Synergistic cavitation-milling for cement groutability enhancement: Particle fragmentation mechanisms and parameter optimization

Abstract

The limited groutability of conventional cement grouts in narrow fractures and micropore networks remains a major challenge for effective seepage control in grouting engineering. This study proposes a novel cavitation-milling synergy processing methodology (CMSP) to enhance cement groutability through particle fragmentation. By integrating theoretical analysis, computational fluid dynamics (CFD) simulations, and experimental validation, the cavitation-driven mechanisms of particle fragmentation and optimal parameters were systematically investigated. Theoretical analysis revealed that the critical conditions for cavitation-driven fragmentation become more stringent with decreasing particle size and water-cement (W/C) ratio, requiring higher wall-impact velocities, reduced effective dimensionless distances, and smaller critical maximum cavitation bubble radius. Numerical simulations demonstrated that cavitation intensity is positively correlated with inlet pressure (P_in) and W/C ratio, with an optimal jet stand-off distance (D = 15 mm) identified for maximizing the cavitation effect. Experimental results confirmed that the CMSP system effectively suppresses cement particle agglomeration and enhances size reduction efficiency, achieving remarkable comminution performance under optimal condition: D₉₀ < 30 μm, D₅₀ < 10 μm, and nano-scale particle fraction (<1 μm) increased to 8.72 % after 60 min treatment. Parametric analysis indicated that P_in is the dominant control factor, followed by W/C ratio, with optimal fragmentation efficiency achieved at a grinding media filling rate (FR) of 20 %. This research provides fundamental insights into cavitation-driven cement fragmentation mechanisms and establishes practical guidelines for enhancing cement groutability in engineering applications through CMSP.