Influence of the bleeding characteristic on density and rheology in cement slurry

The bleeding characteristic of Portland cement influences its density and rheological behaviour, but the nature and extent of this influence are unclear. This study investigated the development of cement slurry density and rheological characteristics during the entire bleeding period. Portland cement PO42.5 with water-cement ratio (W/C) ranging from 0.8 to 2.0 was used in the experiments. Twelve percentage time periods were divided based on the entire bleeding period, and rheological measurements were carried out at each percentage time period. The results showed that at the end of bleeding, the slurry density with W/C ranging from 2.0 to 0.8 was close to those of the slurry with W/C ranging from 0.8 to 0.6. The slurry with higher W/C behaved a faster density growth speed and degree during the bleeding. The variation of the slurry apparent viscosity as bleeding time showed two stages: a slow growth phase followed by a phase with fast growth. It can be attributed to the weak interaction within cement slurry particles gradually changed into a stronger interaction. The cement slurry behaved like a shear-thinning material after bleeding. The Herschel-Bulkley model could describe rheological characteristics during slurry bleeding better than other empirical models.