Effect of power ultrasound-assisted mixing on the hydration and microstructural development of cement paste

Power ultrasound (PUS) was first used to assist the mixing of cement paste. Five ultrasonic power levels (0 W, 240 W, 480 W, 720 W, and 912 W) were adopted. The compressive strength was tested. The hydration process and products of the cement paste were analyzed by inductively coupled plasma–optical emission spectrometry (ICP–OES), isothermal calorimetry, thermogravimetric analysis (TGA), quantitative X-ray diffraction (QXRD), mercury intrusion porosimetry (MIP), backscattered electron–energy dispersive spectroscopy (BSE–EDS), and environmental scanning electron microscopy (ESEM). The results indicated that the compressive strength was improved by using the PUS-assisted mixing. Moreover, PUS-assisted mixing significantly promoted the formation of calcium hydroxide (CH) and ettringite. The crystallization and densification process of the C-S-H phase was accelerated. The macroscopic voids and large capillary pores were substantially reduced. Therefore, PUS-assisted mixing is a promising technology for improving hydration behaviors and strength of cement paste, which could be used in fabricated production.