Surface Treatment of Cementitious Composites by Ultrasound and Its Effect on Durability Performance.

In this study, the method of changing the surface layer microstructure of cementitious composites by ultrasonic surface treatment at the early stage of hydration is introduced, and the formation mechanism of the gel phase powder layer (GPPL) formed by ultrasound is analyzed. The microstructure of GPPL is observed and analyzed by laser confocal microscopy scanning (LCMS), scanning electron microscopy (SEM) and backscattered electron (BSE) imaging. The phase component is measured by X-ray diffraction (XRD) and thermogravimetry (TG). Four ultrasonic frequencies (28, 40, 80, and 120 kHz) were used in the experiment. Apparent density and water vapor permeability of the cement paste specimens with GPPL structure were tested. The accelerated carbonation test of concrete and mortar specimens with GPPL structure were carried out. It is proved that GPPL structure can significantly improve the carbonation resistance performance of cementitious composites. Finally, the prospects for engineering applications of this method are presented. [ABSTRACT FROM AUTHOR]