Basic properties and mechanism of high activity phosphate-based slurry for dynamic water blocking-A feasibility research

Abstract The water inflow into a karst pipeline is characterized by great flow rate and fast flow speed, which makes it difficult to block. Phosphate cement has the characteristics of rapid setting, fast hardening, and good interface bonding, which have inherent advantages for plugging pipelines. However, under the condition of high water ratio, whether the performance of phosphate cement can still maintain the characteristics of rapid setting and fast hardening needs to be studied. In this paper, based on the characteristics of phosphate cement, the feasibility of using high activity phosphate slurry to block the water gushing in karst pipeline was studied. The basic properties of the slurry with different the molar ratio of the MgO to the KH2PO4, such as setting time, strength and viscosity were studied with the condition of high water-binder ratio. The hardened slurry was tested by X-ray diffraction, thermogravimetric Analysis and scanning electron microscopy analysis, and its microscopic mechanism was analyzed. The results show that under the condition of water-cement ratio 1.0, using light burned magnesia as raw material, the slurry can achieve quick setting and hardening, and it is found that the molar ratio of the MgO to the KH2PO4 has a great influence on setting time, strength and micro properties. The research showed that potassium magnesium phosphate cement is feasible to prepare dynamic water plugging material that use light burned MgO as raw material under high water-cement ratio.