Bleeding occurs when freshly mixed cement-based materials settle in a form, and this phenomenon influences the quality of the fresh state as well as the hardened state. This paper attempts to measure the bleeding of Portland cement and ground granulated blast furnace slag (GGBFS) paste mixtures. To investigate the influence of water-to-powder ratio and the used powders under high pressure on bleeding, a pressure vessel and various types of freshly mixed paste were prepared. The packing density and permeability were measured and discussed to understand material effects on the bleeding phenomenon.