Producing concrete with the correct yield and being able to verify that yield is extremely important to every ready mix producer and to every contractor. Many times questions of yield are raised by a contractor who believes he has not received all of the concrete that the ready mix producer is certain he has delivered.
YIELD MEASUREMENT BASED ON A UNIT WEIGHT TEST
The common method for measuring yield is based on a simple unit weight test, usually using a 1/2-cubic-foot container. Procedures used for determining unit weight are described in ASTM C 138, the standard test method for unit weight.
YIELD CALCULATION BASED ON ABSOLUTE VOLUME
Concrete mixes are designed by the absolute volume technique. In a batch of concrete, the sum of the absolute volumes cement, aggregate and water plus the volume of air is equal to the volume of concrete produced per batch. Weights of the various ingredients must be chosen to yield a design volume (usually one cubic yard) of concrete with the desired cement content, water-cement ratio and air content. To calculate the absolute volume of a material for a given weight, the specific gravity of the material must be known. Specific gravity is the weight of a material divided by the weight of an equal volume of water.