Understanding the thermal effect of power ultrasound in cement paste

The thermal effect of power ultrasound (PUS) converts acoustic energy into heat energy and promotes cement hydration, whereas the effective propagation distance and mechanisms are poorly understood. This study employed two distinct water-to-cement (w/c) ratios, specifically w/c = 0.30 and 0.50, in conjunction with four ultrasound power levels (0 W, 100 W, 450 W and 900 W) and four varying durations of ultrasound irradiation (0 min, 3 min, 10 min and 30 min), as independent variables. The temperature-time (T-t) curves of cement paste under different treatment conditions were recorded and analyzed. The improved heat evolution model was used to analyze cement hydration evolution at the sonication stage. The results indicated that the effective ultrasonic distance corresponding to significant temperature elevation was below 100 mm. Additionally, the hydration degree of cement paste showed a conspicuous gradient characteristic when subjected to ultrasonic irradiation. Applying 900 W ultrasound irradiation for 10 min resulted in a more homogeneous temperature field compared to the other experimental groups. This work provides the potential of employing the thermal effect for prestressed cement panels.