For many years experts in concrete technology have advised that bleeding of concrete be limited as much as possible. Nevertheless, a great deal of concrete is placed each year which contains an admixture that purposefully increases the amount of bleeding experienced. Just what are the pros and cons? Bleeding may not be objectionable under some circumstances or it may even be desirable. For example, when a hydroxylated carboxylic acid water-reducing admixture is used, the amount of bleeding is considerably increased. If the concrete is to be revibrated, this will permit the contractor to use a concrete mix which is highly placeable; and yet the bleeding of the water from the mix will reduce the water content of the mix to a reasonable level, and the revibration will thoroughly reconsolidate the concrete. Most authorities, however, feel that bleeding is a phenomenon which should be avoided or minimized in most construction situations. Concrete with a great deal of mobile water tends to segregate as it stands in the plastic state. The larger aggregates and larger cement particles gravitate toward the bottom of the mix with the finer aggregates and cement particles together with lightweight materials in the mix, moving toward the top surface. This results in a layer of diluted cement paste and latence at or near the surface. Another serious problem is the collection of water beneath large aggregate particles, reinforcing bars, and other obstructions to the upward migration of the bleed water. This results in voids, poor aggregate-to-paste bond, and lowered bond strength of the concrete to the reinforcement. Taking into consideration all factors, under the great majority of construction situations it is desirable to limit bleeding as much as possible. How is this accomplished? The first step is taken while designing the mix. This can be done by increasing the cement content while keeping the unit water content constant; increasing the cement/water ratio; employing a finer cement; and increasing the proportion of fine aggregate.