments, enlarges the specific surface area and accelerates dissolution rate. Simultaneously, the exfoliated nano-sized particles act as nucleation seeds, lowering the nucleation barrier and promoting the precipitation of hydration products. Results indicate that a 15-minute PUS treatment (360 W, 20 kHz) reduces the induction period of ettringite crystallization to 4 h and increases its content at 3 days by 68.52% compared to the control group. At 28 days, the slag hydration degree and C-S-H gel content increase by 21.5% and 19.19%, respectively. Furthermore, the densification of SSC samples is significantly improved, yielding mortar compressive strengths at 1, 3 and 28 days that are enhanced by 44.6%, 23.5%, and 29.9% over the control group, respectively. This research provides a promising reference for the performance optimization of solid waste-based cement.