Bleed and Water Retention

Bleeding is the process in which water in the cement mix “bleeds” upward through the cement as a result of heavy particles sinking or settling. A certain level of bleed is tolerable (and, in some cases, desirable), but if your cement bleeds too much, it can adversely affect the material’s durability. Usually, excess bleeding is a product of an unbalanced ratio of cement to water. However, there are some other potential causes as well, such as not using enough fine aggregates in the cement mix, and the pressure and height of the cement can also be contributing factors.

To determine the bleed level in a cement mix, you can use a cement bleeding apparatus like the one sold by Forney. This device can analyze the rate and capacity of bleeding in cement paste and mortar. The unit comes with a non-corrosive metal container to hold your mortar, along with a collection ring, a support stand, a funnel assembly, a stopcock, and burette clamps.