Understanding the influence of ultrasonic power on the hydration of cement paste

Abstract

This paper studied the dispersion and hydration of cement paste prepared by power ultrasound (PUS)-assisted mixing technology. The ultrasonic power used were 0 W, 480 W and 912 W. The hydration process and microstructure were tested by using isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), solid-state nuclear magnetic resonance silicon (29Si-NMR) spectroscopy, mercury intrusion porosimetry (MIP), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM‒EDS). The results indicated that the dynamic hydration kinetics of cement paste under ultrasonic irradiation can be categorized into crystallization nucleation and growth (NG), phase boundary (I) and diffusion (D) processes. The apparent rate constant KNG in the NG process and KI in the I process both increased as the ultrasonic power increased, suggesting that PUS-assisted mixing accelerated the early hydration process. PUS shortened the dormant period and enhanced the total hydration heat release. The capillary pores and gel pores were both reduced at 28 days. Similarly, compared with those of C0 and C480, the gel porosities of C912 decreased by 35.17% and 31.87%, respectively. In addition, the mean chain length of the C–S–H gel increased with increasing ultrasonic power, which effectively filled the nanoscale defects. PUS improved the early strength and increased the strength at late hydration ages. Compared with that in the reference group, the compressive strength in the C912 group was enhanced by 26.1% at 1 day and 18.3% at 28 days. These findings demonstrate that power ultrasound-assisted mixing is advantageous for enhancing the sustainability of building materials, thereby contributing to the development of future circular buildings.