Quality concrete is the kind of concrete we are all interested in. What is quality concrete? Quality concrete is concrete that has been properly designed, produced, placed, compacted, finished, and cured. The designing of the nix involves the selection of suitable materials of each to perform a given function. Production must be well controlled so that the concrete is uniform within the batch as well as from batch to batch. Uniformity within the batch must be secured while the concrete is in the mixer; once the concrete is out of the mixer most placing, compacting and finishing operations tend to produce varying degrees of non-uniformity- a sort of unmixing of the concrete. Inclusion of additional amounts of water almost inevitably means that the concrete for that particular job can't be properly classed as quality concrete. If water is added while the concrete is still plastic, or if too much water is used in mixing the concrete, the space which was occupied by this extra water will be void space since the additional water will have evaporated. If the water were not present in the beginning the concrete would not occupy as much space and the volume of voids would be smaller. Now that basic principles concerning mixing water have been explained, why is it important to place water on the concrete, or to prevent loss of water from the concrete, during the curing period? In order for concrete to develop strength, the cement paste must develop strength. In the development of this strength there is a chemical reaction between the cement and the mixing water, often called the hydration of the cement. This process of hydration may continue for a long time so it is important to retain a sufficient amount of water in the concrete for hydration purposes. Retention of water in the concrete may be accomplished by maintaining a supply of water on exposed surfaces, or by use of watertight barriers at the surface. This in brief is why the water content of fresh plastic concrete should be kept at the minimum. After the concrete sets or obtains its final volume, the added water permits the hydration process to continue and thus permits the concrete to develop its maximum strength and durability with the minimum of shrinkage. The lower the slump within the range of workability the more economical the concrete will be. If these basic principles are fully understood and practiced, strong, durable, economical quality concrete will be the resulting product.