Time-varying characteristics and mechanisms of hydrostatic pressure descent of Portland cement slurry

Abstract In this paper, the experimental results indicated that the hydrostatic pressure descent (HPD) curves of cement slurry include a stabilization stage, slow descent stage, and rapid descent stage. In the stabilization stage, the gravity of the solid particles dispersed in pore water was effectively transferred by the pore water. In the slow descent stage, the microstructure of cement slurry changed from “dispersed particles” to “gel network”, causing the gravity of the particles to be diverted to external interfaces. In the rapid descent stage, hydrostatic pressure of the cement slurries was attributed to the pore water. But the rapid reduction in the pore size increased the capillary pressure of the pore water, causing the gravity of pore water to transfer to external interfaces via the “gel network”. Finally, when the most probable pore diameter decreased to approximately 50 nm, the hydrostatic pressure of the cement slurry was reduced to zero.