Experimental study on stability and hydration process of ultra-fine cement-based slurry

Abstract

Ultra-fine cement overcomes the limitations of ordinary cement, such as large particle size that hinders injection into micro-cracks and pores, and reduces the high costs of chemical slurries. Rheological properties and water-bleeding significantly affect slurry diffusion and grouting effectiveness. This study investigates the impact of the water-cement ratio, admixtures, and hydration time on water precipitation and the rheological behavior of ultra-fine cement-based slurry. The hydration process, including water migration and transformation, was analyzed to reveal the conversion dynamics of slurry water types. The effects of the water-cement ratio and admixtures on slurry hydration behavior are also discussed. The primary findings of this research are as follows: (1) The rheological parameters, including shear stress and apparent viscosity, of ultra-fine cement-based slurry decrease as the water-cement ratio increases. At a constant water-cement ratio, the rheological behavior follows the order: Ultra-fine cement<Bentonite<Hydroxypropyl methylcellulose. (2) The rate of water-bleeding from the ultra-fine cement-based slurry increases with a higher water-cement ratio. The addition of bentonite slightly reduces the water-bleeding rate. Conversely, hydroxypropyl methylcellulose markedly inhibits the water-bleeding rate of the slurry. (3) This study reveals the mechanism of water migration from capillary pores to gel pores and demonstrates that bentonite slows the hydration rate, while hydroxypropyl methyl cellulose accelerates it. The findings offer valuable theoretical insights and practical guidance for optimizing the use of ultra-fine cement slurry in micro-crack sealing and permeability control applications.